Author Topic: Grasshopper RLV  (Read 133498 times)

Offline Zond

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Grasshopper RLV
« on: 09/23/2011 11:44 pm »
Draft Environmental Assessment for Issuing an Experimental Permit to SpaceX for Operation of the Grasshopper Vehicle at the McGregor Test Site, Texas

Quote
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.

 :o
Musk seems to be jealous of Bezos.

Offline grakenverb

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Re: Grasshopper RLV
« Reply #1 on: 09/24/2011 12:07 am »
Is this a test vehicle for a Lunar or Mars lander, or is Spacex going to be competing with Virgin Galactic? ???

Offline Silmfeanor

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Re: Grasshopper RLV
« Reply #2 on: 09/24/2011 12:20 am »
Is that a full size falcon 9 tank? It seems to be smaller, but how much smaller?

And a single merlin 1-D engine?
The 1D can throttle from 70% to 100% - won't that be a problem for coming down again?

I'd love to see this, I wonder if they have any bent metal already..

Offline Lars_J

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Re: Grasshopper RLV
« Reply #3 on: 09/24/2011 12:31 am »
A test vehicle for F9 1st stage powered landing?

Offline HMXHMX

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Re: Grasshopper RLV
« Reply #4 on: 09/24/2011 12:31 am »
Is this a test vehicle for a Lunar or Mars lander, or is Spacex going to be competing with Virgin Galactic? ???

Pretty obviously, this is to develop techniques for F9 first stages to recover on "land" which might include a barge at sea.  Should be amusing to watch the patent fight with Blue Origin, if so.


Offline jedsmd

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Re: Grasshopper RLV
« Reply #5 on: 09/24/2011 04:06 am »
Quote
Pretty obviously, this is to develop techniques for F9 first stages to recover on "land" which might include a barge at sea.

So at least one F9 1st stage engine would have to be restartable after stage separation?
« Last Edit: 09/24/2011 04:13 am by jedsmd »

Offline Lars_J

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Re: Grasshopper RLV
« Reply #6 on: 09/24/2011 04:08 am »
Yep, at least one.

Offline jedsmd

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Re: Grasshopper RLV
« Reply #7 on: 09/24/2011 04:13 am »
.  Wonder if this will be demonstrated on the higher grass hopper fights?

Offline docmordrid

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Re: Grasshopper RLV
« Reply #8 on: 09/24/2011 05:12 am »
Quote
The Grasshopper RLV is a vertical takeoff and vertical landing (VTVL) vehicle. The highest altitude which the Grasshopper RLV would reach during launches conducted under an experimental permit is 11,500 feet above ground level (AGL). SpaceX would need to obtain a Letter of Authorization from the Robert Gray Army Radar Approach Control at Fort Hood to operate the Grasshopper RLV in the proposed airspace before any launches could commence.
DM

Offline arnezami

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Re: Grasshopper RLV
« Reply #9 on: 09/24/2011 07:19 am »
Very interesting. I think this is directly related to this:

Elon Musk: propulsively landing the first stage

Which is "tricky, but its very doable."  ;)

Quote
Pretty obviously, this is to develop techniques for F9 first stages to recover on "land" which might include a barge at sea.

So at least one F9 1st stage engine would have to be restartable after stage separation?

Wouldn't it also mean this Merlin 1D should be able to gimbal?

That would also answer the question how they would control a "re-entry-burn" (see: Elon Musk about shedding velocity by restarting the engines and a basic conceptial idea of re-entering the first stage, engines down first )

Regards,

arnezami
« Last Edit: 09/24/2011 07:21 am by arnezami »

Offline neilh

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Re: Grasshopper RLV
« Reply #10 on: 09/24/2011 08:16 am »
Some other interesting quotes from the FAA/AST report:

Quote
Although an experimental permit would authorize an unlimited number of launches, the
FAA/AST must estimate the number of launches in order to analyze potential environmental
impacts.  In conjunction with SpaceX, the FAA/AST developed a conservative set of
assumptions regarding the possible number of launches that could be conducted under any one
experimental permit for the Grasshopper RLV at the McGregor test site.  The FAA/AST has
assumed that SpaceX would conduct up to 70 annual suborbital launches of the Grasshopper
RLV under an experimental permit at the McGregor test site.  This estimation is a conservative
number and considers potential multiple launches per day and potential launch failures.   

Quote
Launch Phase 3:  Controlled-airspace VTVL (maximum altitude)
The goal of Phase 3 is to verify the Grasshopper RLVs ability to perform a VTVL mission at
higher altitudes and higher ascent speeds and descent speeds.  To achieve this, the maximum
mission altitude would be increased from 670 feet incrementally up to 11,500 feet.  The altitude
test sequence likely would be 1,200 feet; 2,500 feet; 5,000 feet; 7,500 feet; and 11,500 feet.  The
maximum test duration would be approximately 160 seconds.  The Grasshopper RLV would land
back on the launch pad.

Quote
Under the No Action Alternative, the FAA/AST would not issue an experimental permit to
SpaceX for operation of the Grasshopper RLV at the McGregor test site.  Existing SpaceX
activities would continue at the McGregor test site, which include engine testing for the Falcon 9
launch vehicle.  SpaceX averages approximately five Merlin-1D tests per week as well as six
Falcon 9 Stage 1 tests per year.  The Falcon 9 is an expendable launch vehicle that uses RP-1 and
LOX for propellants.  Stage 1 of the Falcon 9 holds approximately 38,700 gallons of LOX and
24,900 gallons of RP-1, for a total of approximately 63,600 gallons of propellant.  Stage 1 is
powered by nine Merlin-1C engines, with each Merlin-1C engine producing 90,000 pounds of
thrust.  The Falcon 9 stage testing occurs on the tripod stand located at the site (see Exhibit 2-2
for general location).  Additionally, SpaceX conducts hypergolic testing at the site, which occurs
in an enclosed vacuum chamber.

