Discussion SpaceX's Grasshopper RLV

[MattBaker]

Anyone else noticed the nozzle of the middle engine being bigger than the others?
Is there like a Merlin 1E in development?

It would be logical, AFAIR the middle engine does the whole last part of the landing. I don't know if the Merlin 1D has enough thrust for that, does anyone have numbers on the empty mass of the first stage (+landing legs)? I have to sleep...new job requires me to wake up at 0530.:dry:

 

[Urwumpe]

Anyone else noticed the nozzle of the middle engine being bigger than the others?
Is there like a Merlin 1E in development?

The same engine is only mounted lower, what makes sense by many factors.

 

[N_Molson]

I hadn't seen these before:

Those aerodynamic shapes already look better.

 

[T.Neo]

Integrating the first stage with the upper stage and payload is the easy part; that is trivial and not where the make-or-break part of the problem lies. SpaceX has already done it several times.

In terms of feats that are directly related to their ability to pull off Falcon 9 recovery, they've already demonstrated post-separation retropropulsion using a flight first stage, and the ability to perform VTOL flights with a vehicle that is (a) based off of their flight hardware and (b) closer to an actual rocket stage in various respects (such as length/width ratio) than other similar projects that have gone before (DC-X, the Armadillo landers, etc).

The landing leg design isn't merely a computer graphic- SpaceX has released an image of an F9 leg construction. This indicates that even though F9 Flight 6 and likely the next few missions lack legs, most of the work pertaining to them has been completed. The vehicles are likely also 'scarred' to accommodate the legs. We also have confirmation that Merlin 1D is restart-capable.

There are a lot of questions, but SpaceX is in a position to answer them through further testing, not simply blow smoke. Grasshopper 2, for example, is likely to be a much closer approximation to the actual flight F9 stage than the first Grasshopper. They're moving quite quickly, and say what one may about them, they're currently doing far more research into recovery and reusability of launch vehicles than any other organisation on the planet.

 

[N_Molson]

How are you Tneo ? 'was a long time :hello:

 

[Thunder Chicken]

Those aerodynamic shapes already look better.

Whatever they use for legs will be in the wake of the rest of the stage during entry, so I don't think that is a problem at all. They will definitely have to think about aerodynamic loads later in the descent, but if they can manage to keep the abort stabilizing flaps on the Soyuz from tearing off during ascent I don't think SpaceX will have problems with the legs.

Is there any data available on the 1st stage test on the last F9 v1.1 flight? I know that the fuel flow was lost due to tank centrifuging, but I am really curious to know how slow did they manage to get that stage before it lost thrust.

Between these tests of the actual stage during flight and the Grasshopper tests, the operating envelope for the stage where no flight experience is available is getting smaller and smaller. They seem to have the slow flight approach and touchdown phase understood, and they know where the weak points of the stage deceleration phase are. Once they can get the altitude and speed envelopes to overlap they will have a much clearer picture of what must happen to get the entire process to work from separation all of the way to touchdown. They are still connecting those dots.

 

[orb]

Space News: SpaceX Retires Grasshopper, New Test Rig To Fly in December:

LAS CRUCES, N.M. -- Space Exploration Technologies Corp. (SpaceX) has retired its Grasshopper prototype, a 10-story, first-stage Falcon 9 rocket the Hawthorne, Calif., company used to develop and test vertical landing technologies.

In its place, SpaceX plans a December debut of a new test rig, known as Falcon 9R, and a new test site at Spaceport America in New Mexico, said company president and chief operating officer Gwynne Shotwell.

{...}

 

[math12]

Just a little question: After the first stage separation, how does it lands at Cape Canaveral? Does it make a 180° turn or it puts itself on a huge sub-orbital flight? I've searched on Google but I didn't find anything...

 

[Loru]

It lands roughly wherever ballistic trajectory brings it.

 

[Thunder Chicken]

It lands roughly wherever ballistic trajectory brings it.

Not so. RTLS for the first stage is not out of the question or energetically infeasible. Not so much fuel is required to decelerate the stage and send it back to launch site for recovery. It is "only" going about Mach 3 and is relatively light at staging.

A downrange recovery is also possible, with some crossrange capability.

 

[MattBaker]

SpaceX is still working on a launch site in Texas. Probably Brownsville, I think.
If you launch from Texas you could fly over Florida, making a landing over Cape Canaveral easier.

Although I still have my concerns with staging in such a fashion that your full second stage+payload could land somewhere in Florida in case the engine doesn't fire.

 

[Urwumpe]

Although I still have my concerns with staging in such a fashion that your full second stage+payload could land somewhere in Florida in case the engine doesn't fire.

You could divert slightly south, but that would be a pretty nasty small corridor for launching.

 

[MattBaker]

You could divert slightly south, but that would be a pretty nasty small corridor for launching.

And you'd end up over the Bahamas, not sure if they'd be to happy about...
But didn't the shuttle cross the Bahamas as well during launch? Or did it always stay east of them?

 

[RGClark]

There has been some debate on whether the upgraded version of the Grasshopper labeled the Falcon 9R will have all 9 Merlin engines during its tests. At least from the test viewpoint, only one engine would be used so it would make sense not to risk all 9 engines so you would put dummy engines in of the same mass.
Nevertheless, Gwynne Shotwell during the October 2013 ISPCS meeting does say the F9R will use the full 9 engines:

At about the 23:30 point after showing a video of the Grasshopper 1, she discusses the upgrade to the F9R and that it will be a full F9 v1.1 first stage with the full 9 engines.


Bob Clark

 

[Urwumpe]

Using only one true engine and 8 dummies makes sense for landing tests, but if you also want to lift off and reach higher altitudes during the tests, you need 9 flight articles for the engines.

 

[Cosmic Penguin]

The new "Grasshopper 2", formally known as F9R-Dev1, on a recent static test firing:

 

[RGClark]

The new "Grasshopper 2", formally known as F9R-Dev1, on a recent static test firing:

F9R Static Fire

Thanks. Still can't tell the number of engines.


Bob Clark

 

[Kyle]

Hearing rumors that F9R flew today, 250m divert and was successful.

 

[Cosmic Penguin]

Hearing rumors that F9R flew today, 250m divert and was successful.

And just before the attempt on the real thing......we got this:

 

[RGClark]

And just before the attempt on the real thing......we got this:

F9R First Flight Test | 250m

Thanks for that. Saw this on another forum that seems to confirm this "Grasshopper 2" will use three engines, not nine:

Grasshopper's successor flies at SpaceX's McGregor site.
"Reports have been confirmed that SpaceX's Falcon 9-R development vehicle made its first free flight today at McGregor taking off, hovering, moving sideways and landing. I've seen video of it (though it turns out that video wasn't supposed to be made public yet and is no longer available).
SpaceX McGregor will be testing the rocket the three-engine successor to the single-engine Grasshopper at lower altitudes before sending it to Spaceport America in New Mexico for higher (and farther) flights."
http://m.wacotrib.com/blogs/joe_sci...cle_66310240-c67f-11e3-bf29-001a4bcf887a.html


Bob Clark