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L
TA09 Entry, Descent, and Landing Systems
INTRODUCTION
The draft roadmap for technology area (TA) 09, Entry, Descent, and Landing Systems, consists of four level 2
subareas:1
• 9.1 Aeroassist and Entry
• 9.2 Descent
• 9.3 Landing
• 9.4 Vehicle Systems Technology
Entry, descent, and landing (EDL) systems is a critical technology that enables many of NASA’s landmark
missions, including Earth reentry, manned Moon-landings, and robotic landings on Mars. EDL technologies support
all of the systems and demonstration thereof necessary to perform any or all of the three mission phases defined
by entry, descent, and landing. NASA’s draft roadmap for TA09 defines entry as the phase from arrival through
hypersonic flight, with descent being defined as hypersonic flight to the terminal phase of landing, and landing
being from terminal descent to the final touchdown. EDL technologies can support all three of these mission phases
or just one or two of them. For example, aerocapture or aerobraking technologies support only the entry phase.
Entry, Descent, and Landing are the three main level 2 technology subareas; the fourth, Vehicle Systems
Technology, encompasses technologies that cover multiple phases of EDL.
Before prioritizing the level 3 technologies included in TA09, several technologies were renamed, deleted,
or moved. The changes are explained below and illustrated in Table L.1. The complete, revised technology area
breakdown structure (TABS) for all 14 TAs is shown in Appendix B.
Technology 9.1.5, Instrumentation and Health Monitoring, is applicable to descent and landing as well as entry,
and so it has been moved to technology subarea 9.4, Vehicle Systems Technology, which encompasses technologies
that cover multiple phases of EDL, and has been redesignated 9.4.6.
Modeling and Simulation appears as separate line items in Entry (9.1.6), Descent (9.2.5), and Landing (9.3.6).
However, there is so much overlap among these three areas, and the factors that determine priority vary so little
from one to another, that they have been combined into a new level 3 technology (9.4.5 EDL Modeling and Simu -
lation) in technology subarea 9.4, Vehicle Systems Technology.
1 The draft space technology roadmaps are available at http://www.nasa.gov/offices/oct/strategic_integration/technology_roadmap.html.
244
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APPENDIX L
TABLE L.1 Technology Area Breakdown Structure for TA09, Entry, Descent, and Landing Systems
NASA Draft Roadmap (Revision 10) Steering Committee-Recommended Changes
Several items have been merged and/or relocated or deleted.
TA09 Entry, Descent, and Landing Systems
9.1. Aeroassist and Atmospheric Entry
9.1.1. Rigid Thermal Protection Systems
9.1.2. Flexible Thermal Protection Systems
9.1.3. Rigid Hypersonic Decelerators
9.1.4. Deployable Hypersonic Decelerators
9.1.5. Instrumentation and Health Monitoring Move: 9.1.5 into added 9.4.6, Instrumentation and Health Monitoring
9.1.6. Entry Modeling and Simulation Merge 9.1.6 with 9.2.5 and 9.3.6 and move to added 9.4.5, EDL
9.2. Descent Modeling and Simulation
9.2.1. Attached Deployable Decelerators
9.2.2. Trailing Deployable Decelerators
9.2.3. Supersonic Retropropulsion
9.2.4. GN&C Sensors Merge 9.2.4 with 9.3.4 and move to added 9.4.7, GN&C Sensors and
9.2.5. Descent Modeling and Systems
Simulation Merge 9.2.5 with 9.1.6 and 9.3.6 and move to added 9.4.5, EDL
9.3. Landing Modeling and Simulation
9.3.1. Touchdown Systems
9.3.2. Egress and Deployment Systems
9.3.3. Propulsion Systems
9.3.4. Large Body GN&C Merge 9.3.4 with 9.2.4 and move to added 9.4.7.
9.3.5. Small Body Systems
9.3.6. Landing Modeling and Simulation Merge 9.3.6 with 9.1.6 and 9.2.5 and move to added 9.4.5.
9.4. Vehicle Systems Technology
9.4.1. Architecture Analyses Delete: 9.4.1. Architecture Analyses
9.4.2. Separation Systems
9.4.3. System Integration and Note: In some places in the roadmap, 9.4.3 “Systems Integration and
Analyses Analyses” is titled “Vehicle Technology.” “Systems Integration and
9.4.4. Atmosphere and Surface Analyses” more accurately describes the content of this technology.
Characterization
Add: 9.4.5. EDL Modeling and Simulation
Add: 9.4.6. Instrumentation and Health Monitoring
Add: 9.4.7. GN&C Sensors and Systems
GN&C sensors (9.2.4) are applicable to entry and landing as well as descent. In addition, there are entry
and descent aspects to large-body GN&C (9.3.4). Therefore, these items have been combined into a new level 3
technology (9.4.7, GN&C Sensors and Systems) in technology subarea 9.4, Vehicle Systems Technology.
Technology 9.4.1 Architecture Analyses appears in the TABS and in two summary figures in the TA09 road -
map, but it does not appear in the roadmap table of contents or in the text in the main body of the roadmap. It has
been deleted.
Technology 9.4.3 in the TABS is titled Systems Integration and Analyses. In some places in the roadmap
it is titled Vehicle Technology. Systems Integration and Analyses more accurately describes the content of this
technology.
TOP TECHNICAL CHALLENGES
EDL is commonly a challenging aspect of NASA missions; EDL problems have been associated with some
significant failures as well as many near misses.
NASA’s draft EDL roadmap may be too narrow because it is focused on the development of human class,
large payload delivery to Mars as the primary emphasis, even though such a mission may be three decades away.
While this mission beneficially stresses and challenges EDL technology development, it would be prudent to
consider the benefit of advanced EDL technologies to other possible applications to ensure that the technology
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246 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES
under development is not tied too closely to a specific mission or destination. EDL technologies that enable the
broadest spectrum of future missions by accommodating the widest range of variations in destination and timing
would be of particular value. This is reflected in the broad set of six top technical challenges and the discussion
of generic reference missions that follows. The top technical challenges defined by the panel are listed below in
priority order. The first four challenges would make EDL systems more technically capable, the fifth challenge
would make them safer and more reliable, and the sixth challenge would make them more affordable.
1. Mass to Surface: Develop the ability to deliver more payload to the destination.
NASA’s future missions will require ever greater mass delivery capability in order to place scientifically sig -
nificant instrument packages on distant bodies of interest, to facilitate sample returns from bodies of interest, and
to enable human exploration of Mars. For a given launch system and trajectory design, the maximum mass that
can be delivered to an entry interface is fixed. Hence, increasing the mass delivered to the surface (or other desti -
nation, such as a planetary orbit or a mobile flight platform) will require reductions in spacecraft structural mass;
more efficient, lighter thermal protection systems; more efficient, lighter propulsion systems; and/or lighter, more
efficient deceleration systems. In a sense, increasing mass delivery to a planet surface is “the name of the game”
for EDL technology because it may enable missions that are presently impossible (such as a human Mars landing)
and/or provide enhancements such as more sophisticated science investigations and sample return capability for
currently planned missions.
2. Surface Access: Increase the ability to land at a variety of planetary locales and at a variety of times.
Ideally, any exploration mission would have the ability to land at a variety of locales, including those at
higher latitudes or elevations that may be difficult to access, at whatever time best satisfies other mission require -
ments and goals. Access to specific sites can be achieved by landing at one or more specific locations or by
transiting (e.g., via a rover) from a single designated landing location to other locations of interest. However,
it is not currently feasible to transit long distances and through extremely rugged terrain on Mars. In addition,
improving the robustness of entry systems to better withstand a variety of environmental conditions (atmospheric
winds, solar incident angle, etc.) could aid in reaching more varied landing sites. Alternatively, uncertainties in
the entry environment could be better dealt with if the entry vehicle first went into orbit. Increased surface access
could be achieved by tailoring the mission entry (i.e., the ability to control the inclination of entry and/or cross
range capability during entry). Systems that have higher lift-to-drag ratios are an area for potential investigation
in improving surface access on exploration destinations, such as Mars, that have a significant atmosphere.
3. Precision Landing: Increase the ability to land space vehicles more precisely.
A precision landing capability allows a vehicle to land closer to a specific, predetermined position in order
to assure that the vehicle lands safely (without damage to itself or other personnel that may already be on the
surface), or in order to meet other operational or science objectives. The level of precision (e.g., 1000 m, 100 m,
etc.) that is achievable at touchdown is a function of the design of the guidance, navigation, and control (GN&C)
system, the control authority of the vehicle, and the entry environment. Precision landings require accurate GN&C
performance throughout the entire descent and landing phases. This requires accurate control of vehicle position,
velocity, attitude, and other vehicle states (Paschall et al., 2008).
4. Surface Hazard Detection and Avoidance: Increase the robustness of landing systems to surface hazards.
The surface hazards associated with exploration destinations remain uncertain to some degree until the site has
been visited. Relying on passive systems alone to characterize a landing site can be problematic, as was evident
during the Apollo Program, where each of the six landing missions faced potentially mission-ending hazards at the
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APPENDIX L
landing sites. Hazardous rocks, craters, and slopes were perilously close to each of the successfully landed missions
and brought to light the incredible challenge each mission faced (Brady and Paschall, 2010). Active hazard detection
methods can quickly optimize safe sites and reduce fuel costs while directly characterizing a landing surface in real
time, but technology development is needed to improve key capabilities in this area (Brady et al., 2009).
