14

C-4

"Ted was not yet convinced that you can detonate a high-explosive charge in close proximity to a structure without causing substantial damage to it," remembers Jaromir (Jerry) Astl, born in Czechoslovakia in 1922, who joined General Atomic in late 1958 from Ryan Aeronautical office for advanced design. "We were after a quick, easy test to settle the dispute. After many ideas were discussed in a staff meeting one afternoon, we piled into a car and went shopping—to a nearby supermarket—for a suitable spaceship model we could blow up. Within minutes we found a set of three matching mixing bowls made out of fifteen-mils-thick stainless steel. The next day I assembled the 'Spaceship Number One'—an aluminum pusher plate with three mixing bowls sitting on top of each other and all components held together by a long bolt anchored to the pusher. The assembly looked more like a beehive than a spaceship."

The first flying model of spaceship Orion was launched that night shortly after 7 P.M. "I detonated the approximately 60 grams of C-4, suspended 10 inches under the center of the pusher plate," says Astl. "A few coyotes and some deer got scared, a skunk in the nearby bush fired back, but 'Spaceship Number One' was unharmed."

The active ingredient in C-4 is RDX, or cyclotrimethylenetrinitramine, bound by wax, oil, and polyisobutylene plasticizer into a stiff dough. C-4 resists detonation under all but severe impact and will bum harmlessly if ignited with a match. RDX, first widely used in World War II, detonates (or goes "high order") at 8,700 m/sec (20,000 mph) producing pressures of over 300 kilobars, or about 5 million pounds per square inch. Besides its application, in plastic form, to sabotage and demolition, it can be formed into precise, stable castings used in fabricating implosion assemblies for nuclear bombs.

The trade secrets of nuclear weapon design are in large part the details of how to shape and detonate conventional high explosives so that a convergent shock wave produces the pressures required to turn an otherwise subcritical mass of fissile material into a bomb. Project Orion's physicists were quick to apply their knowledge of high explosives to nonnuclear experiments aimed at gaining a sense of how Orion would perform. Flying models were propelled with high explosives; one-shot explosive-driven plasma guns were used to test ablation; spherical high-explosive charges were used to simulate pusher-plate and shock absorber stress; sheet explosive was used to model the pusher-plate pressure pulse. "It was at least as important to find out what not to do as what to do," says Ted. "So we tried a lot of different things, some of which just blew all to pieces."

Small quantities of explosives were obtained informally by Carroll Walsh, a retired Navy electronics technician hired by Ted in August of 1958. Walsh had worked at the Navy Electronics Laboratory at Point Loma, where C-4 was used for sonar tests. "Commander Walsh could get anything, because he knew everybody," says Astl. "When I needed those high-resistance detonators with long leads, he said, 'Well, I know they have them there but they are guarding them like hawks because they are expensive.' Half an hour later he was back and I had six of them." Larger quantities of C-4 were requisitioned through Walsh's contacts in the Navy and delivered by barge from the regional explosives depot at Seal Beach. "We would get in there and take this dough and mix it up," says Walsh. de Hoffmann wanted to use unmarked trucks to transport explosives among the different General Atomic test sites, but, says Walsh, "the highway department insisted that we paint the damned things yellow. And de Hoffmann raised hell because people would see General Atomic, and then see the explosive truck coming back and forth, so he said, 'You can't do that!' " Walsh, who knew when to bend the rules and when to follow them, made sure the explosives were carried in yellow trucks.

Jerry Astl owed his expertise with high explosives not to Los Alamos but to the Czechoslovakian underground. Upon receiving his degree in aeronautics during the German occupation of Czechoslovakia, he was assigned to the A.T.G. Leipzig (Messerschmitt) aircraft design bureau, overseeing work at a nearby factory that was building and upgrading sections of German warplanes, initially piston-driven fighters and later the Messerschmitt 262 twin-engine jet. The limits of aerodynamics, engineering, and armament were being pushed to the point of failure, with safety margins suspended for the duration of the war. "On takeoff you were loaded so heavily that if anything went wrong, you wrote not just the airplane off but the pilot as well," he recalls. "There were no ejection seats." Airframes and control systems had to withstand accelerations in the same range as the early Orion vehicles designed to lift off at two-bombs-per-second from the ground. "The fighter planes we were designing were for around 7 to 8 g's, and some of them were designed to 10 g's standard, when you expected high-speed dive-bombing and you had maximum loads. And they worked—no problem. So you can build a structure that will not weigh too much to fly, yet it can take a pretty damn good shocking."

Jerry Astl (foreground) and Jim Morris inspect the pusher plate of an early 1-meter tethered model, in front of a high-explosive storage bunker at the Point Loma test site.

