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SPACE TECHNOLOGY

World's Largest light Gas Gun Nears Completion at Livermore BRECK W. HENDERSON/LIVERMORE, CALIF:

Construction of the world's largest two­stage light &as gun,. a 425-ft.-long set

of steel tubes laId out across a remote test site east of here, is about to be completed by physicists and engineers at Lawrence Livermore National Laboratory. -

When the final pieces are in place late this fall, the Super High Altitude Reo ~arch Project (SHARP) gun is expected to send a projectile weighing 5 kg. ill Th,) hurtling into a pile of sandbags at 4

1Oii.,{sec. (8,945 mph.). -, ~ no(~ It should be the biggest projectile ever

fired at such velocity, but John W. Hunt­ew he principal scientist for the SHARP project, has more ambitious goals for his gun research.

Hunter and other gun experts believe it is feasible to build light gas gunS7ajiiilit'e of finn a loads of several tons into low

r orbit or unar orbit. The SHARP gun project, started about tlfree years ago, is the first step in the development pro­cess (AW&ST July 23, 1990, p. 78).

However, building a classic light gas gun with a useful payload would be ex­tremely difficult, experts say. Fortunately, new technology since work began on SHARP is expected to allow gun builders to sidestep me engtneenng problems In­

herent in a conventional, two-stage gun:-Researchers at GT-Devices, In Alexan­

dria, Va., have developed a means to ~eat h dro en gas electricall and in'ect it into t e Sl e 0 t e un barrel as the ro'ectile is aunched. Anot er new concept devel­oped at Brookhaven f'latJon'1it Laboratory would use particle beG heaters to rapidly heat hyarogen for use in the gas gun.

these Ideas could ehmInate the need for a pump tube and its huge piston, thus revolutionizing the design of big gas guns and removing most of the engineering problems, Hunter said.

Although the cost to build a large-scale super gun, using the new technology, could reach several billion dollars

1 it has

potential to be a much cheaper way of getting materials needed for space explo­ration into orbit. "It seems silly to dedi­cate a shuttle launch to putting water into space," one scientist said.

Hunter has calculated that a big gun could put 90% of the materials needed for space exploration into low Earth orbit for a fraction of the cost of space shuttle launches. The only items that could not be gun-launched are those that would not survive acceleration of about 1,500g.

LOWER LAUNCH COSTe:z.if.,pA~ Hunter and his colleagues et the cost at about $7 billion to build nd operate for 10 years a gun capable of aunching ~ metric-ton projectile at 9 km./sec. (5.6 ft./ fec.). if the goal is low Earth orbit, the projectile could be about 70% payload, resulting in costs of about $500/kg. Shut­tle launches cost about $20,000/kg. of payload.

With a jar er booster rocket, the same projectile cou e e into lunafOfbit w Ich many Mars mission p anners be­lieve is the best place from which to stage a trip to Mars. Payload would be reduced to 1-2 tons, resulting in a cost to lunar orbit of about $2,200/kg. The calculations assume a 400 metric ton per year launch rate in both cases.

Soon after SHARP fires its initial test shots into sand bags, Hunter plans to move the gun from Livermore to Vanden-erg , were it can be fired into tbe

Super High Altitude Research Project's two­stage light gas gun nears completion at law­rence livermore National laboratory's Site 300. It will fire 5-kg. projectiles at 4 km./sec.

AVIATION WEEK & SPACE TECHNOLOGY/August 10, 1992 57

SPACE TECHNOLOGY

Hydrogen gas is compressed inside the high pressure chamber at left. It then boosts Ihe projectile down the gas gun's launch tube (bot­tom right).

million over three years. "My hat's off to John [Hunter] because he has done a lot with a bare bones project through very astute technical and political work," Hal ~t, manager of Titan COR?:' 's Physics Applications Div., said. SWI 's company manufactures li!~ht gas guns for use in scientific research. - .