I learned a new term today, "environmental justice." Apparently SpaceX is compliant.

It also mentions in 2.3 that other sites were evaluated as potential alternatives for the Grasshopper launches; perhaps this is why there was that news a while back about SpaceX looking at a site on the Texas coast?
« Last Edit: 09/24/2011 08:16 am by neilh »
Someone is wrong on the Internet.
http://xkcd.com/386/

Offline HMXHMX

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Re: Grasshopper RLV
« Reply #11 on: 09/24/2011 04:35 pm »
Very interesting. I think this is directly related to this:

Elon Musk: propulsively landing the first stage

Which is "tricky, but its very doable."  ;)

Quote
Pretty obviously, this is to develop techniques for F9 first stages to recover on "land" which might include a barge at sea.

So at least one F9 1st stage engine would have to be restartable after stage separation?

Wouldn't it also mean this Merlin 1D should be able to gimbal?

That would also answer the question how they would control a "re-entry-burn" (see: Elon Musk about shedding velocity by restarting the engines and a basic conceptial idea of re-entering the first stage, engines down first )

Regards,

arnezami

The Merlin 1D does gimbal.

Offline arnezami

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Re: Grasshopper RLV
« Reply #12 on: 09/24/2011 04:42 pm »
The Merlin 1D does gimbal.

Oh sorry. I meant roll control. Stupid me.

Falcon 1 had it (using the pump exhaust), but will this one falcon 1D have it? Or will they use roll control thrusters?

Hmm. I guess that's still unanswered.
« Last Edit: 09/24/2011 04:44 pm by arnezami »

Offline kkattula

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Re: Grasshopper RLV
« Reply #13 on: 09/24/2011 04:42 pm »
Wow. SpaceX don't mess about with endless paper studies etc.

Just stick some legs and an engine on a first stage tank, and fly it around.

I wonder if they're getting help from Masten or Armadillo, who (excluding Blue Origin) would be the current VTVL experts.

Offline HMXHMX

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Re: Grasshopper RLV
« Reply #14 on: 09/24/2011 04:47 pm »
The Merlin 1D does gimbal.

Oh sorry. I meant roll control. Stupid me.

Falcon 1 had it (using the pump exhaust), but will this one falcon 1D have it? Or will they use roll control thrusters?

Hmm. I guess that's still unanswered.

For landing roll control might be omitted.  The GNC is smart enough to do that easily.  Or turbine exhaust might be used if it is really deemed necessary.
« Last Edit: 09/24/2011 04:48 pm by HMXHMX »

Offline simonbp

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Re: Grasshopper RLV
« Reply #15 on: 09/24/2011 05:13 pm »
Well, they'll likely need a couple of RCS packs (Dracos) on there to do the turnaround for boostback, so presumably that RCS could also handle the roll control.

Still, the sight a full-length F9 first stage landing vertically on a singular pillar of flame would be very Buck Rogers-esque...

Offline jongoff

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Re: Grasshopper RLV
« Reply #16 on: 09/24/2011 06:44 pm »
Well, they'll likely need a couple of RCS packs (Dracos) on there to do the turnaround for boostback, so presumably that RCS could also handle the roll control.

Still, the sight a full-length F9 first stage landing vertically on a singular pillar of flame would be very Buck Rogers-esque...

I'll definitely pay for a plane ticket to the cape when they try that maneuver the first time operationally...  :-)

~Jon

Offline oldAtlas_Eguy

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Re: Grasshopper RLV
« Reply #17 on: 09/24/2011 07:02 pm »
A Merlin 1DVAC, like the Merlin VAC, without skirt would work perfectly, since its basically a Merlin 1D that has a skirt extension and a gimbal on the GG exhaust. It would have gimbal and roll control as part of its normal configuration. It would have multiple restart capability as well.

Offline arnezami

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Re: Grasshopper RLV
« Reply #18 on: 09/24/2011 07:13 pm »
Still, the sight a full-length F9 first stage landing vertically on a singular pillar of flame would be very Buck Rogers-esque...

It's weird. Whenever Elon Musk says "it's tricky, but doable", most people's first reaction would be: "that's insane".  (mine was)

But when you start to think about what he means, it usually seems physically possible. Still outrageous though.

But I'm really curious about the specifics. :)

Seeing a video of an almost empty F9 1st stage take off with only one engine is pretty cool. Seeing it land, is priceless.

Regards,

arnezami

PS. I don't see the flying-back-to-the-launch-pad happening though. Without wings that won't happen, I think. More likely to be a sea-platform landing.
PPS. @oldAtlas_Eguy: clever. Might be what they will actually do.
« Last Edit: 09/24/2011 08:02 pm by arnezami »

Offline docmordrid

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Re: Grasshopper RLV
« Reply #19 on: 09/24/2011 08:12 pm »
Perhaps this will also give them experience for a Dragon propulsive landing. 

The beauty no excessive bureaucracy - just get a few key guys in a room with the boss, make a decision, then go for it. 

I'm with Jon - say when & I'll hop a flight :)
« Last Edit: 09/24/2011 08:14 pm by docmordrid »
DM

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