Encounter With Tiber Page 5
Unfortunately, the next step, the X-33, had revealed where the problem would be. With the materials and fuels of the 1990s it looked like perhaps, just barely, it could be done. The DC-X experiments in 1993–95 were indeed encouraging—except that relative to fuel weight, the dead weight (percentage that wasn’t fuel) of the DC-X was 80 percent too heavy, and still it was too fragile to hold up under the forces generated in test maneuvers—and those forces were a small fraction of what could be expected in an actual trip to and from orbit.
The specific weak link became clearer with the tests in 2001. A single stage to orbit vehicle, in order to get to orbit, needed to be about 90 percent fuel by weight, and the fuel-engine combination had to be something with a very high specific impulse. The specific impulse is the number of seconds that one pound-mass of fuel can put out one pound of thrust.
One of the many confusing things you have to deal with once your imagination gets off the ground and into the sky is that weight and mass are different things. The mass of an object is the same no matter where it is; you could think of it as the amount of matter in the object, or as the thing that causes the object to have inertia. The weight depends on where you are; it’s the downward force of gravity and it can vary from enough to crush atoms (in a neutron star) down to almost zero (in orbit). Imagine a fifty-pound ball on a frictionless table: on Earth, you would need quite an effort to lift it; on the Moon you could lift it easily; on Jupiter you probably couldn’t lift it at all. But if you gave it a push to start it rolling, regardless of where it was, the same push would always start it rolling at the same speed; and the same amount of force would be required to stop it.
A pound-mass, then, is simply the mass that, on the Earth’s surface, would be pulled downward by gravity with a force of one pound. Thus on Earth, specific impulse is the number of seconds that a pound of fuel would burn with enough power to keep one pound of weight in the air. It is a measure of how much energy is left over after the rocket fuel has lifted its own weight and so of how much energy is left over to do anything useful.
The highest specific-impulses achieved with any common fuel could be gotten with liquid hydrogen—which was both very bulky (so the tanks would have to be large) and had a very small molecular radius (which meant it leaked out easily, through any kind of pores in the material enclosing it). So a tank to hold liquid hydrogen for an SSTO would have to be very large, extremely strong, highly resistant to cold (at normal air pressure, liquid hydrogen must be kept colder than minus 425 degrees Fahrenheit), very small in its pores, and extraordinarily light in weight. There simply was no such material, nor any prospect of it anytime soon. The X-33 tanks, made with the very best available materials, were much too heavy and leaked frequently, and some cryonic vibration tests suggested the risk of cracking over time. There would be an SSTO, someday, just like in Buck Rogers—but the time was not yet. And meanwhile, the most promising effort to find something to replace the shuttle had run into a dead end that would probably stay dead for at least another decade.
All this trouble was made far worse by the loss of the U.S. Hab. First of all it had been a large fraction of the total American investment in ISS, and as such it was a great deal of money down the drain, with little prospect of finding more. To replace that module, Congress would have to cut something—a couple of bombers, a major dam, an urban interstate spur, a dozen rural hospitals—that had already been promised to constituents somewhere and would have to be taken away from them. The prospects of this were zero; some money might be scared up somewhere, but nothing like what was going to be needed to replace the hab module.
For some of those in Congress, there was an obvious solution: shut down the space program, hand over the surviving three shuttles to some private commercial operator, and offer to let the Europeans, Japanese, and Russians buy out our interest in the ISS—something which they didn’t have the money to do, and which was even dumber when you considered that we were getting embroiled in the Cold Peace and badly needed Japan and Russia, at the least, as allies.
The president knew all this, of course—he could hardly have avoided knowing it—and he also knew that a large part of Congress had perfected the art of running against government programs. Where fifty years before, a congressman’s standard move to get reelected was to talk about the programs he had voted for, nowadays it was to talk about what he had blocked, stopped, frustrated, investigated, or marginalized. Now that the space program rested on international cooperation, it made an even better target—no one had ever lost a seat if he could run against the Russians or the Japanese, demanding that they “carry their fair share” (though they were spending a higher proportion of budget than the United States) and that they “stop their free ride on the U.S.A.” (even though for the last three years other nations had been lifting a lot of American payloads while we tied up the shuttles in the ISS, which had always been an American sponsored and operated project).
Against all this, there were two factors that were favorable: the president had a vision of where the space program fit into the national purpose, and like it or not the United States was going to have to do something, for a variety of reasons. First of all, there was the emerging Cold Peace with China. During the nineties, relations had veered all over the place between China and the other major powers, but for the last few years, several concerns had defeated every attempt to improve relations, and whether the United States liked it or not, we had drifted into the Cold Peace. First of all, under the gun to improve economic conditions in the countryside, especially in light of an abysmal human rights record that had alienated most of the young educated class and a ferocious population-control policy that had infuriated the peasant majority, the government in Beijing had responded by a program of “rural industrialization,” chiefly meaning that they were going to get electricity and hot and cold running water to everyone, ASAP, regardless of cost, to be followed as quickly as possible with refrigerators and motorbikes. That required energy, and as strapped as the PRC was for foreign capital, energy meant burning their vast reserves of coal at an unprecedented rate.
