Chapter 4

CONTENTSPage

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Advanced Manned Launch System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Personnel Launch System (PLS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55Crew-Rated Advanced Launch System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Stand-Alone LRB System.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57Foreign Crew- and Passenger-Carrying Vehicle Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Soviet Space Shuttle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Soviet Spaceplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59European Space Agency Hermes Spaceplane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Japanese HOPE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60German Saenger. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60United Kingdom Hotol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

FiguresFigure Page4-1. Advanced Manned Launch System Concepts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544-2. Role of Technology in Advanced Manned Launch System... . . . . . . . . . . . . . . . . . . . . . 554-3. Crew Emergency Rescue Vehicle (CERV)/Space Taxi and Return (STAR)... . . . . . 574-4. Soviet Space Shuttle Buran and Mir Space Station.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584-5. Soviet Spaceplane. ..... . . . . . . . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594-6. European Space Agency Hermes Spaceplane.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604-7. Japanese HOPE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614-8. Federal Republic of Germany Saenger II. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614-9. United Kingdom Hotol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Chapter 4

Advanced Rockets

INTRODUCTIONNASA is currently studying several proposed

advanced crew-carrying launch systems that wouldhelp augment or supplant the current Shuttle fleet asit ages. They include the NASA Advanced MannedLaunch System (AMLS-previously called ShuttleII), a Personnel Launch System (PLS), a crew-carrying version of the joint DoD/NASA AdvancedLaunch System (ALS), and a crew-carrying stand-alone Liquid Rocket Booster (LRB) system. NASAexpects the AMLS to supplant the current Shuttle,but provide less payload capacity. The PLS orcrew-carrying ALS could help augment the Shuttleif either is introduced before the Shuttle is retired.The intent of each concept is to provide for morecost-effective, reliable human access to space.

ADVANCED MANNED LAUNCHSYSTEM

NASA’s Langley Research Center is leading theAMLS program, which will define advanced crew-carrying launch system concepts, including theirdevelopment, system and operational characteris-tics, and technology requirements. The AMLSprogram could by the year 20051 lead to a vehiclesignificantly different than the Shuttle. NASA willcompare the AMLS and the PLS with the option foran improved Shuttle, under study by the JohnsonSpace Center (JSC), and decide how best to proceed.NASA is evaluating five AMLS concepts (figure4-1) listed below in order of increasing technologi-cal risk:2

●

●

●

●

An expendable in-line two-stage booster witha reusable piloted glider.3 This configuration atfirst appears similar to the U.S. Dyna-Soar4

concept of the early 1960s, which would havebeen launched atop a Titan III, but would carrya larger crew. Dyna-Soar would have carriedone or two pilots.5 The European Space Agencyand the Japanese NASDA have selected thisapproach for their spaceplanes Hermes andHOPE, respectively (see below). It might bepossible to use an ALS to launch an AMLSorbiter.A partially reusable drop-tank vehicle similarto the fully reusable rocket concept describedbelow, except that hydrogen propellants for thepiloted orbiter are carried in expendable side-mounted drop tanks and the payload is carriedin an internal canister. This configurationeliminates the need for a separate propulsionand avionics module seen in the next option,thus reducing its relative development andoperations costs.A partially reusable vehicle with a glider atopa core stage, which has expendable tanks butrecoverable engines and avionics. The corestage would be side-mounted on a reusableglideback booster. This partially reusable con-figuration may be economical at moderatelaunch rates.

A fully reusable rocket with a piloted orbiterparallel-mounted (side-by-side) to an unpilotedglideback booster. This vehicle would beshorter than the in-line or glider atop a corestage version, making launch preparation eas-ier. To facilitate payload integration or swap-

IThl~ ~wl~y ~mes hat he Prewnt Shutfle system, even with improvements and possible fkt ildditions, Will k IleMhg the end of its useful life

(as a result of wearout and/or attrition or cost reduction potential of new crew-cmying systems) titween 2005 ad 2010. Some argue that the presentShuttle system, having made its first flight in 1981, is still a relatively new aerosp~e system. md wi~ well-consider~ improvements and additions tothe fleet could serve effectively until the yew 2020. In ei~er LWSC, ~ d~-ision to pr~=d wi~ m *S would not ~ rwuire-d until at least 1995.

