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IRVE-3  (Source:
IRVE-3 embarked on a 20-minute test flight, where it was launched by a three-stage Black Brant rocket at 7:01 a.m. on Monday

NASA recently had a successful test flight for its Inflatable Reentry Vehicle Experiment (IRVE-3) heat shield. 
IRVE-3 is a 680-pound cone-shaped, inflatable heat shield that is covered with heat-resistant materials. The idea behind IRVE-3 is to protect space capsules as they enter or return an atmosphere at hypersonic speeds. It is the successor to IRVE-2, which was an inflatable heat shield of the same size, but carried a lighter payload and was subjected to lower re-entry heat than IRVE-3. 
IRVE-3 embarked on a 20-minute test flight, where it was launched by a three-stage Black Brant rocket at 7:01 a.m. on Monday. It took off from NASA's Wallops Flight Facility on Wallops Island, Virginia. 
Six minutes into the flight, the heat shield and its large payload detached from the rocket's nose cone (kind of like a mushroom) over 200 miles above the Atlantic Ocean. Nitrogen was pumped into the IRVE-3 using an inflation system. This caused IRVE-3 to inflate about 10-feet in diameter. 
From there, the heat shield dropped through Earth's atmosphere and managed to hold its shape through the heat and force of re-entry. NASA researchers were able to collect information like pressure and temperature data via tools onboard, which will help with future improvements of the heat shields. 
IRVE-3 ended its flight by splashing down into the Atlantic Ocean near North Carolina. It will be retrieved by a U.S. Navy Stiletto boat. 
"It's great to see the initial results indicate we had a successful test of the hypersonic inflatable aerodynamic decelerator," said James Reuther, deputy director of NASA's Space Technology Program. "This demonstration flight goes a long way toward showing the value of these technologies to serve as atmospheric entry heat shields for future space."

Source: NASA

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RE: Inflation
By m51 on 7/25/2012 9:43:00 PM , Rating: 2
It's possible to retro brake the spacecraft, but the mass penalty is exorbitant.

The MSL rover which is currently on the way to Mars was launched on one of the largest versions of the Atlas V (541) currently available. The total spacecraft (the payload) weight at launch was about 3.9 tons. The Atlas V 541 launch weight is about 532 tons.

0.9 tons of Rover
2.4 tons of Entry/Descent and landing system (aeroshell, descent stage, and 0.39 tons of propellant)
and 0.5 ton fueled cruise stage for the earth to mars journey.

It would take many tons of fuel to do the same job with braking rockets, which would require a much larger rocket than an Atlas V 541 to do the job. It's just not mass efficient.

Aerobraking is an incredibly mass efficient method of decelerating a vehicle if you can take advantage of it. Earth's atmosphere is great for it, we can already make heat shields that dissipate all the velocity and energy at even interplanetary approach speeds. Mars is unfortunately in a sort of no-man's land for atmosphere. Too much atmosphere to make retro braking with rockets simple, too little atmosphere to do a lot of braking before your vehicle hits the surface.

Doing the job with rockets just takes an enormous amount of fuel. Look at the size of the rocket needed to get something to orbit. You are essentially trying to do that in reverse, a similar fuel to payload ratio.

RE: Inflation
By JediJeb on 7/25/2012 10:17:36 PM , Rating: 2
That makes a lot of sense, thanks.

Another question, could you plan a trajectory that would bring you to Mars so that when you arrive you would essentially be pacing the planet at its own relative speed. Say maybe you overshoot the distance slightly ahead of Mars, then as you are pulled back by the Sun's gravity you cross back over Mars' orbit with little relative velocity as it arrives at the same point in space? I guess what I am thinking is a elliptical solar orbit where the apogee point is at Mars' orbit with orbital velocity matching that of Mars and arriving simultaneously at the same point in space as Mars?

This would allow you to arrive at Mars with little delta V relative to Mars which would require no braking thrust, as long as you worked out the proper slingshot trajectory around the Sun.

RE: Inflation
By m51 on 7/25/2012 11:01:47 PM , Rating: 2
yes, but the spacecraft is still going to accelerate toward Mars because of the gravity well and you can't fix that part of the velocity with orbital paths. At the minimum you'll still have to deal with the low mars orbit orbital velocity, which is still pretty high.

RE: Inflation
By Jaybus on 7/26/2012 8:43:48 AM , Rating: 2
It would also require a longer Earth-Mars flight path. "Just falling" in a single direction toward the center of Mars is not really possible, but even if it were, the acceleration is 3.71 m/s^2. Starting from zero Mars relative velocity from say 100 km up, in 60 seconds it would fall just 6.7 km and already be approaching supersonic speed at 222 m/s.

RE: Inflation
By JediJeb on 7/26/2012 10:32:37 AM , Rating: 2
Of course, thinner atmosphere means higher terminal velocity.

If it was the opposite and returning to Earth under the same scenario would the craft still reach hypersonic speeds in the upper atmosphere from acceleration due to gravity, or max out at somewhere around normal supersonic speeds due to air resistance, which would be more manageable in terms of heat generation and parachute braking ability?

RE: Inflation
By m51 on 7/26/2012 10:47:47 AM , Rating: 2
Just falling towards Mars starting from zero relative velocity you are going to reach essentially Mars escape velocity, which is 5 km/sec. or 18000 km/hr. You can reduce that with multiple aerobraking passes through the upper atmosphere, but your entry speed can't be lower than the orbital velocity at say 100km altitude which is about 12000 km/hr.

RE: Inflation
By JediJeb on 7/26/2012 11:44:15 PM , Rating: 2
Another crazy twist. What if you can place your craft into Mars' orbital path ahead of the planet and slow it slightly so that you are moving away from Mars but its gravity is slowing you down as it gets closer. Essentially Mars collides with your craft by catching up to it, could that be done without reaching such high relative speeds in the freefall?

RE: Inflation
By Paj on 7/26/2012 7:12:07 AM , Rating: 2
Interesting - thanks for the information.

I love it when Dailytech is like this. Straightforward scientific discussion, instead of arguing over how Marxist Obama is, or whether pollution is bad for the environment.

RE: Inflation
By JediJeb on 7/26/2012 10:33:25 AM , Rating: 2
Yes very nice, I am actually learning things in this thread that are useful :)

RE: Inflation
By Reclaimer77 on 7/26/2012 10:40:40 AM , Rating: 2
But he IS a Marxist! Let me tell you something you Liberal mother fu-----

AHAHA fooled ya. Just kidding :P

RE: Inflation
By Paj on 7/27/2012 6:57:44 AM , Rating: 2


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