Author Topic: A Matter of Height  (Read 17879 times)

Offline arachnitect

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Re: A Matter of Height
« Reply #20 on: 09/07/2014 06:14 PM »
The whole idea seems to be a one launch lunar mission, so you're not gonna want to hear my suggestions.

Just out of curiosity, why are you trying to do the mission in one launch?

Yeah, I'm also wondering if moving up the door a little wouldn't be cheaper than modifying the whole architecture.

Is it just the door mechanism that's in the way or is there roof structure behind the door that the stack can't clear?

Offline Herb Schaltegger

Re: A Matter of Height
« Reply #21 on: 09/07/2014 07:24 PM »
Yes, that would help a lot. We could also avoid common bulkheads. The problem is that MLAS needs to be fully developed.

Sure. But so, too, do your 6 engine first stage, 2 engine second stage and your entire lander. I'd think once you're going THAT far, what's a bit more effort for the MLAS? I mean, seriously ...
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Offline Burninate

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Re: A Matter of Height
« Reply #22 on: 09/07/2014 07:43 PM »
1) Is post-rollout integration of the LAS itself, from a crane in the open air, feasible?

2) "This results in significantly worse performance. We need four RL-10 engines, otherwise the gravity loss is too high for TLI. "

Have you considered a two-orbit or three-orbit, split TLI burn?  Less TWR needed, at the cost of some additional Van Allen Belt exposure, and less gravity loss.

Something along the lines of: A) Liftoff to LEO, B) LEO to GTO, C) inclination correction to correct plane near lunar orbit, D) GTO to TLI

3)
Yeah, I'm also wondering if moving up the door a little wouldn't be cheaper than modifying the whole architecture.

Myself as well.  That door has already been brought up as limiting launch vehicle integration methodologies to a certain width - and IMO if it's doing that, it's not doing its job of being a door.

Constructing a building of this scale is relatively expensive, but much less expensive than the average manned exploration mission.  The Aerium airship hangar, while not designed for rockets, is one example of recent construction of somewhat larger than this volume, and it cost around $100M to build.  Inflate that arbitrarily to, say, $1B, and it still looks pretty reasonable if it lets you use cheaper / already-designed rockets in a series of exploration missions.
« Last Edit: 09/07/2014 09:17 PM by Burninate »

Offline floss

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Re: A Matter of Height
« Reply #23 on: 09/07/2014 09:08 PM »
A moblie gantry would be pretty cost effictive seeing as it is only a shed with a crane .It would be even better if you could remove the payload if safety concerns delay the rocket.

Offline sdsds

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Re: A Matter of Height
« Reply #24 on: 09/07/2014 10:24 PM »
1) Is post-rollout integration of the LAS itself, from a crane in the open air, feasible?

Wow! It breaks the concept of LC-39 operations, but ... yeah. Were you imagining integration of the LAS just outside the VAB, or at the pad?
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Offline Burninate

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Re: A Matter of Height
« Reply #25 on: 09/07/2014 11:08 PM »
1) Is post-rollout integration of the LAS itself, from a crane in the open air, feasible?

Wow! It breaks the concept of LC-39 operations, but ... yeah. Were you imagining integration of the LAS just outside the VAB, or at the pad?

Either-or, it's just a matter of the easiest place to have the crane.  An external LAS is a very tall, skinny, lightweight feature - putting it on outside the VAB allows for a lot of literal headroom.  If you want to get inventive, it's also plausibly lightweight enough to apply by helicopter at the pad, with locking mechanisms engaged at the level of the crew loading mechanism (though I'm not sure that makes any sense from a safety perspective).

In a long-run concern, you might also plausibly improve the safety of the whole system, because in the event that a liquid booster is ever approved for the SLS, they can eliminate solids from the building entirely - perhaps even equip the LAS after crew loading for minimum risk surface.

Offline Lars_J

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Re: A Matter of Height
« Reply #26 on: 09/07/2014 11:22 PM »
Yes, that would help a lot. We could also avoid common bulkheads. The problem is that MLAS needs to be fully developed.

I keep being mystified regarding the aversion to common bulkheads. It was done 45 years ago for LOX/LH2, and at 10m diameter even. So why?

Offline jg

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Re: A Matter of Height
« Reply #27 on: 09/07/2014 11:38 PM »
There is a nice movie about the Saturn V stage w. common bulkhead.  LH2 is so cold it would freeze the LOX.  Doing the insulation was a PITA...

Offline sdsds

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Re: A Matter of Height
« Reply #28 on: 09/08/2014 01:00 AM »
Doing the [common bulkhead] insulation was a PITA...

Yes but, "No pain, no gain," and to do the trade requires quantifying both the pain and the gain in terms of both dollars and schedule.

I keep being mystified regarding the aversion to common bulkheads. It was done 45 years ago for LOX/LH2, and at 10m diameter even. So why?

Do you mean for upper stages, or boosters? For the SLS core I'm pretty sure the decision was based on schedule. The core found itself on the critical path. Separate tanks meant essentially zero schedule risk....
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Offline arachnitect

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Re: A Matter of Height
« Reply #29 on: 09/08/2014 01:33 AM »
For the SLS core I'm pretty sure the decision was based on schedule. The core found itself on the critical path. Separate tanks meant essentially zero schedule risk....

putting the thrust beam anywhere else [i.e. not in the intertank] would be a nightmare.
« Last Edit: 09/08/2014 01:33 AM by arachnitect »

Offline mike robel

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Re: A Matter of Height
« Reply #30 on: 09/08/2014 01:34 AM »
For the larger Saturn variants, NASA did consider a crane just outside the door to lift the spacecraft onto the booster.  might be tricky in bad weather

Offline Lars_J

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Re: A Matter of Height
« Reply #31 on: 09/08/2014 02:14 AM »

I keep being mystified regarding the aversion to common bulkheads. It was done 45 years ago for LOX/LH2, and at 10m diameter even. So why?

