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Sophisticated Balloons Could Help Steer Spacecraft
coondoggie writes "Getting spacecraft traveling at hypersonic speeds to slow down and land or achieve a particular orbit on a dime is no easy feat.
But researchers are developing a tool that will let engineers model and ultimately build advanced flight control systems that meld balloon and parachute technologies known as a ballute (BALLoon-parachUTE). Basically a ballute is a large, inflatable device that takes advantage of atmospheric drag to decelerate and capture a spacecraft into orbit around a planet, according to NASA who is funding Global Aerospace to build such a tool."
OK, this idea's been around for awhile. Its major useage in Hollywood was in the movie 2010 when the Russian spacecraft used one for aerobraking in Jupiter's atmosphere. Cute effect, but like Dr Floyd said, "Nice in theory, but the guys who did the numbers aren't here."
Understanding the scope of the problem is the first step on the path to true panic.
advanced flight control systems that meld balloon and parachute technologies known as a ballute (BALLoon-parachUTE).
I'd have called it Paraloon.
Or possibly Ballachute.
"Ballachute! I choose you!"
Yep. It works.
I officially think that the folks at NASA are a bunch of jerks for not respecting the results of their ISS node naming contest. :-(
Indeed.
It kills our best chance of making our first contact with a ship called "Skullfuck Soulshitter".
The key problem with atmospheric braking is heat dissipation. Craft in orbit have considerable energy (since they have orbital velocities of around 7.5 km/s or more) while craft returning from the Moon or Mars have far greater velocities (the Apollo capsules returning from the Moon had velocity of roughly 11 km/s, which is double the kinetic energy per kilogram of a low Earth orbit satellite). Entering orbit around a gas giant (like Neptune) will require even velocity dissipation. If you and everything on your spacecraft were indestructable, you could just dive straight in. In practice, since spacecraft aren't indestructible and payloads (eg, living humans) are somewhat fragile, you need to decelerate at a much more gradual pace. As it turns out, the sooner you can start deceleration, the better. The key way to decelerate early is to increase the cross-section area of the vehicle relative to its mass. This also has the advantage of distributing the heat load from atmospheric braking across a wider area and reduces the overall temperature of the vehicle. This reduces the complexity of the structures used to protect the vehicle from atmospheric heating (called "thermal protection systems" or TPS).
Capsules like Soyuz or Apollo have the highest mass per cross-section area and hence have high heating loads and decelerations. The Shuttle has pretty high heating loads as well. If it had been made considerably "fluffier", it wouldn't need the special tiles for its TPS.
Ballutes are cheap ways to greatly increase the cross-sectional area of the vehicle. For a fictional example of a ballute, the film 2010 portrays the Soviet spaceship, Leonov using one as it aerobrakes to slow down enough to orbit around Jupiter. Technically, in this case, it is aerocapture. This is aerobraking with only one pass through atmosphere. The usual process involves many passes through atmosphere, shedding some velocity on each pass.
The innovation in this article is the ability to control a ballute which has some lift. There are two possible uses that I can think of, off the top of my head. First, it can be used to steer the vehicle so that more of its path is in the less dense high atmosphere. In other words, we can steer to some degree the trajectory so that we get better deceleration and heating loads. Second, aerocapture is very hard. The key problem is that any changes in the atmosphere will change the trajectory, possibly enough to make the attempt unsurvivable. Even if the vehicle isn't in danger, small differences in the atmosphere or the vehicle's reentry trajectory mean the vehicle may end up on a different trajectory. If it is landing, it may end up far away from the desired landing spot. Ability to steer reduces the uncertainty of aerocapture and provides some valuable margin of error for a spacecraft.