Author Topic: SpaceX Reusable Falcon 9 (Grasshopper ONLY) DISCUSSION Thread (3)  (Read 665760 times)

Offline Chris Bergin

THREAD FOR SPECIFIC DISCUSSION OF REUSABLE FALCON 9/GRASSHOPPER.

Articles:

http://www.nasaspaceflight.com/2012/01/spacex-testing-reusable-falcon-9-technology-this-year/

http://www.nasaspaceflight.com/2012/02/spacex-dragon-advancing-launch-abort-system-new-heights/

http://www.nasaspaceflight.com/2012/12/spacexs-grasshopper-conducts-40-meter-leap/

SpaceX Article Section:
http://www.nasaspaceflight.com/tag/spacex/

The previous thread (2) was continually taken off topic. This will not be allowed on this thread.
Read this before posting on this thread:
http://forum.nasaspaceflight.com/index.php?topic=31044.0

Members who drag this off topic, respond to off topic posts - usually with "OMG, this is so off topic" - and those who shout down people - will have their posting privileges removed for one week and their post removed without warning.
« Last Edit: 02/10/2013 09:06 pm by Chris Bergin »

Offline R7

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Just to be clear, is this for Grasshopper only discussion or suitable for general Falcon 9 reusability issues (which are pretty much general SpaceX reusability issues) ?
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Offline Chris Bergin

Grasshopper only.
« Last Edit: 02/10/2013 08:50 pm by Chris Bergin »

Offline sanman

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Anybody know what the latest state of progress is for Grasshopper in relation to its next test flight?

It seems like Grasshopper tests are not announced in advance, and we only learn of them after the fact, once a video has been posted on Youtube.

Offline Lars_J

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Anybody know what the latest state of progress is for Grasshopper in relation to its next test flight?

It seems like Grasshopper tests are not announced in advance, and we only learn of them after the fact, once a video has been posted on Youtube.

Musk's latest tweet indicates that it will happen very soon, IMO.

Offline Chris Bergin

Due to popular demand, we're doing this only for Grasshopper.

Thread needed trim, as people were starting to vote for it.

Offline mlindner

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So this has been run over before, but now that we have a tweet from our benevolent leader, Elon Musk, (sarcasm implied) what do people expect, with regards to the FAA Environmental Assessment, that they will attempt this flight? Are they going to stay in phase 1 or is this a jump to phase 2?

Edit: Re-link for those who haven't seen it.
http://www.faa.gov/about/office_org/headquarters_offices/ast/media/20110922%20spacex%20grasshopper%20draft%20ea.final.pdf
See section 2.1.1 and sub sections.
« Last Edit: 02/10/2013 09:14 pm by mlindner »
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Offline Ludus

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So this has been run over before, but now that we have a tweet from our benevolent leader, Elon Musk, (sarcasm implied) what do people expect, with regards to the FAA Environmental Assessment, that they will attempt this flight? Are they going to stay in phase 1 or is this a jump to phase 2?

Edit: Re-link for those who haven't seen it.
http://www.faa.gov/about/office_org/headquarters_offices/ast/media/20110922%20spacex%20grasshopper%20draft%20ea.final.pdf
See section 2.1.1 and sub sections.

Quote
The goal of Phase 1 is to verify the Grasshopper RLV’s overall ability to perform a VTVL mission. During a Phase 1 test, the Grasshopper RLV would be launched and ascend to 240 feet AGL and then throttle down in order to descend, landing back on the pad approximately 45 seconds after liftoff. The Grasshopper RLV would stay below Class E Airspace (700 feet AGL). In Phase 2, there would be slightly less propellant loaded, a different thrust profile, and the maximum altitude would be increased to 670 feet, still below Class E Airspace. The mission duration during Phase 2 is again approximately 45 seconds.

Seems like a pretty trivial difference though it might be useful if ur doin something called a hover and slam to put a few extra feet of altitude into the margins.

Offline Avron

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That phase II - 'a different thrust profile," is key.. like a period of close to zero thrust.. still all within 700 ft agl,
« Last Edit: 02/11/2013 12:08 am by Avron »

Offline Ludus

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That phase II - 'a different thrust profile," is key.. like a period of close to zero thrust.. still all within 700 ft agl,


Yep. You're right. The details do all match. Slightly LESS propellant, higher altitude and different thrust profile...actually sound like they had something like relighting the engine hover and slam in mind.

Offline Ludus

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Fly to more than twice the altitude, complete the flight in exactly the same time (45 seconds), use slightly less propellant, different thrust profile...that phase II profile matches the speculation based on Elon's tweet perfectly. Other than cutting the engine, dropping and restarting what other profile would match? I guess I just scanned through it the first time without getting it but they really did specify the Johnny Cash style run up front.

Offline Norm38

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The 240 feet Above Ground Level (AGL) limit for Phase 1 is the distance from the ground to the landing legs correct?  The last flight was only 131 feet.  So wouldn't the next flight be to the full 240 ft before moving on to Phase 2?

Given that it doesn't sound like there would be time for an engine restart just yet. Instead, get to 240 ft quickly, throttle back to minimum, drop quickly and stick the landing.

Phase 2 to 670 ft will probably have the first restart attempt with the altitude to allow for the free fall time.  If they need to stick the landing there based on fuel availability, they'd test that part first, right?

Offline dbhyslop

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The 240 feet Above Ground Level (AGL) limit for Phase 1 is the distance from the ground to the landing legs correct?  The last flight was only 131 feet.  So wouldn't the next flight be to the full 240 ft before moving on to Phase 2?

I suspect SpaceX is measuring to the landing legs while the FAA is measuring to the top of the craft.  Remember, the FAA is probably only concerned that it doesn't bust into Class E airspace.  They don't care where the feet are, just the top.

If that's correct, it seems reasonable to assume they're moving on to Phase 2 bases on Elon's tweet. 

Offline Norm38

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So you're saying that 131ft plus 106ft for the vehicle equals 237ft, thus fulfilling Phase 1. And that Phase 2 is 670ft minus 106ft, and thus we should expect the landing legs to be 564ft above the ground at the peak?

They did 131ft, so will the next flight go straight to 564ft, or stop somewhere below that first?  I still think they'd want to try and stick the landing first with a shorter hop and then try restart on the full height flight, unless they can't.

Offline Kaputnik

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It's amazing really that we need to consider the height of the vehicle when talking about how many hundred feet it is above the ground.
Is Grasshopper the tallest heavier-than-air aircraft ever landed?
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Offline kevin-rf

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Only one I can think of coming close was the B-36 tail at 46 ft 9 in.
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Online Robotbeat

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Only one I can think of coming close was the B-36 tail at 46 ft 9 in.
A380 is 80 feet:
http://en.wikipedia.org/wiki/Airbus_A380
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Offline Zed_Noir

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There is a wikipedia comparison diagram of the biggest aircrafts not including the Birdzilla (Stratolauncher Carrier).

http://upload.wikimedia.org/wikipedia/commons/thumb/5/52/Giant_planes_comparison.svg/550px-Giant_planes_comparison.svg.png

Offline R7

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It can be argued that GH is not an aircraft.
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Offline kch

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It can be argued that GH is not an aircraft.

Good luck with that ... ;)

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