Author Topic: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion  (Read 673838 times)

Offline Johnnyhinbos

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #960 on: 09/23/2019 05:25 pm »
In this photo by BocaChicaGal, one of the header tanks appears to have a heat shield section and further mounting assemblies for its place in the outer hull.
I was thinking that object might be a heat exchanger.
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Offline Rix4

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #961 on: 09/23/2019 05:26 pm »
In this photo by BocaChicaGal, one of the header tanks appears to have a heat shield section and further mounting assemblies for its place in the outer hull.
Can it be battery that EM was talking about?

Offline RotoSequence

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #962 on: 09/23/2019 05:30 pm »
In this photo by BocaChicaGal, one of the header tanks appears to have a heat shield section and further mounting assemblies for its place in the outer hull.
I was thinking that object might be a heat exchanger.

I hadn't thought of that. That's a good thought.

Offline CapitalistOppressor

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #963 on: 09/23/2019 05:32 pm »
The Shuttle Orbiter had a propulsion section in the nose ahead of the crew compartment. It supplied local engines rather than feeding down to the main engines, but I don't see that as much different.

In the attached picture from Twitter of LUVOIR in the Starship cargo bay, you can see that there is a lot of wasted space in the nose. Filling that with mechanical components and tankage saves space and provides better center of mass. For crew, the windows are all on the side anyway so I don't think scooting them down a bit will make any notable difference.

Not everything about shuttle was bad. The placement of its cargo bay may just be proving itself an idea worth keeping for a massive reusable orbital craft.

Also, moving the header tanks out of the main tanks may allow them to reduce the size of the main tanks, giving a bit more wide space above the main tanks. No real payload space should be lost, and may actually be more useful since it will be full width.

Also easier to apply insulation to tanks that are not immersed in cryogens. And as others have said the conical space was hard to use efficiently.

Any notional transpiration cooling system would also require plumbing for the methane reach all the way from the nose to the tail anyways, so moving the headers might not be adding a lot of plumbing anyways.

Offline ShaunML09

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #964 on: 09/23/2019 05:37 pm »
If a complete Starship cannot be launched from Boca Chica (regardless of reason), can it be shipped by sea to 39A for launch? 

Offline OTV Booster

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #965 on: 09/23/2019 05:46 pm »
Let's not forget that this is a test vehicle and SpaceX is going to test only what it needs to test to get the data they need.

Except if the intent is to slam this test model into the upper atmosphere and simulate as much as possible a return from LEO to test reentry heating on the outer skin, which is one of the stated intended purposes... Then aluminum fins with rivets makes to my limited knowledge, no sense. I don't buy into the few on here that think MK1 will never be launched or be a 1 and done. From what I have read my guesstimate is MK1 and 2 will probably see at least 5 flights each if they don't RUD. But with aluminum wings, I'm trying to wrap my head around how they will not RUD the first time they get slammed into the atmosphere.
Heat shield tiles, yet to be added?

I have not seen any TPS. We are looking at bare airframe.  All windward surfaces will require TPS.

John

It’s hard to make out the structural detail on the ‘leading’ edge of the fins. The outer and rear look open and unfinished. As y’all have patiently mentored on EDL this won’t fly, so to speak. The shock holding the plasma off from the windward face would, AIUI, squeeze closer to the fin face as it approaches the edges and and as it slips close to and past the edge, cause high local heating.

IIRC, there is a formula for calculating the optimal radius to minimize this at various Mach numbers. Don’t know it and can’t find it. My guess is there will be radiused edge treatment, maybe not symmetrical from windward to lee.  Probably with heat tiles.

Sure wish I could make out that top edge better.

Phil

They're not finished.  Since the edges of the fins will tend to be hot spots during reentry, its probably safe to assume that they will put tiles on them.  In this case, the sharp angle and flat surfaces should make them easier to fabricate and/or attach.
Maybe one piece thermal for the fin edges?
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Offline OTV Booster

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #966 on: 09/23/2019 05:56 pm »
Per Musk's indication that the header tanks will be in the nose and Mary's latest photos, I get the feeling that Starships Mk1/Mk2 are going to have one or two raceways running almost top to bottom. That design choice obviously isn't compatible with Starship cargo/crew sections as we know them, could be that outfitting for either role will provide enough balance on its own.

Edit: I see they could also be chines, but seems probable that it/they will also serve as raceways for cabling/plumbing/ACS pods.

Chines all the way to the top make sense. Space for the lines to the header tanks and they would broaden the profile and ease max heat a bit during EDL. I’m surprised they’re not blended into the curve better and reaching further down towards the centerline. I also expect the gap between the fineraters and the chine to be filled in. Leave it open and I’d expect shock impingement.

Phil
We are on the cusp of revolutionary access to space. One hallmark of a revolution is that there is a disjuncture through which projections do not work. The thread must be picked up anew and the tapestry of history woven with a fresh pattern.

Offline RotoSequence

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #967 on: 09/23/2019 05:59 pm »
Per Musk's indication that the header tanks will be in the nose and Mary's latest photos, I get the feeling that Starships Mk1/Mk2 are going to have one or two raceways running almost top to bottom. That design choice obviously isn't compatible with Starship cargo/crew sections as we know them, could be that outfitting for either role will provide enough balance on its own.

