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To the Space Station and Beyond

February 22, 2011

Entrepreneurial space companies are developing technologies that promise to put people and cargo in space more cheaply and frequently than has been possible with systems built and operated by governments, such as the American space shuttle or the Russian Soyuz.

These technologies can be divided into two classes: suborbital systems that will let tourists take an arcing flight above the atmosphere before falling back to Earth, and orbital systems designed to carry astronauts and cargo for longer trips into space, visiting destinations such as the International Space Station.

Getting to suborbital space is a lot cheaper than orbiting Earth; the rockets can be much smaller and don’t need the heat shields required for reëntry from orbit. The trade-off is time: passengers are in space for only a few minutes. But companies like Blue Origin hope a few minutes of microgravity and spectacular views will be enough to lure enthusiasts and scientists. The company’s New Shepard spacecraft combines a crew capsule with a propulsion module. After about two and a half minutes of boost, the New Shepard will shut off its engines and coast. The capsule and propulsion module will separate for landing, and the propulsion module can be jettisoned in case of problems during the ascent.

Safety is a big concern for companies that plan on carrying civilians. Virgin Galactic’s SpaceShipTwo will use a hybrid rocket motor powered by a combination of solid and liquid fuels. The hybrid design retains much of the simplicity of a solid-fuel engine (the sort used to provide additional thrust to the space shuttle), but the burn rate can be carefully controlled in flight like that of a liquid-fuel engine, improving operational safety. SpaceShipTwo will be carried part of the way to space by the WhiteKnightTwo aircraft. This system is based on the one used by SpaceShipOne, which won the Ansari X Prize in 2004 by becoming the first private craft to complete a manned spaceflight (see “Beyond Low Earth Orbit). Virgin Galactic hopes to take its first passengers into space this year or early next year.

Some of the companies building orbital spacecraft are developing both the craft and the means to get them into space. Orbital Sciences’ Cygnus cargo capsule, for example, will be boosted into low Earth orbit by the company’s Taurus II rocket (which will also be used to launch satellites) and then use smaller motors to navigate to the International Space Station. Orbital has an eight-mission contract with NASA to carry supplies to, and waste from, the station between this year and 2015. Orbital plans to launch the Taurus II for the first time this summer, and it is also working on spacecraft designs that could carry astronauts.

SpaceX, too, is developing a paired capsule and propulsion system. The company is developing three versions of its Falcon launch vehicles, each with a different lift capacity; they will be able to send payloads (including satellites and probes) into low Earth orbit (where the space station is), geosynchronous orbit (used by many communications satellites), and beyond (for planetary exploration). The SpaceX Dragon capsule is being funded in part by NASA grants to develop a cargo spacecraft, but it is being designed so it can be easily upgraded to accommodate up to seven people.

Capsules are an efficient way to cram a lot of volume into a relatively small but strong structure. However, it’s not possible to exert much control over where they land; they use parachutes to alight in the ocean or on some unpopulated patch of land. Sierra Nevada (see “Chasing the Dream), on the other hand, is developing an orbital vehicle that has a lifting-body shape, like an airplane. The Dream Chaser will be propelled into orbit by United Launch Alliance’s Atlas V rocket and will use hybrid rockets for a controlled landing on airport runways.

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