Do you mean for upper stages, or boosters? For the SLS core I'm pretty sure the decision was based on schedule. The core found itself on the critical path. Separate tanks meant essentially zero schedule risk....

Just the upper stage(s). The SRB thrust beam makes an SLS core common bulkhead a tricky thing. But there is no reason why an upper stage can't have it.

Offline Lars_J

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A Matter of Height
« Reply #32 on: 09/08/2014 02:17 AM »
There is a nice movie about the Saturn V stage w. common bulkhead.  LH2 is so cold it would freeze the LOX.  Doing the insulation was a PITA...

Yes, it wasn't easy, but that is no reason to throw your hands up essentially saying "can't be done!". It HAS been done. It isn't impossible. The reluctance to even contemplate it reminds me of this scene from "Iron man":

« Last Edit: 09/08/2014 02:19 AM by Lars_J »

Offline jg

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Re: A Matter of Height
« Reply #33 on: 09/08/2014 04:14 AM »
Doing the [common bulkhead] insulation was a PITA...

Yes but, "No pain, no gain," and to do the trade requires quantifying both the pain and the gain in terms of both dollars and schedule.

The reason why they bothered was that the LEM+Apollo capsule got heaver than expected, and they could not redesign everything; the weight had to be saved somewhere.  That happened to be the SII second stage.  There are easier ways to get the 7900lb's saved.

The only people they could find who could do the insulation work successfully were surfers who had been working on building surf boards; the problem was that if the surf was up, they'd lose schedule, as their workforce would head for the waves!

Offline Steven Pietrobon

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Re: A Matter of Height
« Reply #34 on: 09/08/2014 06:32 AM »
Since you are not using the SLS core why not just make it wider?

Yes, that might work, but it also means that a new MLP is needed. I'm trying to use as much of the existing core as possible.

0) One or two RS-25 on the u/s instead of J2.

The RS-25 is about the same height as J-2X, so I don't think that helps much.

Quote
Move u/s O2 tank above the H2 tank, and somehow wrap it around the CPS's RL10s.

Good idea, but I believe the four RL-10's take up too much room.

Just out of curiosity, why are you trying to do the mission in one launch?

Yes. I think that's the way that has the greatest chance of success.

Yes, that would help a lot. We could also avoid common bulkheads. The problem is that MLAS needs to be fully developed.
Sure. But so, too, do your 6 engine first stage, 2 engine second stage and your entire lander. I'd think once you're going THAT far, what's a bit more effort for the MLAS? I mean, seriously ...

Which is why I've decided to use MLAS in the baseline configuration. I would have preferred not too, but it seems to be the best solution to the problem. It also avoids using common bulkheads and using existing US and CPS designs from Boeing and NASA.

I keep being mystified regarding the aversion to common bulkheads. It was done 45 years ago for LOX/LH2, and at 10m diameter even. So why?

The experience with S-II put a lot of people at NASA off the idea of common bulkheads. It is seen as expensive and time consuming. However, with modern tooling I would think it is now much easier to do. In fact, I was all ready to use common bulkheads, but I was still left with the vehicle being 3.7 too high. Had the vehicle met the height limitation, I would have gone with common bulkheads.

Thankyou everyone for your ideas.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline MP99

Re: A Matter of Height
« Reply #35 on: 09/08/2014 07:03 AM »


Doing the [common bulkhead] insulation was a PITA...

Yes but, "No pain, no gain," and to do the trade requires quantifying both the pain and the gain in terms of both dollars and schedule.

The reason why they bothered was that the LEM+Apollo capsule got heaver than expected, and they could not redesign everything; the weight had to be saved somewhere.  That happened to be the SII second stage.  There are easier ways to get the 7900lb's saved.

The only people they could find who could do the insulation work successfully were surfers who had been working on building surf boards; the problem was that if the surf was up, they'd lose schedule, as their workforce would head for the waves!

Is ULA's solution to this any simpler?

Dual layer dome with small void filled with CO2. Freezes out as soon as cryos are loaded into the tank above, instant vacuum insulator.

Cheers, Martin

Offline MP99

Re: A Matter of Height
« Reply #36 on: 09/08/2014 07:06 AM »


0) One or two RS-25 on the u/s instead of J2.

The RS-25 is about the same height as J-2X, so I don't think that helps much.

I was assuming that the higher Isp would reduce tank size a bit. But no, I can see now, not enough to help.

Cheers, Martin

Offline Nibb31

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Re: A Matter of Height
« Reply #37 on: 09/08/2014 08:35 AM »
Couldn't the height of Orion be reduced by redesigning its service module? The narrow design makes it tall. Make the width of the SM match the diameter of the CM, like on the CST-100, and it will be significantly shorter.

Offline spacenut

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Re: A Matter of Height
« Reply #38 on: 09/08/2014 03:06 PM »
Common bulkheads would work great with methane/oxygen since their liquid point is only a few degrees apart.  That way they could also use the same pumps, fittings, valves, etc.  Shorter overall stack with each stage.  I think this is what Space-X is trying to do with their Raptor engine and future 10m large rocket. 

Offline Ronpur50

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Re: A Matter of Height
« Reply #39 on: 09/08/2014 04:00 PM »
1) Is post-rollout integration of the LAS itself, from a crane in the open air, feasible?

Could it be done the same way the lighting mast was added to the top of the MLP tower for the Apollo Soyuz Saturn 1B?  It was attached from a structure added to the top of the VAB over the door.

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