NASA/TM—2006–214547

The State of Space Propulsion ResearchR.L. Sackheim, J.W. Cole, and R.J. LitchfordMarshall Space Flight Center, Marshall Space Flight Center, Alabama

August 2006

National Aeronautics andSpace AdministrationIS20George C. Marshall Space Flight CenterMarshall Space Flight Center, Alabama35812

https://ntrs.nasa.gov/search.jsp?R=20070008232 2020-08-06T09:24:47+00:00Z

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NASA/TM—2006–214547

The State of Space Propulsion ResearchR.L. Sackheim, J.W. Cole, and R.J. LitchfordMarshall Space Flight Center, Marshall Space Flight Center, Alabama

August 2006

Nat�onal Aeronaut�cs andSpace Adm�n�strat�on

Marshall Space Fl�ght Center • MSFC, Alabama 35812

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Ava�lable from:

NASA Center for AeroSpace Informat�on Nat�onal Techn�cal Informat�on Serv�ce7121 Standard Dr�ve 5285 Port Royal RoadHanover, MD 21076–1320 Springfield, VA 22161301–621–0390 703–487–4650

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Table of conTenTS

1. INTRoDuCTIoN ......................................................................................................................... 1

2. wHitHer SpAce propulSion innoVAtion ..................................................................... 2

3. enAbling tHe SpAce explorAtion ViSion .................................................................. 5

4. tHe neeD for A SpAce propulSion reSeArcH initiAtiVe ..................................... 7

5. STRATegIC FRAMewoRk ....................................................................................................... 9

6. TeChNICAl FoCuS ................................................................................................................... 11

7. CoNCluSIoNS AND ReCoMMeNDATIoNS ......................................................................... 14

ReFeReNCeS ................................................................................................................................... 15

�v

lIST of fIGUReS

1. Summary of nat�onal �ntellectual cap�tal �nvestment �n h�gh-speed/hyperson�c X-veh�cles .............................................................................................................................. 4

2. Ideal�zed program l�fe cycle �llustrat�ng relat�ve d�str�but�on of R&D efforts over t�me ...... 8

3. l�m�ts of convent�onal thermal propuls�on performance. Innovat�ve methods are needed to bypass sol�d state thermal constra�nts ............................................................. 11

4. Illustrat�on of technology maturat�on w�th plateau of d�m�n�sh�ng returns and quantum-l�ke leap �n �mprovement through revolut�onary breakthrough ...................... 12

5. h�stor�cal and future trends �n cost d�str�but�ons for propuls�on system development ......... 13

1

TeChNICAl MeMoRANDuM

The STaTe of SPace PRoPUlSIon ReSeaRch

1. InTRodUcTIon

As the Nat�on attempts to re�nv�gorate �ts space technology programs and prepares to embark on a new era of space development and explorat�on, �t �s an appropr�ate t�me to recons�der future long-term research and technology �nvestment plans and seek better al�gnment w�th newly establ�shed goals and v�s�ons for the new space systems that w�ll be needed for �mplementat�on. It �s part�cularly �mportant to exam�ne how space propuls�on technology has progressed over the �nterven�ng years s�nce the last era of explorat�on, as ep�tom�zed by the Apollo program; to understand current gaps and needs; and to make alterat�ons and adjustments as appropr�ate.

Space propuls�on deserves spec�al attent�on �n th�s regard s�nce the fundamental techn�cal obsta-cles to broader human engagement w�th space are the l�m�tat�ons �n state-of-the-art transportat�on capa-b�l�t�es for both launch and deep space penetrat�on. More d�rectly to the po�nt, trad�t�onal propuls�on system performance �s approach�ng fundamental theoret�cal l�m�ts that cannot be overcome through further investment, and the specific energy and specific power characteristics of traditional systems are, �n fact, s�mply too low to ever support a robust and v�gorous explorat�on agenda throughout the solar system. object�ve cons�derat�on of these fundamental l�m�tat�ons leads to one overr�d�ng conclus�on: Revolut�onary advancements �n space transportat�on w�ll only emerge from susta�ned bas�c research on h�ghly energet�c propuls�on methods.

