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Intelligent Machines

Countdown for Rocket Planes

Planes powered by cheap reusable rockets could be the future of space transportation. But don’t look to NASA: the initiative is coming from a group of small, maverick companies.

The sun-baked town of Mojave, CA, with a population of only 3,700, boasts an airport that takes up almost as much area as Los Angeles International. The vast, isolated site at the mountain-rimmed edge of a wide expanse of high desert plain, has been home to several maverick aerospace companies. Voyager, the extremely lightweight airplane that in 1986 became the first to fly nonstop around the world without refueling, was spawned here. Now, in an unassuming low building at the airport’s edge, the future of space transportation is, just possibly, being born.

Mind you, that future doesn’t look like much yet: a tiny two-seat airplane that resembles a jet fighter with its tail chopped off and stubby winglets installed near its nose. Last July this lightweight craft, dubbed EZ-Rocket, reached a new aviation milestone when pilot Dick Rutan, who had also piloted Voyager, put its twin rocket motors through a pivotal “touch and go” maneuver: taking off, shutting down the engines, landing, firing up the motors again, and taking off without stopping. This represented a high-water mark in giving airplanelike flexibility and controllability to a rocket-powered craft: an achievement that carries heightened significance since the Space Shuttle Columbia catastrophe raised new questions about the viability of the U.S. government’s manned space program.

Each of those two flights lasted less than 15 minutes and neither reached altitudes higher than 3,000 meters. But they showed that Xcor Aerospace, the company behind EZ-Rocket, may have the best shot yet at actually giving the world a reusable rocket plane-bringing routine airlinelike operations to the world of rocketry and slashing launch costs to as little as one-tenth those of launching the space shuttle and today’s expendable rockets. Such a craft could, within several years, allow cheap satellite deployment for research and communications and jump-start space tourism. Over a longer time frame, successor craft might provide a New York City-Tokyo passenger flight that takes less than three hours. And because breaking free of Earth’s gravity is the largest cost of every space mission, cheaper launches are essential prerequisites for such visionary ventures as space-based solar collectors that beam energy to Earth 24 hours a day and precious-metals mining from asteroids.

This story is part of our April 2003 Issue
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History of Failure

Creating reusable rocket planes should have been NASA’s job. But NASA’s effort-the X-33, an ambitious concept for a reusable rocket plane that by 2005 was supposed to demonstrate technologies that could eventually replace the space shuttle program-became the biggest white elephant ever produced by the U.S. space program. Between 1997 and 2001 almost $1.3 billion was spent on the hydrogen-powered craft, and there’s virtually nothing to show for it. Fatefully, NASA chose a plan that employed a host of technically challenging (read: risky) technologies-including unique rocket engines, fuel tanks, and heat shields-and a complex vehicle design. Each of those technologies would have had to work for the craft to successfully unseat the space shuttle fleet-now more than two decades old-for missions that include ferrying astronauts to the International Space Station and launching scientific payloads such as the Hubble Space Telescope.

But one part, a composite liquid-hydrogen fuel tank built by Lockheed Martin, failed in tests. In 2001 NASA, facing the prospect of waiting another year for a new version, “walked away from the effort and started something new,” says Lori Garver, a former NASA associate administrator. “Every time you do that, you lose ground.” Now, two years after the X-33’s cancellation, NASA’s still largely undefined new effort is not expected to produce a space shuttle replacement earlier than two decades from now. However, there will undoubtedly be pressure post-Columbia to accelerate that timetable.

One result of the X-33 debacle was to put a serious damper on private investment in the field. Conventional wisdom held that if NASA couldn’t build a reusable rocket, no one could, says Collins. But the world lacks a rocket plane “not because it’s difficult to build,” he says. “It’s just that virtually all rocket research has been done by a monopoly government agency.” Buzz Aldrin, who in 1969 became the second man to walk on the moon, says the United States simply lacks a coherent national program for developing affordable launch technology. Although Columbia’s fate could sharpen the focus, Aldrin says that for the time being anyway, “we’re in a mess.”

Into this mess arrive Xcor Aerospace and its competitors. Their vision: to build a new breed of rocket. Unlike every rocket launched so far, this craft would fly into space and return intact. (Some designs call for the rocket initially getting aloft by piggybacking atop a jet.) Even each of the space shuttles, the world’s first and only reusable spacecraft, discards parts of the twin booster rockets and all of the huge external fuel tank with every launch.