By 2000, the Japanese and Koreans, who had cleaned up their own environmental problems a decade before, were infuriated by the sheer quantity of foul-smelling gases drifting downwind onto them; Chinese diplomats in Seoul and Tokyo had to be escorted to and from their embassies by police and were often pelted with rocks and bottles by gas-masked protesters. Acid rain in the South China Sea and northern Pacific was killing the surface-level microorganisms upon which the ocean food chain depended, wreaking havoc on already-depleted fishing grounds and threatening the Asian part of the Pacific Rim with protein starvation. There were unmistakable signs of forest die-offs from southern Alaska down through British Columbia to as far south as Eureka, and measurable damage extended as far inland as Banff, Helena, and Pocatello; the scientific basis had been well established decades before when power plants in the American Midwest had been killing forests in Scotland and Norway, and better satellites and remote sensing equipment meant that this time the world didn’t have to wait for trees to die by the square mile before both the damage and the culprit could be identified.
All this earned China intense anger from its neighbors, but matters grew worse with a long string of “incidents” (the polite code word for “petty human rights outrages”) associated with the British return of Hong Kong to China in June 1997. Objectively speaking, China’s occupation and “firm hand” policy in Hong Kong probably had been gentler than the old Soviet Union’s occupation of Prague thirty years before. But Hong Kong was a modern and well-equipped city, intimately tied into the global information net, and China had wanted it for its modernity; they couldn’t shut down the modems, phones, and fax machines without destroying everything they had gained. So accounts of arbitrary arrests, police brutality, and sporadic rioting came not just from journalists interviewing refugees weeks or months later, as with earlier resistance to Communist occupations, but live as it happened, pou
ring over the broadcast systems and computer nets.
The embarrassment was compounded by China’s failures in space. The first Chinese astronauts had been scheduled for 1999, in a licensed version of the old Soyuz capsule mounted on a purchased Russian Soyuz launcher, but had not flown till 2001. Now the launch facility on the island of Hainan was expanding rapidly, and the Chinese began to demand agreements from Vietnam and the Philippines to place down-range tracking stations in the Spratleys, access to the Philippines for an abort field, and a dozen other requirements for operating a large sea-coast launch facility, all of which alarmed China’s neighbors. Persuaded by the U.S. and Russia, an embargo against oil and uranium for China was imposed; the Chinese burned still more coal and began trying to jam satellite broadcasts into China; and as Chinese missile “tests” splashed down off California, the design teams who had been working on space-based missile defenses, quietly and on shoestring budgets, for decades, suddenly found that they had more money and attention.
Matters had only gotten worse with the Chinese attempt to upstage the 2000 Olympics (which they had wanted for Beijing and which had gone to Sydney instead on human rights grounds). Their second attempt to launch a manned Soyuz had ended ignominiously with the rescue of Chinese astronauts from the South China Sea in front of foreign journalists.
The eventual success of their first crewed launch the following year did not seem to remove the sting. Following that success, they announced the intention to construct a permanent base on the Moon, with their first landing to occur in 2011, to coincide with the hundredth anniversary of the outbreak of the Chinese Revolution. Since that time they had been launching with, at the least, an aggressive frequency, apparently driving to build up a base of experience as quickly as possible. Though they had not suffered any more serious mishaps, there always seemed to be a chip on the shoulder of their press spokespeople, and it probably didn’t help that most of the global newscasters seemed to regard every Chinese launch as an occasion for crossing their fingers and holding their breath.
Thus China had become intensely determined to succeed in space, defiant on environmental and human rights issues and, because of the coal-burning problem and the festering embarrassment of Hong Kong, more and more antagonistic.
The foreign policy experts of both parties thought this was the wrong time to cut back on space; the Chinese had clearly signaled their intention to compete there, and leaders of both political parties agreed that this was a challenge we had to take up. Further, the Endeavour/U.S. Hab disaster, by producing a new set of heroes, had given the administration a set of ideal tools for selling the American public—and with them, the Congress—on a renewed and expanded effort in space.
The way to sell it, and the makings of such a program, were there. After every major disaster in American policy, there is almost always a presidential commission intended, at the least, to persuade people that things are being looked into and that the government is thinking about the problem. Historically, every so often such a commission exceeds its mandate drastically—just such maneuvers brought the Federal Reserve Board into existence after the Depression of 1907, and produced the basic American policy on nuclear nonproliferation in the late 1940s.
“Aunt Lori” always told me afterwards that when she got the phone call from the president and was told that she would be on the commission to review the Endeavour disaster, the next thing the president said was, “Now partly I want you on that commission because after that accident you and Chris Terence are the most publicly credible astronauts since Story Musgrave; people know you know your stuff. And Terence is not a real political guy, but I have a feeling you could be if you put your mind to it. Now, about the job itself, what your mission is for the inquiry. You’re supposed to just figure out what happened and tell us how not to have it happen again. But if you maybe see some other improvements that could be made … or if you think more than just the shuttle needs overhauling … well, I can’t say I would object to reading the report. I read too many reports that only talk about one little problem, right now.”