2~d thus roug~y in order of incre~~g initial development cost. Total Iifc-cy]e COSL’3 would WUY ~eally, however, depending primarily onreusability and flight rate.

3Thjs Vehjc]e could be Vev t~l, m~~g la~Ch preparation difficult. Its design would depend on the booster selected and on the mission requirements

of the orbiter. In addition, the orbiter engines could not b @itCd On the launch @ Pfior to liftoff md must ~ fired in flight after stage separation, whichwould eliminate an abort mode on the ground. (An alternative mat would rcmovc ~is con~cm wo~d be to require only an orbltat maneuvering systemin the orbiter, as in the Soviet shuttle and rely on the booster to place the orbiter in orbit.) Another obvious disadvantage is that this cancept takes a step

back from reusability.413W Ch. 5 of this rew, or for a much more det~]~ description sw ‘ ‘The Hypersonic Revolution—Eight C= Studies ~ tie Histow of HYPCmOI’IiC

Twhnology, ” vol. 1, case 11, Richard P. Hallion (cd.), WPAFB, Ohio, 1987.SThe PLS concep[ could resemble the Dyna-Soar.

-53-

98-133 0 - 89 - 3

54 ● Round Trip to Orbit: Human space flight Alternatives

Figure 4-1-Advanced Manned Launch System Concepts

Fully reusable

Glider

All vehicles designed to samereference mission (polar, 12 Klb)and same 1992 technology level(A/B ATR system more advanced)

Airbreather/rocket

Partially reusable Expendable stages (Horizontal takeoff)

KEY: A/B = airbreather; ATR = air-turbo-rocket.SOURCE: National Aeronautics Space Administration, Langley Research Center.

●

ping, the orbiter would have a payload pod atopits fuselage, rather than an internal payload bay.The second-stage engines would be on theorbiter. Fully reusable configurations such asthis are believed (but not proven) to minimizecost per launch at high launch rates. The fullyreusable cryogenic tanks on both booster andorbiter are a critical technology requirement forthis option.A horizontal takeoff and landing air-breather/rocket, which would resemble the Germantwo-stage Saenger spaceplane (see later discus-sion in this chapter). This configuration wouldutilize the same technologies as for the AMLSrocket concepts summarized above, except thatit would use an advanced air-turbo-rocket(ATR) air-breathing engine for the first stage.This vehicle would be fully reusable.

These alternate configurations also span a widerange of reusability. The higher the anticipatedlaunch rate, the more attractive reusability becomesfrom the standpoint of cost.

Because development of an AMLS vehicle neednot begin until the mid to late 1990s, NASA coulddefer a decision on whether to start AMLS develop-ment until it has completed preliminary designs ofalternative vehicles in sufficient detail to estimatetechnological risk and life-cycle cost.

Critical technology needs for all AMLS conceptsinclude:

light-weight primary structures,reusable cryogenic propellant tanks,low-maintenance thermal protection systems,reusable, low-cost propulsion,electromechanical actuators,fault-tolerant/self-test subsystems, andautonomous flight operations.

Figure 4-2 illustrates typical technology needs fora fully reusable version of the AMLS. Althoughmeeting these advanced technology requirementswould be challenging, none is considered a “show-stopper.” Thus, most experts feel that this technol-

Chapter 4--Advanced Rockets ● 55

Figure 4-2--Role of Technology in Advanced Manned Launch System (reusable version)

KEY:

Reusabletanks

Smaller payload(compared to shuttle)

Appropriatecrew size

Advanced avionics and endurance

Common propellantOMS/RCS(no hypergolics)

Light-weightdurable thermalprotectionsystem (TPS)

Reusable,* low-cost engines

Light-weightstructures

OMS = Orbital maneuvering system; RCS . Reentry control system. design (tip fins)

SOURCE: National Aeronautics and Space Administration, Langley Research Center.

ogy could be available in time for an AMLS, sincethe AMLS would not be needed until after 2005.

