There is nothing conventional about the Roton’s propulsion. It uses 72 small rocket engines arranged in a ring at the bottom of the rocket. That’s been done before on some Russian rockets, but what’s unusual in this case is that the engines will be mounted on a disk that spins at 720 revolutions per minute. Kerosene and liquid oxygen travel from the tanks above, down through a pipe at the center. When the fuel reaches the disk, centrifugal force flings it out to the perimeter and forces it into the engines’ combustion chambers. With this setup, the Roton doesn’t need fuel pumps, or turbopumps, which are famously unreliable.
Hudson says that he and his team have bent over backward to keep things simple and reduce risk. Whenever possible they have used off-the-shelf parts and techniques that at the very least have been used experimentally before. On the other hand, how many conventional helicopter rotors have had to slow down a 400,000 pound vehicle traveling at 25 times the speed of sound? And the spinning engine has only been tried on a very small scale by Soviet and American researchers. Still, Hudson says, “there’s nothing we’re doing that’s obviously a showstopper. Okay, we’re doing some sporty things in the engines. This is the first sort of big, rotating engine. But if that doesn’t work, we could go out and buy turbopump engines and still make the vehicle work. It would be a year or year and a half delay, and it would be traumatic, but it would work. The technical challenges can be overcome.”
So far Hudson has raised more than $30 million, and he’s spent just about all of it. “When investors come into this company,” he says, “I tell them somewhat in jest that we’re going to waste half the money they give us. Investors just freak when you say this. When you really get down to the type of decisions we have to make, you’re really doing well if you only waste half of it. Because you make mistakes.” Although his rocket is coming in under budget, he needs another $120 million just to get him through to the flight test of an experimental version of the Roton. If he gets it, he hopes to fly a prototype some time in 1999. If all goes well, a big if, he expects to achieve orbit some time in 2000. How much will it all cost in the end? “The answer is, we won’t know till we’re done,” he says. “I think it’s important to understand how revolutionary what we are doing is.”
George Mueller makes no claim to being revolutionary. Like just about everybody in the rocket business, his motivation is at least partly idealistic—to beat the rocket equation. But he is a pragmatist. In running NASA’s manned space program for most of the Apollo project, he amply demonstrated an ability to make tough decisions. He had taken charge of NASA’s manned space program in 1963 at the age of 45, when engineers were just starting to build the Saturn V rocket. They wanted to test each one of its five stages separately, which would have meant building and flying five experimental rockets before even starting to put together the final Saturn. Although it was standard engineering practice, Mueller saw right away that such a schedule would never do. Instead, barely a month on the job, he announced his decision to go with “all up” testing—build all five stages, stack them one on top of the other, fill them with fuel, and fly the thing all at once. It was not popular, but it happened to work. As much as anybody else, Mueller was responsible for meeting John F. Kennedy’s end-of-the-decade deadline for putting astronauts on the moon.
Even as Mueller watched the Apollo program leap to success, he knew it was winding down, and he knew what he wanted to do next. He threw his considerable reputation behind building a cheap, reusable rocket. His idea was to spend money like crazy in the design stage, use all the latest materials, build right to the edge of the envelope, and wind up with a vehicle that was dirt cheap to operate. NASA officials embraced the idea but couldn’t summon enough seed money from Congress. So they built the space shuttle instead—cheap to design, expensive to fly, partially reusable. “It was a disappointment,” Mueller says. By the time the shuttle flew, he had left for private industry.
In 1993 the founders of Kistler Aerospace sought Mueller’s advice about their new venture to build a reusable rocket. They found him tending the jojoba trees on his Arizona ranch full-time, but he was restless. “My wife tells me I flunked retirement,” he quips. At the age of 75, he surprised everybody by offering to head the project. “I told them I would sit on the board of directors, but only as the chief executive,” he says.
The Kistler venture is a product of the space race turning commercial: the company was formed with the idea of exploiting the burgeoning satellite-launch market. The end of the cold war helped, too. Two hot Russian rocket engines had recently become available, the NK-33 and NK-43. The Soviets had developed these engines during the moon race, and they are the best kerosene-burners ever made. “The Russians kept building them and improving them over a period of 15 years,” says Mueller. “They built maybe 500 of them, and they probably destroyed 200 of them in testing, just to see how they could improve the design.” As a result, the engines produce 20 percent more thrust per gallon of fuel than do the Saturn V engines developed for Apollo. Because they burn kerosene, they are far safer and cheaper to operate than the hydrogen engines used on the Saturn V. There are 100 of these engines left. Kistler has 46 of them under wraps in a Sacramento warehouse.
Mueller turned to the rocket design. He scrapped the K0 because he worried about the design and problems with the central control system, and opted instead for a more conventional two-stage design. He was willing to sacrifice the elegance of a single stage vehicle, but he was loath to give up on reusability, which he saw as a key to keeping down costs.
When the new design, the K1, is completed, it will look every bit as homely as the Roton. It will consist of a cylindrical first stage, with a slightly thinner, blunt-nosed second stage on top—119 feet in all. Upon launch, the three NK-33 engines in the first stage will power the rocket for the first 25 miles or so. Then the rocket will separate, turn itself around, and the engines will fire once more to bring it back into the atmosphere. At about 40,000 feet, six parachutes will deploy to slow the rocket. Just before it reaches the ground, air bags similar to the ones used in automobiles will open to cushion the impact. Meanwhile, the second stage’s single NK-43 will take the payload into orbit, turn around and land, too, using parachutes and air bags.
If you had to put your money on either Kistler or Rotary Rocket, Kistler would seem to have the odds in its favor. For one thing, the K1 is further along in development than the Roton. At the end of 1998, the shell for the first rocket was almost finished, two of three fuel tanks were complete, and the software and guidance electronics were 90 percent finished. Kistler got an earlier start, and it has farmed out much of its work to subcontractors. Northrup-Grumman is building the airframe, Aerojet is modifying the engines, Irvin is making the parachutes. Of course, Kistler has spent far more money than Rotary Rocket—$400 million—and it will need a lot more, $400 million, Mueller says, before it delivers its first payload to orbit. If the money is raised, K1 could be launched from Australia late this year.
Kistler also stands a better chance of raising the money it needs than Rotary, not least because of Mueller’s reputation. He has put together a roster that includes senior managers from just about every big NASA program. Like it or not, investors are more likely to put their money on engineers with impressive résumés than on a loner with big ideas.
If Kistler does get there first, however, it will be due in no small part to Mueller’s conservative approach. Although the K1’s two-stage design would give him more leeway to squeeze a few pilots aboard than Hudson’s single-stage design would, Mueller does not entertain any notions about putting people in space. And even though Mueller has the world’s best rocket engines, he judges them to be inadequate for anything but a two-stage rocket. “Remember, a reusable rocket has got to be heavier than an expendable one, because you need some extra fuel to get back to Earth safely,” he says. “The engines do not exist that can power a single-stage reusable rocket.”
Hudson disagrees. “I do not believe that in this era of lightweight thermal protection, composite materials, lightweight avionics, et cetera, we could not find several vehicle designs that are reusable. I find it inconceivable.”
Hudson and Mueller do agree on one thing: that the biggest obstacle they each face is money. “Technical challenges can be overcome,” says Burt Rutan on a Rotary Rocket promotional video, “but engineers don’t even get to try unless they have the resources.” And resources could get scarcer: three other firms have joined the race to build reusable rockets.