Th�s Techn�cal Memorandum (TM) d�scusses some bas�c �ssues and �mped�ments that have ham-pered or prevented the effect�ve pursu�t of such �nnovat�ve technolog�cal solut�ons over the years and that w�ll cont�nue to hamper and �mpede progress �n the future unless some changes are �mplemented. to address these concerns, specific recommendations and a practical plan of action are suggested.

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3

2. whITheR SPace PRoPUlSIon InnoVaTIon

where is u.S. space flight today, and how did we get here? After 40 years, why are we slowly converging on a slightly updated Apollo architecture? why is there no Moore’s law analogy for rock-etry? clearly, we have arrived at a watershed moment in u.S. space flight history, and it is essential that we reflect on such questions in a forthright way. Decisions are now being made that could set our future course �n space for decades to come, and �t �s appropr�ate that we exam�ne the log�c that brought space transportat�on full c�rcle almost back to where we started.

The c�rcumstances lead�ng to th�s crossroad are complex, but �n large part, the current s�tua- t�on can be attr�buted to �nadequate or �neffect�ve past �nvestments �n bas�c space propuls�on research. generally speak�ng, the Nat�on has �nvested �n var�ous space veh�cle hardware development programs, but nothing seems to have transitioned to flight application. the history of high-speed hypersonic x-vehicles, as depicted in figure 1, is a prime example. the lesson, which we seem unable to heed, is that a good conceptual �dea w�ll not mature and become pract�cal w�thout sound underly�ng research and hard-won solutions to critical technical issues. At the risk of oversimplification, it is propulsion tech-nology more than any other s�ngle factor that governs space transportat�on system arch�tecture. The s�m-ple fact �s that there has been no quantum-l�ke leap �n space propuls�on capab�l�ty over the last 40 years that would rad�cally change our opt�ons and enable truly rout�ne, safe transport to earth orb�t and �nto the solar system. Desp�te the expend�ture of money on programs a�med at technolog�cal advancement, we continue to find ourselves bound by the limits of traditional chemical rocket propulsion technologies.

Thus, we are faced w�th an uncomfortable propos�t�on: Does the fact that there �s currently not a clear path to a breakthrough solut�on �mply that none ex�sts because the ult�mate technolog�cal l�m-its of propulsion truly have been reached? Virtually everyone, even the most entrenched technologist, would d�savow th�s conclus�on; however, there �s real, vehement d�sagreement w�th�n the propuls�on commun�ty on how best to address the obv�ous gaps. In general, the major�ty op�n�on �s t�lted toward �nvestment �n appl�ed research a�med at evolut�onary �mprovement of trad�t�onal technolog�es unt�l a clearly definable alternative with a simple development path can be identified. it is our position, how-ever, that no innovative alternative will ever emerge without a significant level of investment in basic research. because such investments are inherently high risk and may provide inefficient or negative returns, pr�vate �nvestors, unless possessed w�th �nord�nate v�s�on and wealth, are unable to just�fy the costs. The publ�c sector, on the other hand, has been so constra�ned by r�sk avers�on and so focused on near-term operat�ons that �t has proven unable to comm�t to a susta�ned, long-term, forward-look�ng program of bas�c propuls�on research. we bel�eve that th�s current �mbalance �s read�ly correctable, but �t w�ll requ�re a cr�t�cal reevaluat�on of research and technology focus and a del�berate reemphas�s on research that can move us well beyond establ�shed technolog�cal capab�l�ty.