PERSONNEL LAUNCH SYSTEM(PLS)

The Personnel Launch System is a new conceptthat stems from “The Next Manned TransportationSystem” (TNMTS) study organized by NASAHeadquarters. The TNMTS, a 2-year effort thatbegan in spring 1989, is now analyzing five primaryapproaches:

1. purchase additional orbiters,2. improve the current Space Shuttle system

(Shuttle evolution),3. develop a Personnel Launch System (PLS),4. develop advanced rocket-powered launch vehi-

cles (AMLS), and5. develop advanced launchers based on air-

breather technology,

JSC was named the lead center for the PLS optionas well as for Shuttle evolution work. NASA’SLangley Research Center will examine a lifting bodyoption6 for the PLS. The NASA centers, Marshalland Kennedy, would have major roles in developinga PLS but responsibilities for various tasks are stillto be determined.

As the PLS concept is so new, little can be saidabout it, including its potential cost. It was promptedby the desire for a crew-carrying vehicle that couldbe available sooner than an AMLS and would alsobe cheaper and simpler. It could range from a smallthree- or four-person transport (similar to the spacetaxi and return concept described in ch. 6) to avehicle sized to carry as many crewmembers as thepresent Shuttle.

A PLS vehicle could in principle be designed tobe highly flexible and might also be configured tocarry cargo as well as people. For example: it mightbe designed to carry small logistics payloads for the

6SU ~h, b for de~tiptions of lifting bodies.

56 ● Round Trip to Orbit: Human Spaceflight Alternatives

Space Station. It could also be designed to launchcapsules capable of providing emergency rescuefrom the Space Station.

CREW-RATED ADVANCEDLAUNCH SYSTEM

Several aerospace experts have suggested thatshould the United States decide to build the ALS, itwould be prudent to give this vehicle the capabilityto launch people as well as cargo. If affordable,resilience in human access to space is a desirablefeature, since today people can only be launched onthe Shuttle, which continues to be susceptible tomajor delays or loss from attrition.

The ALS Civil Mission Needs Statement requiresthat the ALS “provide a highly reliable (above 99percent), fault-tolerant launch system capable ofhaving a man-rated variant.”8 ALS stages or compo-nents could be used in an AMLS, and a crew-ratedALS launch vehicle could be used to launch a crewrescue vehicle (CERV-discussed in ch. 6) oralternatives to AMLS that have been proposed byindustry (figure 4-3). Finally, it might be used tolaunch a PLS.

Current crew-rating procedures require the use ofgreater strength margins in structural components,additional redundancy in subsystems, and addedoversight and paperwork in the design, manufactur-ing, and operation of a launch vehicle compared tonon-crew-rated vehicles. ’” Some officials in theALS program, however, feel that the ALS would beso highly reliable and robust that the additionaldevelopment cost or time required for crew-rating

the ALS would be small. As proposed, the ALS,which could use all-liquid propulsion, would bedesigned for high reliability and would include suchfeatures as “engine out” capability (the ability tocomplete the mission even if an engine fails tooperate), redundant electronics, and other highreliability features; and thus is intrinsically designed

At present, theremuch like a crew-rated version.11

no “ALS crew-rating program” per se. Althoughthe work statement for the ALS contractors doesstate that the ALS must “be capable of flyingmanned cargos,’ none of the contractors have yetfound a need to identify different cargo or crew-carrying configurations. ’2

Along with improved resiliency, a crew-ratedALS would have three additional advantages:

1.

2.

3.

if the crew-rated ALS were designed to carrya capsule like Apollo, crew escape could beeasier than with the Shuttle, and escape couldbe possible during the whole trajectory, unlikethe Shuttle from which escape is impossibleduring most phases of liftoff;the crew-rated ALS could launch a crew-carrying PLS; andthere may be cases where it will be necessaryto take personnel and cargo up to the SpaceStation but not down on the same mission. Inthat case, there is no need to risk an orbiter.

Redundancy in crew-rated launchers has manybenefits, including improved resilience. But it wouldcome at a cost. Policymakers would have to decidewhether to saddle the ALS with the additionaldevelopment and operating costs for crew-rating or

7Having ~und~t luch systcms (usually of difl~nt technological heritages) capable of accomplishing the desired mission so that if one launchsystem has to standdown, another can rapidly be used in its place.

