SpaceX's Grasshopper

[Wanderlust]

Grasshopper did its first test today! This is the first step in working out full reusability for Falcon 9!



http://www.youtube.com/watch?v=ObJb3...layer_embedded

[gturner]

Ooooo.....

[gturner]

It needs a memorable quote.

"That's one small hop for a rocket, one giant leap for ... um, cheaper rocketry."

[Crazy Eddie]

Ironically, between the Falcon 9 and the Dragon capsule, this means SpaceX is closer to a manned moon landing than NASA is now.

[MANT!]

How much for a ride?.. If I was stupid rich, I know the Russians could shoot my ass around the moon for a small fee...

http://www.zmescience.com/space/150-...-left-4323445/

Of course this would be their first attempt...

[YellowSubmarine]

newtype_alpha wrote:

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Ironically, between the Falcon 9 and the Dragon capsule, this means SpaceX is closer to a manned moon landing than NASA is now.

I think closer is an understatement, SpaceX would soon have hardware that's almost capable of a Moon landing. And if the Grasshopper achieves its stated goals dropping the price of launches low enough, they could do a Moon landing with their own money. Regularly.

I'm not sure if the SuperDraco engines provide enough thrust for landing on the Moon, but that aside, they can do an unmanned in 2013-2014 if they have $200-300M to waste. Or even less if they utilise the Falcon Heavy demo flight due to a lack of customers.

By the way, I'm not sure if gturner's post is intended to be serious or humorous, but it is spot on. The Grasshopper and SuperDraco will be SpaceX's first* technical firsts. Being the first private company in orbit is something, true, but so far they have been doing what has been already done by governments. On the other hand, nobody has ever landed a rocket, or even a capsule propulsively. Which is the reason I'm excited for SpaceX much more than I would be for a random company that would provide launch capability and a capsule as requested.

Even that feeble hop in the video in the OP is an example of an imaginative technical first, because I'm pretty sure that nobody has done that either.

* Well, there were probably some small ones in the design of the rockets and capsule, including the launch abort, but nothing substantial.

[sojourner]

^You're totally forgetting DC-X and about 3 other companies that have been building propulsive landing rockets for about the last 10 years. Now, when and if they get it into service, THAT will be a first, if one of the other companies don't beat them to it.

As for the Superdraco having enough thrust to land on the moon, you do remember it's designed to land the dragon capsule on earth right? Earth having higher gravity?

[YellowSubmarine]

Oh, I didn't know about DC-X, I actually like how it looks. But as far as I can tell all the tests have been limited in duration, and it neither has actually gone to orbit, nor it has had a big enough version capable of doing so?

As for the SuperDraco and the Moon –

I don't think that gravity is as important as air drag here. For landing on Earth, the delta-v required from the engines is far less, because the atmosphere does most of the job. For the Moon, you have less gravitational acceleration to deal with, but your initial speed will be a problem anyway. So unless you pick some crazy trajectory, I have some doubts that the Earth SuperDraco engines will do it, but I'm sure they can be upgraded for the Moon.

Unless I'm missing something?

Edit: Hm, I guess someone who has worked more with celestial mechanics could clarify that, but now that I think about it, when Dragon is inserted into lunar orbit, it has to deal mostly with cutting horizontal speed, at least initally, and if I understand correctly you would have more time to do it, so thrust might be not as important as fuel? I'm still not sure that it would be enough though.

Edit 2: Right, I think I figured that out, the lack of air would make almost no difference, except for the fuel expenses. Gosh, I'm stupid. You only need thrust force to cancel out the force of gravity. If it can do it on Earth, the Moon would be a piece of cake. At the speed you'd be touching down, air resistance doesn't play a role at all. Feel free to laugh at me.

Now, having learnt this, I'm betting on a private moon landing in 2013.

[Crazy Eddie]

YellowSubmarine wrote:

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I'm not sure if the SuperDraco engines provide enough thrust for landing on the Moon

They don't. Depending on the fuel loads, their delta-vee is around 400m/s: just enough to escape from an exploding rocket, or enough to slow to a stop from a terminal velocity of around 250m/s and then hover for a second or two just before touchdown. That, combined with Dragon's RCS thrusters, would give you about 700m/s, about a third of what you'd need for lunar deorbit and controlled landing (The Apollo LEM needed just under 2100m/s on its way down and the ascent stage needed 1500 on its way up).

Actually, though, I was thinking that the grasshopper's landing system wouldn't be hard to modify into a lunar landing vehicle. The grasshopper stage is the same diameter as Dragon's trunk, after all, so mounting the landing system to a Dragon capsule along with propellant tanks and life support equipment is a natural evolution path.

Being the first private company in orbit is something, true, but so far they have been doing what has been already done by governments. On the other hand, nobody has ever landed a rocket, or even a capsule propulsively.

True that. If SpaceX continues to meet its technical goals the way it has in the past, they WILL supplant NASA as America's front line space program. It's fair to say that NASA's big dreams and long-range ambitions are slightly more impressive, but they're not doing the grunt work it takes to REACH those goals in a way that makes sense. It's like a kid who never does his homework and never shows up to class and studies really really hard for the final exam because he wants to get into Harvard.

[YellowSubmarine]

newtype_alpha wrote:

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Actually, though, I was thinking that the grasshopper's landing system wouldn't be hard to modify into a lunar landing vehicle. The grasshopper stage is the same diameter as Dragon's trunk, after all, so mounting the landing system to a Dragon capsule along with propellant tanks and life support equipment is a natural evolution path.hard for the final exam because he wants to get into Harvard.

Given how SpaceX designs things, I'm half sure that's already an intended part of the design.

[sojourner]

all they would really have to do is cut a short version of the tankage. A bigger problem with grasshopper might be how deeply the Merlin engine can throttle for a moon landing.

[Crazy Eddie]

AFAIK, the Merlin isn't throttlable, but I could be wrong about that.

More importantly, the Merlin runs on RP-1 and Liquid oxygen, a precarious mix for a spacecraft trying to land on the moon. That, plus the lighter gravity of the moon means you'd be better off using the landing platform with a cluster of five or six superdracos or a modified Kestrel engine fueled by hydrazine.

If SpaceX was smart, though, they would probably take a page out of the old Soviet playbook and have the landing platform and its propellant tanks as a separate unit from the actual engine. This way, the ship blasts off from the landing platform using the ascent/descent engine and leaves the spent propellant tanks and the landing legs behind. Saves weight on the descent that way.

[sojourner]

SpaceX has a version of Merlin-1D that is throttle-able. Otherwise, no grasshopper. This variant will also be capable of at least 2 restarts.

[Crazy Eddie]

But again, they're going to need an engine that can run on hydrazine, while the Merlin is still burning RP-1/LOX, propellants which are NOT ideal for a lunar landing vehicle despite the higher ISP.

[sojourner]

Oh, most likely they wouldn't use Merlin for a lunar lander. I was just correcting the throttle remark.