Discussion SpaceX's Grasshopper RLV

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SpaceX testing VTVL prototype

A couple of readers pointed me to this FAA document: Draft Environmental Assessment for Issuing an Experimental Permit to SpaceX for Operation of the Grasshopper Vehicle at the McGregor Test Site, Texas - September 2011 (pdf)
2.1.1 Grasshopper RLV
2.1.1.1 Description
The Grasshopper RLV consists of a Falcon 9 Stage 1 tank, a Merlin-1D engine, four steel landing legs, and a steel support structure. Carbon overwrapped pressure vessels (COPVs), which are filled with either nitrogen or helium, are attached to the support structure. The Merlin- 1D engine has a maximum thrust of 122,000 pounds. The overall height of the Grasshopper RLV is 106 feet, and the tank height is 85 feet.

The propellants used in the Grasshopper RLV include a highly refined kerosene fuel, called RP- 1, and liquid oxygen (LOX) as the oxidizer. The Grasshopper RLV has a maximum operational propellant load of approximately 6,900 gallons; however, the propellant loads for any one test would often be lower than the maximum propellant load. Even when the maximum propellant load is used, the majority of the propellant would remain unburned and would serve as ballast to keep the thrust-to-weight ratio low.​
 

T.Neo

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Oh wow! What an interesting development...

I wonder if this is a testbed for technologies intended for F9 first stage reuse, or some new, odd R&D program. I would imagine more of the former.

Still, I wonder how much cash SpaceX is spending on this. Aren't they supposed to be building rockets and gearing up for an acceptable flight-rate with Falcon 9? ;)
 

Tacolev

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Not sure the F9 would be able to keep enough fuel for a powered descent of the first stage and get the upper stage going fast and high enough to deliver a useful payload. My bet's on this being for something akin to Blue Origin or Virgin's intended suborbital joyride service. Stick a dragon with a vestigial service module on top and use the LAS if something goes wrong.
 

T.Neo

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It doesn't necessarily need to be a powered descent, just a re-firing of the Merlin engines to reduce velocity upon return to Earth.

That lower stage is only some 15 tons, so it isn't that much to slow down (relative to the vehicle when full of propellant).
 

Tychonaut

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About seven minutes into this video,
Musk states they're investigating engine re-start on the F9 first stage to shed velocity as it returns.
I'm also curious how that will affect payload, and if these developments are related. Guess we'll have to wait and see.
 

T.Neo

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I think Elon Musk is mad. :blink:

I think he's totally crazy...

Good for SpaceX if they pull this stuff off. I'll be watching closely.
 

Ark

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I knew Musk was crazy, but I didn't think he was THAT crazy. :lol:

I don't think NASA has ever even talked about first and second stage recovery like that, let alone built test articles. How cool would it be if they didn't have to build an entirely new rocket for every launch? Even getting 2 launches per rocket would mean a huge cost reduction. It's still just vaporware until we see the test platforms, but given what they've accomplished already I have more faith in this stuff becoming a reality than NASA's last powerpoint rocket.

Is that the original soundtrack, or did the uploader add it?
 

N_Molson

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I think this animation is wild, wild anticipation. And the "cool rock soundtrack" behind, that's a little like rendering a non-existing launch vehicle like a Saturn-V.

Seems pretty dangerous too, what if there is a problem (winds, guidance) and the stage lands on the White House roof ? :blink:

Won't believe in this until I see a successful demonstration with the first stage.
 

T.Neo

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How cool would it be if they didn't have to build an entirely new rocket for every launch?

space-shuttle-discovery-launch-pad.jpg


Would certainly be cool, wouldn't it? ;)

Even getting 2 launches per rocket would mean a huge cost reduction.

You also have to refurbish the vehicle after flight.

Admittedly, there's a lot of a sentiment out there that reusability simply isn't practical... maybe SpaceX proves that wrong. After all, they test-fire their engines, surely they must have done repeat firings of those same engines and figured out what refurbishment needs to be done after use.

Maybe.

I think this animation is wild, wild anticipation.

Would you say the same thing about a NASA animation? ;)

I would, even if it is a pretty mundane animation.

And the "cool rock soundtrack" behind, that's a little like rendering a non-existing launch vehicle like a Saturn-V.

The difference is that the cool rock soundtrack is to make the video not half-boring, a Saturn V paintjob is to distract people from potential criticism. ;)

If you have ever made a video vaguely similar to this one, you will understand this fact. And sometimes be continually embarassed by the soundtrack you choose for the video, anyway. :lol:

Seems pretty dangerous too, what if there is a problem (winds, guidance) and the stage lands on the White House roof ?

I'd be more worried about it crashing onto Orlando or someplace like that, since that's what its flightpath takes it over... more or less.

Won't believe in this until I see a successful demonstration with the first stage.