‘Thomaa M. Irby, “Status of the ALS Program,” Proceedings of the Space Systems Productivity and Man@cturing Conference-V, Aug. 16-17,1988, El Segundo, CA. Another ALS Systems Requirement Document states that the ALS design ‘will not preclude human cargo’ (Thaddeus Shore,SDIO).

‘WhiU makea a launch system “man-rated” is open to variott.. interpretations. NASA is working on a consistent set of guidelines for crew-ratingspace systems. This document, still undergoing review, defines crew-rating as follows:

A man-rated space system inewporates those design features and requirements necessary to accommodate human participmts. This provides the capability to safelyconduct InamEd operations, including safe rucovery from any credible enmgwxy situation Man-rating is the process of evaluating and aastuing that the hardwareand software can rmet prescribed, safety tiented design and operational criteria. 1[ is an integral pan of the design, developmeztt, verification, management and cam-cd-. It c~u~ tighOU[ the operational life of the system.

(Guidelines for Man-Rating Space Systems-preliminary, Advanced Programs Office, NASA Johnson Space Center, JSC-23211, September 1988,p. 5.)

l~s wo~d ~SO m&e it mm difficult to reach the ALS goal of reducing vehicle and operations C05C8.1 l~r Vw ~~.v~w paylo~s, rn~y argue that a vehicle should ~ CreW-rti ~YWaY.1- -cm of ALS ~iWen is that g Iot@s for the ALS may reach as high as 6 or 7, which is survivable by humans but not ve~ comfortable.

In contrast, the Shuttle is deaigned for a maximum of 3 g’s.

Chapter 4--Advanced Rockets ● 57

Figure 4-3--Crew Emergency Rescue Vehicle (CERV)/Space Taxi and Return (STAR)

Titan Ill Titan IV

1995

CoreStage

1998SOURCE: National Aeronautics and Space Administration, Langley Research Center.

whether resilience would be better served by a PLSor a stand-alone LRB system.

STAND-ALONE LRB SYSTEMIf LRBs were developed as part of a Shuttle solid

rocket booster replacement program, or in conjunc-tion with an ALS engine program, these boosterscould be used to propel a stand-alone system capableof carrying people to orbit. Because the engineswould have already been developed, a launch systembuilt around an LRB could be cheaper to developthan an entirely new launch system.

FOREIGN CREW- AND PASSENGER-CARRYING VEHICLE

PROGRAMSThe United States and the Soviet Union are

currently the only nations capable of sending people

Single-stageto orbit

Mach 6 staging

I

Air turbo rocket/rockethorizontaltake-off

2005

to and from space. The Soviet Union has recentlydeveloped a reusable space shuttle orbiter that islaunched on its heavy-lift launcher, Energia.

The European Space Agency (ESA), Japan, theFederal Republic of Germany, and the UnitedKingdom are all in various stages of developing theirown reusable launch systems, some of which, ifsuccessful, would be capable of transporting humansto orbit. The designs for these launch systems stillexist largely on paper. Nevertheless, these countriespossess a high level of technological capability andcould develop crew-carrying vehicles if they wishedto make the necessary investment, For these coun-tries, building launch systems has become animportant part of decreasing their dependence on theUnited States and the Soviet Union for reachingspace. Developing crew-carrying capability wouldbe a national achievement signaling their status as

58 ● Round Trip to Orbit: Human Space flight Alternatives

major space powers, able to develop and use abroader range of advanced technology.

Non-U.S. concepts differ widely as to configura-tion, reusability, crew size, and payload capability,and their project status ranges from preliminarydesign, like the Hermes, to the Soviet Buran, whichhas already completed its first test flight. Except forthe Soviet shuttle, none of these systems yet pose acompetitive challenge to the United States. TheUnited States should monitor the progress of theseprograms both for competitive concerns and coop-erative opportunities in order to respond appropri-ate y.