5. Safety and Mission Assurance: Increase the safety, robustness, and reliability of EDL.
Loss-of-mission events during EDL for NASA and the international community have been unacceptably high
for Earth-entry and especially planetary entry missions. For example, the failure rate for U.S. missions to Mars
over the past 20 years is 27 percent (i.e., 3 of 11). U.S. lander missions to Mars have a failure rate of 20 percent
(i.e., 1 of 5) (NASA, 2011). High-profile U.S. failures include the Mars Polar Lander and the Mars Climate Orbiter.
Other nations have also experienced failure during EDL (e.g., Beagle 2 and numerous Soviet missions), especially
in the earlier years of planetary exploration. These events are costly setbacks for high-profile robotic missions,
which are the result of many years of effort in design, development, flight, and operations resources. For crewed
missions, EDL failures can result in tragedy, such as the Columbia accident.
Safety and mission assurance are necessary constraints for mission and vehicle design. Some level of risk is
unavoidable with planetary exploration missions. This challenge seeks to improve safety and mission assurance
while achieving important mission objectives in an affordable manner.
6. Affordability: Improve the affordability of EDL systems.
EDL missions with large payloads are expensive. Improving EDL system affordability would allow more
missions to be flown within fixed and predictable budgets, and it would enable new missions previously deemed
unaffordable. In fact, the issue of affordability led the Planetary Decadal Survey to question whether a Mars sample
return mission belongs in its roadmap of future planetary missions (NRC, 2011). The affordability of EDL systems
can be improved either by (1) improving EDL capabilities so that it is less expensive to get a payload of some
particular mass to the surface or (2) improving payload technologies so that the same mission objectives can be
achieved with a smaller payload mass delivered to the surface. Technology development in TA09 is focused on
the first approach; the second approach will occur naturally as a result of advances in other TAs.
QFD MATRIX AND NUMERICAL RESULTS FOR TA09
Figure L.1 shows the QFD scores for each technology in TA09. Figure L.2 shows the relative ranking of each
technology, grouped into high, medium, and low priorities. The process by which the QFD scores were generated
is described in Chapter 2. The panel assessed eight of the technologies as high priority. Four of these were selected
based on their QFD scores, which significantly exceeded the scores of lower-ranked technologies. After careful
consideration, the panel also designated four additional technologies as high-priority technologies. 2
The four technologies selected based on their QFD scores were: 9.4.7 GN&C Sensors and Systems, 9.1.1
Rigid Thermal Protection Systems, 9.1.2 Flexible Thermal Protection Systems, and 9.1.4 Deployable Hypersonic
Decelerators. These technologies received that ranking based on their significant overall benefit, their ability to
meet NASA needs (generally driven by supporting a wide range of missions), and their risk and reasonableness.
9.4.7 GN&C Sensors and Systems was also noted to meet non-NASA aerospace needs. The four additional tech -
nologies did not score as high on the QFD scale, but investments in these technologies will support a wide range
of expected future EDL missions.
2 In recognition that the QFD process could not accurately quantify all of the attributes of a given technology, after the QFD scores were
compiled, the panels in some cases designated some technologies as high priority even if their scores were not comparable to the scores of
other high-priority technologies. The justification for the high-priority designation of all the high-priority technologies for TA09 appears in
the section “High-Priority Level 3 Technologies.”
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248 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES
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Alignment Risk/Difficulty
Technology Name Benefit
378 H
9.1.1. Rigid Thermal Protection Systems 9 9 3 1 9 1 -3
370 H
9.1.2. Flexible Thermal Protection Systems 9 9 3 1 9 -1 -3
142 M
9.1.3. Rigid Hypersonic Decelerators 3 9 1 0 3 -1 -3
356 H
9.1.4. Deployable Hypersonic Decelerators 9 9 1 0 9 -3 -3
180 M
9.2.1. Attached Deployable Decelerators 3 3 1 0 9 -1 -1
210 M
9.2.2. Trailing Deployable Decelerators 3 9 1 0 9 -1 -1
58 L
9.2.3. Supersonic Retropropulsion 1 3 1 0 3 -1 -3
140 M
9.3.1. Touchdown Systems
y 3 9 1 1 1 1 -1
52 L
9.3.2. Egress and Deployment Systems 1 3 0 0 1 1 -1
120 M
9.3.3. (EDL) Propulsion Systems (Interaction) 3 3 1 0 3 -1 -1
126 M
9.3.5. (EDL) Small Body Systems (No Gravity) 1 3 1 0 9 -1 -1
88 L
9.4.2. (EDL) Separation Systems 1 9 3 0 1 1 -1
216 H*
9.4.3. (EDL) System Integration and Analyses 3 9 3 1 9 -1 -1
220 H*
9.4.4. Atmosphere and Surface Characterization 3 9 3 3 9 -1 -1
224 H*
9.4.5. EDL Modeling and Simulation 3 9 3 1 9 1 -1
222 H*
9.4.6. (EDL) Instrumentation and Health Monitoring 3 9 3 0 9 1 -1
402 H
9.4.7. GN&C Sensors and Systems (EDL) 9 9 9 3 9 1 -1
FIGURE L.1 Quality function deployment (QFD) summary matrix for TA09 Entry, Descent, and Landing Systems. The jus -
tification for the high-priority designation of all the high-priority technologies appears in the section “High-Priority Level 3
Technologies.” H = High Priority; H* = High Priority, QFD score override; M = Medium Priority; L = Low Priority.
0 50 100 150 200 250 300 350 400
9.4.7. GN&C Sensors and Systems (EDL)
High Priority
9.1.1. Rigid Thermal Protection Systems
9.1.2. Flexible Thermal Protection Systems
9.1.4. Deployable Hypersonic Decelerators
9.4.5. EDL Modeling and Simulation
Medium Priority
9.4.6. (EDL) Instrumentation and Health Monitoring
9.4.4. Atmosphere and Surface Characterization
9.4.3. (EDL) System Integration and Analyses
9.2.2. Trailing Deployable Decelerators
9.2.1. Attached Deployable Decelerators
9.1.3. Rigid Hypersonic Decelerators
9.3.1. Touchdown Systems
High Priority (QFD Score Override)
9.3.5. (EDL) Small Body Systems (No Gravity)
9.3.3. (EDL) Propulsion Systems (Interaction)
9.4.2. (EDL) Separation Systems
Low Priority
9.2.3. Supersonic Retropropulsion
9.3.2. Egress and Deployment Systems
FIGURE L.2 Quality function deployment rankings for TA09 Entry, Descent, and Landing Systems.
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249
APPENDIX L
CHALLENGES VERSUS TECHNOLOGIES
Figure L.3 shows the relationship between the level 3 technologies in TA09 and the top technical challenges.
The high-priority technologies have a strong relationship to many of the technical challenges. The top-rated level
3 technology, 9.4.7 GN&C Sensors and Systems, would likely have a major impact on four of the six technical
challenges and a moderate impact on the remaining two technical challenges. The next two highest ranked tech -
nologies (9.1.1 Rigid Thermal Protection Systems and 9.1.2 Flexible Thermal Protection Systems) would likely
have an impact on five of the six technical challenges. For both of these technologies, improvements in reusable
TPS could specifically help meet the affordability challenge, especially for human return from low Earth orbit.
The fourth ranked technology, 9.1.4 Deployable Hypersonic Decelerators, contributes to four of the six technical
challenges. The four additional high-priority technologies also play an important role in meeting the technical
challenges. In fact, three of them could contribute toward meeting all six technical challenges. These technologies
can in particular help to improve knowledge of the EDL system, thereby reducing required margins.
GENERIC REFERENCE MISSIONS FOR TA09
Development of EDL technologies with a broad focus will help prevent potentially important missions from
being eliminated for consideration because they are perceived as unachievable due to their EDL requirements.
Additionally, technology that can enable only a few missions may have less payoff than a building block approach
to technology development that supports a series of progressively more challenging missions. Furthermore, because
of resource constraints, EDL technology investments must be time-phased. EDL technologies that enable the
broadest spectrum of future missions by accommodating the widest range of variations in destination and timing
will tend to be the most highly valued. This is reflected in the broad set of technology challenges above and in the
discussion of generic reference missions (GRMs) below and in Figure L.4, which is provided as a replacement to
Table 1 in NASA’s draft roadmap; Figure L.4 is more comprehensive.
The GRMs in Figure L.4 capture the broad spectrum of EDL missions that have flown or could be flown in
the foreseeable future. For example, there is not a human mission to Pluto GRM because this type of mission is
too far out on the horizon to be reasonably achieved. The 35 GRMs in Figure L.4 are distinguished from each
other in terms of destination, local environmental discriminators (presence of atmosphere, gravity, and extreme
environments), and mission-defined discriminators (entry or landing, hard or soft landing, and class of lander, such
as human, cargo, or robotic).
