//1/--.:20 NASA Technical Memorandum 107095 5:3d-/ AIAA-95-2631 f lF' Human Lunar Mission Capabilities Using SSTO, ISRU and LOX-Augmented NTR Technologies­ A Preliminary Assessment Stanley K. Borowski Lewis Research Center Cleveland, Ohio Prepared for the 31st Joint Propulsion Conference and Exhibit cosponsored by AIAA, ASME, SAE, and ASEE San Diego, California, July 10-12, 1995 (NASA-TM-I07095) HU~AN LUNAR . --.................. N96-12353 ~... MISSION CAPA ILITIES USING SSTO ..... ~. ~~. ISRU AND lOX-AUGMENTED NTR • TECHNClOGIES: A PRELr~I ARY .' Unc)as National• Aeronautics and ASSESSMENT (NASA. Lewis Research Space Administration Center-) 15 p G3/20 0011561 HUMAN LUNAR MISSION CAPABILITIES USING SSTO, ISRU AND LOX-AUGMENTED NTR TECHNOLOGIES --A PRELIMINARY ASSESSMENT Stanley K. Borowski * NASA Lewis Research Center Cleveland, OH 44135 ABSTRACT The feasibility of conducting human missions rich" mare soils and impact / volcanic glass-- to to the Moon is examined assuming the use of three produce LUNOX will also be key to minimizing "high leverage" technologies: (1) a single-stage-to­ IMLEO, the size and number of LTS elements, and orbit (SSTO) launch vehicle, (2) .. in-situ" resource the cost for each lunar mission. At present, NASA is utilization (ISRU)--specifically "lunar-derived" liquid focusing considerable resources on the construction oxygen (LUNOX), and (3) LOX-augmented nuclear of the international space station (ISS) and on thermal rocket (LANTR) propulsion. Lunar development and demonstration of a reusable, transportation system elements consisting of a single-stage-to-orbit (SSTO) vehicle1 to replace the LANTR-powered lunar transfer vehicle (LTV) and a current Space Shuttle in the post-2005 timeframe. It chemical propulsion lunar landing / Earth return is envisioned that an industry-developed and­ vehicle (LERV) are configured to fit within the operated SSTO would have an average flight rate of "compact" dimensions of the SSTO cargo bay -40 missions per year with -50% of these flights (diameter: 4.6 m/length: 9.0 m) while satisfying an procured by NASA to provide logistics resupply to initial mass in low Earth orbit (IMLEO) limit of -60 t the ISS. (3 SSTO launches). Using -8 t of LUNOX to "reoxidize" the LERV for a "direct return" flight to Planning future human missions to the Moon Earth reduces its size and mass allowing delivery to and Mars is also beginning anew--albeit in a less LEO on a single 20 t SSTO launch. Similarly, the dramatic fashion than the previous Space LANTR engine's ability to operate at any Exploration Initiative2--in response to the "Human oxygen/hydrogen mixture ratio from 0 to 7 with high Exploration and Development of Space" (HEDS) specific impulse (-940 to 515 s) is exploited to component of NASA's just released strategic plan.3 reduce hydrogen tank volume, thereby improving Activities are focusing on the development of key packaging of the LANTR LTV's "propulsion" and "high leverage" technologies and systems, their "propellant modules". Expendable and reusable, demonstration on precursor missions, and on the piloted and cargo missions and vehicle designs are identification of viable mission architectures that presented along with estimates of LUNOX production could be supported by NASA in the future given the required to support the different mission modes. expected tight budgets and the trends toward Concluding remarks address the issue of lunar commercialization. transportation system costs from the launch vehicle pe rspective. This paper addresses the feasibility of conducting human lunar missions using SSTO, INTRODUCTION ISRU and LOX-augmented nuclear thermal rocket (lANTR) technologies/systems. For " access to Future human exploration missions to the space," the lure of the SSTO is its full reusability, Moon will require an "economical" lunar improved operability, high flight rate and reduced transportation system (L TS) providing efficient launch costs estimated at -40 M$ per flight. 4 Its lift "access to and through space: Utilizing locally capability is limited, however, and varies from -25 available resources--specifically "iron oxide (FeO)- klbm (-11 .3 t) to 45 klbm (-20.4 t) depending on the *Ph .D.lNuclear Eng ineering, Senior Member AIAA low Earth orbit (LEO) altitude and its inclination. The SSTO, LUNOX, AND LANTR TECHNOLOGY SSTO's cargo bay volume is also small (-50 to 75% DESCRIPTION that of the current Space Shuttle) which makes packaging of payload and LTS elements a particular The SSTO Reusable Launch Vehicle challenge. In January 1993, NASA initiated a The development of LUNOX production, comprehensive "in-house" study called "Access to storage and tanker transport / transfer technologies Space," The goals of the study were to identify and systems for "reoxidizing" expendable lunar attractive options for the next generation of U.S. landing/Earth return vehicles (LERVs) initially, and launch vehicles which would : (1) allow major then reusable, lunar landing and transfer vehicles reductions in the cost of space transportation (by at (LLVs and LTVs) is expected to dramatically