Newsletter

Title : The Way to Go in Space
Author : Tim Beardsley
Date : February, 1999

To go farther into space, humans will first have to figure out how to get there cheaply and more efficiently.� Ideas are not in short supply SUBTOPICS: After the Gold Rush Buck Rogers Rides Again Beyond Earth Beam Me Up The year 1996 marked a milestone in the history of space transportation. According to a study led by the accounting firm KPMG Peat Marwick, that was when worldwide commercial revenues in space for the first time surpassed governments' spending on space, totaling some $77 billion. Growth continues. Some 150 commercial, civil and military payloads were lofted into orbit in 1997, including 75 commercial payloads, a threefold increase over the number the year before. And the number of payloads reaching orbit in 1998 was set to come close to the 1997 total, according to analyst Jonathan McDowell of Harvard University. Market surveys indicate that commercial launches will multiply for the next several years at least: one estimate holds that 1,200 telecommunications satellites will be completed between 1998 and 2007. In short, a space gold rush is now under way that will leave last century's episode in California in the dust. Space enthusiasts look to the day when ordinary people, as well as professional astronauts and members of Congress, can leave Earth behind and head for a space station resort, or maybe a base on the moon or Mars. The Space Transportation Association, an industry lobbying group, recently created a division devoted to promoting space tourism, which it sees as a viable way to spur economic development beyond Earth. The great stumbling block in this road to the stars, however, is the sheer difficulty of getting anywhere in space. Merely achieving orbit is an expensive and risky proposition. Current space propulsion technologies make it a stretch to send probes to distant destinations within the solar system. Spacecraft have to follow multiyear, indirect trajectories that loop around several planets in order to gain velocity from gravity assists. Then the craft lack the energy to come back. Sending spacecraft to other solar systems would take many centuries. Fortunately, engineers have no shortage of inventive plans for new propulsion systems that might someday expand human presence, literally or figuratively, beyond this planet. Some are radical refinements of current rocket or jet technologies. Others harness nuclear energies or would ride on powerful laser beams. Even the equivalents of "space elevators" for hoisting cargoes into orbit are on the drawing board. "Reach low orbit and you're halfway to anywhere in the Solar System," science-fiction author Robert A. Heinlein memorably wrote. And virtually all analysts agree that inexpensive access to low-Earth orbit is a vital first step, because most scenarios for expanding humankind's reach depend on the orbital assembly of massive spacecraft or other equipment, involving multiple launches. The need for better launch systems is already immediate, driven by private- and public-sector demand. Most commercial payloads are destined either for the now crowded geostationary orbit, where satellites jostle for elbow room 36,000 kilometers (22,300 miles) above the equator, or for low-Earth orbit, just a few hundred kilometers up. Low-Earth orbit is rapidly becoming a space enterprise zone, because satellites that close can transmit signals to desktop or even handheld receivers. Scientific payloads are also taking off in a big way. More than 50 major observatories and explorations to other solar system bodies will lift off within the next decade. The rate of such launches is sure to grow as the National Aeronautics and Space Administration puts into practice its new emphasis on faster, better, cheaper craft: science missions now being developed cost a third of what a typical early-1990s mission did. Furthermore, over its expected 15-year lifetime the International Space Station will need dozens of deliveries of crew, fuel and other cargo, in addition to its 43 planned assembly flights. Scores of Earth-observing spacecraft will also zoom out of the atmosphere in coming years, ranging from secret spy satellites to weather satellites to high-tech platforms monitoring global change. The pressing demand for launches has even prompted Boeing's commercial space division to team up with RSC-Energia in Moscow and Kvaerner Maritime in Oslo to refurbish an oil rig and create a 34,000-ton displacement semisubmersible launch platform that will be towed to orbitally favorable launch sites. After the Gold Rush Even the most sobersided scientists would like to see many more research spacecraft monitoring Earth's environment and exploring the farther reaches of the solar system. The more visionary ones foresee a thriving space industry based on mining minerals from asteroids or planets and extracting gases from their atmospheres for energy and life support. K. R. Sridhar of the University of Arizona borrows the rhetoric of Mars enthusiasts when he says space pioneers will have to "live off the land": he has a developed an electrochemical cell that should be able to generate oxygen from the Martian atmosphere. Already one firm, SpaceDev, has talked about mining minerals from asteroids, earning a complaint from the Securities