When Can We Look Forward to the Next Generation of Space Planes?

Technically, space planes have been around for a long time. The X-15 began flying in the late 1950s and the Space Shuttle was certainly a space plane of sorts, and other less impressive ones have flown as well. But no space plane has been able to launch from the ground, without the aid of external fuel tanks, fly into space with orbital capability, and then perhaps venture forth to the moon, the planets or beyond - now that’s the kind of space plane many people would like to see!

Let’s find out how long it will be before aerospace engineers develop the next generation of those powerful, elegant, winged spacecraft.

History of Space Planes

The X-15 was the first operational space plane, because it could maneuver both in the air and space. First flown in 1959, the X-15 was a rocket glider launched from the underbelly of the B-52 Stratofortress. The X-15 could accelerate to about 4,500 miles per hour and attain an altitude of 50 to 70 miles. (By international standards, anything above 100 kilometers or 62.1 miles is considered the threshold of space.) At present, the X-15 is still the world’s fastest manned rocket-powered aircraft.

The next great leap for space planes came with the launch of America’s Space Shuttle in 1981. The Space Shuttle was big and bulky, requiring the use of external fuel tanks, but it could launch from the ground and obtain an orbital trajectory, while carrying a large payload and astronauts, thus making it the space workhorse of the United State from 1981 to 2011.

Please keep in mind, it’s one matter for a space plane to reach orbit but it’s another for the craft to survive the tremendous heat of re-entering the earth’s thick atmosphere. The Space Shuttle needed heat-resistant ceramic tiles to protect its underside from temperatures approaching 3,000 degrees Fahrenheit. The X-15, in comparison, had no such heat-resistant capability, so it was strictly a suborbital space plane.

During its time, the Space Shuttle was often called the most complicated machine in the world, a title it almost certainly deserved. Nevertheless, there were mishaps. Two flights ended in disaster, one during launch and the other during landing, the two most dangerous times for any space plane.

Then SpaceShipOne was launched in September 2004. It was the world’s first privately funded space plane. The craft was air-launched and suborbital in capability, reaching speeds of Mach 3, so its possibilities were limited (Mach 1 is 768 mph). After this flight, which earned the developers, Paul Allen and the company, Scaled Composites, $10 million for winning the Ansari X Prize, SpaceShipOne was retired to a museum.

One day soon, however, the developers of SpaceShipOne and the Virgin Group hope to produce a successor space plane, SpaceShipTwo, designed to carry paying customers into space on a regular basis, essentially making all of them astronauts in the process.

The Biggest Problem for Space Planes

In the 1980s, the Reagan administration envisioned the development of an “Orient Express,” which could fly from New York to Tokyo in two hours, flying at Mach 25. Well, this marvelous vehicle remained little more than theoretical. Then in the middle 1990s the Clinton administration wanted to build a national aero-space plane, one surpassing the limitations of the Space Shuttle at the very least, but the technology simply wasn’t available.

The critical problem with producing a space plane that takes off from the ground without the use of external fuel tanks and then flies into orbit or beyond is that it must have a very powerful propulsion system and also weight practically nothing. For perspective, it takes 60 times more energy to propel a vehicle into orbit than it does to accelerate one to Mach 3, the top speed for many jet fighters.

The only propulsion system available at present for use in space planes is chemical rockets similar to those used by the Space Shuttle. These rockets produce great thrust but also use massive amounts of fuel, which adds much weight to the craft. The fuel tanks weigh a lot too.

One option is that while this proposed space plane flies through the atmosphere it could take advantage of an air-breathing engine such as the scramjet, the existence of which has been around since the 1950s (a version of the X-15 was proposed to use one). The scramjet operates at supersonic speeds and can theoretically accelerate an aircraft from Mach 12 to 24. (Earth Escape Velocity is Mach 33 or 25,000 mph.) However, in order for a scramjet to operate efficiently, the space plane must first be accelerated to hypersonic speeds with the use of a turbojet, turbofan or rocket. Unfortunately, this arrangement is complicated and heavy and would only work in the atmosphere.

The Air Force X-37B Space Plane

Perhaps the most advanced space plane at present is the Air Force X-37B mini shuttle (aka the Orbital Test Vehicle). This space plane is much smaller than the Space Shuttle and is launched from atop an Atlas V rocket. It can stay in orbit for months at a time and land horizontally as a glider. Unfortunately, the X-37 is an unmanned vehicle, uses conventional rocket technology and has a payload the size of a pickup truck.

Much about the X-37 is classified. It apparently operates as a reconnaissance space vehicle, but some think it may be used as a space weapon. Whatever its usage, the X-37 certainly has its limitations, though theoretically it could one day carry astronauts into space.

The Future of Space Planes

Here’s a pertinent quote from the website www.space.com: “Some of it is pop culture – things like Buck Rogers – but we see this space plane concept throughout history,” says Roger Launius, space history curator at the Smithsonian’s National Air and Space Museum. “We have this longstanding belief that coming back on wings, and using wings for flying into space, is the right way to go, and we haven’t abandoned that yet.”

Indeed, many haven’t abandoned that belief. The future is where the space plane's continued development lies, because it obviously needs a revolutionary new propulsion system. Chemical rockets are strictly “old tech” and decidedly twentieth century. Humankind doesn’t need another Space Shuttle; it needs imagination, advanced engineering and almost certainly a fair amount of cash.

Well, what futuristic propulsion system could be used for the next generation of space planes? One possibility would be using an engine that runs on antimatter. A so-called positron reactor could propel the space plane much faster than chemical rockets, and the fuel would weigh milligrams rather than the thousands or millions of pounds needed for a comparable amount of thrust from chemical rockets. The NASA Institute for Advanced Concepts is working on this positron reactor engine. Let’s hope we see a prototype soon!

Other possibilities would be nuclear propulsion, a hydrogen reaction engine or even antigravity, but clearly something else will be needed to power future space planes – the ones many people envision, the ones they want to see soaring through the sky, destination the moon or Mars - something like the proverbial flying saucer perhaps.

Unfortunately, that space plane probably won’t be developed for many years - unless, of course, more money is spent on development. Will the people open their wallets? We could build one within years!

Well, maybe we could or couldn't, but Roger Launius and other experts believe space planes will definitely be a major aspect of future space exploration. After all, there's nothing more beautiful than a winged space vehicle!

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