Author Topic: FX, FXH, FXX, Merlin 2  (Read 66335 times)

Offline aameise9

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Re: FX, FXH, FXX, Merlin 2
« Reply #80 on: 01/05/2012 02:43 pm »

Sounds like they are building in extra capacity at the new stand for bigger things like Merlin 2.

Wouldn't this stand be required in order to test cross-feeding in FH?

Offline go4mars

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Re: FX, FXH, FXX, Merlin 2
« Reply #81 on: 01/05/2012 02:54 pm »

Sounds like they are building in extra capacity at the new stand for bigger things like Merlin 2.

Wouldn't this stand be required in order to test cross-feeding in FH?
Not necessarily.  It could be tested on the fly with a dummy payload.  To reduce risk to the pad, cross-feeding might begin at some point after takeoff. 
« Last Edit: 01/05/2012 02:56 pm by go4mars »
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Offline Robotbeat

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Re: FX, FXH, FXX, Merlin 2
« Reply #82 on: 01/05/2012 03:18 pm »
Now this is a little off-topic (I really don't think SpaceX will be developing FX anytime soon), but if they're going to build a test stand capable of firing Falcon Heavy at once (not counting the upper stage, which will, of course, have to be test-fired separately), I see no reason they wouldn't test cross-feeding on the stand.

Testing on a stand before flight is almost always a good idea if you can afford it. (Falcon 9 upper stage was not vacuum-fired before being launched on Falcon 9 flight 1, and although it reached orbit quite successfully, it did mean the restart didn't work... But since it was a demo flight and orbit was still achieved, I'd still say that it was still a reasonably good decision not to do the very expensive vacuum test for that stage... though for smaller stuff, it probably is worth testing in a vacuum on the ground first.) That's the real reason the Soyuz N-1 project failed to reach orbit, IMHO... They failed to ever test the whole first stage on the ground, thus they blew up 4 N-1 rockets before even getting past the first stage.
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Offline go4mars

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Re: FX, FXH, FXX, Merlin 2
« Reply #83 on: 01/05/2012 03:33 pm »
if they're going to build a test stand capable of firing Falcon Heavy at once, I see no reason they wouldn't test cross-feeding on the stand.
Agreed.  Most likely. 

Unless timeframe is a big factor:  For example, some customer might need a cross-feeding FH demo by a certain date that is sooner than the test stand completion date.  I have no idea if that's the case though. 
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Offline Jim

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Re: FX, FXH, FXX, Merlin 2
« Reply #84 on: 01/05/2012 03:50 pm »
if they're going to build a test stand capable of firing Falcon Heavy at once, I see no reason they wouldn't test cross-feeding on the stand.
Agreed.  Most likely. 

Unless timeframe is a big factor:  For example, some customer might need a cross-feeding FH demo by a certain date that is sooner than the test stand completion date.  I have no idea if that's the case though. 

There are no customers

Offline Robotbeat

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Re: FX, FXH, FXX, Merlin 2
« Reply #85 on: 01/05/2012 04:08 pm »
It's true. Nobody has a payload (or is building one) that needs a Falcon Heavy with cross-feed right now. Every payload that would need the extra boost is still conceptual right now.

You might talk about putting a Dragon on a Falcon Heavy, but that's still conceptual right now. Without cross-feed (and with vertical payload integration....), they should be able to launch just about anything out there.
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Offline RocketmanUS

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Re: FX, FXH, FXX, Merlin 2
« Reply #86 on: 01/05/2012 08:20 pm »
go4mars  thanks for the underground test stand link.


If they can test 27 Merlin 1d engines at the same time , then they could most likely test a 1.7Mlb engine at the Texas site as a future possibility if they wanted to.

As for the FX,FXH that would be for after the F9/Dragon and FH are flying and the FH was not enough or the FXH would be cheaper for BEO missions.

I think SpaceX should look into their FX,FXH design now a little bit to see how they might work it into their plans now and the near future ( infrastructure ).

Offline ArbitraryConstant

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Re: FX, FXH, FXX, Merlin 2
« Reply #87 on: 01/05/2012 10:55 pm »
Maybe that's what the huge underground test stand is really for.
Sounds like it's intended to reflect the sound upwards, otherwise it would be too loud for the surrounding communities.

Offline baldusi

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Re: FX, FXH, FXX, Merlin 2
« Reply #88 on: 01/06/2012 11:12 am »
The Texas test stand is rated for 15MN. Almost for two Merlin 2, if those are ever to be developed. So if they actually wanted to design such an engine, they already have the test stand for it.