4

1940 1950 1960 1970 1980 1990 2000 2010

Hyp

erso

nic

Vehi

cle

Inte

llect

ual C

apita

l

Rocket PoweredTurbine PoweredRamjet/ScramjetUnpowered

X–33M=63 Flts

X–34M=60 Flts

X–43AM=72 Flts

X–38M=63 Flts

X–30NASP0 Flts

X–24BM=1.7636 Flts

X–24AM=1.628 Flts

X–23M=163 Flts

X–20Dynasoar

0 Flts

X–15A–2M=6.722 Flts

X–15M=6.06177 Flts

X–17M=14.434 Flts

X–10M=2.0527 Flts

X–9M=2

28 Flts

X–7M=4.31130 Flts

X–3M=0.9551 Flts

X–2M=3.19620 Flts

X–1EM=2.2426 Flts

X–1BM=2.4454 Flts

X–1M=1.45157 Flts

?

F�gure 1. Summary of nat�onal �ntellectual cap�tal �nvestment �n h�gh-speed/hyperson�c X-veh�cles.

Th�s should not be v�ewed as a call to arms for unrestra�ned research fund�ng, but rather as a calm and clear statement of the need to ach�eve a balanced research and technology �nvestment approach. To be sure, the expend�ture of taxpayer dollars should be undertaken �n a thoughtful and prudent manner, but a hardnosed, short-s�ghted �nvestment strategy that avo�ds all elements of r�sk �s technolog�cally ster�le. w�thout quest�on, ma�nta�n�ng operat�onal space access capac�ty �s of h�ghest priority, but we also need the foresight to look to the future and to attempt the difficult and seemingly �mposs�ble tasks that w�ll create new poss�b�l�t�es. These dual object�ves requ�re oppos�ng m�ndsets and are generally in direct philosophical conflict, which inevitably leads to a difficult struggle when both goals must coex�st w�th�n the same compet�t�ve env�ronment. In all but the most extraord�nary cases, the mainstream high-profile operations activities quickly achieve dominance and naturally subju-gate and subsume the �mmature, far-reach�ng research efforts that offer the only real hope of chang�ng the status quo. the significant challenge, therefore, is to create circumstances where both objectives can coex�st and thr�ve. our purpose �s to suggest a course of act�on that could help generate these c�r-cumstances and thereby re�nv�gorate space propuls�on �nnovat�on based upon far reach�ng research and �nnovat�on.

5

3. enablInG The SPace exPloRaTIon VISIon

in simplest terms, the Space exploration Vision is concerned with expansion of human ecology from earth and �nto the cosmos. If properly framed and executed, �t w�ll be a quest not of pure adventur-�sm but of a determ�ned outward expans�on of human presence and act�v�ty. ult�mately, �t �s about go�ng to stay and l�ve. Th�s stands �n stark contrast to the trad�t�onal v�ew of sc�ence-based explorat�on, wh�ch has been pr�mar�ly concerned w�th the acqu�s�t�on of fundamental understand�ng and knowledge through unmanned autonomous m�ss�ons. we are now enter�ng an era when these prev�ously separate object�ves w�ll be conjo�ned and �ntertw�ned �n ways heretofore un�mag�ned, hopefully, to the betterment of both.

the initial phases of this bold, long-term agenda, including establishment of the first perma-nently manned lunar base and mounting the first human expedition to Mars, will require a long-term susta�nable program. Moreover, th�s program cannot be v�ewed as a s�mple matter of systems eng�- neer�ng s�nce the technolog�es, knowledge, and �nfrastructure requ�red to accompl�sh these goals do not currently ex�st. Most cr�t�cal, among the many needs to enable meet�ng these amb�t�ous goals, w�ll be new high-performance space transportation systems for efficient heavy lift launch and rapid move-ment of large masses and people across vast d�stances of �nterplanetary space. Full real�zat�on of th�s h�ghly amb�t�ous agenda w�ll therefore demand space propuls�on performance beyond the realm of current capab�l�ty.

