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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."
"...will be cheaper and easier-to-build than NASA's space shuttle." I would hope they could build something cheaper and easier than the 30-plus-year-old shuttle.
Remember, German technology put the first man on the moon.
Re-entry heat shields are useless in space too, just as landing gear are useless for flying!
I think you want them for the same reason that we don't all parachute to our destination when our plane gets there. Although I can't say I haven't been tempted.
Bruce Perens.
In short, no.
Nitroglycerin is formed by mixing nitric acid and sulfuric acid (both highly concentrated, purified forms).
Atmospheric nitrogen, 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.
...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.
Indeed -- look at the history of capsules -- the sinking of Mercury 4, the Voskhod 2 crew's night surrounded by wolves, Soyuz 18a's high-G roll that nearly sent it tumbling off a 500' cliff, etc.
I think the best example is Soyuz 23: a mistargetted landing led to the capsule landing on a frozen lake and crashing through the ice. No problem as it was designed to float, right? Well, the parachute got wet and, weighed down, dragged the capsule upside down. The vent tube -- open, as per standard practice -- now began to fill the craft with ice-cold water. The cosmonauts luckily stopped it up before it sent the craft to the bottom. So there they waited, half submerged, upside down in a frozen lake, with no air, in -22C weather. They had to cut way their space suits and get into clothes so as not to freeze; it took an hour and a half. They relied on regenerated air, and did everything possible to conserve power -- they'd leave the system off until they nearly blacked out from the CO2, then turned it on just long enough to clear up. Nonetheless, they still ran out of power. Helicopters couldn't land in the blowing mist, and rescue attempts failed until they ultimately got a hook on the parachute and dragged the craft half a dozen kilometers across the frozen landscape before they could be rescued.
Being able to control where you land is a very good thing. ;)
Present day. Present time.
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
It is one thing I wish they would save a shuttle for.
NASA as a publicity fund raising stunt should save one shuttle's worth of parts and go retrieve the Hubbell Space telescope instead of crashing it into the ocean. Have the shuttle land and the load it directly for a flight to DC. Giving the whole pile (shuttle with Hubbell inside) to the Smithsonian.
Now that would be an awesome display. Heck I would donate money to help make that happen. To bad NASA doesn't think like awesome anymore.
i thought once I was found, but it was only a dream.
I am glad we have you to make these observations, I am sure the scientist and engineers working on this project have not thought about such issues. I urge you to email them right away with your insight into their project.