Given the GRM definitions in Figure L.4, Figure L.5 shows the linkage between the GRMs and the EDL
technologies evaluated by the panel. Figure L.5 confirms that the high-priority technologies (and many of the
medium-priority technologies) are applicable to a wide range of GRMs.
HIGH-PRIORITY LEVEL 3 TECHNOLOGIES
Panel 6 identified eight high-priority technologies in TA09. The justification for ranking each of these tech -
nologies as a high priority is discussed below.
EDL technologies in general do not benefit from access to the International Space Station (ISS). However,
advanced EDL technology could lead to new vehicles with improved capabilities for returning crew or payloads
from the ISS, and return flights from the ISS could provide flight testing opportunities for EDL technologies.
Technology 9.4.7, Guidance, Navigation, and Control (GN&C) Sensors and Systems
A primary objective of many EDL missions is to safely land a vehicle in new destinations such that human
or robotic exploration can be achieved. The ability to accurately hit entry corridors, to control the vehicle during
entry and descent, to navigate the vehicle during all phases of EDL, and to safely and precisely land a vehicle in
hazardous terrain are examples of a high-performing EDL GN&C system.
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Top Technology Challenges
250
4. Surface Hazard
2. Surface Access: Detection and 5. Safety and Mission
1. Mass to Surface: Increase the ability to 3. Precision Landing: Avoidance: Increase Assurance: Increase 6. Affordability:
Develop the ability to land at a variety of Increase the ability to the robustness of the safety, Improve the
deliver more payload planetary locales and land space vehicles landing systems to robustness, and affordability of EDL
to the destination. at a variety of times. more precisely. surface hazards. reliability of EDL. systems.
Priority TA 09 Technologies, Listed by Priority
H 9.4.7. GN&C Sensors and Systems (EDL) ○ ● ● ● ● ○
H 9.1.1. Rigid Thermal Protection Systems ● ● ○ ○ ●
H 9.1.2. Flexible Thermal Protection Systems ● ● ○ ○ ●
H 9.1.4. Deployable Hypersonic Decelerators ● ● ○ ○
H 9.4.5. EDL Modeling and Simulation ○ ○ ● ○ ● ●
H 9.4.6. (EDL) Instrumentation and Health Monitoring ○ ○ ○ ● ○
H 9.4.4. Atmosphere and Surface Characterization ○ ● ● ● ○ ○
9.4.3. (EDL) System Integration and Analyses
H ○ ○ ○ ○ ● ●
M 9.2.2. Trailing Deployable Decelerators ● ● ○ ○ ○
M 9.2.1. Attached Deployable Decelerators ● ● ○ ○
M 9.1.3. Rigid Hypersonic Decelerators ○ ○ ○ ○
M 9.3.1. Touchdown Systems ○ ○ ○ ○
M 9.3.5. (EDL) Small Body Systems ○
9.3.3. (EDL) Propulsion Systems
M ○ ○
L 9.4.2. (EDL) Separation Systems
L 9.2.3. Supersonic Retropropulsion ○
L 9.3.2. Egress and Deployment Systems
Strong Linkage: Investments by NASA in this technology would likely have a
● major impact in addressing this challenge.
Moderate Linkage: Investments by NASA in this technology would likely have a
○ moderate impact in addressing this challenge.
Weak/No Linkage: Investments by NASA in this technology would likely have
[blank]
little or no impact in addressing the challenge.
FIGURE L.3 Level of support that the technologies provide to the top technical challenges for TA09 Entry, Descent, and Landing Systems.
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251
APPENDIX L
MISSION CHARACTERISTIC
EDL MISSION LIST EXAMPLE MISSIONS
Human, Cargo, or Robotic?
Extreme Environment?
Hard or Soft Landing?
Entry or Landing?
Atmosphere?
Gravity?
GRM
ID# Identifier Destination
1 L S Y Y N Apollo, Orion, Commercial Crew
Human Earth Low L/D Return
2 L S Y Y N Shuttle, Xcor
H
Human Earth High L/D Return
3 L S Y Y N SpaceX Dragon
Human Earth Retro Return
4 L S Y Y N SpaceX Dragon
Earth Cargo Low L/D Return
5 L S Y Y N Dreamchaser
Earth C
Earth Cargo High L/D Return
6 L S Y Y N
Earth Cargo Retro Return
7 L S Y Y N Hayabusa, Stardust, Genesis
Robotic Earth Capsule Return
8 L S Y Y N X-37
R
Robotic Earth High L/D Return
9 L S Y Y N Masten, Armadillo
Robotic Earth Retro Return
10 L S Y Y N
H
Human Mars
11 L S Y Y N
C
Cargo Mars
12 L S Y Y N Viking, Phoenix, Pathfinder, MER
Mars
Robotic Mars
13 L H Y Y N DS2
R
Penetrator Mars
Mars Airplane, MGS, Odyssey
14 E - Y Y N
Robotic Entry Mars
15 L S N Y N Apollo, Altair
H
Human Lunar
16 L S N Y N Altair
C
Cargo Lunar
Lunar
17 L S N Y N Lunar Sample Return
Robotic Lunar
R
18 L H N Y N Lunar-A
Penetrator Lunar
L S N N N
19 H
Human Asteroid / Small Body
Asteroid /
20 L S N N N NEAR
Robotic Asteroid / Small Body
R
Small Bodies
21 L H N N N Hayabusa
Penetrator Asteroid / Small Body
22 L S N N N Stardust
Robotic Comet Sample Return
23 L S N N N
Comet R
Robotic Comet Lander
24 L H N N N Deep Impact
Penetrator Comet
25 E - Y Y Y Huygens, Titan Balloon
Robotic Venus/Titan Entry
26 L H Y Y Y Pioneer Venus, Venera 7
Venus / Titan R
Robotic Venus/Titan Lander
27 L H Y Y Y
Robotic Venus/Titan Penetrator
28 L S N Y Y
Robotic Icy Moon Lander
Icy Moon R
29 L H N Y Y
Penetrator Icy Moon
30 L S N Y Y BepiColombo
Robotic Mercury Lander
Mercury R
31 L H N Y Y
Mercury Penetrator
32 E - Y Y Y Galileo
Giant Planet R
Robotic Saturn / Jupiter Entry
33 E - Y Y Y
Robotic Uranus/Neptune Entry
34 L S Y Y Y
Outer Planet R
Robotic Uranus/Neptune Lander
35 L H Y Y Y
Penetrator Uranus/Neptune
FIGURE L.4 Generic reference missions for TA09 Entry, Descent, and Landing Systems.
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252 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES
EDL TECHNOLOGY MAPPING
EDL MISSION LIST
High Priority Medium Low
Atmosphere and Surface Characterization
Instrumentation and Health Monitoring
Flexible Thermal Protection Systems
Attached Deployable Decelerators
Deployable Hypersonic Decelators
Rigid Thermal Protection Systems
Trailing Deployable Decelerators
System Integration and Analysis
Egress & Deployment Systems
Rigid Hypersonic Decelerators
EDL Modeling and Simulation
Supersonic Retropropulsion
GNC Systems and Sensors
Touchdown Systems
Small Body Systems
Separation Systems
Propulsion Systems
GRM
ID# Identifier
1 Y Y Y Y Y Y Y Y Y Y Y Y - - Y - -
Human Earth Low L/D Return
2 Y Y Y Y Y Y Y Y Y Y Y Y - - Y - -
Human Earth High L/D Return
3 Y Y Y Y Y Y Y Y Y Y Y Y - Y Y Y -
Human Earth Retro Return
4 Y Y Y Y Y Y Y Y Y Y Y Y - - Y - -
Earth Cargo Low L/D Return
5 Y Y Y Y Y Y Y Y Y Y Y Y - - Y - -
Earth Cargo High L/D Return
6 Y Y Y Y Y Y Y Y Y Y Y Y - Y Y Y -
Earth Cargo Retro Return
7 Y Y Y Y Y Y Y Y Y Y Y Y - - Y - -
Robotic Earth Capsule Return
8 Y Y Y Y Y Y Y Y Y Y Y Y - - Y - -
Robotic Earth High L/D Return
9 Y Y Y Y Y Y Y Y Y Y Y Y - Y Y Y -
Robotic Earth Retro Return
10 Y Y Y Y Y Y Y Y Y Y Y Y - Y Y Y Y
Human Mars
11 Y Y Y Y Y Y Y Y Y Y Y Y - Y Y Y Y
Cargo Mars
12 Y Y Y Y Y Y Y Y Y Y Y Y - Y Y - Y
Robotic Mars
13 Y Y Y Y Y Y Y Y Y Y Y - - - Y - -
Penetrator Mars
14 Y Y Y Y Y Y Y Y Y Y Y - - - Y - -
Robotic Entry Mars
15 Y - - - Y Y Y Y - - - Y - Y Y - Y
Human Lunar
16 Y - - - Y Y Y Y - - - Y - Y Y - Y
Cargo Lunar
17 Y - - - Y Y Y Y - - - Y - Y Y - Y
Robotic Lunar
18 Y - - - Y Y Y Y - - - Y - - Y - -
Penetrator Lunar
19 Y - - - Y Y Y Y - - - Y Y Y Y - Y
Human Asteroid / Small Body
20 Y - - - Y Y Y Y - - - Y Y Y Y - Y
Robotic Asteroid / Small Body
21 Y - - - Y Y Y Y - - - - Y - Y - -
Penetrator Asteroid / Small Body
22 Y - - - Y Y Y Y - - - Y Y Y Y - Y
Robotic Comet Sample Return
23 Y - - - Y Y Y Y - - - Y Y Y Y - Y
Robotic Comet Lander
24 Y - - - Y Y Y Y - - - - Y - Y - -
Penetrator Comet
25 Y Y Y Y Y Y Y Y Y Y Y - - - Y - -
Robotic Venus/Titan Entry
26 Y Y Y Y Y Y Y Y Y Y Y Y - Y Y - Y
Robotic Venus/Titan Lander
27 Y Y Y Y Y Y Y Y Y Y Y - - - Y - -
Robotic Venus/Titan Penetrator
28 Y - - - Y Y Y Y - - - Y - Y Y - Y
Robotic Icy Moon Lander
29 Y - - - Y Y Y Y - - - - - - Y - -
Penetrator Icy Moon
30 Y - - - Y Y Y Y - - - Y - Y Y - Y
Robotic Mercury Lander
31 Y - - - Y Y Y Y - - - - - - Y - -
Mercury Penetrator
32 Y Y Y Y Y Y Y Y Y Y Y - - - Y - -
Robotic Saturn / Jupiter Entry
33 Y Y Y Y Y Y Y Y Y Y Y Y - Y Y Y Y
Robotic Uranus/Neptune Entry
34 Y Y Y Y Y Y Y Y Y Y Y Y - Y Y Y Y
Robotic Uranus/Neptune Lander
35 Y Y Y Y Y Y Y Y Y Y Y - - - Y Y -
Penetrator Uranus/Neptune
FIGURE L.5 Mapping of generic reference missions to level 3 technologies for TA09 Entry, Descent, and Landing Systems.