Consequently, �f we truly w�sh to �mplement a susta�ned and affordable human and robot�c exploration program and desire to extend human presence throughout the solar system, we must first acknowledge the bas�c shortcom�ngs and then persue a course of act�on that could lead to revolut�on-ary technolog�cal solut�ons and quantum-l�ke leaps �n space transportat�on capab�l�ty. otherw�se, human space exped�t�ons w�ll cont�nue to be v�ewed as unsusta�nable feats of romant�c�sm, and real ecology change w�ll forever rema�n unreal�st�c. Most desperately needed are �nnovat�ve methods to effect order-of-magnitude or more increases in propulsion energetics, as defined by system-specific energy and power. it is difficult to imagine how such dramatic gains can ever be attained, however, unless we mount a ser�ous program of bas�c research now. even then, success w�ll only be ach�evable through the comb�ned comm�tment of publ�c, pr�vate, and academ�c ent�t�es and by unprecedented cooperat�on on an �nternat�onal scale.

6

7

4. The need foR a SPace PRoPUlSIon ReSeaRch InITIaTIVe

Currently, there �s no coord�nated bas�c research program for space propuls�on technology. There has been and cont�nues to be a modest level of program support for appl�ed research and advanced tech-nology development, but not for bas�c research. Th�s �s a ser�ous long-term l�m�tat�on s�nce long-term real�zat�on of the explorat�on v�s�on w�ll depend on revolut�onary advancements �n space propuls�on capab�l�ty lead�ng to ent�rely new transportat�on systems. Thus, there �s a real need for a more balanced �nvestment approach �n space propuls�on research, and th�s longstand�ng need has become even more cr�t�cal and obv�ous �n l�ght of the outstand�ng techn�cal challenges ahead.

Bas�c research proper, whereby we probe the edge of ex�st�ng knowledge and techn�cal know how, is inherently a slow and inefficient process and must be undertaken with a long-term perspective and a high tolerance for failure. this is an exceedingly difficult position to sustain within the modern era of the monol�th�c profess�onal manager, �n wh�ch extraneous adm�n�strat�ve ab�l�t�es and �mage projec- t�on are more valued and pr�zed than �n-depth knowledge and competence w�th�n the doma�n of respon- sibility. this trend, when coupled with the nation’s tendency to fund research & Development (r&D) on a fragmented year-to-year basis, while imposing stiflins and costly oversight, goes a long way towards expla�n�ng the absence of a strong and healthy bas�c research program as well as our current deficit in research capitol, which would normally serve as the wellspring for technical innovation.

what �s most needed, �f we hope to meet the needs of the future, �s a stable and protected research env�ronment w�th the capac�ty, strength, and techn�cal backbone to support worthy h�gh-r�sk projects and to susta�n that support to a conclus�ve outcome. Most essent�al �s a susta�ned fund�ng com-m�tment �ndependent of budgetary cr�s�s �n ma�nl�ne programs, m�ss�ons, and operat�ons and the wher-w�thal to ma�nta�n support over the long haul. A long-term perspect�ve w�ll be absolutely necessary since, from a historical perspective, the life cycle for the development and fielding of new space propul-s�on technology can be measured �n decades. Therefore, the ava�lab�l�ty of new propuls�on technology for some future space transportation system must be predicated upon significant up-front research and development, as illustrated by an idealized program life cycle in figure 2.

It �s our content�on that the Nat�on should �n�t�ate, organ�ze, and adm�n�ster a space propuls�on research �n�t�at�ve that w�ll meet these cr�t�cal needs. Because future space transportat�on requ�rements, part�cularly as they relate to deep space explorat�on, go far beyond the needs of more convent�onal earth orbital spacecraft, it is clearly the public sector’s responsibility in this arena. one can hope that private sector efforts will help fill the shortfall, but it is difficult to imagine any impact in this regard since the �nherent h�gh r�sk and poor returns of long-term research d�ssuades commerc�al enterpr�ses from mak�ng any significant investments.