Soviet Space Shuttle

The Soviet counterpart to the U.S. Space Shuttlemade its maiden flight on November 15, 1988.Lifted into space by an Energia booster (presentlythe world’s largest booster), the 100-ton shuttlenamed Buran (Snowstorm) remained aloft for twoorbits of the Earth, some 3 hours and 25 minutes. Thespacecraft is nearly identical in physical shape tothat of its American cousin (see figure 4-4), but itdoes exhibit several key differences. The primarydifference is that Buran lacks its own main engines,relying instead on propulsion provided by theEnergia to place the shuttle craft into orbit. Buranalso uses a set of small maneuvering thrusters toreach orbit and later deorbit.

Similarities between the U.S. and Soviet designsare striking. The delta wing, vertical tail structure,payload bay, window placement, as well as thermalprotection patterns are common to both vehicles.Initial reaction from Western experts held that theidentical profile of the two spacecraft had saved theSoviets years of development time and expense bycopying U.S. plans. Soviet space engineers claim thesimilarity derives from the same mission objectivesof both craft: ferrying people and payloads into Earthorbit and maneuvering from space to a runwaylanding. Soviet reports state the Buran can place66,000 pounds of payload into orbit and return fromspace with 44,000 pounds. ’s The Soviets claim thatspecial-purpose missions using Buran can last up to30 days. Eventually, four flights per year areenvisioned using these shuttle vehicles.

Figure 4-4--Soviet Space Shuttle Buran andMir Space Station

35

30 30.

25

15

I meter

SOURCE: Teledyne Brown Engineering.

In some respects, the Energia-Buran is moreversatile than the U.S. Shuttle. For example, theEnergia rocket can launch an orbiter, or it can belaunched without an orbiter, in which case it cancarry a payload weighing more than 220,000pounds. It has four reusable first-stage boostersclustered around an expendable second (“core”)stage, which has four engines. First- and second-stage engines are ignited on the launch pad, and,because all engines use liquid fuel, they can be shutdown on the pad or in flight to abort a launch if oneor more fails to achieve sufficient thrust. In somecases the orbiter may still reach orbit, even if anengine has been shutdown during flight. In anyevent, the vehicle is expected to maintain controlledflight-to an emergency landing site if carryingcrew, or to a place where it can ditch or crash withoutendangering people or structures.14

Perhaps the most interesting feature of the Sovietapproach to winged space flight is the Soviet abilityto use automated landing systems. Buran’s firstflight was unpiloted and relied on ground controllersfor on-orbit maneuvering, Buran then used onboardcomputers to carry out an automatic approach and

13T’ a 100.~i high orbit; sw U.S. Department of Defense, Soviet hlifilu~ power, 1988.Iq_j. Gubanov, Prmda, July 30, 1988, M cd., p. 4. [in Russian]

Chapter 4-Advanced Rockets ● 59

landing at a special shuttle runway at Baikonur. 15

Three parachutes slowed the shuttle vehicle to astop.

By contrast, although the U.S. Shuttle fleet doescarry some automated landing equipment,l6 astro-nauts to date have vetoed its use below a certainaltitude. The Soviet technology used for Buran’sautomatic flight ability appears to be coupled to thehardware developed for the Tu-204, a new Sovietmedium-range twin turbofan aircraft.

Reports remain sketchy as to overall capabilitiesof the Soviet shuttle design. Six Soviet shuttlecraftare believed to be in various stages of construction.Another shuttle, named Ptichka (little bird) isexpected to be launched next. As many as 10individuals can be accommodated in the Buranshuttle, Soviet experts have stated.

The Soviets have modified MiG 25 ejection seatsfor use in its space shuttle when it makes a pilotedflight, Soviet engineers state that the ejection seatscan even be used when the shuttle is on the launchpad. The maximum speed at which they can be usedis Mach 3.17

Soviet Spaceplane 18

Still an enigma to the United States is the SovietUnion’s subscale prototype spaceplane and whatpart it plays in their space program. This l-tonwinged mini-spaceplane (see figure 4-5) in its firstfour flights between 1982 and 1984 orbited Earthonly once and touched down in water. It has by nowpossibly made a dozen flights.