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Fundamentally, an EDL mission is supported by a design architecture to achieve its goals. The ability of the
GN&C system to achieve its mission objectives is a function of GN&C sensor performance, vehicle actuator abil -
ity, and the designer’s ability to craft them sensibly together onboard a capable, real time, computing platform.
The technology readiness level (TRL) widely varied among GN&C sensors and systems. Tried and true GN&C
sensors such as inertial measurement units (IMUs) and star cameras typically are at a high TRL, but they could
benefit from reduced size, weight, and power, while also increasing performance and noise immunity. EDL capable
velocimeters and altimeters generally have a lower to mid-level TRL and would benefit from increased accuracies,
range, and update rates while also decreasing size, weight, and power. Finally, GN&C sensor and system advance -
ment in the following currently low-TRL items would significantly improve or even enable future EDL missions.
• Terrain relative navigation systems, sensors, and algorithms
• Precision landing systems, sensors, and algorithm design
• Hazard relative navigation systems, sensors, and algorithm design
• Hazard detection sensors and systems
• Adaptive control systems
• Autonomous GN&C sequencing and mission managers
• Inertial swarm sensing methods and instrumentation
• Enhanced fault tolerance
As shown in Figure L.5, GN&C Sensors and Systems are common to all of the foreseen EDL generic refer-
ence missions. They align extremely well with NASA’s expertise, capabilities, and facilities. Given their broad
applicability, other non-NASA agencies (European Space Agency, Japanese Aerospace Exploration Agency) and
military organizations (National Reconnaissance Office, Missile Defense Agency, U.S. Navy, U.S. Air Force, etc.)
will and have improved the state of the art of some GN&C sensors, but additional work is needed to improve
operational systems. NASA could lead by example and invest in an aggressive, planned, and sustained NASA
technology development effort to advance GN&C sensors and systems given such broad applicability to a multitude
of their missions. It will take a sustained and coordinated effort, possibly shared among organizations, to raise the
TRL of necessary GN&C sensors and systems, particularly across the “valley of death” levels of TRL 5-6 where
validation in the relevant environment is required.
This technology is game-changing because it significantly enhances the ability to increase mass to the surface,
the ability to land anywhere, and the ability to land at any time. This technology was evaluated as a high-priority
technology since significant technology advancement is likely to provide transformational capabilities that would
enable important new missions that are not currently feasible during the next 20 years, and because it is broadly
applicable across the entire aerospace community and in multiple NASA mission areas. Furthermore, the technical
risk associated with development of this technology is moderate to high, which is a good fit to NASA’s level of
risk tolerance for technology development, and the likely cost to NASA and the timeframe to complete technology
development is not expected to substantially exceed that of past efforts to develop comparable technologies.
Technology 9.1.1, Rigid Thermal Protection Systems
Thermal protection systems (TPS) are used to protect the payload of the entry vehicle (both human and robotic)
from the high-temperature and high-shear flow environment experienced during the hypersonic entry phase. Rigid
TPS materials are typically separated into two major classes, reusable and non-reusable, and some missions will
use a combination of the two. An example of reusable rigid TPS is the thermal protection tiles used on the space
shuttle. Though reusable, these materials do have a finite lifetime due to the thermal and mechanical environments
experienced during re-entry. For high-energy entries, like an Earth return beyond low Earth orbit (LEO) or entry
into the atmosphere of another planet or moon, non-reusable or ablative thermal protections systems have been
historically used since the currently available reusable systems cannot handle such high heat loads. Several materi -
als (e.g., AVCOAT, PICA, and SLA-561V) have been flight qualified and are at TRL 7 to 9. However, the process
for making AVCOAT had to be redeveloped for the Orion vehicle and its TRL is likely less (i.e., 5 to 7). Materials
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254 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES
such as carbon phenolic, which are also widely used for military applications, are also in the TRL 7 to 9 range.
However, carbon phenolic in particular presents availability issues because of a lack of U.S. suppliers of rayon.
Most NASA flight experience has been with rigid thermal protection systems, where the TPS is installed
onto a rigid aeroshell structure. These systems can handle both high velocities and high heat fluxes. Rigid TPS,
however, can account for a large percentage of the entry vehicle mass. Vehicle designs use conservative estimates
of heating to account for uncertainties, which contributes to the large mass of a TPS system. Recent research has
been focused on the development of lower density ablators. For higher speed entries into the outer planets or their
moons that have atmospheres, new materials will need to be developed that can also handle extreme environments
that include both high convective and radiative components.
While it is clear that flight quality heritage materials exist (or need to be re-constituted) for return-from-LEO
applications, next-generation EDL systems for return from LEO would benefit from additional research and devel -
opment to improve reliability and maintainability and to reduce cost. However, the draft roadmap’s description of
rigid TPS focuses on ablative, single-use TPS with application to planetary entry. As noted during the TA09 EDL
workshop, the value of this technology would be enhanced if its scope were increased to include return-from-LEO
applications (Grantz, 2011; Picetti, 2011). For new ablative and reusable materials, the TRL is between 1 and 3.
Commercial applications are primarily focused on lower-energy LEO return, while rigid TPS for high-energy
entries primarily have application to NASA or military missions. Therefore, there should be opportunities for NASA
to partner with other organizations in the development of this technology. Also, since many other nations are enter-
ing the civilian space arena, there are also opportunities to partner with them. An example is the ESA EXPERT
(European Experimental Reentry Testbed) mission (Thoemel et al., 2009; Muylaert, 2011). Additionally, there
could be spin-off opportunities for other high-temperature applications requiring thermal protection (i.e., rocket
motor nozzles or nuclear reactors). Because the thermal protection technology is unique to these applications and
requires both small-scale ground testing and large-scale flight testing, it is unlikely that industry would take the
lead in either developing or qualifying new materials or systems. Therefore, NASA (and perhaps the Department
of Defense) is likely the best option for maintaining facilities such as arc-jets and investing in state-of-the-art
computational tools (and the human capital to develop and apply these tools).
This technology is game-changing because advances in this area would enable new missions in extreme
thermal environment or reduced mass to increase vehicle payload and performance, far beyond what has been
previously achieved. Because of the applicability of this technology to the military, it can also have high impact
on non-NASA aerospace needs. Moderate to high levels of risk are involved to further this technology.
Technology 9.1.2, Flexible Thermal Protection Systems
Like rigid TPS, flexible TPS can be reusable or ablative (or some combination thereof). Because of their flex -
ible nature, these TPS systems could be packaged into tighter volumes, applied to irregular surfaces, and deployed
when necessary. In addition to thermal protection, these systems can also be expected to carry significant aerody -
namics loads (primarily for deceleration). Because of their flexibility, it might be possible to tailor the shape of the
TPS to improve both the aerodynamic performance during the hypersonic entry phase (to provide lifting and cross
range capability). It may also be possible to use these flexible materials to control local boundary layer state (i.e.,
laminar versus turbulent) and heating loads. While flexible TPS has been used on the leeside of the space shuttle
(i.e., advanced flexible reusable surface insulation blankets), they have not been demonstrated for high-energy
entries or where significant aero-thermal-structural interactions might occur. The TRL for advanced flexible TPS
materials is 1 to 2.