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Life of a Program

% L

evel

of E

ffort

New Idea(s) and Concept Definition Product Design & Development

ConsultationArchitecture DevelopmentRequirements Definition

Basic andApplied Research

Basic andApplied Research

SystemsDevelopment

SystemsDevelopment

FormulationFormulation ImplementationImplementation

Research and Analysesof Concepts

New

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/Con

cept

Res

earc

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f Con

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Flig

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catio

n

Con

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Def

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SRR

CoDR

PDR

CDR

F�gure 2. Ideal�zed program l�fe cycle �llustrat�ng relat�ve d�str�but�on of R&D efforts over t�me.

9

5. STRaTeGIc fRamewoRk

The most �mportant step �n mov�ng forward w�th a Space Propuls�on Research In�t�at�ve �s estab-lishing a long-term, sustainable framework. this framework would define the focus, scope of activities, goals and object�ves, and gu�d�ng pr�nc�ples for pract�cal �mplementat�on of a mean�ngful and effect�ve program. we proffer the follow�ng thoughts and suggest�ons.

To �nsure that long-term needs are addressed w�thout los�ng near-term relevance, �t �s suggested that such an initiative encompass both basic and applied research in support of the nation’s space pro-puls�on needs. heav�est emphas�s would be placed upon new sc�ence and revolut�onary technology to enable voyages and commerc�al ventures that are not currently feas�ble, but the �n�t�at�ve should also address special innovative solutions and technical improvements having nearer term potential for flight system ut�l�zat�on. The �nclus�on of some appl�ed research �s cons�dered v�tal as a means of ma�nta�n�ng a l�nk to broader explorat�on program object�ves and develop�ng a programmat�c reputat�on as an �nno-vat�ve problem solver and pract�cal contr�butor. one cannot l�ve on dreams alone.

Ideally, the bas�c research component of the proposed �n�t�at�ve would be structured to conduct fundamental feasibility assessments and demonstrate scientific proof-of-principle of highly enabling propuls�on concepts. It �s env�s�oned that the technolog�cal scope would embrace �nnovat�ve solut�ons appl�cable to both launch and deep-space transport systems. By emphas�z�ng a longer term, h�gher pay-off strategy, it is hoped that the nation will be better positioned to define and fill future technology gaps and ma�nta�n a more balanced �nvestment portfol�o that avo�ds the class�c down-select�on process where-by promising but premature ideas are strangled in favor of well-defined low-risk approaches based on ex�st�ng technology. To be effect�ve, these bas�c research �nvestments must be rooted �n sound techn�cal analysis and follow a sequential tract encompassing scientific feasibility, technical maturation, relevant demonstrat�ons, and trans�t�on to pract�ce.

h�story tells us that such h�ghly a�med research �s bound to be controvers�al and subject to �ntense cr�t�c�sm by var�ous detractors. Thus, successful execut�on and long-term surv�val of the �n�t�a-t�ve w�ll requ�re cred�b�l�ty and �ntegr�ty beyond reproach. of foremost �mportance w�ll be the establ�sh-ment of a culture ded�cated to “excellence �n research” and a staunch comm�tment to “good sc�ence” w�th the w�dest poss�ble d�ssem�nat�on of results and complete openness and respect for peer-dr�ven cr�t�ques and assessments.

There has been and w�ll cont�nue to be �ntense debate over the proper placement of R&D respon-s�b�l�t�es. on one hand, there are the overt extramural�sts, who would prefer to transfer all research to academ�a and all development to �ndustry wh�le promot�ng a “leave the adm�n�ster�ng to us” mantra. on the other hand, there are the overt �ntramural�sts, who would generally prefer to hold complete com-mand over R&D act�v�t�es desp�te the suscept�b�l�ty to over-central�zed control and the “not �nvented here” syndrome. In our cons�dered op�n�on, ne�ther of these extreme v�ews �s sens�ble or des�rable.

