In September, the Genesis space probe will eject a capsule to Earth carrying fragile samples of the solar wind - particles spewed out from the Sun.
Dan Rudert is optimistic about the mission's chances
The capsule's fall will be slowed by two parachutes, but its fast descent means the container must be caught in mid-air by a helicopter with a hook if a damaging impact with the ground is to be avoided.
The US space agency turned straight to Hollywood for this job. BBC News Online spoke to Dan Rudert, Genesis pilot and one of the US film industry's top stunt men.
What was your reaction when you first heard the idea of dropping an object from space to Earth and snatching it in mid-air with a helicopter - did it seem a little far-fetched?
DR: Probably like all of us, when you hear that someone is capturing a space capsule, coming in from re-entry, you picture flames coming off it and pieces of it burning up as it comes in through the Earth's atmosphere.
So, when Cliff (Fleming, co-pilot on the capture) told me about it, my initial reaction was: "You want to use a helicopter to catch that!" When Cliff did the first catch here in 1999, I was brought in to take the replica capsule up to 18,000ft and drop it and I took that challenge because I have never been up that high in a helicopter.
When I saw the rigging on this helicopter and this big hook for the first time - it was pretty wild - I was kind of like: "Cliff, what are you doing?" But it was really interesting to drop the capsule and watch Cliff do the first catch and now that I have done it too, it seems a little more sane.
How does it work?
You get asked to do a lot of crazy things by directors - but that is made for movies and TV. This stunt is not fiction; it's the real deal.
DR: We use a Eurocopter Astar and under the helicopter there is a boom that is 18 feet and 5 inches long with a capture hook on the end. Inside the helicopter there is a winch assembly that plays out a line down to the hook on the end of the boom.
Once we have lifted off the ground, we lower the boom and put it at a 50-degree angle so that it is clear of the tail rotor. That hook takes about 200lbs of force to pull it off, so when we fly over the parafoil and catch it, it pulls the hook off and the line plays out on the winch to about 60-100ft - kind of like a decelerator. So you feel a firm tug, but it's actually quite smooth. It's pretty benign.
The hook is catching two lines that are sewn into the parafoil on the leading and aft edges. The hook bunches up the chute and a lot of times you get a lot of the parafoil out here floating. But what we care about is that the hook catches those lines inside the parafoil - if we are lucky it catches them both.
We don't want it to slip back out so there is a pyrotechnic device loaded in the hook, which fires a pin to secure the chute once it's hooked. We have shown that it will go through seven layers of parachute and once that pin is in place we've got it - it's not coming out.
Then we land it gently on the ground and take the parafoil off because it causes so much drag. Then we just take the capsule alone and fly it back to the clean room slung beneath the helicopter.
What special skills are you bringing to this project?
DR: You've got two Hollywood stunt pilots doing this and that is what Cliff and I do. We got into the film business because of our background doing utility work.
Cliff and I have done all sorts of mountain work and long-line work (where a load is slung beneath the helicopter); we've done helicopter skiing and I used to do a helicopter ambulance service at Lake Powell (in Utah) for years and we took that experience and did well in Hollywood.
The helicopter will catch the capsule thousands of feet in the air
The analogy with doing movies and doing this is that a lot of the work we do with helicopters in movies is to have cameras on board and it requires us to get very close - directors always want to be lower, slower and you have to come right overhead - say someone on a horse or in a car and you have to catch them right on the curve or as he comes over the hill.
A lot of those skills actually parallel what it's like to get sight to acquire the parafoil, getting lined up to it, hitting the mark on it. We try to capture it a little off-centre on purpose to collapse the chute and you've got to hit it right on time; so flying camera a lot has helped quite a bit.
What movies have you done?
DR: The Hulk, Swat, XXX, We Were Soldiers, Charlie's Angels, Swordfish, Con Air.
Is this the most unusual thing you've ever been asked to do?
DR: Just about. You know you get asked to do a lot of crazy things by directors - people grappling out of your helicopter or flying over buildings or cars that blow up. But that's kind of made for movies and television.
This stunt is not fiction; it's the real deal. To capture a capsule that has been in outer space - if Cliff and I do this it will be the first time any helicopter pilots have ever attempted to catch something that has been in outer orbit.
A lot of time and money has been spent in collecting these solar samples and when this thing comes down you know there's a big chain - and you are one link of it - but you better be able to capture it.
So is it just like you're doing another movie stunt?
DR: Well, it's an interesting analogy because on a big movie, there's a lot of people and a lot of money involved, a lot of trying to get your timing down, to try to get the shot just right.
But in movies if you don't get the shot you can sometimes go around and reset. On 8 September, the space capsule comes in on this day and this day only and you better be ready and able to catch it because you don't get another chance to try it again the next day.