and Exchange Commission for its incautious enthusiasm. Some dreamers even devote themselves to finding ways of sending probes beyond the sun's domain into the vastness of interstellar space. The clamor for a ticket to space is all the more remarkable in light of the extremely high cost of getting there. Conventional rockets, most developed by governments, cost around $20,000 per kilogram delivered to low- Earth orbit. The space shuttle, now operated privately by United Space Alliance, a joint venture of Boeing and Lockheed Martin, was intended to be an inexpensive ride to space, but its costs are no less than those of typical expendable rockets. In any event, the shuttle has been unavailable for commercial launches since the Challenger disaster in 1986. If a shuttle were outfitted today to take 50 passengers for a flight, they would have to pay $8.4 million a head for its operator to break even. Getting into space is expensive today because boosters carry both the oxidizer and the fuel for their short ride and (with the exception of the partly reusable space shuttle) are abandoned to burn in the atmosphere after their few fiery minutes of glory. Engineers have long hoped to slash launch costs by building reusable craft that would need only refueling and some basic checks between flights, like today's commercial airliners. An energetic group of companies dedicated to reducing launch costs has sprung up in recent years, many of them populated with former NASA top brass. Most are adapting existing technology to gain a commercial edge for launching small payloads into low-Earth orbit. Nobody should underestimate the risks of building rockets, even ones based on conventional designs. The very first Boeing Delta 3, which was the first large booster developed privately in decades, exploded shortly after liftoff from Cape Canaveral last August, setting back Boeing's plans. A U.S. Air Force/Lockheed Martin Titan 4A had detonated over the cape two weeks earlier, and European Arianespace had a costly failure of a new launcher in 1996. In the U.S., disagreements over costs and demand have led to the cancellation of several government-sponsored efforts to develop new expendable rockets in the past decade. Buck Rogers Rides Again The entrepreneurs are not easily deterred. One of the farthest along and best financed of this new breed is Kistler Aerospace in Kirkland, Wash., which is building the first two of five planned launchers that will employ Russian-built engines. The first stage of each vehicle would fly back to the launch site; the second would orbit Earth before returning. Both stages would descend by parachute and land on inflatable air bags. The company has raised $440 million and seeks hundreds of millions more; it says that despite world financial turmoil, flights should start this year. Privately financed Beal Aerospace Technologies in Texas is developing a three-stage launcher that is scheduled to fly in the third quarter of 2000. A reusable version may be developed later, says Beal vice president David Spoede. Several firms plan to increase their advantage by using oxygen in the atmosphere, thereby reducing the amount of it that their rockets have to carry. This can be done most easily with a vehicle that takes off and lands horizontally. Pioneer Rocketplane in Vandenberg, Calif., is developing a lightweight, two-seater vehicle powered by a rocket engine as well as conventional turbofan engines. The plane, with a payload and attached second stage in its small shuttle-style cargo bay, takes off from a runway with its turbofans and climbs to 6,100 meters (20,000 feet). There it meets a fuel tanker that supplies it with 64,000 kilograms (140,000 pounds) of liquid oxygen. After the two planes separate, the oxygen is used to fire up the smaller plane's rocket engine and take it to Mach 15 and 113 kilometers' altitude, at which point it can release its payload and second stage. A fail-safe mechanism for the cryogenic oxygen transfer is the main technical challenge, says the company's vice president for business development, Charles J. Lauer. Kelly Space and Technology is also developing a horizontal takeoff plane for satellite launches, but one that can handle larger payloads, up to 32,000 kilograms. Kelly's Astroliner, which looks like a smaller version of the shuttle, has to be towed to 6,100 meters. At that altitude, its rocket engines are tested, and a decision is made either to zip up to 122,000 meters or to fly back to the launch site. The first two vehicles should cost close to $500 million, and Kelly is now lining up investors. Other companies are being more technologically adventurous. One of the most intriguing is Rotary Rocket in Redwood City, Calif., which is building a crewed rocket that would take off and land vertically. The most innovative feature of the design, called the Roton, is its engine. Oxidizer and fuel are fed into 96 combustors inside a horizontal disk seven meters in diameter that is spun at 720 revolutions per minute before launch. Centrifugal force provides the pressure for combustion, thereby eliminating the need for massive, expensive turbo pumps and allowing the vehicle's single stage to go all the way to orbit. The Roton descends with the aid of foldaway helicopter blades that are spun by tiny rockets on their tips, like a Catherine