10

Rather, proper stewardsh�p of propuls�on R&D w�ll requ�re government adm�n�strators possess�ng �n-depth techn�cal knowledge and competence over the�r doma�ns of respons�b�l�ty and the good sense to seek expert contr�but�on at �ts source, external and �nternal to the government.

As a strateg�c pr�nc�ple, �t �s suggested that the proposed research �n�t�at�ve be organ�zed to �nclude both extramural and �ntramural elements, w�th separate compet�t�ons for each sector. Imple-mentation of such an approach will require a small and technically strong project office capable of understand�ng the deta�led techn�cal �ssues assoc�ated w�th a part�cular l�ne of research and us�ng th�s understand�ng to set pr�or�t�es and develop focused l�nes of attack. The goal would be to structure pack-ages of �nd�v�dual research tasks that, as a whole, exh�b�t a cohes�ve and concerted movement towards a des�red object�ve.

As a gu�d�ng pr�nc�ple, un�que expert�se, fac�l�t�es, and capab�l�t�es should be ut�l�zed to the max-�mum extent poss�ble. Th�s should �nclude NASA, Department of Defense, and Department of energy laborator�es, un�vers�t�es, pr�vate sector ent�t�es, and �nternat�onal collaborat�ons and partnersh�ps. The extramural component of the �n�t�at�ve should also �nclude efforts a�med at st�mulat�ng educat�on and extend�ng graduate research opportun�t�es for future sc�ent�sts and eng�neers. From an �ntramural per-spective, it would be highly desirable to enhance and develop nASA’s in-house expertise and capabili-t�es, beyond appl�ed systems eng�neer�ng. Th�s type of �n-house �nvestment �s d�rely needed to ma�nta�n techn�cal competency and rema�n a world-class contr�butor to space propuls�on �nnovat�on.

It should be noted �n pass�ng that many un�vers�t�es around the Nat�on have managed to �n�t�ate and susta�n some excellent space propuls�on research, desp�te the lack of rel�able fund�ng and support. As a result, these activities have tended to suffer at the mercy of year-to-year fluctuations in funding and underappreciation of their contributions, which has made it difficult to maintain continuity and cohesive-ness �n the�r programs. In our op�n�on, th�s valuable resource �s too often overlooked as a major source of new ideas and innovative solutions to our most difficult technical problems, and any attempt to erect a new research �n�t�at�ve should bu�ld on th�s ex�st�ng capab�l�ty to the max�mum extent poss�ble.

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6. TechnIcal focUS

The central techn�cal shortfall for better space transportat�on �s the general unava�lab�l�ty of highly energetic propulsion technologies. that is, the specific energy and specific power characteristics of trad�t�onal space propuls�on systems are s�mply too low to effect dramat�c �mprovements �n m�ss�on capab�l�ty. The energy content of chem�cal fuels, for �nstance, has reached �ts natural plateau, beyond wh�ch only marg�nal �mprovements can be expected, and th�s fundamental l�m�tat�on places severe con- stra�nts on the amount of payload that can be del�vered for a g�ven veh�cle s�ze. even w�th energy den-s�t�es equ�valent to sol�d core nuclear rocket performance, one should note that convent�onal thermal propulsion is fundamentally constrained by definite material temperature limits, as illustrated in figure 3. Moreover, the low thrust-to-weight ratio and high specific-mass characteristics associated with avail-able low-power electr�c propuls�on �nvar�ably y�elds excess�vely long �nterplanetary tr�p t�mes. There �s, therefore, a broad techn�cal gap between the presently ava�lable level of propuls�on system perfor-mance and the level that will ultimately be required to fulfill the exploration agenda.