Realizing this ambition looks relatively straightforward on paper. Rocket engines are basically combustion chambers with pumps that bring in fuel and oxidizer-oxygen or an oxygen-rich chemical that allows the fuel to burn even in the vacuum of space. They don’t need a jet engine’s high-speed turbofans and compressors, which provide oxygen from the air and account for about 80 percent of the engine’s size, weight, and complexity. And as a result, rockets can fly far higher than jets, which cannot exceed altitudes of 16 kilometers because the air becomes too thin to burn aviation fuel and provide lift to their wings.

No one is saying that such upstarts as Xcor Aerospace can reach space in one step. Reaching orbit means attaining speeds of 27,800 kilometers per hour, carrying enormous amounts of fuel, and withstanding extreme stresses. Meeting these challenges will, by all accounts, take at least a decade. In the meantime, though, a lot can be learned while shooting for a much more modest goal: a rocket-powered craft able to reach the edge of space-an altitude of 100 kilometers-without actually going into orbit. Achieving that altitude requires a speed of about 4,500 kilometers per hour, not much faster than the top speeds of today’s jet fighters, so designers of the rocket craft should be able to adapt the fighters’ relatively tried-and-true systems and engineering procedures.

Xcor Aerospace president Greason says meeting the design goal is possible within the next few years. Six years ago he left the booming microchip industry because he saw the space business as being where computers had been back in the 1970s: a few companies controlled a market for big, expensive, exclusive hardware, and they were oblivious to the sea change being brought about by a few obsessed college dropouts who, working in garages, used off-the-shelf parts to produce amazing new personal computer systems. “It’s very similar to the early days of the PC,” says Peter Diamandis, chairman and founder of the X-Prize Foundation. “Suborbital vehicles that can make thousands of flights a year will create a marketplace by changing the perspective on space: it’s not just for governments, but for the public.”

Small, Nimble Competition

Xcor Aerospace’s EZ-Rocket is like those early PCs-simple, basic, and from the standpoint of the conventional aerospace business, practically microscopic. Its twin rocket engines, fueled by alcohol and liquid oxygen, separately produce only one-thousandth the thrust of each of the space shuttle’s three main engines. But unlike their shuttle counterparts, the EZ-Rocket engines can be fully controlled and even shut down and restarted in flight. Still, the EZ-Rocket is just a demonstration vehicle. The tiny craft is designed to rack up experience for building a two-seat suborbital space plane called Xerus, which is now in development.

For the Xerus, Xcor Aerospace is developing a rocket engine with five times the power of EZ-Rocket-an engine that can be throttled up and down through a wide range of speeds. A cluster of four or five such engines would lift the rocket plane to an altitude of 100 kilometers; then smaller rockets would allow the craft to maintain stability during an edge-of-space jaunt.

Xcor Aerospace is pursuing the two-person Xerus even though it will not meet the three-person criterion of the X-Prize. Prize or no prize, Greason, Rutan, and their handful of coworkers see plenty of financial incentive. Greason says the Xerus could launch a small satellite payload-about 10 kilograms-into a low orbit using a booster rocket on the satellite. Similarly small satellites are used for university research projects, which often must wait years to piggyback onto a larger satellite launch. And the Xerus itself could also be used for research such as collecting atmospheric data or carrying out engineering experiments that require brief periods of time in a zero-gravity environment.

The real target, though, is tourism. Greason says the Xerus could provide tourists with half-hour joyrides-three minutes of weightlessness and a chance to see the Earth’s curvature and the darkness of space-then land on an ordinary runway. One Xerus alone, he says, could earn $24 million a year in tourist revenues on development costs of less than $10 million. Fueled by such visions, Xcor Aerospace hopes within three years to have flown and tested Xerus and readied the craft for production. “We decided to do the smallest steps we could, with as many of them as possible generating revenues,” Greason explains. If Xerus works and tourist profits roll in, he says, the company’s developers would begin to tackle the ultimate task-getting into orbit.

The idea of “smallest steps,” of course, has a certain historical resonance when it comes to space technology. But while Xcor Aerospace focuses on the incremental approach, several competing companies are already pursuing the grand vision: a craft that can go all the way into orbit. One player is Pioneer Rocketplane in Solvang, CA. The company has designed a tourist or cargo-carrying rocket-and-jet hybrid called Pathfinder, which will take off with traditional jet engines. Once at a cruising altitude of about 5,500 meters, a fuel tanker plane will rendezvous with the Pathfinder and pump liquid oxygen into an empty tank on board the craft. Then, propelled by a combination of liquid oxygen and kerosene, the Pathfinder will light its rocket motor and soar to an altitude of 139 kilometers, where it could also release an unmanned upper stage to deliver a 2,280 kilogram payload into orbit.