The Soviet mini-spaceplane program resemblesthe effort undertaken in the 1960s in the U.S.Dyna-Soar program, and the European Hermesproject presently underway. Some U.S. expertsspeculate that it was designed to evaluate theaerodynamic and reentry characteristics of the muchlarger Soviet shuttle. Others theorize that the planecould be built for quick launch and turnaround, aswell as for occasional reconnaissance. A full-scalespaceplane, capable of runway landings, is expected

Figure 4-5-Soviet Spaceplane

SOURCE: Royal Australian Air Fore@.

to fly with two to three cosmonauts, launched by theSL-16 booster. Some experts have hypothesized thatthe spaceplane could serve as a crew escape vehicleattached to the Soviet Mir space station.

European Space Agency Hermes Spaceplane

This piloted shuttle has been championed byFrance as an effort to provide an independent,European, crew-carrying launcher. As a small,winged spaceplane 15 meters long with a wingspanof 10 meters, Hermes could carry a crew of three andslightly over 2 tons of payload to a 500-km orbit. Thespaceplane itself originally was meant to be com-pletely reusable but as now envisaged, the vehiclewill have an expendable adapter called the HermesResource Module that will separate from the space-

15Rw-n~y, *C SovletS have exwes~ concerns about their automatic systems, and cite this m one reason for delaying the next flight (which willcarry no crew) until 1991. The first crew-carrying flight may not occur before 1992.

l~e U.S. Shuttie is not fully automatic as pilots must brake artd steer it on landing. Automating these tasks has been proposed, however--- Ch. 2.17L$wCe, jMuq.Febmq 198$I! P. 5~.

Inpeter M. Banks and Sally K, Ride, “Soviets in SpWe, ” Scientific American, February 1989.

60 ● Round Trip to Orbit: Human Space flight Alternatives

plane and burn up during reentry. Current missionplanning calls for an initial unpiloted test launch onan Ariane 5 in early 1998, crew-carrying flightsbeginning in late 1998 or early 1999, and regularoperational flights twice annually starting in 1999 or2000. Total development cost for the Hermes projectis estimated at over $4.5 billion,19 with most of thefinancing coming from France and the FederalRepublic of Germany. Two vehicles would initiallybe built, leading to an eventual fleet of four. EachHermes could make two to three flights per year.One recent Hermes concept is shown in figure 4-6.

Japanese HOPEThe Japanese National Space Development

Agency (NASDA) is studying a concept called“HOPE” (H-II Orbiting Plane), an unpilotedwinged mini-shuttle. HOPE would be launched atopthe Japanese H-II launch vehicle, an indigenouslydesigned and built expendable rocket, expected tofly in 1992 (see figure 4-7).

Japan is considering HOPE for several missions,such as delivery and return of materials from theJapanese Experiment Module (JEM) of the interna-tional Space Station, polar-orbital missions, andwhat the Japanese call “space technology experi-ments. The HOPE design still is emerging butcurrent plans call for it to land horizontally. NASDAsuggests a first flight date in late 1996.20

HOPE actually may be Japan’s first step towardan autonomous piloted spaceflight capability earlyin the 21st century. A national “Advisory Commit-tee on Space Plane’ recommended a broad researchand development plan for a fully reusable aerospaceplane. The committee urged that the Space Plane“be promoted as an important national R&D pro-ject,” but promised that the program would beopened to international cooperation in its earlystages.

German Saenger

The Federal Republic of Germany is studying thistwo-stage launch vehicle (figure 4-8), which wouldbe a piloted craft carrying a cargo plane piggybackinto space. Stage 1 would be a large hypersonic

aircraft propelled by six hybrid turbo-ramjets andwould be designed to take-off and land horizontallyat several large European airports. For flightswithout a crew, the second stage would be of anexpendable cargo upper stage (“ Cargos”), capableof placing 33,000 pounds into LEO or 5,500 poundsinto GEO. Cargus would use a single LOX/LH2engine, the same powerplant being developed for theAriane 5 core. For piloted flights, a spaceplanecalled “Horus” (Hypersonic Orbital Upper Stage)would serve as Saenger’s second stage. Its presentconfiguration gives it the same basic shape asHermes with twice as much volume. Designers planfor Saenger to operate as a ferry craft with limitedorbital duration—perhaps not more than 1 day.Horus could lift 4,000 to 6,000 pounds of cargo, plustwo pilots and four passengers to a 270-mile orbit ata 28.5-degree inclination. Horus would use twoLOX/LH2 engines similar in size to the U.S.Shuttle’s SSMEs.

