Spaceplanes

The US Air Force's Automated Space Shuttle X-37B (US Air Force/Sipa Press/Newscom/File)

The final mission of the Space Shuttle Discovery is currently underway.  Additionally, the X-37B, the “secret” robot space shuttle operated by United States Air Force, just concluded a successful seven month mission last December. The Air Force is primed to launch a second X-37B robot shuttle at 3:39 p.m. (EST) today. This flurry of activity leads to general reflection concerning spaceplanes, crafts designed to operate in outer space, fly back through earth’s atmosphere, and land on ground.  With two in orbit at the same time spaceplanes are now more in use then ever…while simultaneously fading away.

First let’s look at NASA’s space shuttle program. Here’s what NASA’s website has to say about the Discovery:

It’s certainly earned its retirement. Discovery has flown more missions than any other shuttle – more than any other spacecraft, in fact. After 38 missions to date, and more than 5,600 trips around the Earth, Discovery has carried satellites such as the Hubble Space Telescope into orbit and sent the Ulysses robotic probe on its way to the Sun. It was the first shuttle to rendezvous with the Russian Mir Space Station, and it delivered the Japanese Kibo laboratory to the International Space Station.

The objective of the current mission is to deliver spare parts and supplies to the International Space Station. Along with water, new personnel, sundry modules, and widgets, Discovery is also delivering Robonaut 2.  Despite the misleading number, Robonaut 2 is the first humanoid robot in outer space.

Robonaut 2--wait, what?

When the mission is complete the Discovery is scheduled to go off to some museum. The entire shuttle program is winding down: the program was supposed to end in 2010 but international obligations compelled NASA to tack on a few missions in 2011.  Endeavor is already on the pad for what may be its final flight and Atlantis is on standby.  Enterprise (which never made it to space) is already at the Smithsonian. And, of course, Challenger and Columbia are both gone, lost along with their heroic crews in our first doddering steps into space.

Space Shuttle Discovery Lifting Off (Photo by Matt Stroshane/Getty Images North America)

The shuttles seem so much a part of our culture that it is hard to recognize how revolutionary they were in the seventies and eighties (and still are). It’s true that they are shockingly dangerous but the technology used to create them pushed the limits of materials technology a long way.  For example the thermal shields of the shuttle protect the orbiters from re-entry temperatures that could otherwise reach as high as 1,650 °C (about 3,000 °F), well above the melting point of steel. The program also advanced rocketry by leaps and bounds.

The American Space Shuttle and the Soviet Buran

The shuttles were the first spaceplanes to go into orbit.  The only other spaceplanes that are known to have done so were the unmanned Soviet Bor-4 test craft, the Soviet Buran (a space-shuttel knock-off scrapped during the Soviet meltdown after one successful manned fligth), and the OTV-1 and OTV-2. Both of these latter vehicles are Boeing X-37B robot shuttles used by the United States Air Force to test (note to the Air Force and Boeing, please give your robot space planes cooler names).  The X-37B is a automated shuttle with a payload about the size of a Ford Ranger pickup.  Originally a NASA program which was scrapped for budget reasons the robot shuttle was picked up by DARPA and built by the Air Force which claims to use it to test guidance, navigation and control systems.  Since the OTV-1’s mission (which was tracked by amateur astronomers) took the craft over Iraq, Iran, Afghanistan, North Korea, and China, it is reasonable to speculate that the craft may have reconnaissance purposes as well.

There are a number of suborbital spaceplanes which have managed to reach above the Kármán line but were incapable of going into orbit. Lately private companies have been jockeying to make more of these space hoppers and conventional wisdom asserts that the market will step in and deliver the next generation of spaceplanes. Hopefully private innovators will come up with some bright ideas. Budget and technical constraints have lead NASA to scrap its plans for ramjet scramjet and spaceplanes. There isn’t much else on the drawing board that we know about right now (other than the Japanese Space Program’s origami airplanes which are seemingly designed to be tossed into space for fun pictured below) .  The foreseeable future apparently belong to rockets.

The Japanese Space Program's 29-gram origami shuttle made of treated ricepaper--the future of spaceplanes?