Cha

mbe

r Tem

pera

ture

(K)

SSME

Lox/RP Lox/H2H2

Material Limit

Isp (s)

6,000

5,000

4,000

3,000

2,000

1,000

0

0 200 400 600 800 1,000 1,200 1,400

F�gure 3. l�m�ts of convent�onal thermal propuls�on performance. Innovat�ve methods are needed to bypass sol�d state thermal constra�nts.

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To address th�s shortcom�ng, �t �s recommended that bas�c research be techn�cally focused on high specific-energy/high-power propulsion and power. the broad scope of coverage should include advanced chem�cal propuls�on emphas�z�ng h�gh energy-dens�ty matter and advanced eng�ne cycles; advanced h�gh-power electr�c/plasma propuls�on emphas�z�ng Mw-class thrusters, h�gh-temperature technologies, electromagnetics, and flight-weight magnetic systems; utilization of nuclear energy sources emphasizing high-temperature fission-based thermal propulsion methods, low specific-mass fission-based space power plants, and fusion propulsion; and advanced energetics emphasizing off- board resources, beamed power, and ultra-energy storage. As a hedge, the proposed program of research should also contain a low level of activity targeted on new scientific discoveries and fundamental phys-�cs breakthroughs w�th revolut�onary relevance to space transportat�on.

h�story has repeatedly shown that when a technology has matured to a performance plateau for which evolutionary improvements yield diminishing returns, as graphically illustrated in figure 4, a rev-olut�onary breakthrough �s requ�red to obta�n a quantum-l�ke leap �n capab�l�ty. Th�s general rule should be expected to apply to space propuls�on technology, as well.

LastBreakthrough

RevolutionaryBreakthrough

Technology Plateau

Evolutionary Improvements

Time

Stat

e of

Tec

hnol

ogy

F�gure 4. Illustrat�on of technology maturat�on w�th plateau of d�m�n�sh�ng returns and quantum-l�ke leap �n �mprovement through revolut�onary breakthrough.

As a means of ma�nta�n�ng relevance and cred�b�l�ty, the proposed �n�t�at�ve should also �nclude an appl�ed research component to address spec�al �nnovat�ve solut�ons and techn�cal �mprovements hav-ing nearer term potential for flight system utilization. because technologies are often pressed into ser-v�ce before full understand�ng has been establ�shed, so-called mature systems often exper�ence recurr�ng problems and performance anomal�es that are not clearly understood. In th�s sense, appl�ed research can be v�ewed as means of br�dg�ng up techn�cal gaps by �dent�fy�ng, assess�ng, and promot�ng modern tech-nolog�cal �mprovements to legacy systems. Recent revolut�onary advancements �n �nformat�on technolo-g�es, for example, offer tremendous opportun�t�es for autonomous fault detect�on and correct�on.

From a more pract�cal perspect�ve, appl�ed research �s an �mportant key to reduc�ng total system development costs. Based on h�stor�cal exper�ence, propuls�on system development normally proceeds through a repet�t�ve cycle whereby hardware test fa�lures result �n redes�gn and repa�r or replacement

13

of the fa�led components followed by subsequent test to fa�lure. gradually, as the number of “test-fa�l- fix-test” cycles grow, our knowledge and understanding improve and we rise up a learning curve lead-ing to a final optimized design. consequently, hardware costs tend to drive the overall cost of any engine development program.

Analysis of historic detailed cost distributions on major development programs tends to confirm th�s bas�c conclus�on. These results clearly show that roughly half of the development cost �s for hard-ware with the remaining half split between test, engineering, and management. thus, our tragic flaw �s a repeated fa�lure to conduct up-front appl�ed research before embark�ng �nto major development act�v�t�es. By �ncorporat�ng some appl�ed research �nto the proposed �n�t�at�ve, �t �s our �ntent to help encourage a trans�t�on towards more cost effect�ve �ntegrat�on of research w�th ma�nstream systems development, as illustrated in figure 5.