Offline grr

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Re: FX, FXH, FXX, Merlin 2
« Reply #89 on: 01/07/2012 04:00 pm »
if they're going to build a test stand capable of firing Falcon Heavy at once, I see no reason they wouldn't test cross-feeding on the stand.
Agreed.  Most likely. 

Unless timeframe is a big factor:  For example, some customer might need a cross-feeding FH demo by a certain date that is sooner than the test stand completion date.  I have no idea if that's the case though. 


I would think that the ground-based test would not only be cheaper, but also faster. If any serious anomalies are going to show up, it would be better on the ground. Then that just leaves one test flight, fix minor bugs and away you go.

Offline mrhuggy

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Re: FX, FXH, FXX, Merlin 2
« Reply #90 on: 01/07/2012 05:23 pm »
500000 divided by 90 seconds.  That's 5555 gallons per second.  Does that sound excessive for 27 merlin 1D's? 

Sounds like they are building in extra capacity at the new stand for bigger things like Merlin 2.
Is there a rule of thumb for gallons per second per unit thrust? 

no, you are not going to find indirect proof that Merlin 2 is being developed

Building excessive capacity  in the test stand only future proofs the stand, so you don't have to upgrade it later.

And no i wasn't jumping on "oh my god they doing merlin 2"

Offline go4mars

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Re: FX, FXH, FXX, Merlin 2
« Reply #91 on: 02/08/2012 01:50 pm »
The Texas test stand is rated for 15MN... So if they actually wanted to design such an engine, they already have the test stand for it.

http://www.popularmechanics.com/science/space/rockets/elon-musk-on-spacexs-reusable-rocket-plans-6653023?src=rss

I think this article implies 40% for just the first stage reusability alone but he might have meant including the effect of both stages.

It seems to me that due to the payload loss from reusable stages, when a BFR is required eventually (making life multi-planetary), that to get 50 tonne chunks to Mars' surface (a stated goal) will require something pretty impressive at lift-off (especially since the rocket needs to be about 40% more potent than its expendible version). 

So perhaps a BFR who would in non-expendible version be 400+ tonnes to LEO or so (240 tonnes to LEO in reusable version to get 50 tonnes to the surface of Mars)?  Seems to me a cross-fed version would be the most likely.  So assuming a scale-up of FH, 54 tonnes to 400, they need a Merlin 2 to be just over 1 million pounds of thrust.  Since SpaceX is talking about 1.6 million, maybe the BFR will have less engines per stage or will be bigger than my guess. 

If Elon intends to make a fully reusable BFR for this purpose, will this new test stand be sufficient to test a BFR engine? 
 
500000 divided by 90 seconds.  That's 5555 gallons per second.  Does that sound excessive for 27 merlin 1D's? 

Is there a rule of thumb for gallons per second per unit thrust? 
 
« Last Edit: 02/08/2012 02:29 pm by go4mars »
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Offline go4mars

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Re: FX, FXH, FXX, Merlin 2
« Reply #92 on: 02/08/2012 02:20 pm »
Is there a rule of thumb for gallons per second per unit thrust? 
 
Just discovered that the sound suppression system for Saturn V was 15000 gallons per second.

If that scales the same, then this new test stand should be able to handle a 2.8 million pound thrust engine. 
« Last Edit: 02/08/2012 02:24 pm by go4mars »
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Offline bulkmail

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Re: FX, FXH, FXX, Merlin 2
« Reply #93 on: 02/08/2012 05:38 pm »
Can somebody calculate the LEO lift capacity of a hypothetical Falcon XX Heavy (three 10m cores with cross feeding - with 6? Merlin2 engines each) with Merlin2 and/or Raptor upper stages?

Are there any fundamental technical issues preventing such configuration?

Offline baldusi

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Re: FX, FXH, FXX, Merlin 2
« Reply #94 on: 02/08/2012 06:07 pm »
Can somebody calculate the LEO lift capacity of a hypothetical Falcon XX Heavy (three 10m cores with cross feeding - with 6? Merlin2 engines each) with Merlin2 and/or Raptor upper stages?

Are there any fundamental technical issues preventing such configuration?
If you copy the FH equation (3.3 times the 16tonnes of the F9b2), you'd get somewhere around 500tonnes.
I guess that you should start thinking differently. You should start with a desired mission, then decide a vehicle that can do the mission in one or two launches.
Let's say that you make it a two launches mission, where first you send the return vehicle and some exploration vehicle plus a surface habitat. On the second launch you send the crew with a space habitat, the Mars descent vehicle and the Earth return capsule.
You've got to calculate some mass at Trans Mars Insertion orbit. That's what you should optimize then. LEO is not a good benchmark if you're going with straight launches, since low energy and high energy orbits require very different optimizations.

