Machine Design

The X Prize is up for grabs ... 100 kilometers up!

Several teams are competing to send the first manned, privately funded, and reusable spacecraft into suborbital space.

Senior Editor

The Ascender is a spaceplane that will use jet engines to climb to the outer edge of the atmosphere and a rocket to boost it into space.


The Canadian Arrow rocket ship was on display at Rockefeller Center in New York City.


The Wild Fire, a rocket from the da Vinci Project in Canada, launches from beneath a helium balloon floating at 80,000 ft.


The X-Trophy is ready for when a team meets the challenge of sending a spacecraft into suborbital space.


The Rocketplane XP from Pioneer Rocketplane uses rocket power and standard aviation practices to fly into space.


TGV's Michelle-B deploys a metal-mesh dive brake to slow descent to where the engine can safely land it vertically on four landing legs.

Be the first privately funded group to build and fly a vehicle carrying three people to an altitude of 100 km (62.5 miles), land back on Earth, then do it again in the same vehicle two weeks later, and you can share the $10 million X Prize. The 1995

X-Prize, modeled after the $25,000 Orteig Prize won by Charles Lindbergh for flying nonstop from New York to Paris, aims to jump-start space business, including tourism. There are already more than 20 teams vying for the prize, including one headed by Burt Rutan (Machine Design, May 22, pg. 83). Some teams plan on going on to further exploit space, others will be satisfied if they just compete, but none seem poised to make a profit on the $10 million prize alone.

Rocket science

Of the 20 teams, several are developing traditional tubular rocket ships, including TGV Rockets, Bethesda, Md. Their craft, the Michelle-B, uses six rocket engines burning kerosene and LOX to produce 30,000 lb of thrust per engine. On take-off, the ship will weigh 61,300 lb, including a little over a ton of cargo. (The team's motto is “One metric ton to 100 km.”) The engines fire for the 200-sec boost into space, are switched off for 200 sec in space, then restarted when the craft is about 6,000 ft from touchdown on its descent to Earth. Reentry is initially slowed by a metal-mesh dive brake that increases the craft's coefficient of drag by two orders of magnitude. The drag gives the empty, 17,600-lb rocket a terminal velocity of 50 m/sec. It then makes a powered landing that leaves it standing upright on four landing legs.

The Michelle-B is about 40 ft tall with an 8-ft diameter, roughly the size of a standard cargo container, making it easy to transport the craft by sea, land, and air using common commercial equipment. The craft never exceeds 5 g's during its essentially vertical flight plan. Using the same engines for launch and reentry saves money and reduces complexity, as does using only off-the-shelf components to build the rocket ship. The entire craft is reusable, the only consumables being fuel and oxygen for the crew. The rocket carries a full avionics suite, including GPS, inertial navigation, radar, and a self-contained approach system. There is little ground support needed beyond fueling, ground power, and payload preparation, and no need for external tracking, range safety, and ground-based telemetry.

Even if they don't earn the X Prize, the TGV team intends to make money by launching orbital payloads from its suborbital perch and providing a microgravity environment for testing Space Station components and other equipment destined for space.

The Canadian Arrow, another rocket going for the X prize, is based on engine technology from Germany's World War Two-era V-2 rocket. The first stage of their two-stage rocket measures 33.5 ft high, has a 5.4-ft diameter, and carries a single engine fueled with alcohol and liquid oxygen. It can turn out 57,000 lb of thrust for about one minute. Once the engine runs out of fuel, the first stage separates and air brakes between the fins unfold to slow the descent. Four 64-ft-diameter parachutes also unfurl, slowing the first stage's fall to 30 fps before it splashes into the water 10 miles down range from the launch. It floats while awaiting pick up and preparation for the next flight.

The second stage, which doubles as an escape system and crew cabin, carries four solid rockets for thrust and cold gas jets for attitude control. After separation, the rockets fire, taking the second stage up to 100 km. For re-entry, an inflatable ballute changes the aerodynamic shape of the cabin, slowing and stabilizing it. Then three parachutes deploy, reducing the fall to 26 fps before it hits the water. It is weighted to float hatch-up, and inflatable floats keep it stabilized while the crew waits for the recovery ship.

