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SpaceX Grasshopper Flies High

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Re: SpaceX Grasshopper Flies High

#81

Post by danielweber »

TeMPOraL wrote: post #52
EthanHeilman wrote: post #42

Earlier quoted context omitted.

You can't direct where the rocket ends up, highly likely that the rocket will get damaged or much less likely that the rocket will damage something else (This is why NASA dumps it's rockets over the ocean). Then you have find a way to get the rocket home, which involves time and money. Why not just burn fuel (rocket fuel is only a few times more expensive that burning water) and bring the rocket home? If you need mor…

> highly likely that the rocket will get damaged And because you don't know whether it is damaged or not (sometimes the damage may not be obvious), it's likely that the rocket will have to get a long post-flight inspection to check if it is suitable for another flight. It's something you can almost completely avoid if you land the rocket gently. I read somewhere, that the costs of recovering SRBs of Space Shuttle fro…

Maybe you are thinking of the costs of "re-using" the Space Shuttle. $250 Million to refurb it each time. But we do it for cost savings!

Re: SpaceX Grasshopper Flies High

#82

Post by JshWright »

jordan0day wrote: post #75
deepblueocean wrote: post #25

Earlier quoted context omitted.

I find this confusing. It's awesome, that's for sure. But it seems like lifting all the fuel needed to do a soft landing is inherently a tradeoff for less payload capacity. What is the benefit, then? Is it just so much cheaper to be able to re-use the first two stages?

I imagine there's a lot less fuel required to land than is required to take off. That is, on launch, the rocket is probably (eventually) reaching speeds of several thousand miles per hour. Upon landing, the atmosphere does most of the slowing-down for you, so you only need enough fuel to reduce the speed from terminal velocity (not sure what this would be for a rocket, probably several hundred miles an hour, at least…

Not to mention that the giant flying fuel tank (er... 'rocket') is _substantially_ lighter now that you've burned most of the fuel off.

Re: SpaceX Grasshopper Flies High

#84

Post by mikeash »

InclinedPlane wrote: post #58
deepblueocean wrote: post #25

Earlier quoted context omitted.

I find this confusing. It's awesome, that's for sure. But it seems like lifting all the fuel needed to do a soft landing is inherently a tradeoff for less payload capacity. What is the benefit, then? Is it just so much cheaper to be able to re-use the first two stages?

Almost the entirety of the cost of an orbital launch is in manufacturing and operational costs. Cost of fuel is basically just noise. If you can reduce operational turnaround time and operational complexity, even at a cost of payload, then you'll save so much money it'll be worth it in the long term. SpaceX is aiming for a re-assemble, gas up and go workflow. If they can pull it off it might reduce their per flight l…

To put it in perspective, the fuel used to launch a Space Shuttle cost in the neighborhood of $1 million, while the cost of the entire launch was somewhere around $500 million to $1 billion.

Re: SpaceX Grasshopper Flies High

#85

Post by deletes »

rays wrote: post #77

Poor bird gets killed in the video as it tries to fly away as the rocket takes off

The bird is way closer to the camera than the rocket. Check the video again when the bird starts to land it is approximately the size of half the width of the rocket. That would make the bird be positioned halfway between the camera and the rocket and well clear of the blast.

Re: SpaceX Grasshopper Flies High

#86

Post by JshWright »

baggers wrote: post #48
smackfu wrote: post #45

That aerial shot they have in the video is pretty neat... I wonder if they are using a UAV for that, or just some ballsy helicopter pilot?

".from SpaceX’s hexacopter." They have all the nicest toys!

Even buying something off the shelf, that's not an absurdly expensive 'toy' (If you build it yourself, you could put together a video platform like that for under $1k (including the gyro stabilized camera gimbal).

Re: SpaceX Grasshopper Flies High

#87

Post by mikeash »

ryanbrush wrote: post #50
stuff4ben wrote: post #37

Earlier quoted context omitted.

I thought the same thing. One of the Youtube commentswas pretty insightful in that it mentioned that when you do a parachute landing into the ocean, it's landing in salt water. Therefore the craft has to be taken apart inspected, cleaned, and put back together. So I'm assuming they've done the cost benefits and figured it's cheaper this way. I wonder if a combination parachute/thruster landing would be more feasible…

Not to mention the operational costs of a small navy to recover the rocket and transport it to a launch site.

I believe the "small navy" was a political and technological requirement and not something you'd need today. A single ship ought to do now.

Political, because it was the Space Race, and a lot of it was about shows of force. And hey, why not? You have a bunch of carrier battle groups just waiting around for a hot war, and you need to have them out training anyway, so why not use them to pick up spacecraft from time to time?

Technological, because guidance wasn't necessarily very accurate. It's interesting to look at the miss distances here:

http://en.wikipedia.org/wiki/Splashdown_(spacecraft_landing)...

Some of these landed hundreds of miles from their target. However, by the time Apollo came around, they were all very close. You definitely want a big recovery fleet to cover a lot of area when you can't be sure it'll land on target, but that's not so much of an issue these days.

Re: SpaceX Grasshopper Flies High

#89

Post by JshWright »

nkoren wrote: post #69
rplnt wrote: post #12

Earlier quoted context omitted.

I believe same thing was done by NASA in the 70s. So not really big step forward in this particular regard. edit: Can't find it at the moment. So far I've found http://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X which did what grasshopper and more almost 20 years back. I still believe I've read something earlier though. Will edit when/if I find it.

Nope, aside from the Lunar Excursion Module and its simulators, NASA did nothing like this until the 1990s, with the Delta Clipper. And that wasn't really NASA - it was a BMDO project which later got taken over by NASA. (NASA then crashed the Delta Clipper on their first flight with it, and promptly went back to their preferred innovation strategy: very large contracts which result in absolutely nothing).

>very large contracts which result in absolutely nothing

That's a moderately ironic statement, given the fact that SpaceX wouldn't be doing anything remotely close to what they're doing today without the very large contract they got from NASA.

Re: SpaceX Grasshopper Flies High

#90

Post by BaconJuice »

JshWright wrote: post #86
baggers wrote: post #48

Earlier quoted context omitted.

".from SpaceX’s hexacopter." They have all the nicest toys!

Even buying something off the shelf, that's not an absurdly expensive 'toy' ( If you build it yourself, you could put together a video platform like that for under $1k (including the gyro stabilized camera gimbal).

Hey JshWright, I recently got very interested in creating one of these and you seem to be pretty knowledgeable about this. Can you please give me advice on where a newbie can start with this? I would like to learn how to build one on my own from scratch.

Thank you.

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