A major incentive for developing Saenger is thepotential reduction in space transportation costs.The West German Research Minister states that, intheory, Saenger has the potential of reducing thecosts of placing payloads into orbit from about$3,500 per pound to $500 per pound. Recently, the

19’(cm~a Joins Hermes program, “ Avktion Week and Space Technology, Mar. 13, 1989, p. 30.mst~eyw.K~debo,‘‘Jw~e~ f@fining u~~~ HOPE ~biter for pl~cd 1996 Lalmch, ’ Avi~iOn Weekati Space Technology, Apr. 3, 1989,

pp. 57-58.

Chapter 4-Advanced Rockets ● 61

Figure 4-7— Japanese HOPE Figure 4-8--Federal Republic of Germany Saenger II

SOURCE: Japanese National Space Development Agency.

German Government agreed to fund the initialdevelopment work for Saenger with a first demon-stration of components between 1993 and 1999. Theprototype could be finished by the turn of thecentury. Development work carried out through theEuropean Space Agency (ESA) could begin as earlyas 2004. For the first phase, which will run to the endof 1992, the West German Research Ministry isproviding $122 million, 7 percent of its total budgetfor space activities. The German Aerospace Re-search establishment is contributing $48 million,and the German Research Society $17 million. Afurther $22 million is being invested by the West

German aeronautics and space industry for a totalinitial commitment of $209 million.21

SOURCE: Messer schmitt-Bolkow-Blohm GmbH, Space Systems Group.

United Kingdom Hotol

As early as 1978, British Aerospace Corp. beganstudying the prospects for lowering the cost ofsatellite launchings by 80 percent. Out of thesestudies, and revolving around a new engine pro-posed by Rolls-Royce, British Aerospace draftedplans to develop Hotol, a fully recoverable andreusable unpiloted launcher capable of taking offand landing from a runway and reaching orbit witha single stage (figure 4-9).

The heart of the project is Hotol’s propulsivepower, the still-secret Rolls-Royce RB-545, calledthe Swallow engine. This radically new hybridrocket engine is designed as a dual-rotor motor, firstburning onboard liquid hydrogen while liquefyingoxygen as the vehicle moves through the Earth’satmosphere. Above the atmosphere and on into orbit,the engine then uses onboard liquid oxygen to bumthe fuel. This engine concept would halve theamount of liquid oxygen required to be carried attakeoff thus dramatically reducing the weight of thecraft compared to one using a conventional booster.

Hotol is designed to reach orbital velocity at aheight of 90 km. The craft would then coast into astable operational orbit of about 300 km. The designgoal is to deliver 7 to 11 tons into low-Earth orbit ata cost of $300 per pound. Hotol is designed tooperate without human crews aboard for mostmissions, although a pressurized habitable modulecould be situated in the payload bay to supportastronauts, not as pilots, but in an “executive role. ”

2Jw Kirk, ‘ ‘Germany Enters l-ly~rsonic, Race, ’ Science, VO1. 243, Mar. 10, p. 1284, 1989.

62 ● Round Trip to Orbit: Human Spaceflight Alternatives

Hotol mission scenarios call for the vehicle to launchand recover satellites, service space stations andplatforms, conduct microgravity and scientific ex-periments, and carry out military operations. A fleetof 5 vehicles was planned, each with a 120-missiondesign life. Hotol’s recurring launch cost wasestimated at just $5 million.

Hotol design teams completed a 2-year, $4million proof-of-concept study in late 1987. Theyoutlined a follow-on “enabling technology” pro-gram that would lead to a development start in 1994and a first flight by Hotol near the year 2000. Despitethe momentum built up by British Aerospace andRolls-Royce, the U.K. Government, in July 1988,refused to provide a requested $9 million per year for3 years to continue Hotol’s research and develop-ment. The two firms were to match the governmentfunding made available through the British NationalSpace Centre. Hotol’s future may depend on interna-tional participation but this would require declassifi-cation of the Swallow engine, something that theBritish have been loath to do.

Figure 4-9-United Kingdom Hotol

SOURCE: British Aerospace.