Offline go4mars

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Re: FX, FXH, FXX, Merlin 2
« Reply #95 on: 02/08/2012 06:30 pm »
If you copy the FH equation (3.3 times the 16tonnes of the F9b2), you'd get somewhere around 500tonnes.

to get 50 tonne chunks to Mars' surface (a stated goal)
   

I'm pretty confident there's an Elon quote out there somewhere that talks about a desire for direct throw to get 50 tonnes at a time to the surface of Mars in a fully reusable architecture. 

I assume that represents the heaviest need of the colonists (nuclear power plant maybe)? 

Anyway, with your 500 tonne rocket, that drops by some percent for reuse (40% for single stick apparently).  Say a cross-fed version only drops by 20%.  Would a 400 tonne to LEO rocket be likely to get 50 tonnes to the surface of Mars?   
« Last Edit: 02/08/2012 06:37 pm by go4mars »
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Offline bulkmail

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Re: FX, FXH, FXX, Merlin 2
« Reply #96 on: 02/08/2012 06:35 pm »
Can somebody calculate the LEO lift capacity of a hypothetical Falcon XX Heavy (three 10m cores with cross feeding - with 6? Merlin2 engines each) with Merlin2 and/or Raptor upper stages?

Are there any fundamental technical issues preventing such configuration?
If you copy the FH equation (3.3 times the 16tonnes of the F9b2), you'd get somewhere around 500tonnes.
I guess that you should start thinking differently. You should start with a desired mission, then decide a vehicle that can do the mission in one or two launches.
Let's say that you make it a two launches mission, where first you send the return vehicle and some exploration vehicle plus a surface habitat. On the second launch you send the crew with a space habitat, the Mars descent vehicle and the Earth return capsule.
You've got to calculate some mass at Trans Mars Insertion orbit. That's what you should optimize then. LEO is not a good benchmark if you're going with straight launches, since low energy and high energy orbits require very different optimizations.

OK, so the mission I'm thinking about is Moon outpost/base and Moon cargo delivery on a big scale.

But, WOW, 500mT to LEO...  this is more than the whole ISS - in a single launch! Aren't there any problems with that? Maybe 3x6 engines configuration doesn't fit, maybe there is no fairing big enough for 500mT, maybe a much more powerful upper stage is needed?

Offline go4mars

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Re: FX, FXH, FXX, Merlin 2
« Reply #97 on: 02/08/2012 06:38 pm »
OK, so the mission I'm thinking about is Moon outpost/base and Moon cargo delivery on a big scale.
The mission Elon is thinking of is Mars colonization.

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Offline bulkmail

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Re: FX, FXH, FXX, Merlin 2
« Reply #98 on: 02/08/2012 06:50 pm »
Anyway, with your 500 tonne rocket, that drops by some percent for reuse (40% for single stick apparently).  Say a cross-fed version only drops by 20%.  Would a 400 tonne to LEO rocket be likely to get 50 tonnes to the surface of Mars?   

I would assume yes - if Falcon Heavy can deliver a Red Dragon, then ~10 times more lift to LEO should be capable to deliver ~10 more at Mars?

Offline Tass

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Re: FX, FXH, FXX, Merlin 2
« Reply #99 on: 02/13/2013 03:09 pm »
Hi. I have this (quite possibly hare-brained) idea that I would like to see discussed.

As you all know SpaceX is planning the Falcon Heavy rocket, which is basically three Falcon 9 first stages strapped together with a stage on top. What is special is that it is going to use propellant cross feed, using up the propellant from the side stages first and then dropping them when empty. Thus they become better than the "half stage" strap on boosters that many rockets use in that they leave what is basically a full falcon 9 which is all ready moving fast. And they have an advantage over a full stage in that the engines of the center stage have been working the whole time rather than being dead weight.

Now this seems to suggest an obvious further step, if we ever needed a super heavy lift rocket. What if you strapped nine cores together basically three falcon heavy first stages side by side, then cross fed from the two outer rows with a total of six cores first, followed by regular falcon heavy cross feed.

Would it even need a top stage to achieve orbit then? How much could it lift? Since it is in a way just a repeated application of the original falcon heavy technology could it be done with *relatively* limited extra development cost (still expensive, everything in this field is).

Now I know we don't need it for the foreseeable future. I know SpaceX are not planning to do it. It is still interesting to discuss the possibility though.

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