At any time during the flight, even on the pad, the Canadian Arrow's second stage can fire its rockets, separate from the first stage, and act as a crew-escape system. If there were trouble on the countdown, for example, the four rockets would fire, lifting the crew cabin to 5,000 ft. Four extendable fin plates, similar to those on Russian escape vehicles, stabilize the cabin during a parachute-aided landing.

To give their straightforward plan some pizzazz, the team, headquartered in London, Canada, proposes using its rocket for spacediving. They want to take thrill seekers up to 40 miles or higher for the freefall of their lives. They envision these extreme athletes will wear counterpressure suits. These not-yet-developed jumpsuits will use elastic materials instead of air pressure to protect passengers against the thin atmosphere at high altitudes.

Another Canadian team, the da Vinci Project in Toronto, is also building a rocket. But their rocket won't fire its engines until it's already 80,000 ft off the ground and tethered beneath a reusable, piloted helium balloon. It will hang in an 80° up angle. After starting its engines and cutting the tether, it will fly a 90°, straight up profile. This lets the designers reduce the propulsion system to one-fourth of what a ground-launch would require. The craft, weighing 7,200 lb on take off (3,200 lb, empty), uses two kerosene and LOX engines, each generating 5,000 lb of thrust, to take it the rest of the way to 100 km. The engines are newly designed with emphasis on light weight, reliability, and low cost.

A helium-fueled cold gas-reaction control system (RCS) will give the ship attitude control. The pilot uses two control sticks, one for main-engine gimbals, the other for the RCS, or relies on an autopilot. Like other X-Prize contestants, the da Vinci rocket uses an inflated shuttlecock or ballute to increase drag on descent.

Space planes

Some X-prize teams are working on space planes and Space Shuttle-like craft. The Ascender, for example, will be the first suborbital plane since the X-15, according to its British developers. It uses two Williams-Rolls FJ44 turbofan jet engines to take-off and climb subsonically from a conventional airfield to about 4.5 miles high. Then its Pratt & Whitney RL 10 rocket engine fires, putting the craft in a near-vertical climb at Mach 2.8. It coasts up to an altitude of 62.5 miles and, after 2 min of weightlessness, steeply dives back into the atmosphere. Once in thicker air, the pilot pulls out of the dive and lands like a conventional aircraft. Within hours, say its designers, the 10,000-lb spaceplane could be ready for another 30-min trip to suborbit and back.

The British team wants to develop the Ascender into Spacecab, a reusable craft with flights costing only 1% that of a U.S. Space Shuttle mission. That, in turn, would evolve into Spacebus, a 50-passenger craft. They believe tourism will be the biggest commercial use of space, and that they can get the cost of a few days in a “space hotel” down to about $15,000. A second-generation Spacebus would carry passengers and cargo from Europe to Australia in 75 min.

Another spaceplane builder, Pioneer Rocketplane in Solvang, Calif., plans to build several spacecraft. The Rocketplane XP is their X-Prize contender. “But the X Prize doesn't drive us,” they say. “To win the X Prize, you could build a vehicle simpler and cheaper than the Rocketplane XP and succeed.”

The XP is a four-seat, fighter jet-sized craft powered by two jet engines and two kerosene/LOX rocket engines. It will take off and land like a conventional aircraft, and spend about 4 min in microgravity. It will use jet engines to get up to altitude, then off-the-shelf rockets to take it that last step to suborbit. And unlike NASA's Space Shuttle, which only uses its wings during reentry, the XP uses its wings to climb up into the atmosphere and for reentry and landing. This means the rockets can devote their thrust solely to canceling aerodynamic drag and accelerating the craft into orbit. The rockets don't have to work as hard when augmented by wings, according to Pioneer. This all fits in with the company's catch phrase: Building “aircraft that spend a small amount of time in space, rather than spacecraft that spend a small amount of time in air.”

The company plans to become commercially successful with its follow-on craft, the Pathfinder. Shortly after take-off, the Pathfinder hooks up with an aerial tanker to take on 150,000 lb of LOX. Taking rocket fuel onboard at this point significantly reduces the plane's empty weight, letting engineers specify smaller and lighter wings, engines, and landing gear. More importantly, it lets the plane take a good-sized payload into suborbit. The company points out that aerial refueling is routinely done everyday by military planes all over the world.

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