Like Xcor Aerospace, Pioneer is starting with a smaller version-the Rocketplane XP-which will compete for the X-Prize. Though neither the XP nor the Pathfinder has reached even the prototype stage, Pioneer Rocketplane is considered a serious player. Its CEO, Mitchell Burnside Clapp, was responsible for an Air Force design of an airplanelike reusable rocket that later evolved into the Pathfinder concept. Because of that design, Pioneer Rocketplane is a leading competitor for a Defense Advanced Research Projects Agency project to develop an inexpensive rocket-propelled satellite launcher. (The agency was expected to announce the award of two final design contracts on March 1.)

Most of the reusable-rocket players are thinking in terms of carrying people-both pilots and tourists. But Germany’s Astrium is expressly leaving out human cargo. Instead, it is developing an autonomous rocket craft called Hopper, designed to provide cheap satellite launches. The first step in this direction is the Phoenix, a one-sixth-scale version of the Hopper. The Phoenix is mainly a test bed for autonomous landing technology. The craft’s designers are incorporating laser-based altimeters-altitude sensors-and digital Global Positioning System equipment together with intelligent-navigation algorithms that enable the craft to make a gliding runway landing without help from humans or equipment on the ground. The first test of the vehicle, which is under construction, is expected next year: a helicopter will drop the Phoenix from an altitude of about 1,400 meters, leaving it to land on its own. Astrium estimates that the full-size Hopper could launch satellites in 15 to 20 years, at half today’s launch costs.

And NASA isn’t sitting on the sidelines. Although the exact shape of a successor program to the ill-fated X-33 is still being worked out by agency administrator Sean O’Keefe, who took the helm in late 2001, NASA had begun to fashion long-term plans for a bigger, more ambitious craft even before the Columbia disaster. The Orbital Space Plane is just a blank sheet of paper now, but the idea is that it would be ready to deliver crew and small amounts of cargo to the International Space Station by 2012.

If it does fly by 2012 or sooner, the Orbital Space Plane would get to orbit atop a conventional expendable rocket. But NASA hopes eventually to replace that rocket with a reusable system. To do this, researchers at NASA’s Marshall Space Flight Center in Huntsville, AL, are simplifying and streamlining rocket engine design and incorporating built-in diagnostic systems to detect problems such as cracks, leaks, and stuck valves. Such systems would yield tremendous savings compared to the space shuttles, whose engines are dismantled and inspected after every mission by hundreds of engineers. “The goal is to bring rocket engine reliability into the same category as today’s jet engines,” says Garry Lyles, who is in charge of propulsion systems for NASA’s program to develop technology for future launch vehicles. Right now anyway, NASA’s plans call for a reusable space-shuttle replacement by 2025.

Private Push

Despite its poor track record with rocket planes, NASA remains a serious long-term competitor. But the agency’s somewhat leisurely timetable has left the field wide-open for the private sector. And excitement about the potential for small companies to actually produce a reusable rocket craft is growing. An X-Prize victory by one of them would dispel skepticism and jump-start investment too. “It’s a psychological step,” says Rand Simberg, an aerospace engineer and consultant. “The little companies are going back and doing it like it should have been done in the first place.”

Indeed, anticipating the ability of small companies to blaze new paths, one firm is booking tourist flights on rocket planes that exist today only on paper. Space Adventures, of Arlington, VA, already sends tourists on zero-gravity airplane flights in Russia, and it arranged Russian space flights-costing $20 million apiece-to the International Space Station for U.S. businessman Dennis Tito in 2001 and South African tycoon Mark Shuttleworth last year. The company has contracted for 600 Xerus flights and taken deposits from more than 100 customers.

“We’ve been impressed with Xcor’s team of people and their ability to produce actual flying hardware and to carry out demonstrations on a low budget,” says Eric Anderson, president of Space Adventures. And though Anderson initially feared that Columbia’s frightening demise might cause some of his customers to think twice about space travel, none had asked for a refund in the first few days after the shuttle was lost-a fact he says shows a strong human commitment to space flight. Instead of scaring people off, he adds, what happened to Columbia “will serve as a wake-up call. Ten years from now, people will feel safer, will be safer” going into orbit as a result of improvements that will inevitably result from the investigation of the accident.

Space Adventures’ backing of Xcor and other rocket companies provides a synergy that might be crucial for realizing the decades-old visions of reusable rockets, says Bruce Lusignan, an electrical engineer at Stanford University and director of the Center for International Cooperation in Space, a worldwide consortium of universities. He says space-related tourism revenues could finance a new generation of tourist-oriented launch vehicles, and “that might be the core to building the capability up. That might be the right way to go.” And that means the EZ-Rocket-that unimposing test vehicle at the vast Mojave Airport-just might end up being the first PC of a new space age.

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