Astl worked for the Germans during the day and against them during the night. "Nobody knew more than two other associates," he explains. "That way if you get caught you can divulge no more than two names in torture and there was hope that sooner or later you get somebody in that chain who will simply not talk." The saboteurs concentrated on communication lines and railway switches, where small amounts of high explosive had maximum effect. "You learned it by hard knocks," Astl says. "But I must have been good at it because I survived. A lot of people didn't, because we were working with explosives we didn't know. We had to steal them from the Germans. And especially the plastic-explosives, they were guarding it pretty tight." In mid-1944 Astl's moonlighting was found out. "They finally traced down that this group was being managed from the A.T.G. Messerschmitt design office," he explains. "The Gestapo caught up with our group and started eliminating them, brutally." A German supervisor, risking his own life, gave Jerry fifteen minutes' warning and he disappeared into the full-time underground. "At the peak of power our group had five hundred fifty to six hundred people we could put in the field. When we laid down our weapons there were thirty-two left. And two in hospital who didn't survive."

Astl learned about convergent shock waves by forming shaped charges with his own hands. He also discovered, long in advance of Orion, that it was possible to blow something up without blowing it apart. "We once tried to blow up a bridge—it was near the end of the war when the Germans were retreating, just running from the Russian army," he explains. "It was a bridge that would have stopped probably half of that retreating army, and it was built in the old professional Czech way. We put all the explosives we had on the damn sucker, and we lighted it up. Biggest boom we ever created. I saw the whole bridge jump up and drop back, and you could drive over it again. It was incredible. We couldn't have put one ounce more explosive because we didn't have any. And the Germans didn't even know we tried to blow up that bridge, because it came right back down where it started from. There was a crack in the pavement on both sides. When I was there in 1992, I went back to see what happened. That bridge is still there. Nothing happened!"

After the Nazi exit from Czechoslovakia, Astl became a county secretary of the Union of National Revolution. He began arguing with Rudolf Slansky, secretary of the Communist Party, who warned him (not long before his own execution) that he had better watch his step. Astl escaped to Vienna. The American embassy turned him away but the British embassy provided shelter, and, when they saw that be had maps of the border region, asked him to guide a group of other refugees, including a Hungarian whose legs had been shot off at the knees by the Russians, in the next stage of his escape. "It was bad enough to get through the guards on our border, but to cross from Russian-occupied Austria to Western-occupied Austria was ten times worse." They reached the demarcation line and waited in the forest for nightfall to try to get across. Every time Astl probed between the Russian watchtowers, "there would be suddenly a burst of machine-gun fire, the floodlights will zero on the spot when they were shooting, and there will be four or five Russian soldiers with burp guns going to see what they shot." Things looked bad, especially for the Hungarian amputee. Astl saw that the Russian firepower offered them a chance. "When you fire machine guns during the night, you are not going to hear anything for half an hour later. When you look in these searchlights, you are not going to see much. So the next night I got everybody positioned and before long, there was gunfire and searchlights. I said, everybody, get going, forget about noise, forget about being seen, we have to cross in a few seconds. We dragged that guy by his hands and we got beautifully across."

Astl spent a year in a refugee camp in Ludwigsbourg, where his weight dropped to 96 pounds before the International Refugee Organization took over and the food allowance was boosted from 900 to 1,400 calories a day. Using a 24mm x 24mm "Robot" gun camera salvaged from a Messerschmitt fighter and film secured in trade for American soap, he went into business taking ID photos of fellow refugees so they could apply to foreign embassies for immigration papers allowing them to leave the camp. In April 1949 Astl sailed for Boston on the SS Mercy, a converted hospital ship, arriving with one dollar, a few words of English, an extreme distrust of Communists, and the name of an uncle in Baltimore who had sponsored his entry to the United States. He worked first at a printing plant and then at a shoe factory where he was paid $32 a week—"But boy, I was happy like a flea on a fat dog!" When the projectionist at the employee cinema got sick, Astl took over the after-hours job and kept it for two years. "I learned the English by showing movies," he says. "I usually grabbed somebody who spoke Czech. I said, 'Look, you are going to find out now how beautiful it is inside the projectionist room, and all you have to do is tell me what they are talking about!' You learn very quickly if you see and hear it three or four times in a row."