Like their rigid counterparts, flexible TPS will have use in the commercial, civilian, and military space market.
The ability to morph the shape of the TPS could have application in long-range strike applications where precise
aerodynamic control is essential. Similar to the rigid TPS, it is expected that NASA will be the prime agency
involved in maturing this technology with industry eventually being able to commercialize the capabilities devel -
oped. Advanced flexible TPS will require significant research as the primary TPS for atmospheric entry. Significant
challenges exist with most any deployable decelerator concept, including the associated thermal protection in
terms of handling, manufacturing, packing, and deployment following interplanetary transit or LEO storage. Like
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256 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES
dynamics analysis, finite element modeling, fluid-structural interaction analysis, aerothermodynamics modeling
(including ablative surface and thermal radiation physics, coupled stability, and trajectory analysis), multi-disci -
plinary analysis tools, and other high-fidelity analysis required for EDL missions.
Because of the limited range of test conditions available in experimental tests, and because of the high cost of
such testing, M&S tools are highly valued in every phase of design and analysis of EDL systems. In addition to
development of physical models, numerical methodologies, and software tools to conduct M&S, this technology
also includes development and application of experimental validation including flight tests. Only if high-fidelity
models are also well-validated can they be useful in reducing margins, thereby increasing mission capability without
a loss in safety. Legacy flight data is often not sufficient to validate the codes, particularly because uncertainties in
the measurements were often not well understood and the boundary conditions required for M&S were not well
characterized. The entire process is further complicated by the wide range of operational conditions experienced
by EDL systems.
NASA conducts primarily mission-related modeling and simulation work in the Aeronautics Research Mis -
sion Directorate and in ESMD. This technology would build on the well-known foundational research carried out
by NASA’s Aeronautics Research Mission Directorate to advance the state of the art in critical areas for missions
planned over the next 20 years.
Current M&S technology is at TRL 4 to 7; in that it can already conduct accurate, steady aerodynamic analysis
of rigid configurations. EDL missions, however, require accurate analysis in areas for which current predictive
capability is insufficient, and is generally at TRL 3. For example, because the ability to reliably predict TPS reces -
sion rate at every location in a radiative environment does not exist, heat shields tend to be over-designed, thereby
increasing weight and reducing mission capability.
This technology is well aligned with NASA’s expertise, capabilities, and facilities. NASA has taken a lead role
in the development of thermo-chemical nonequilibrium modeling for aerospace applications but would benefit by
working closely with Department of Defense and Department of Energy laboratories and industry partners who
conduct research in this technology for weapon systems in continuum and rarefied high-temperature flow environ -
ments. NASA has significant in-house expertise in physical modeling and software development to conduct and
help guide research conducted by academic, federal, and industry partners in this technology. NASA’s investment
in high-performance-computing facilities also makes it well suited to conduct this work, and it currently possesses
unique ground and flight test capabilities to conduct experimental validation required for EDL Modeling and
Simulation. Continued investments in ground test facilities, such as large scale wind tunnels, arc-jet facilities, and
supersonic and hypersonic wind tunnels, will ensure that the means to validate codes are available when required.
NASA is uniquely motivated to pursue this technology and major investments from industry are not expected in
the absence of NASA involvement.
The panel overrode the QFD score for this technology to designate it as a high-priority technology because
the QFD scores did not fully capture the value of this technology in terms of how widely applicable it is to EDL
missions and to the successful development and implementation of other high-priority technologies in TA09,
particularly the TPS and decelerator technologies. Furthermore, EDL modeling and simulation supports all six of
the top technology challenges. It also is characterized by the appropriate level of risk and difficulty in physical
modeling, numerical technique development and experimental validation, yet it builds upon a long-standing core
competency which NASA possesses in these subjects. The development plan is clear and there is a likelihood of
joint funding by federal agencies and the industrial space industry.
Technology 9.4.6, Instrumentation and Health Monitoring
NASA draft roadmap for TA09 notes that, “Entry instrumentation for both engineering data and vehicle health
monitoring provides a critical link between predicted and observed performance of entry vehicle systems.” This
is particularly true for entry thermal protection systems because complete simulation of the entry environment is
impossible in ground-based test facilities. Hence, while ground-based test facilities are indispensable in develop -
ing thermal protection systems, the complete, rigorous validation of TPS design algorithms can only be achieved
through comparison of predictions with flight data. Also, health monitoring instrumentation can provide system
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performance data as well as evidence that vehicle systems are operating properly prior to entry. The value of invest -
ments in this technology would be greatly enhanced if NASA heeded the call in the draft roadmap to “develop a
NASA policy for required EDL instrumentation and data acquisition in order to advance and build confidence in
models that are essential to EDL system qualification.”
As pointed out in the draft roadmap, major technical challenges in entry instrumentation include high-temper-
ature systems capable of direct heat flux measurements in situ, measurements (temperature and strain) in flexible
TPS, advanced optical and other non-intrusive measurement techniques, and shock layer radiation measurements
in ablative TPS. Challenges in health monitoring include development of low-data, low-power networks, elimina -
tion of false positives, and the ability to initiate and monitor repair of detected damage.
The TRL of this technology could be said to be 9 since such instrumentation has been successfully flown
on previous missions (e.g., Apollo, space shuttle). However, current instrumentation systems are heavy and, in
some cases, unacceptably intrusive. What are needed are new lighter, smaller, less intrusive, and more accurate
approaches. Such systems are currently at TRL 2 or 3.
The panel overrode the QFD score for this technology to designate it as a high-priority technology. The QFD
scores did not fully capture the value of this technology in terms of how widely applicable it is to all EDL mis -
sions, as well as the contribution it would make to improving the safety and reliability of EDL missions. This
technology is well aligned with NASA’s expertise and capabilities and requires NASA involvement for its suc -
cessful development. The data obtained and the resulting improved heat shield design algorithms will be of great
interest to NASA, DOD, DOE, university researchers, and the commercial space transportation community.
The scope of this technology overlaps the scope of some of the technologies in the autonomy subarea in TA04
Robotics, TeleRobotics, and Autonomous Systems.
Technology 9.4.4, Atmosphere and Surface Characterization
The goal of this technology is to provide a description of the atmosphere and surface of a planet in sufficient
detail to facilitate the planning and execution of planetary missions. In the case of planetary atmospheres, a predic -
tive model is required that will define the spatial and temporal atmospheric characteristics on global, zonal, and
local scales, including annual, seasonal, and daily variations. Such models exist for the Moon, Mars, and Venus,
but they do not provide the needed level of detail. The current state of the art is represented by the Mars Global
Reference Atmospheric Model (Justus et al., 2005; Justh et al., 2011). This model allows predictions of the needed
atmospheric profiles and dynamics but its accuracy is limited by an inadequate data base. For other planets, the
models that exist provide only gross descriptions with very little detail. Surface models are extremely important for
rover missions and are critical for missions involving human landings where the grain size and abrasive character
of the regolith can cause serious damage to bearings, drive motors, and space suits. Atmosphere models are of
critical importance for entry missions that involve aeromaneuvering for increased landing accuracy and aerocapture
to increase landed mass. The inaccuracies of the present atmospheric models result in conservative designs and
large mass margins that degrade performance and have contributed to the lack of acceptance of these techniques
by project managers.
Future investments in this technology could include distributed weather measurements (short and long dura -
tion) on Mars; the development of a standard, low-impact measurement package for all Mars landed missions
to provide future Mars landers with surface pressure and upward-looking wind measurements; the development
of orbiter instruments for wind and atmospheric property characterization at altitudes relevant to aerobraking,
aerocapture, and aeromaneuvering; and the development of higher fidelity atmospheric models based on these
data. Another major contribution would be the development of automated data fusion for visible stereo imagery,
multispectral imagery, and altimetry and its conversion to onboard topography and albedo surface maps suitable
for use by a terrain tracker. Other high-priority work areas include the development of “scout” probes that would
measure atmospheric properties ahead of an entry vehicle and the development of vehicle-based sensors for making
real-time measurements of local and far-field atmospheric properties.
The TRLs of the current models range from 6 (for the surface characterization of the Moon and the atmosphere
of Mars) to 2 or 3 for the more distant planets. The associated programs, described above, are currently at relatively
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258 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES
low TRLs from 2 to 4. The panel overrode the QFD score for this technology to designate it as a high-priority
technology because the QFD scores did not capture the value of this technology in terms of its importance in
achieving all of the EDL top technical challenges, and having a strong linkage to three of the top six challenges.
There is a critical need for this technology in designing and carrying out most future planetary missions. This
technology is well aligned with NASA’s expertise and capabilities and requires NASA involvement for its success -
ful development. These models will be of interest to the scientific community and basic science investigations can
provide important inputs in their development. Both basic science investigations and the development of predictive
engineering models should be carried out in parallel to maximize the benefits.