reduce least 50%); (2) provide an order of magnitude IMLEO requirements, the number of SSTO launches increase in crew flight safety; and (3) substantially and the cost of delivering payload to the lunar improve overall system operability. The study surface. For example, with -7 kilograms of mass examined three major architectural options which required in LEO for each kilogram of mass landed on included: retaining and upgrading the current Space the lunar surface, the ability to reoxidize an LERV Shuttle and expendable launch vehicle fleet with -8 tons of LUNOX for a "direct Earth return" (Option 1); developing new expendable vehicles mission would save three 20 t-class SSTO using conventional technologies (Option 2); and launches compared to an "all Earth-supplied" developing new reusable vehicles using advanced mission requiring twice that number. technology (Option 3). A conservative "launch needs" mission model was defined and used in the To improve "access through space," a LANTR­ study.4 It included all U.S. civilian (NASA), defense based LTV mission scenario has been assumed. and commercial missions anticipated during the The ability to alter the engine's thrust and specific period 1995 through 2030, but did not consider impulse (/sp) by varying the liquid oxygen-to-liquid future human missions to the Moon and Mars--a hydrogen (LOXlLH2) mixture ratio (MR) in LANTR's major omjssion. "LOX-afterburner" nozzle leads to small engines (both in terms of physical size and reactor power In its final summary report4 issued in January output) capable of providing "big engine" 1994, NASA concluded that a fully reusable, pure­ performance. Supersonic combustion of LOX with rocket SSTO (SSTO-R) launch vehicle was the most reactor preheated hydrogen emerging from the attractive/beneficial option for development. The engine's sonic throat also results in higher Isp values preferred Option 3 reference vehicle described in the than LOX/LH2 chemical engines operating at the "Access to Space Study" Summary Report4 is shown same mixture ratio (-100 s at MR = 6) . Lastly, the in Figure 1. It is a vertical takeoff, horizontal-landing increased use of high-density LOX in place of low­ winged concept with a circular cross-section density LH2 reduces hydrogen tank volume and fuselage for structural efficiency (other configurations improves LTV component packaging within the are presently being examined under NASA­ "volume-constrained" SSTO cargo bay. supported industry contracts). It uses aluminum­ lithium (Al/Li) cryotanks, graphite composite material for all non-pressurized primary structure and a This paper describes results of preliminary tripropellant (LOX/LH2/RP) propulsion system system and mission analysis conducted by Lewis employing seven RD-704 engines. The payload bay Research Center for NASA Headquarters' Advanced is located horizontally between the forward LOX tank Concepts Office over the past two months. The and the LH2 tank positioned in the vehicle's paper first discusses the relevant technologies and midsection. The crew cabin is situated on top of the describes their characteristics. Mission and vehicle next to an airlock/work-station area which transportation system ground rules and assumptions provides crew access to both the payload bay and are then presented along with a description of the the ISS through an overhead hatch. A "LOXlLH2" reference lunar mission scenario. Next, a version of the SSTO-R would have an overall length comparison of different LTS element options--both and diameter -15% larger than its tripropellant for the LERV and L TV--is provided and the counterpart and a gross liftoff weight (GLOW) of requirements/performance gains from transitioning -2.48 million pounds (-1125 t) . from an expendable to reusable LTS architecture are discussed. The paper concludes with a discussion of The reference SSTO-R cargo bay is 15 feet lunar transportation system and launch vehicle costs. (-4.6 m) in diameter and 30 feet (-9.15 m) long. A 2 c ___________________________________________________________ r --- -- ------_._--- l'lu:lluuJ.' fllib.tJ:.w!: fini.l..Qr!2i1 2Sklbm None Station: 220'nmi cire@ 51.6" IS.Sklbm 2 Person Station: 220 Ilmi eire @ 51.6" 45klbm . No"" 100 nmi eire @ 28.5· 3H lbm None 220 nmi eire @ 28.5· 24 klbm No .. 100 nmi chi: @900 · 'ndudes Payload and ASE Vehicle: GLOW: 1.96 Mib Dry Mass: 159.51db Propellant Mass: 1.74 Mlb CltXXi Propellant Type: LoxllHiRP Main Engine Type/No.: RD-704!7 Vac Thrust (ea.) Mode 1/2: 441.4/175.5 klb Var. ISP Mode 1/2: 4071452 10( 150ft-----J~~1 Area Ratio: 74:1 OMS Engine Type/No ~ New LoxllH2 Notes: • Vertical takeofflhorizorrtaJ landing Vat; Thrust (ea.): 6 klbf • 15 percent dry weight margin Vat; Isp: 462s • Option for carrying two on-orbit opel1i!ions Area Ratio: 100:1 crew for 7 days CryoTanks A1-U • Option for carrying four 5.5. Freedom rotation Primary Structure: Gr-COmposite crew in payload bay Control Surfar:.es: ACC • Option for carrying high energy transfer stage TPS: ACC/TABIIAFRSI for Atlas class (5k Ib) GEO missions Payload Bay-Usable Volume 15ftDx30ftL Fig .