Extracted From Published NASA and Contractor Data

HISTORICAL TREND FUTURE PRACTICE

CorrectiveActions

Costs

Applied Research & Technology Activities

Manufacturing

IOC

F�gure 5. h�stor�cal and future trends �n cost d�str�but�ons for propuls�on system development.

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7. conclUSIonS and RecommendaTIonS

The current state of space propuls�on research, based on thoughtful and cand�d cons�derat�on, is dismal. the simple fact is that full realization of the nation’s space exploration goals can never be accompl�shed w�thout revolut�onary advancement �n space transportat�on capab�l�ty. Moreover, even the earl�est lunar explorat�on goals of th�s bold agenda w�ll requ�re some modest propuls�on system advancement. Desp�te the desperate need, however, there �s no coord�nated bas�c and appl�ed research program for space propuls�on technolog�es.

To address th�s cr�t�cal need, a Space Propuls�on Research In�t�at�ve ought to be establ�shed, which would run parallel with exploration systems development and include a significant basic research component. As an �mplementat�on approach, we recommend the establ�shment of susta�ned fund�ng for a Nat�onal Space Propuls�on Research In�t�at�ve. Th�s would create a d�rect l�nk to future space explora-tion needs and serve to revitalize the nation’s traditional r&D focus and heritage of technical innova-t�on. It �s bel�eved that such an �n�t�at�ve would result �n a more balanced portfol�o of bas�c and appl�ed research and y�eld the �nnovat�ve solut�ons that w�ll be requ�red to enable a robust, exc�t�ng, and susta�n-able human and robot�c space explorat�on program for years to come.

15

RefeRenceS

1. Ramo, S.: “The Bus�ness of Sc�ence: w�nn�ng and los�ng �n the h�gh-Tech Age,” h�ll and wang, New York, NY, 1988.

2. bennis, w.: “why leaders can’t lead: the unconscious conspiracy continues,” Jossey–bass Publ�shers, San Franc�sco, CA, 1989.

3. Von braun, w.: “Management in rocket research,” 16th National Conference on the Management of Research, French l�ck, IN, September 1962.

4. rich, b.r.; and Janos, l.: “Skunk works: A personal Memoir of my Years at lockheed,” little, Brown and Company, Boston, MA, 1994.

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The State of Space Propuls�on Research

r.l. Sackheim, J.w. cole, and r.J. litchford

george C. Marshall Space Fl�ght CenterMarshall Space Fl�ght Center, Al 35812

Nat�onal Aeronaut�cs and Space Adm�n�strat�onwash�ngton, DC 20546–0001

Prepared by the Propuls�on Systems Department, eng�neer�ng D�rectorate

unclassified-unlimitedSubject Category 20Ava�lab�l�ty: NASA CASI 301–621–0390

The current state of space propuls�on research �s assessed from both a h�stor�cal perspect�ve, spann�ng the decades since Apollo, and a forward-looking perspective, as defined by the enabling technologies required for a mean�ngful and susta�nable human and robot�c explorat�on program over the forthcom�ng decades. Prev�ous research and technology �nvestment approaches are exam�ned and a course of act�on �s suggested for obta�n�ng a more balanced portfol�o of bas�c and appl�ed research. The central recommendat�on �s the establ�shment of a robust nat�onal Space Propuls�on Research In�t�at�ve that would run parallel w�th sys-tems development and �nclude bas�c research act�v�t�es. The bas�c framework and techn�cal approach for this proposed initiative are defined and a potential implementation approach is recommended.

20

M–1167

Techn�cal MemorandumAugust 2006

NASA/TM—2006–214547

space transportat�on, propuls�on, research and �nnovat�on

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NASA/TM—2006–

The State of Space Propulsion ResearchR.L. Sackheim, J.W. Cole, and R.J. LitchfordMarshall Space Flight Center, Marshall Space Flight Center, Alabama

May 2006

National Aeronautics andSpace AdministrationIS20George C. Marshall Space Flight CenterMarshall Space Flight Center, Alabama35812