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Comment by bprater | Hacker News Reader

They mention returning items from ISS. Does anyone know if this is the old standard method of using a parachute and dropping into the ocean for recovery?

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Previous Dragon Capsule recovery (and it was only once before) was parachute to ocean landing. [1] So presumably to limit the number of things being tested on this flight to a reasonable number they won't try to return it to land.

I am very hopeful that these guys succeed, and will be impressed as hell. Elon is not kidding when he says it is 'tricky.' Although I think the speed thing is over blown (17,000 MPH, wow! except you're both going about 17,000 MPH and you're both going the same direction, so relative speed is more interesting) But you do have to navigate there, rendezvous, and dock.

If successful they will have duplicated everything in Gemini and next up will be the Mercury program (first manned missions) :-)

[1] http://news.discovery.com/space/spacexs-dragon-capsule-retur...

I think the reason they're saying it's a bit more tricky than people realise is because, even when dealing solely in terms of relative speed, you're dealing with orbits.

If you try to accelerate, you'll actually end up in a higher orbit. It would be like putting down the gas to overtake someone on the highway and end up flying above them and even if you let off the gas, you will slowly drift further away as you're now dealing with a small amount less gravity.

It's tricky, because the common person doesn't have any clue how to relate to three dimensional movement in an orbit.

Actually, another funny story ...

One of the first programs I ever wrote was a BASIC game called 'orbit' which simulated docking with other space ships and satellites in orbit. No graphics other than things like closing speed and distance from target, sort of like the old Lunar program at the time.

One of the things that always got people thinking it was 'broken' was that you had to slow down to catch up, basically by slowing you moved to a lower orbit and moved faster relative to an object in a higher orbit, and then you went to a higher orbit to slow down (accelerating).

For now, at least. They have signaled the intention to use the launch abort rockets to make powered landings. I am not sure if they'd try to do it straight from atmospheric braking or if they want to use parachutes to slow down and then use the rockets to land.

In any case, it's very 60's sci-fi style. Quite cool.

By the way, currently it’s only possible to return up to 50kg of cargo from the ISS. After the Space Shuttle was retired, Soyuz became the only spacecraft that can actually return anything to Earth from the ISS and there is pretty much only space for three people and nothing else in that thing.

Dragon is supposed to bring back 600kg in its first test flight to the ISS, but it can bring back up to 3.000kg. That’s still not much compared to what the Space Shuttle could do (14.000kg), but it’s a lot more than what is currently possible.

So even if it takes another three years until the first manned flight, Dragon can be very useful as a cargo ship for the ISS (despite the fact that the ISS already has three cargo ships: the Russian Progress, the Japanese HTV and the European ATV – those three ships can deliver tons of cargo but they all can return nothing).

The ability to do about 4 Dragon flights to the ISS for the incremental cost of a single 2011 Shuttle launch does mean the raw down-mass capability is actually pretty comparable, though.

One thing, though, Dragon won’t deliver is volume. There was lots of space in the Space Shuttle. (But I just wanted to add that for completeness sake, not to claim that the Shuttle was super awesome.)

Yes, but that volume would not have been used for station maintenance missions. If you look at the manifests for the shuttle, they hardly ever used all that volume even for station construction.

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