After saving enough money to buy a used 1950 Mercury Astl left the shoe factory for a tool-and-die-making job, quickly advancing to a position as engineer. He took up recreational flying and joined the local sailplane fraternity, in which Czechs had long excelled. After three more years he became an American citizen, bought a brand-new 1955 Mercury, and, encouraged by a glider pilot who worked for Convair in San Diego, piled his belongings in it and headed west. "I said I'm not going to stop until I hit the Pacific Ocean, and that's what I did." After two weeks living in a trailer in El Cajon, he found work as an aeronautical engineer, first with Rohr Aircraft (on the Lockheed Electra), then with Ryan and Douglas (on the DC-8). When Project Orion received its initial funding from ARPA, he obtained an interview with Ted and was hired by General Atomic, where he gained a reputation for solving problems when the engineering got tough. "I was always asked to do the impossible," he says.

During Project Orion, Astl published only a few reports. "I didn't have time to write," he explains. "There are a type of people who thrive on writing reports and there are people who can do miracles with their hands and with their ingenuity but they see writing as a waste of time." Astl's Multi-ICBM Weapon System (November 1959) anticipated the MIRV (Multiple Independently-targeted Reentry Vehicle) missiles that began to shift the strategic nuclear landscape in the 1970s. In 1959 the challenge was how to get a single thermonuclear warhead launched by a single intercontinental ballistic missile. Astl saw that Orion offered the possibility of launching multiple warheads at once.

"The Air Force needed some justification to give us more money and sent a request for us to come up with ideas of what Orion can be used for, military applications," Astl recalls. "To me it was obvious that the best use would be to make smaller Orion vehicles, and put aboard maybe 15, 20, or 50 individually targeted nuclear warheads together with maybe 150,200 decoy 'warheads.' You launch that, they will pick it up on radar, and until you reach apogee they will see one missile coming at them. Then you launch your decoys, and suddenly they see swarms of them. There is no way they could handle that. After the defenders deploy their defense missiles, then you sublaunch your real warheads. They will be very small, because all you need is just to change a few degrees of the trajectory to route them to their targets. There would be no defense against an approach like that."

Astl saw the potential military applications of Orion not just as an excuse for supporting space exploration, but as a necessary show of strength. "Russian people, if you get them sober, will split their heart with you," he says, "but you get them in a bunch, give them a bottle of vodka, and you don't know if they are going to cut your throat, or what." He got along especially well with Captain Donald M. Mixson, the project officer assigned to Orion by the Air Force Special Weapons Center, who, among his other duties, had to sell the project to the generals at the Strategic Air Command. "I wrote a small proposal," Astl remembers, referring to the multiple-warhead plan, "and Mixson said, 'This is really something!' " If the prospect of incinerating fifty Russian targets at once was more than SAC was comfortable with, Astl had another suggestion. "I said, if this is not acceptable, why don't we put aboard Orion a hundred tons or so of tranquilizer powder, and spread it all over the Russia. Later we can have a tea party with them instead of war." According to Astl, Mixson liked the idea. "He was probably ready to spray it over Washington!"

Ed Day (left) and Reed Watson preparing a pneumatic shock absorber test at Torrey Pines, early 1959.

Astl's Nuclear-Pulse Propelled Vehicle Launching System (May 1960) suggested how Orion vehicles could be boosted to a certain initial velocity out of a shallow launching silo. The meter-diameter model had refused to fly until boosted by a small initial charge of slow-burning gunpowder, as Freeman Dyson had predicted in his December 1958 study, Optimal Programming for Vertical Ascent in Atmosphere, where he concluded that "in particular, the starting velocity V(0) at height zero is not zero."[154] As Astl explains it, "Where do you consume most of the fuel? At the start point!" He envisioned a fleet of small, silo-launched Orions as a retaliatory force. The underground silos would serve as launching tubs, protect the ships against surprise pre-launch attack, and provide for convenient burial of any launch-pad mistakes. "If it is for defense you don't need to worry one hundred percent about safety, and if you have it underground and something goes wrong—nothing happens. You just bring in bulldozers and smooth off the top after an explosion. You leave it right there."

Astl's third Orion paper, Split-Cylinder Long-Stroke Shock Absorber System, was issued in February 1961. The original idea for Orion's shock absorbers was to use inflated tubes, layered in concentric rings. This was simple and lightweight but had serious drawbacks, notably, as Don Mixson put it after a visit to General Atomic in July of 1958, "a very serious problem is what happens in event of a dud. In this case the shock absorber is flying out and must be built to take this back motion."[155] One thousand tons of pusher plate rebounding off into space is not an easy thing to stop.

As the design of Orion evolved, more and more of the pusher-plate acceleration (and rebound in the event of a misfire) was expected to be handled by longer piston-type shock absorbers, but the pneumatic rings remained the first line of defense. Astl worked on a series of tests of this concept that went on for seven years—beginning with the first tests at Torrey Pines in 1958 using inner tubes wrapped in duct tape to a final high-speed photographic analysis of the behavior of pneumatic shock absorbers under high-explosive loads, which continued into 1965, after all other experimental work on Orion had stopped.