Technology 9.4.3, System Integration and Analyses
EDL systems are a highly coupled and interdependent set of capabilities consisting of software and hardware
components as well as multiple disciplines. The nature of this problem lends itself to technologies that develop
improved methods of performing systems integration and analysis such as multidisciplinary design optimization.
Optimizing an EDL system involves various disciplines (e.g., thermal, fluid dynamics, and trajectories), multiple
flight phases (entry, descent, and landing), overall system reliability and cost, and a host of tools that address all
of the above. This technology is closely coupled with 9.4.5. Modeling and Simulation.
System performance is enhanced, life cycle costs are reduced, and development times are shortened when the
interplay between system requirements, system concepts, and the potential benefit of new technologies is explored
as early as possible in the development of new systems, especially when overly restrictive or arbitrary requirements
are filtered out (Mavris and DeLaurentis, 2000).
Existing systems integration and analyses technologies have not been widely applied to EDL mission design,
certainly not to the degree that will likely be necessary to design an EDL system for a human mission to Mars.
The whole EDL technology portfolio would benefit from the expanded use of these technologies across a larger
mission set since they can help to understand the benefits that other technologies can bring to a given mission or
a whole set of missions once the systems integration and analysis techniques are validated. Like 9.4.5. Modeling
and Simulation, systems integration and analysis would benefit immensely from flight engineering data to validate
and improve systems integration and analysis tools. However, as the fidelity of systems integration and analysis
techniques improves, the need for further (expensive) testing can be reduced.
This understanding of and the need for this technology largely resides within NASA and, to some extent, in
DOD, but its nature lends itself to projects that universities could perform.
While systems integration and analyses is not expected to be game-changing technology, the panel overrode
the QFD score for this technology to designate it as a high-priority technology because it supports the complete
mission set and all six of the EDL top technology challenges.
MEDIUM- AND LOW-PRIORITY TECHNOLOGIES
One group of medium- and low-priority technologies in TA09 had a lower overall benefit than the high-priority
technologies as well as development challenges. Technologies 9.2.2 Trailing Deployable Decelerators, 9.2.1
Attached Deployable Decelerators, 9.1.3 Rigid Hypersonic Decelerators, and 9.2.3 Supersonic Retropropulsion all
fell into this category. Trailing and Attached Deployable Decelerators were the highest ranked of the medium- and
low-priority technologies. Both of these technologies were judged to have limited benefit, however, particularly
because they apply to the descent phase and were not deemed to be game-changing. Rigid Hypersonic Decelerators
were the next highest ranked technology. While additional improvements can be made in this technology, benefits
are generally limited by the maximum payload size of current launch vehicles. Supersonic Retropropulsion was
also judged to have limited benefit, and it was technically the most challenging. While often described as a game-
changing technology, the panel deemed that its applicability was limited mainly to landing large payloads on the
surface of Mars, but in that application disadvantages associated with transporting extra propellant on a mission
to Mars would likely outweigh any other possible mission improvements.
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Another group of medium- and low-priority technologies are less technically critical and typically include
engineering developments that normally are addressed in the development of individual missions. Technologies
9.3.1 Touchdown Systems, 9.3.3 Propulsion Systems, 9.4.2 Separation Systems and 9.3.2 Egress and Deployment
Systems all fall into this group.
Technology 9.3.5 Small Body Systems was judged to have a low benefit because of its very limited mis -
sion applicability. This technology may actually fit better in the roadmap for TA04, Robotics, TeleRobotics, and
Autonomous Systems, because it is essentially a rendezvous and docking problem.
DEVELOPMENT AND SCHEDULE CHANGES FOR THE
TECHNOLOGIES COVERED BY EACH ROADMAP
The ebb and flow of EDL missions make it difficult for the EDL community to maintain core capabilities
and knowledge. EDL technology development requires continuous effort and sustained funding over a number of
years in order to be successful and to generate industry participation (Peterson, 2011; Grantz, 2011; Rohrschnedier,
2011).
After the Apollo program, Viking and other planetary probes capitalized on the ablative heat shield technolo -
gies developed during Apollo. However, in more recent years, the focus has been more on the reusable TPS used
on the space shuttle for return from low Earth orbit, and momentum was lost in the ablative material development
and supply chain. Today, given the end of the Space Shuttle Program (for human spaceflight) and the long gap
between development of the Mars Science Laboratory and the Mars 2018 mission (for robotic exploration), the
process of advancing reusable TPS could itself lose momentum in the coming years. For example, key materials
suppliers are terminating production and high-temperature coating developments for ceramic tiles are under-funded
(Grantz, 2011).
Ideally, EDL research and technology development by NASA would build on past work to meet future
requirements. Since EDL is not a high demand opportunity for industry, it is important that NASA maintain these
capabilities. A successful technology program would preserve test capabilities and advance key technologies at a
steady pace that does not depend solely on flight mission approvals. By ensuring knowledge capture, NASA will
not have to relearn lessons from the past. Struggles with Avcoat are a good example of loss of knowledge, experi -
ence, and lessons learned.
PUBLIC WORKSHOP SUMMARY
The workshop held by the Entry, Descent, and Landing Panel for the NASA Technology Roadmaps study
took place on March 23-24, 2011, at the Beckman Center in Irvine, California. The discussion was led by panel
chair Todd Mosher. Mosher started the day by giving a general overview of the roadmaps and the NRC’s task to
evaluate them. He also provided some direction for what topics the invited speakers should cover in their presenta -
tions. This introduction was followed by an overview of the NASA draft EDL technology roadmap, presented by
the roadmap authors. Each panel session began with a brief introduction by the panel moderator, followed by a
presentation from each of the invited panel members. Time was then left for open discussion among all workshop
participants regarding the topics addressed by the panelists. At the end of each day, there was additional time for
general discussion among all of the workshop participants.
Roadmap Overview by NASA
The workshop began with a presentation on the NASA draft roadmap for TA09 by Mark Adler. Other roadmap
authors were also in attendance. Adler addressed the general EDL challenges: “not burning up, slowing down in
time, hitting the target, and surviving the impact.” Related to the challenges, Adler presented the benefits of EDL
technologies, particularly focusing on enabling and enhancing capabilities: increased mass to destination, increased
planet surface access, increased delivery precision to the surface, expanded EDL timeline to accomplish critical
events during entry, increased robustness of landing system to surface hazards, enhanced safety and probability
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of mission success, human safety during return from beyond low Earth orbit (LEO), and sample return reliability
and planetary protection. In developing the roadmap, Adler commented that the authors tried to take a snapshot
of future missions in order to choose the technologies and map them to those missions. Only technologies that
were deemed feasible in the 2010-2030 timeframe were considered, although they were influenced by longer term
missions (e.g., human Mars surface mission) due to their very long lead times. The remainder of the presentation
presented an overview of each of the level 2 technology areas in the roadmap and the technologies found in each:
Entry, Descent, Landing, and Vehicle Systems. Finally, one slide was presented on crosscutting EDL technolo -
gies, with the comment that there are very few applications outside of NASA for many of the technologies in the
roadmap. A few examples were some TPS overlap with DOD systems, launch abort for commercial crew, and
a potential emerging market for commercial applications of EDL technologies for suborbital and orbital vehicle
recovery.
Adler’s presentation was followed by a question and answer session. One question was asked about the afford -
ability of testing, to which the roadmap authors answered that for many EDL technologies, testing must be done at
the target (e.g., Mars), because it is very difficult to test in a relevant environment at Earth. Because of the cost of
doing this, most Mars missions have built on the technology demonstrated during Viking and Mars Pathfinder—
very little new technology development has occurred since. Another workshop participant asked about the status
of NASA’s arcjet facilities, in light of the cancellation of the Constellation program (arcjet facilities became an
ongoing topic of discussion throughout the 2-day workshop). Other questions focused on specific technologies,
particularly lift-to-drag for aeroshells, initiator technologies, and materials.
Panel A: Non-NASA Government Agencies
James Keeney (AFRL) began this session with a presentation that focused on how AFRL in particular (and
private industry in general) could benefit from the EDL technologies proposed in the roadmap and how AFRL
could play a role in the development of those technologies. He commented that most of the agreements and shar-
ing of expertise, technologies, and assets occur at the principal investigator level through personal associations,
but that it would be beneficial to formalize these associations so that they can occur more at the corporate level.
In terms of EDL, AFRL would be interested in teaming up with NASA to bring some of their experiments back to
the surface from LEO (space weather research was given as a prime example). Commercial entities focus primar-
ily on LEO, and Keeney was concerned as to how NASA is going to bleed their technologies into COTS efforts
to help keep costs down. A key deficiency in the roadmap, as seen by Keeney, is the lack of interdependencies
between other agencies, national labs, and international partnerships. Keeney also pointed out that AFRL has a
lot of facilities that NASA could potentially leverage, such as wind tunnels, and he does not see NASA looking
beyond their current facilities in the draft roadmap.
Audience questions focused on specifics of the experiments (200 kg class), AFRL sensors (lidar and radiofre -
quency-based units), and expertise in building terrain maps (something the DOD excels at and could translate to
planetary applications for NASA). Another audience member asked if there is any cross-correlation with NASA
in terms of modeling activities. Keeney commented that while the roadmap specifically points out that there is a
problem with testing (which he agrees with), there are no solutions proposed to fix this. Most of AFRL’s testing
is Earth-based, while expansion to other planets’ atmospheres falls more within NASA’s purview.
