Author Topic: Grasshopper Discussion (including Grasshopper 2, aka F9R-Dev1) Thread 1  (Read 328851 times)

Offline AJW

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #20 on: 01/25/2014 04:45 PM »
It's interesting that the vehicle goes high enough and on a typical launch profile that re-entry is fast/hot enough to test the way back fully too, testing the whole stage one launch cycle.

I would think that one measure of 'high enough' is to verify the point where the core has time to reach terminal velocity on the way down.  That should help determine minimum fuel requirements for landing from any altitude, which would then impact launch payload capacity.

Offline rst

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #21 on: 01/25/2014 09:47 PM »
With the tests done on F9v1.1/CASIOPE, SES-8 & possibly THAICOM-6 is it possible that F9R-1 has become superfluous?

At least one element of first-stage recovery remains untested:  the legs.  It's conceivable that they'd launch with legs attached and no prior testing.  But if they do, well ... some observers will be surprised.

(Personally I'd be nonplussed if a customer lets them launch with legs attached before they'd been through max-Q on a test flight, but I'm not a customer, and I'm not privy to whatever wind-tunnel testing and simulations they've done on a legs-attached launch stack.)

Online meekGee

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #22 on: 01/25/2014 09:52 PM »
With the tests done on F9v1.1/CASIOPE, SES-8 & possibly THAICOM-6 is it possible that F9R-1 has become superfluous?

At least one element of first-stage recovery remains untested:  the legs.  It's conceivable that they'd launch with legs attached and no prior testing.  But if they do, well ... some observers will be surprised.

(Personally I'd be nonplussed if a customer lets them launch with legs attached before they'd been through max-Q on a test flight, but I'm not a customer, and I'm not privy to whatever wind-tunnel testing and simulations they've done on a legs-attached launch stack.)

They have time to test a little bit of leg in TX and maybe even in NM, but most likely not Max Q.

However, don't forget customer allowed them to test an entire rocket before it ever reached maxQ.  The risk on the way up is pretty small - it's not an active system at that point.  It's nothing that can't be assessed very well with CFD and/or wind tunnels.
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Offline rst

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #23 on: 01/25/2014 10:09 PM »
However, don't forget customer allowed them to test an entire rocket before it ever reached maxQ.  The risk on the way up is pretty small - it's not an active system at that point.  It's nothing that can't be assessed very well with CFD and/or wind tunnels.

And prior testing does make a whole lot less difference on the way down.  If the vehicle gets to stage separation OK, it's all gravy after that.  The result of a leg failure after stage separation is they lose a stage that they would have expended anyway --- but they still get the data.

Online Robotbeat

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #24 on: 01/25/2014 10:36 PM »
With the tests done on F9v1.1/CASIOPE, SES-8 & possibly THAICOM-6 is it possible that F9R-1 has become superfluous?

At least one element of first-stage recovery remains untested:  the legs.  It's conceivable that they'd launch with legs attached and no prior testing.  But if they do, well ... some observers will be surprised.

(Personally I'd be nonplussed if a customer lets them launch with legs attached before they'd been through max-Q on a test flight, but I'm not a customer, and I'm not privy to whatever wind-tunnel testing and simulations they've done on a legs-attached launch stack.)
They're intending to launch with legs on the next flight, SpX3 in a month.
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Online Comga

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #25 on: 01/25/2014 10:56 PM »
With the tests done on F9v1.1/CASIOPE, SES-8 & possibly THAICOM-6 is it possible that F9R-1 has become superfluous?
I did read (but can't find again) that SES-8 successfully re entered unpowered & broke up on the ocean surface. 
I agree!  This seems like quite a reasonable explanation of why GH-2 hasn't flown.  The issues beyond GH-1 it was built to address have already been addressed. 

It would seem more likely that SpaceX could take the F9 legs through supersonic sooner on a revenue flight than by bringing GH-2 through a full development program with the many flights it would take to go supersonic. 
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline ClaytonBirchenough

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #26 on: 01/25/2014 11:02 PM »
With the tests done on F9v1.1/CASIOPE, SES-8 & possibly THAICOM-6 is it possible that F9R-1 has become superfluous?
I did read (but can't find again) that SES-8 successfully re entered unpowered & broke up on the ocean surface.

Hmm. If you do happen to come across that source, that'd be interesting to see.
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Offline ClaytonBirchenough

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #27 on: 01/25/2014 11:04 PM »
It has been speculated that Falcon 9R flights will be needed to show precision landing as a prerequisite for permission for land landing of incoming stages. That sounds reasonable to me and can be shown with the test vehicle.