"The whole exercise with the tubes, to me, was futile," says Astl in retrospect. "You know darn well you cannot apply this principle of supporting the pusher plate like this in space. It's absurd, you could never get it to work there. All materials lose elasticity in the cold. You're going to fire once and you are going to have it all over the stratosphere. Two shots and it will be all over space." The requisite elasticity would be in the gas, not the walls of the tubes, which would have been built like steel-belted radials, but Astl may be right. Six officials from Firestone, all with secret clearance, attended a briefing on Project Orion held for prospective contractors in Los Angeles on July 23, 1959.

"Have you ever seen a steam catapult?" asks Astl when asked to explain his split-cylinder shock absorber plan. "Like for an aircraft carrier—but in reverse. You use the same principle; a steam catapult is actually a split-cylinder shock absorber or actuator. If you have a split cylinder you cut the stroke to half of what you need with a conventional one. I was amazed when I found out they actually had something like this. I had never been on an aircraft carrier, and I had not the slightest idea how the thing operates. I mentioned the idea to Carroll Walsh, and he said, 'This is a steam catapult!' He made it possible for me to visit an aircraft carrier and we looked it over and sure enough, there it was. So the technology is pretty highly developed and could be adapted.

"They assumed very dangerous stuff—they assumed that they licked the shock absorber problem," Astl warns. He envisions a completely different approach. "You have two masses," he explains. "You have to absorb the major shock from the explosion, by pusher plate. The biggest mass sits on top of it. I would reverse that. I would use shock absorbers to just protect the payload, then you can design something much more reasonable. I prefer the pusher plate, the motor, to be a structural unit that stays together. You are going to take impulse without shock absorbers and you are only going to protect, with the shock absorbers, certain defined parts of the ship, inside the major structure. You can make the travel longer. You can adjust the acceleration as you want it." Astl arrived at this idea through discussions with Ted. "I pried out of him information as to how closely he thinks he can control the size of the acceleration he can give to the pusher, with his little tiny nuclear bombs. He said, 'Well, in future we can probably do much better.' And that's what gave me the idea that you build a structure that can take it, and let just the payload move."

Ed Day loading canister #4, containing 2.3 pounds of C-4 high explosive, into position on the meter-model charge ejection stack.

The final part of Project Orion that Astl worked on—with experimentalist Ed Day, who had initiated the Orion testing program six years earlier at Torrey Pines—was a proposed high-explosive test facility for conducting full-size tests of a 10-meter-diameter Orion engine, upside down. This was invoked as General Atomic s answer to NASA's question, "How can NASA develop a space vehicle that cannot be tested on the ground?" NASA administrators were reluctant to support anything that had to be launched full-fledged, as a bird is pushed for the first time out of its nest. In the final two years of Orion, General Atomic countered with a "Ground Development Plan." Part of this plan was a "Repetitive-HE-Pulse Test Facility" designed to test a full-size Orion engine by mounting it upside down next to a 100-disc jukebox delivering 32-foot-diameter, 3/4-ton discs of PETN high explosive, detonated at one-second intervals above the pusher plate.

"With this test facility the nuclear-pulse engine can be tested, developed, and qualified for flight testing and then brought to a preliminary flight rating (PFR) on the ground," it was argued. "Two different HE-pulse unit delivery systems are considered. A fully mechanical system to move the HE pulse unit from a storage silo to the final detonation position directly above the pusher of the engine is described in considerable detail, and a system using rocket thrusters to provide the required driving force is briefly discussed."[156] Coauthor and lead engineer on this proposal was German aeronautical engineer Hans Amtmann, who had begun his career in the shipyard that built the Bismarck, where he helped design the Blohm & Voss BV-238, a long-range flying boat powered by six 1,800-hp Daimler-Benz engines and, at 100 tons, the heaviest airplane of its time. Amtmann had worked on top-secret German design projects during the war, some relying on rocket thrusters to take off. Moving 1,500-pound disks of high explosives around with rocket thrusters might not have occurred to anyone else. "A test stand of this type, because of the character of its operation, will have to be erected in an area remote from densely populated areas," Amtmann advised.[157]

Astl, however, thought it a waste to expend so much high explosive on test-firing Orion upside down. "To hell with that, let's build it so that we could put a cabin inside," he argues. "If we have to fire so many damn charges on it, let's take it for a free flight. Just have parachute with a spare, then on top of the trajectory the pilot bails out. Ed Day was horrified. Of course, he was not a flier. I was tempted. If I would have stayed there some crazy ideas would have popped up."