Germany To Test Actively-Cooled Spacecraft

FleaPlus writes "The German Aerospace Center is planning to launch a novel reusable spacecraft in 2011, incorporating flat, damage-resistant tiles. Nitrogen will be pumped through the porous tiles, creating a protective gas layer that actively cools and shields the hottest parts of the spacecraft from the searing heat of reentry. The €12.5M unmanned 'SHEFEX II' project is a major technological step toward the team's eventual goal of a reusable space glider, which will be cheaper and easier to build than NASA's space shuttle."

Re:why the obession with glider spacecraft?

[Somegeek]

Capsules are great if you don't mind landing in an ocean or a desert; someplace big and empty.

However, if you would like the efficiencies created by being able to land your spacecraft someplace specific and useful near a population center, like a spaceport or airport, than wings are just the ticket.

Re:Nitrogen?

[aquila.solo]

In short, no.

Nitroglycerin [wikipedia.org] is formed by mixing nitric acid and sulfuric acid (both highly concentrated, purified forms).

Atmospheric nitrogen [wikipedia.org], on the other hand is remarkably stable. At very high temperatures, (such as you might find at the leading edges of a reentry vehicle) nitrogen can be oxidized to to various forms of NOx. These can form acids in solution, but not in concentrations high enough to worry about.

And when you consider that there is plenty of naturally-available nitrogen in the atmosphere, this small addition probably isn't enough to worry about.

Re:I've thought of that myself

[aquila.solo]

...but then you still have to re-radiate that heat someplace.

The way I read TFA is that the N2 coolant is consumable. Rather than circulating it to a heatsink, they just expel it through pores in the surface, allowing the gas to buffer the compressed air during reentry. It brings cooling back into a convective mode.

Sure you have to refill the tanks prior to the next launch, but liquid nitrogen is (relatively) cheap.

Re:German technology

[Rei]

That's not entirely true; it's more of a US excuse during the space race. The US was very successful with Operation Paperclip [wikipedia.org], which was an attempt to make sure that the US, not the USSR, got most of the German rocket scientists (as well as several whole V2 rockets). The Soviets got a few German rocket scientists (most notably, Helmut Gröttrup, Wernher von Braun's assistant), but not many. Most of the people they got were low level people, mainly on the assembly lines. They were primarily interrogated for information and little used beyond that point. After 1951, not even Gröttrup was allowed to assist in their rocket program any more, and he was returned to Germany in 1953 -- back when von Braun was just starting to become a big rocketry name in the US, and well before his tenure as NASA's first director (1960-1970).

Re:Liquid nitrogen?

[tsotha]

It's pretty normal for rocket engines to be regeneratively cooled with explosive fuel. This kind of approach has its flaws, but you haven't identified one of them. For a space ship during reentry every point on the airframe is critical.

Re:I've thought of that myself

[wagnerrp]

You're thinking about this completely the wrong way. This is not actually cooling at all. They are injecting cold gas into the flow, against a positive pressure gradient. The pressure keeps the flow pressed against the surface of the craft, producing a protective film. The film prevents the craft from ever heating up in the first place. While this is a novel use of the technology, the technology itself is nothing new. It has been used for decades in rocket nozzles and gas turbines to protect the hot sections, and is a well understood and researched technique.

Re:Thank God it's unmanned

[wagnerrp]

This technique doesn't cool anything, it prevents the tile from ever heating up in the first place. It has been in use for decades in gas turbines and rocket nozzles. http://en.wikipedia.org/wiki/Turbine_blade#Cooling [wikipedia.org]

Re:Liquid nitrogen?

[wagnerrp]

If such cooling systems were prone to failure, we would have airliners regularly falling out of the sky. Jet engines use this same exact technique to protect their combustors and turbines. Were the film to fail, you would have maybe 30 seconds before that whole section of the engine completely melted away.

Re:why the obession with glider spacecraft?

[Anonymous Coward]

Hubble can not be returned with any of the remaining space shuttles - they all have an airlock to dock to ISS permanently mounted in the payload bay. The last shuttle that would have had enough room to transport Hubble would have been Columbia.