The design of the high-pressure cham­ber where the two stages of the gun come together was the most difficult part of the SHARP project. The chamber, wei~hing

SHARP gun is expected to be transported to Vandenberg AFB, where the launch tube will be elevated and projectiles fired to a height of up to 450 km. (280 mi.).

40 tons, is made of AF-1410 high-co­balt, high-nickel steel, the toughest steel alloy current­ly avaIlable, Hunt­

er-sai.d. It was made by National Forge, in Irvine, Pa.

The chamber is made of concentric layers that had to be shrink fitted with 20-70 mils

encased in a ceramic to generate and store beat and transmit it rapidly to hydrogen gas propeliant.

The ceramic particles in a gas gun would contain no uranium. The 300-400 micron beads would be heated by burning natural gas.

The particle beds store tremendous amounts of energy in a small volume. " We can extract about 1,000 mega 'oules per cu lC me er 0 artlc e e Jlm owe, ead of the Reactor Systems Div.

at Brookhaven, said. The beds can be re­heated and made ready to lire"again in just a few seconds. -

rogen pr~ure INJECTOR ADDS EXTRA BOOST reach si. inside the The highly efficient particle bed can raise c amber. the temperature of the hydrogen quickly - To Eiiild a two-stage gas gun large to the 1,500K needed, while the pressure enough to launch meaningful payloads, can be held to"a relatively benign 15,000-however, the pressure inside the high 20,000 psi. "This would ailow a large pressure chamber would go even higher. gun to be easily built with materials avail-

"Developing steel piping capable of able today," Powell said. withstanding this kind of pressure would GT-Devices, a research laboratory take significant advances in material sci- owned by General Dynamics Land Sys­ence," Swift said. terns Div., is building a gas gun for study-

The pump and launch tube piping for ing the lethality of kinetic kill vehicles for SHARP were fabricated by Cameron the Strategic Defense Initiative Organiza­Forge in Houston, Tex. tion. The gun being tested has launched

The BJookhaven and GT-Devices tech- 1.8-gm. projectiles to 7 km./sec. and 10 nology makes the design of a gUD mnch gm. ones to 4.6 kffi./sec. -simpler: The Brookhaven particle bed e gun as no pump tube, using a heaters were developed as part of the high-powered electric arc pulse to heat the Strategic Defense Initiative's previously hydfogen propellant, Derek ndman, the dassified space nuclear thermal propul- project manager at GT-Devices, said. The sion program (AW&ST Jan. 20, p. 20). electric arc heats the hydrogen in ISO mi-_

SDI's nuclear ro ulsion system uses crosec., which lS fast enough to allow pre­...:5~· ~-m~l~~~a!.l.r.1.lti.::.cl~e,,"s ..:.o::.f...le~nn~~ed~I.I..W"'·""'''''' cise timing of the hydrogen injection. The

gun has a hydro en in' ection rt art e arrel in addition to the

usual breech-fed configuration. By adding hydrogen as the projectile

passes, the veloclty can be mcteased wun.­out large increases in pressure. Hunter be­lieves the best design of a full-scale gun will incorporate many side injection ports spaced along the launch tube.

Tidman sald the G'I~ Devlces gun is the first of its kind, but testing has gone well so far. "The technology appears to be scalable to very large sizes and could out­perform conventional gas guns," he said.

When testing of the SHARP gun is complete, Hunter hopes it will find a home in a hypervelocity research pro­gram. 19lbert D . Witcofski, an aerospace engineer at NASA Langley Research Center, said its 4-in. launch tub,e is "get­ting big enough for on-board instrumenta­tion of a hypervelocity modeL"

NASA is studying construction of an advanced hyperveloclty research facility to support Its space aNI \:Hgb speed air­craft programs.

The SHARP gun could also prove use­ful to SDI because it can simulate a kinet­ic kill interceptor hitting a theater ballistic missile. " It could help solve theater mis­sile lethality problems," Hunter said. 0

AVIATION WEEK & SPACE TECHNOLOGY/August 10, 1992 59