Whenever she told that story, her eyes would twinkle and she’d say, “Jason, if you want to get ahead in the astronaut racket, you have to learn to recognize an order when you hear one. Especially when it’s an order to exceed your orders.”
Eight months after the accident, the commission made its report. Less than twenty pages of that report dealt with the accident and its causes; they said only that the SSMEs were getting old and had to be run at very high power, and it wasn’t altogether surprising that the technology that had stretched the envelope in 1975 wasn’t completely up to the challenge twenty-seven years later. A new program was needed—first a way to use off-the-shelf equipment to keep operating in space, because we could no longer afford the kind of shutdown that had happened after Challenger; then a conservatively designed, proven-technology replacement for the shuttles; then systematic movement toward better long-range solutions.
Luckily for the commission, the president, and NASA, all of the pieces for such a program were there already, not so much by design as by good luck. The worldwide space doldrums of the 1990s had allowed large quantities of unrealized designs and ideas, and underused hardware, to accumulate, and the Russian need for hard cash plus their decade of experience working with American companies had brought some of that hardware to a high degree of reliability. Thus the new plan could be presented as making maximum use of off-the-shelf technology and offering relatively few new risks.
Foremost of these opportunities was the remarkable Zenit, a workhorse rocket that Boeing was making under license from the Russian and Ukrainian firms that had privatized it. The Zenit had been originally intended as a strap-on booster for Energiya, the giant Russian booster rocket. Boeing had found another use for the Zenit in sea launches from a floating oil-drilling platform, where it had also performed well.
The Zenit was rugged and simple in design, and in particular its engines, once they were being made by Pratt and Whitney with better-quality Western materials, were simple, efficient, powerful, and cheap. Boeing had enhanced the Zenit further by creating the “Starbooster”—a standard Zenit first stage, surrounded by a shell equipped with fixed wings, a V-tail, landing gear pods, and two off-the-shelf, high-reliability fan-jet engines (the same model that had flown in the 737 for decades) in the nose. The Starbooster was the first really reusable rocket booster: when the fuel in the first stage burned out, the heat shield built into the shell allowed a Starbooster to return to the lower atmosphere without burning up, and the engine and wings allowed robot systems to fly it back to its base. Whereas the shuttle boosters had to be parachuted into the sea, fished out, and reconditioned after a dunking in saltwater, the Starbooster flew back to a runway and could be rolled straight to the mechanics. Turnaround on reconditioning and reflying the solid fuel booster was measured in months; for the Starbooster, in days.
The commission had first considered the possibility of upgrading the shuttle by replacing each of the solid rockets with a “Twin Starbooster”—two Zenits in the same shell, with a “scissor wing” that folded against the body like closing scissors for launch and reentry, then unfolded for flyback. This gave better streamlining and performance on liftoff, made for an easier reentry from the higher flights that the twin engines allowed it to achieve, and most importantly, created a configuration big enough to do the job formerly done by America’s aging fleet of disposable Titans and Atlases—early 1960s technology that was still in use forty years later—and be much cheaper than the Air Force’s proposed EELV (Evolved Expendable Launch Vehicle), then being proposed for the same purpose.
Boeing had also pointed out that if you used Twin Starboosters on the shuttle, it would more than replace the dangerous solid fuel boosters—so much so that you could run shuttle main engines at well below 100 percent, gaining greater performance while avoiding both “Challenger-class” and “Endeavour-class” disasters.
But the commission noted w
ith some regret that the time to do that had been some years ago; the shuttles were now getting old, nearing the end of their usable lives, and a better shuttle booster could only help the system limp a little faster. Ten years before, with four shuttles flying and the prospect of keeping them operating for a long time, two Twin Star-boosters on each shuttle would have greatly enhanced capability and reduced cost; now it was an idea whose time had come and gone. The Starbooster had many uses, and it was a good idea to make use of it; the Twin Starbooster would simply go to the museum with all the other valid ideas that get bypassed on the road to the future.
Rather, they suggested, the thing to do was to concentrate on three problems:
How can we get people and supplies to orbit at acceptable cost and safety, ASAP?
How can we use the best of three decades of well-proven technology to create a certain-to-work low cost shuttle replacement?
How can we eventually achieve the best possible space program combining what we can afford to pay and what we need to do?
Boeing had lost out on the bid for the EELV, but Boeing management had felt very strongly that there should be a market for their simple, proven-technology booster—putting one or two Space Shuttle Main Engines, with their more-than-twenty-year track record, directly under a large hydrogen/oxygen tank (derived from the shuttle’s external tank with minimal modifications), and equipping it with the bare bones of guidance systems and a payload rack on top. The idea was that such a lightweight gadget—it was practically all engine and fuel—equipped with a good booster, would easily put itself into orbit. The reusable engines could be loaded into a shuttle cargo bay or otherwise wrapped up in a heat shield to bring back to Earth; the tank could stay up there to be used for construction. They had dubbed this simple, effective rocket the Centurion.