Carl Peterson (Sandia, retired) discussed the perceptions that have charted the course for NASA EDL thus far.
Peterson asserted that the expense of the “test what you fly, fly what you test” approach has restricted NASA from
testing and using new technologies instead of relying on Viking-era EDL technology and methodology (e.g., entry
vehicle shape, parachutes). Furthermore, Peterson continued, engineering technology often does not get enough
investment, as technologies are developed specific to each particular mission. If NASA wants future missions that
expand current capabilities (to enable new destinations and sample return, for example), past EDL technologies
are not good enough. Peterson commented on the possibility of teaming up with the Air Force (or DOD in gen -
eral), since there are overlapping technology needs. Peterson suggested that continuity of technology development
funding is critical, and bureaucratic oversight and reporting requirements should be kept to a minimum. Also, the
need to re-evaluate and make changes to the R&D goals is periodically necessary. Peterson also stressed that EDL
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technology development is a strategic objective, which requires continuous effort and should not be revised by
every new administration. A NASA participant in the workshop agreed that the constantly shifting priorities and
budgets within NASA have made this a challenge in the past, and that the goal of the roadmaps is to provide that
continuity over the long term. In terms of sequencing and schedule, Peterson believes that the near-term schedule
in the draft roadmap is overly optimistic. Finally, Peterson believes that the predominantly test-based approach is
no longer going to be affordable. Instead, NASA will need to capitalize on advances in computing and in model -
ing and simulation, and full-scale flight tests should be limited in number and used as a qualification tool (not a
design tool).
Several key discussion points came up in the Panel A question and answer session. First was a discussion over
collaboration with other agencies. Suggested collaborations included national labs for supercomputing, and Mis -
sile Defense Agency for reentry modeling. A key point was that contractual agreements should be signed to jointly
maintain facilities. With regards to facilities, there was also significant discussion on the need to emphasize facilities
issues in the roadmap. Second was a discussion over modeling and simulation and its relationship to testing. Several
speakers commented that models must be validated with tests—you cannot believe your computational models until
you have some verification. Every opportunity should be used to gather data, including instrumenting actual flights.
The role of testing has changed though—instead of being used for design, it now needs to be tied into validating
prediction methods. Several audience members also commented on the need for integrated system demonstrations
to avoid the TRL valley of death (aerocapture is a popular example), and the roadmap should include milestones for
dedicated technology demonstration missions. Third was a discussion over the focus of the roadmap—i.e., should
it focus on Mars, or was it already too focused on Mars? A NASA staff member commented that there should be a
core capability of investment that is not tied to a single program office, since programs come and go. However, in a
constrained budget environment, it is difficult to have parallel paths and technologies must be justified by their use in
missions. There was concern over the roadmap focusing too much on a human Mars landing. Instead, many believed
that the roadmap should focus on more near-term goals, since technology may become obsolete by the time NASA
is ready to do a human Mars mission. Finally, in terms of industry, long-term objectives and funding continuity are
also needed—it is the only way to get industry to invest some of their own money into technology development.
Panel B: Industry I
Arthur Grantz, Boeing, focused his presentation on entry from LEO, which he saw as a gap/weakness in the
draft roadmap. Just as TPS materials and technologies were “lost” after Apollo, he fears that the same will happen
now that the space shuttle has been retired. Return from LEO will continue to be important in the coming years,
and should be made a priority. He believes that reusable TPS materials, manufacturing processes, and maintain -
ability are at a critical tipping point. He believes that the roadmap, however, focuses too much on new ablative
TPS materials. He also discussed areas of overlap between high-speed Earth return (e.g., from Moon or Mars) and
LEO return. Additionally, Grantz believes that instrumentation should be required on EDL missions to improve/
validate computation models. Infrastructure also needs to be maintained, particularly arcjet facilities. The roadmap
should also include more Earth atmospheric flight testing of LEO and higher entry velocity systems.
Al Herzl, Lockheed Martin, discussed the EDL technologies that he believes are needed: TPS materials,
high-temperature insulation and structures, aeroshell systems, mechanical separation and deployment systems,
parachutes, propulsion systems, landing and hazard avoidance sensors and algorithms, and landing gear. He believes
that missions must be identified to pull more mature technologies. Along the same lines, he believes that every
mission has the responsibility to further technology development. He also sees seeking out commercial markets as
beneficial, and commented that academia and industry both want to work on technology development, so NASA
should try and collaborate. Finally, be believes that test programs are the key to confidence—you need test data
to build the analysis and then to validate your models.
Steve Jolly, Lockheed Martin, discussed what areas of the roadmap he agreed with and what areas need modi -
fication. Overall, he agreed with the key recommended areas of technology development with the exception of the
small body technologies (should potentially go in a separate roadmap). He also believes that the draft roadmap
does not focus enough on integrated system approaches, which he believes is critical for EDL systems that tend
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262 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES
to be highly integrated and highly coupled. He also believes that the focus is too much on planetary missions, and
not on Earth return from LEO, HEO, Cis-Lunar or NEO destinations, which he commented “hasn’t been solved.”
He agreed with the recommended immediate actions listed in the roadmap, as it is important to pick out the low-
hanging fruit. He listed was he believes to be the top EDL technical challenges: qualification of TPS (and the need
for arcjet facilities), qualification of decelerators (parachutes), re-contact threats, hazard avoidance, horizontal
velocity and touchdown, and ground surface interaction. Finally, he also listed what he sees as the game-changing
technologies: decoupling terminal descent propulsion from touchdown gear, GNC sensors, steerable decelerator
technology, critically damped airbags for touchdown, aerocapture, terminal descent retro propulsion, and supersonic
deployment of FBC-like EDL structures to avoid re-contact.
Don Picetti, Boeing, believed that the roadmap is comprehensive in scope, and a good balance between
near-term and far-term investments. He thought that having parallel paths and quantitative targets for technology
development were strengths of the roadmap. Picetti was also concerned with reusable Earth entry systems, which
could help improve operations by commercial providers. He also emphasized the importance of high-fidelity
modeling and integrated system simulations. In particular, he discussed the need to coordinate with other NASA
technology programs (e.g., Aeronautics) to acquire data, the need to upgrade and maintain ground test facilities,
and the need to instrument future NASA missions. He saw the top technical challenges as follows: deployable and
inflatable decelerators (game-changer), supersonic retropropulsion (game-changer), and precision landing. The
high-priority areas that he identified were: flight testing/ground testing and facilities, rigid aeroshells, deployable
and inflatable decelerator systems, supersonic retropropulsion, and integrated high-fidelity M&S. He believes that
near-term investments should be guided by potential for high impact on future missions. For LEO return, this would
include robust TPS and health monitoring. For solar system exploration, this includes rigid/deployable aeroshells
and TPS, supersonic retropropulsion, adaptive GN&C, integrated system M&S, and ground facilities.
Open Discussion
The first day’s discussion featured several key themes:
1. There was a lot of discussion during the first day of the workshop with regard to industry’s role in the
development/implementation/sharing of EDL technology development. One area of concern was how
NASA would transition these technologies into industry. Some workshop participants did not see a big
push for commercial applications. Others saw applications to venture tourism, and want NASA to provide
a push for the commercial space industry. Furthermore, there was discussion over what the best role for
NASA is, what the best role for industry is, and how the two can effectively work together. Many speak -
ers said that for planetary exploration, NASA should be in the lead with industry participating (since it’s
a science endeavor and there is no current business case). However, in terms of LEO missions (particu -
larly improved performance, lower cost, higher reliability), NASA should spin these technologies off to
industry. Additionally, some comments were made that part of NASA’s role should be to maintain core
technology and facilities.
2. Another common theme was the issue of flight testing. A question was posed as to how game-changing
technologies are going to be tested, in particular with respect to SRP. There was subsequent discussion
about how much testing could be done in Earth’s atmosphere or in ground facilities, or if a technology
demonstration mission at Mars would be required.
3. Related to testing, there was a lot of discussion with regard to facilities, in particular arcjet facilities.
There is significant concern over the potential shutdown of these facilities, in that they are needed for
testing and qualifying TPS materials. There was some commentary about needing mission pull to keep
these facilities up and running, and that testing for technology development and/or model validation can
be used to fill the downtime between missions.
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Panel C: Industry II
Neil Milburn, Armadillo Aerospace, focused on the role that Armadillo Aerospace (and other small, start-up
companies) could play in the EDL technology development. Armadillo Aerospace’s strength is in rapid prototyping
and flight testing. They also have a strong simulation capability that they have a lot of faith in because it is backed
with flight testing. Milburn discussed the test-bed capabilities and vehicles of Armadillo Aerospace. Some areas
that they could do testing in are soft landing, plume mitigation and impingement, and suborbital testing of EDL
technologies like ballutes and parachutes. In particular, they are working on the development of a reusable sounding
rocket that could launch 10 to 20 kg to almost 500 km. Essentially, Armadillo could provide a very inexpensive
test platform at the subscale level for EDL technology development.