wheel. Rotary Rocket says it will be able to deliver payloads to low-Earth orbit for a tenth of today's typical launch price [see illustration]. The first orbital flight is scheduled for 2000; the company has already tested individual combustors, and atmospheric flights are supposed to take place this year. The design "has got a lot of challenges," observes Mark R. Oderman, managing director of CSP Associates in Cambridge, Mass., who has surveyed new rocket technologies. Oderman says the Roton has many features "that imply high levels of technical or financial risk." Space Access in Palmdale, Calif., is designing an altogether different but equally daring craft. Its heavy space plane would take off and land horizontally under the power of a proprietary engine design called an ejector ramjet. This novel engine, which has been tested on the ground, will propel the craft from a standstill to Mach 6, according to Space Access's Ronald K. Rosepink--a performance well beyond anything in service today. Rosepink says the engine is almost 10 times more efficient than existing engines. At Mach 6, the plane will fire up two liquid-hydrogen-fueled rockets. At Mach 9, its nose will open like the jaws of a crocodile to release the second and third stages plus the payload. All the stages have wings and will fly back and land horizontally at the launch strip. Space Access's plane will handle payloads of around 14,000 kilograms, as big as those carried by the shuttle. Commercial service could start in 2003, Rosepink claims. The most prominent launch vehicle in development, the X-33, is under construction at Lockheed Martin's Skunk Works in Palmdale, Calif., as part of a joint industry-NASA effort to reduce launch costs 10-fold. The X-33 is a roughly half-size experimental craft intended to test a type of rocket engine known as a linear aerospike, as well as various other technologies. On paper the linear aerospike can power a fully reusable, vertical takeoff vehicle to orbit with a single stage of engines that would automatically adapt to changing atmospheric pressure. But the X-33, which will not itself achieve orbit, pushes the limits of current construction techniques. And some observers now doubt whether it will be able to provide NASA with enough information for a promised year 2000 decision on whether the agency should continue to rely on current shuttles until after 2020 or instead phase out those expensive workhorses around 2012. Difficulties in building the engines have delayed the first flight of the X-33 by six months, until the end of this year. And Daniel R. Mulville, NASA's chief engineer, maintains that a further "year or two" of development will most likely be needed after flight tests are completed in late 2000 before a decision on building a full-size single-stage-to-orbit vehicle. (Lockheed Martin, however, which calls its design the VentureStar, says it will be ready to commit by the end of 2000.) One problem: the world does not have a large enough autoclave to cure the VentureStar's all-composite liquid-hydrogen tank. More effort is also needed on the metallic tiles that will protect the craft from the heat of reentry. The VentureStar was billed as a potential national launch system, notes Marcia S. Smith of the Congressional Research Service. Yet the timing could be awkward, as the first VentureStar would not carry humans. NASA has recently asked industry to study the options for carrying to orbit both human and nonhuman cargo early next century. Some potentially useful tricks are being explored with a smaller experimental vehicle known as the X-34. It will test two-stage-to-orbit technologies, including a new type of reusable ceramic tile, starting this year. Looking beyond X-33 and X-34 technology, the agency recently beefed up work on hypersonic jet engines, which had taken a back seat since the National Aerospace Plane program was canceled in November 1994. Variants on jet engines called scramjets--which breathe air like conventional jets but can operate at speeds over Mach 6--could help bring the goal of single stage to orbit within reach. Several unpiloted scramjets, designated X-43, will fly at speeds of up to Mach 10 and then crash-land in the Pacific Ocean, starting in the year 2000 [see box]. The difficulty faced by such efforts, explains NASA's Gary E. Payton, is in slowing the incoming air enough so that fuel can be burned in it for thrust without generating excess heat. In principle, it can be done with a shock wave created at the air inlet. But the process wastes a lot of energy. One potentially pathbreaking launch technology is an air-breathing engine that also operates as a rocket both when at low velocities and when the air becomes too thin to be worth taking in. At that altitude, a vehicle heading for space would most likely be traveling at about Mach 10. Such rocket-based combined- cycle engines have yet to advance beyond tests in wind tunnels, and they have to be designed as part of the body of a craft to achieve adequate thrust. NASA recently awarded Boeing a cost-shared contract under its new Future-X program to develop an Advanced Technology Vehicle that will test a variety of hypersonic flight technologies. Payton says that "if things go well" flight tests of rocket-based combined-cycle engines could occur between 2004 and 2006.