Doing repeated flights with dummy second stages emulating real life trajectories and loads seems more sensible done with real stages that have come back from commercial flights.

Dummy second stages will not be possible on GH2 unless more M1Ds are added.
Clayton Birchenough
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Online Comga

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #28 on: 01/25/2014 11:08 PM »
With the tests done on F9v1.1/CASIOPE, SES-8 & possibly THAICOM-6 is it possible that F9R-1 has become superfluous?
I did read (but can't find again) that SES-8 successfully re entered unpowered & broke up on the ocean surface.

Hmm. If you do happen to come across that source, that'd be interesting to see.

There may not be a good source for that but we did see the image of the Cassiope first stage three meters above the ocean surface.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline ClaytonBirchenough

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #29 on: 01/25/2014 11:18 PM »
They're intending to launch with legs on the next flight, SpX3 in a month.

They want to. Is the consensus that they will?

There may not be a good source for that but we did see the image of the Cassiope first stage three meters above the ocean surface.

That is a fascinating picture. (Now attached)

How did they obtain that image?
Clayton Birchenough
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Offline vtirag

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #30 on: 01/25/2014 11:38 PM »


That is a fascinating picture. (Now attached)

How did they obtain that image?

I remember reading at the time that Elon Musk's jet was out over the landing/splasdown area..

Offline ClaytonBirchenough

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #31 on: 01/25/2014 11:53 PM »


That is a fascinating picture. (Now attached)

How did they obtain that image?

I remember reading at the time that Elon Musk's jet was out over the landing/splasdown area..

Haha that's crazy. Do you have a source for that possibly?
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Offline Lar

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #32 on: 01/26/2014 12:01 AM »


That is a fascinating picture. (Now attached)

How did they obtain that image?

I remember reading at the time that Elon Musk's jet was out over the landing/splasdown area..

Haha that's crazy. Do you have a source for that possibly?

I think if you check the update thread for the launch you'll find it. This is starting to drift a little so can we get back on topic please?
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Online Comga

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #33 on: 01/26/2014 12:11 AM »

That is a fascinating picture. (Now attached)

How did they obtain that image?
From Musk's jet
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline ioconnor

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #34 on: 01/26/2014 02:41 AM »
Seems I remember Shotwell saying something, in that long youtube video, about some new grasshopper testing that was suppose to happen in December. Which has come and gone. Then there is Musk saying pretty much the pieces are all in place and just need to be tied together. So what's next?

Perhaps increasing the height by a magnitude or two, adding tumbling and spin with a rapid decent, and beautifully recovering to land within 1cm of where it took off? Perhaps simulation of lost engines on descent? How about testing in extreme weather?

Shotwell said these youtube videos of the grasshopper get more views than anything else related to spacex or tesla including Musk. Spacex could easily make a world cult of good will with more of their surrealistic grasshopper testing.

Offline TrevorMonty

GH2 may have flown but if is only 2m hop they may decide it is not worth releasing to public.

Offline Lars_J

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #36 on: 01/26/2014 05:39 AM »
"GH2" should fly (& land) several times before a land landing of F9R is attempted. They will want to prove that the legs work as advertised, it makes all the sense in the world to do this before RTLS is attempted.

Offline NovaSilisko

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #37 on: 01/26/2014 05:45 AM »
GH2 may have flown but if is only 2m hop they may decide it is not worth releasing to public.

What? The first GH1 flight was only 1.8m high and they still showed it off... GH2 would be even more impressive with its legs and huge height increase, even in such a short hop.
« Last Edit: 01/26/2014 05:45 AM by NovaSilisko »

Offline Jason1701

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #38 on: 01/26/2014 05:50 AM »
GH2 may have flown but if is only 2m hop they may decide it is not worth releasing to public.

What? The first GH1 flight was only 1.8m high and they still showed it off... GH2 would be even more impressive with its legs and huge height increase, even in such a short hop.

It generally took them a few weeks to release information, no matter the height of the hop.

Offline NovaSilisko

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Re: Grasshopper Discussion (including Grasshopper 2, aka F9R-1)
« Reply #39 on: 01/26/2014 06:29 AM »
It generally took them a few weeks to release information, no matter the height of the hop.

I get that, but the meaning I took from Trevor's statement was that they'd never release the video of a 2m hop, for whatever reason.

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