Colin Ake, Masten Aerospace, also discussed the capabilities of Masten Aerospace and how they could contrib-
ute to EDL technology development. As with Armadillo Aerospace, he believes that small start-up companies can
play a role in helping to test and demonstrate EDL technologies. Ake provided an overview of some of the Masten
vehicles, which like Armadillo, also participated in the lunar lander challenge and the NASA Cruiser program.
Masten’s experience is mostly focused on descent and landing, and they’ve been used before as a vertical touch -
down test platform. Ake’s roadmap recommendations focused on the landing aspect of EDL, and include precision
landing, validating plume impingement computational fluid dynamics, propulsion (not adequately covered in the
roadmap), and integrated vehicle health monitoring. Ake emphasized the need to validate models with test data,
and to do as much Earth-based testing as possible. Ake also emphasized facilities and suggested using industry
resources where possible. He suggested that the roadmap should include milestone for technology demonstra -
tions. Finally, he addressed the issue of whether there is a business case for small industry—he believes that small
companies can make a business case out of being a testbed, technology developer and technology demonstrator.
Reuben Rohrschneider, Ball Aerospace, discussed the benefits of creating the technology roadmaps with regard
to industry participation. If industry can see that there is a long-term plan and long-term funding, it is more likely
that they will participate in the technology development. However, one criticism he had of the roadmap was that
it was too focused on Mars. He believes that NASA needs to perform architecture studies (similar to what’s been
done for Mars) for other destinations—this will help to define what the EDL technology requirements are for other
missions. Rohrschneider then discussed the technologies that he believes to be important: safe and precise landing
(particularly terrain relative navigation and hazard detection), deployable aerodynamic decelerators (these have
broad applicability beyond Mars, despite the roadmap focusing the details for these at Mars), and material testing
and development. In terms of materials, Rohrschneider commented that while materials are being developed in
other industries, they often do not test or provide data for the conditions required for EDL. Therefore, he believes
test facilities for materials (beyond just rigid, ablative TPS) are also critical. Rohrschneider also emphasized the
need to reduce margins—this can be achieved through better knowledge of the environment, improving modeling
capabilities, and reducing testing uncertainties. He also commented on the need for instrumenting flight missions
to collect data.
Al Witkowski, Pioneer Aerospace, focused his discussion on decelerators, highlighting two current large
parachute development programs. He commented on the fact that NASA is still using essentially the same para -
chute technology that was used on Viking (for Mars) and Apollo (for Earth). The primary user of these specialized
decelerator systems is NASA and, historically, funding associated with a given mission must be used to reduce risk,
thereby precluding the time and cost of a new decelerator development program. However, heritage decelerator
technology in its current state cannot be used to land heavy payloads on Mars. Witkowski sees the top technol -
ogy challenges as follows: lack of materials data for accurate modeling, lack of validation data for modeling of
flexible systems (parachutes, inflatables, etc.), and affordable ways to do full-scale testing. Overall, Witkowski
believes the draft roadmap is good, but needs consistent and persistent long-term funding for it to be successful.
In addition to technology development, foundational basic research of flexible materials is also needed, which is
where universities can play a role. Finally, he believes that decelerator measurement test capabilities are needed
(e.g., stress, strain, shape, etc.) to develop models and to provide model validation. This can start at small scales,
but full-scale testing will eventually be needed.
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264 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES
Following the four panelists presentations, there was a long question and answer session, with a focus on
materials, in particular with the application toward flexible TPS (although one audience member commented that
the problem is bigger than just flexible TPS). In general, NASA and the United States are not developing new
materials, but instead are borrowing materials from other industries, which are often manufactured overseas. With
regard to modeling and simulation, there was a general sentiment that flexible materials (e.g., parachutes and
inflatables) cannot be currently modeled. While tests are needed to help build and validate models, there is also
technology development that is required with regard to testing techniques (the example of measuring strain in a
flexible material was given as one particular challenge). There were also several comments with regard to the need
for NASA to develop a common materials database—in particular, with materials properties and regimes that are
needed for EDL.
With regard to materials, a question was asked about why inflatable decelerators have not yet reached flight
readiness despite years of funding—it is a technical or funding issue? One panelist answered that there is a techni -
cal hurdle to flexible TPS, particularly with regard to materials. Also, most technology development up to now has
been done as part of flight missions, and no mission is willing to accept the risk of a low-TRL item like inflatables
(aerocapture was another example given in this category). Since most EDL technologies are single-point failures,
it is almost impossible to fly an unproven technology on a science mission. A technology demonstration mission
would be required, where science is not the crux of the mission.
One audience member asked about instrumenting high-altitude flight tests to collect data and suggested that
NASA should provide seed money for this instrumentation. Several comments were made re-iterating the need to
instrument test flights. While some things can be tested in a laboratory setting, flight tests will still be needed.
There was further discussion about the role of NASA versus industry. Several comments were made that NASA
should not be competing with industry, but should be sharing knowledge and encouraging the growth of small
companies in particular. However, technology transfer is difficult, without actually moving the people with the
expertise. Another comment was made with regard to facilities—NASA has to maintain certain facilities because
industry cannot afford to do it.
There was also some discussion on the importance of reducing margins. What mostly impacts margins are
the assumptions going into the modeling. Generally, margin is being added on top of the baseline design, which
already has margin hidden in it. Rohrschneider commented that sensitivity analyses to the assumptions are rarely
done.
Finally, the focus of Mars on the roadmap was discussed. The roadmap authors commented that when the
roadmap was being written, Mars missions were continuing and directed, while other targets were competed, so
there was no guarantee in which targets would be visited. However, there was also an attempt to focus on Earth
return in the draft roadmap. Another roadmap author commented that the hardest EDL problem is landing humans
on Mars, so it warrants attention. There was also discussion about stepping stone technologies that can be done
in the near term, which will eventually contribute to a human Mars mission (decelerators, SRP, inflatable reen -
try vehicle experiment). The general sentiment in the audience was that the Earth-return segment needed to be
strengthened, in particular with regard to supporting commercial missions.
Panel D: Academic Organizations
Robert Bishop, Marquette University, focused his discussion on the GN&C portion of the roadmap. He focused
on three areas:
1. Aeroshells—need more lift; guidance should be integral in the design of aeroshells, not an afterthought
2. EDL = GN&C—need smart sensors and need to think about their role in navigation (and vice versa)
3. Education—roadmap did not address education very well, but need to keep students excited and engaged
to develop the next generation of engineers
Bishop then addressed what the current state of EDL is: at entry (hypersonic), vehicles have a lot of lift and con -
trollability, but don’t have good knowledge of state; once the parachute is deployed, you have a good knowledge
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of your state, but no longer have sufficient controllability. Therefore, he believes the focus should be on more
sensors and location knowledge at high altitudes. He believes that a tipping-point technology is robust modular
GN&C algorithms, where these can move from mission to mission without software holding up the development.
He believes a game-changing technology to be aeroshells with high lift. Echoing many other presenters, Bishop
also emphasized the need to instrument EDL missions. Overall, Bishop believes that the draft roadmap needs a
strong GN&C focus.
Jean Muylaert, von Karman Institute for Fluid Dynamics, began his presentation with general comments with
regard to the draft roadmap. First, he believes that the link between industry, academia, and NASA is important.
Second, he believes in the need to return to a vigorous ground and flight test program (but how?). Third, he
emphasized the importance of physical model validation with testing (and the need for upgrading ground-based
test facilities), risk analysis, and qualification at the integrated EDL level. Muylaert then discussed the in-flight
experimentation strategy carried out in Europe. He believes that in-flight research test-beds should be emphasized
more—in Europe, this is done on cheap launches, suborbital flights, etc., in order to bridge the gap between ground-
based tests and flight data. EXPERT is one example of an in-flight test bed that he discussed in his presentation.
Tayfun Tezduyar, Rice University, focus was on parachutes and, in particular, on fluid-structure interaction
modeling. This is one of the most difficult problems to test, Tezduyar explained: because parachutes are so light,
many of the classical fluid-structure interaction techniques do not work, although much progress has been made
over the past several years. Tezduyar discussed a set of methods developed at Rice University that have produced
good results thus far. He also emphasized the need for flight test data in order to benchmark computational
modeling.
In the question and answer session that followed the Panel D presentations, Muylaert was asked about ESA’s
EXPERT program and how NASA could fund similar technology-dedicated missions. Muylaert discussed how ESA
has a technology directorate and a program directorate—in getting EXPERT funded, they included the programs
directorate in the discussion, which he claims helped tremendously. Essentially, it created a new vision/strategy
with regard to in-flight research.
The panelists were then asked about their view on game-changing technologies. Tezduyar answered that there
needs to be a bigger role for computational modeling in the overall process (particularly fluid-structure interaction).
Bishop believes that developing GN&C technology to do a pinpoint landing at Mars would be game-changing.
However, without a technology demonstration mission, vehicles with more lift will not be utilized.
Finally, there was discussion with regard to education, and how to link products from graduate students to
NASA.
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