Seconded. These "Grasshopper" tests would be an interesting proof-of-concept though.
 
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N_Molson

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The difference is that the cool rock soundtrack is to make the video not half-boring, a Saturn V paintjob is to distract people from potential criticism.

Purely subjective, some people like hearing music, other looking at paintings... :lol:

Seriously, without speaking of the propellant required, 2 landing gears (1 for each stage) on a rocket ? Seems a lot of dead mass to me...
 

T.Neo

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Seriously, without speaking of the propellant required, 2 landing gears (1 for each stage) on a rocket ? Seems a lot of dead mass to me...

Maybe that dead mass is worth it. ;)

Also, I am not sure what amount of propellant would be required (my gut feeling is that it'd be a scary, penalty-inducing amount), but the whole fly-back-and-land-vertically thing might well be better than dumping your stages in the ocean from a reusability perspective.
 

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I'd be interested to see whether it works with the Dragon capsule. I always got the impression it wasn't fesible to land safely using rockets which is why traditionaly all capsule craft have been parachuted back to earth.

Plus could the Dragon capsule store enough fuel to perform a deorbit burn and then slow itself down to land a crew safely on earth? Obviously allot of speed is lost during the re-entry phase but would it be enough?

It will be cool to see this whole concept bcoming a reality though, I often think we can be very wasteful with our rocket parts! Even if it can't be used again at least you have the metal to recycle.
 

Tychonaut

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I think Elon Musk is mad. :blink:

I think he's totally crazy...

Good for SpaceX if they pull this stuff off. I'll be watching closely.
I think it's high time we saw some crazy back in the space business.
After decades of NASA's super-cautious, glacially-slow approach to everything, crazy can't do any worse. "Sanity" gave us an STS that never worked as it was advertised and killed fourteen astronauts, and a gaggle of follow-on programs that have yet to produce a working rocket or capsule.
Let's hear it for the crazy ones. :thumbup:

I think this animation is wild, wild anticipation. And the "cool rock soundtrack" behind, that's a little like rendering a non-existing launch vehicle like a Saturn-V.
Though it's a long way from reality, unlike most of the videos that come out of NASA and their contractors I believe Musk is actually sincere about doing this, and he'll only stop if physics or budgets stand firmly in his way.
Given the lyrics and the context, I suspect the song was chosen as a none-too-subtle middle finger at the existing space industry.

Seems pretty dangerous too, what if there is a problem (winds, guidance) and the stage lands on the White House roof ? :blink:
We can only dream...or perhaps a stage each on both houses of Congress. With a few hundred kg of RP-1 and LOX left in each tank, perhaps SpaceX could be induced to land them a little...hard.

Won't believe in this until I see a successful demonstration with the first stage.
I too will believe it when I see it. But for now it's good to have some fodder for daydreams. Something other than the illegitimate spawn of a Saturn V and STS.
 

Ark

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I don't know the numbers, but how much fuel would you really need to land a near-empty stage? With a basic heat shield on the front end to soak up most of your speed, you just need enough fuel to slow it from terminal velocity to a landing. Yes, it's dead weight, but it's weight that gets ejected along with the first stage. Seems to me like the penalty to your LEO payload wouldn't be that much.
 

Hlynkacg

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The Falcon 9 first stage mass just under 15 tonnes, with aerobraking and maybe some drogue-chutes It shouldn't take all that much Dv to land it.
 

T.Neo

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The thing is, that they are not just trying to land the stage, they are trying to put it on a trajectory that takes it back to the launch site.

More propellant... but less demanding exposure, maybe. It gets rid of the issue of both impact with and exposure to seawater.
 

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The thing is, that they are not just trying to land the stage, they are trying to put it on a trajectory that takes it back to the launch site.

More propellant... but less demanding exposure, maybe. It gets rid of the issue of both impact with and exposure to seawater.

I tend to agree, no sea water, means less corrosion treatment, and lower refurb costs.
 

T.Neo

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Programmatically risky, yes. But not crazy. VTOVL launch vehicles with much larger payload capacities have been designed before: http://www.astronautix.com/lvs/serv.htm

Best of luck to Mr. Musk if he can build a better shuttle.

I don't particularly see the resemblance to SERV. If anything, Grasshopper is comparable to the DC-X. It's like a DC-X built out of Falcon 9 'spare parts'.

It also isn't very comparable to STS. Everything from the different components of the vehicle, to the propellants, to the way they are reused, to minor technical details, is different.

As far as I can tell, the major pitfalls of the Shuttle (from the Orbiter processing standpoint) related to the TPS and the engines. To make reusability (a little more) viable, those two components will likely have to have improved refurbishment and reuse characteristics over what occured with STS.

SpaceX has already done (I'd imagine) quite a bit of R&D on their Merlin engine, so they must know more or less about how it reacts to reuse.
 
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