Edit: I see they could also be chines, but seems probable that it/they will also serve as raceways for cabling/plumbing/ACS pods.

Chines all the way to the top make sense. Space for the lines to the header tanks and they would broaden the profile and ease max heat a bit during EDL. I’m surprised they’re not blended into the curve better and reaching further down towards the centerline. I also expect the gap between the fineraters and the chine to be filled in. Leave it open and I’d expect shock impingement.

Phil

They're looking fairly blended, and optimized for reentry profiles rather than symmetry.

Offline OTV Booster

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #968 on: 09/23/2019 06:00 pm »
Did Elon say anything about how the real Starship would be fabricated? I'm assuming they won't weld the circular sections like this, there has to be a better way to make the shell?


If it works, it works.
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Offline vaporcobra

Did Elon say anything about how the real Starship would be fabricated? I'm assuming they won't weld the circular sections like this, there has to be a better way to make the shell?

No reason to assume anything about the efficacy of Mk1/Mk2 methods until the first WDRs/static fires/flights. If they all fail, easy confirmation that something needs to change. For now, this program is just as much a prototype of an unorthodox method of manufacturing as it is a prototype of a new launch vehicle design.
« Last Edit: 09/23/2019 06:11 pm by vaporcobra »

Offline OTV Booster

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #970 on: 09/23/2019 06:16 pm »
Article with image by BCG of the three Raptors installed at Starship prototype.

https://www.teslarati.com/spacex-starship-three-raptors-installed-says-elon-musk/
"artist's impression" - It's a picture of StarHopper with the engine copy-pasted.


Yup. all three are oriented the same and the blue tape is crumpled up exactly the same one each one.
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Offline OTV Booster

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #971 on: 09/23/2019 06:29 pm »
BocaChicaGal's latest pics show a band  on the windward side with slots cut into it. This may be for anchoring a fairing from here aft to cover the landing gear and smooth out the windward surface. If the front of this fairing (possibly mythical) is free to expand when heated, how would TPS deal with it? Something special is going to be needed.  Mysteries.

John

If it’s a nonstructural fairing wouldn’t it be tps in a sense? Maybe a higher temp alloy that doesn’t respond to cryo stressing. If the expansion is controlled so that it doesn’t buckle and mess with shock standoff... ?

Phil
We are on the cusp of revolutionary access to space. One hallmark of a revolution is that there is a disjuncture through which projections do not work. The thread must be picked up anew and the tapestry of history woven with a fresh pattern.

Offline uhuznaa

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #972 on: 09/23/2019 06:29 pm »
Honestly, I wouldn't read anything about the "final" design from this. Between tankers, sat launchers and Moon/Mars crafts the mass distribution will be so different that they may easily end up with very different designs and these prototypes may just put things where they make the most sense for exactly the prototypes and can be installed in the most easy way.

You really can't expect too much commonality between tankers that are basically just tanks and engines on one hand and crafts that will go the Moon or Mars and will launch and land with lots of mass besides this on the other hand.

The ease of construction by using SS instead of CF certainly helps with this. If you use CF you have to carefully chose a design and stick with it. With SS, not so much (or at all).

Offline Lars-J

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #973 on: 09/23/2019 06:30 pm »
Ok, so it looks like header tanks and batteries and whatnot are being installed in the fairing, as per Elon.  At first I was like, “That’s odd - header tanks are supposed to go inside the main tanks!”

But what if... that’s actually the production design? What if the cargo/crew section is now between the main tanks and the headers in the nose?  That would allow canard actuators and internal bracing to take up the nose section, make a more predictable load distribution during EDL, and place the variable mass of cargo closer to the center of drag?

It is not the production design. Elon's tweets suggest that the Mk1 and Mk2 have some design trade offs to make testing easier and cheaper. But some elements may appear in the production design(s).
« Last Edit: 09/23/2019 06:35 pm by Lars-J »

Offline exilon

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #974 on: 09/23/2019 06:30 pm »
In this photo by BocaChicaGal, one of the header tanks appears to have a heat shield section and further mounting assemblies for its place in the outer hull.
Can it be battery that EM was talking about?

Yes, it's a Model S/X battery pack...



Would be funny if they even left the motor on there for the compressor
« Last Edit: 09/23/2019 06:32 pm by exilon »

Offline RotoSequence

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #975 on: 09/23/2019 06:33 pm »
In this photo by BocaChicaGal, one of the header tanks appears to have a heat shield section and further mounting assemblies for its place in the outer hull.
Can it be battery that EM was talking about?

Yes, it's a Model S/X battery pack...



Would be funny if they even left the motor on there for the compressor

Looks like it might even be two of them, back to back. Wow.  :o

Offline OTV Booster

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #976 on: 09/23/2019 06:34 pm »
Um, what's going on here?


Image credit: BocaChicaGal
Doesn’t make sense for transpiration. Would expect a more even spacing for that.
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Offline exilon

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #977 on: 09/23/2019 06:36 pm »
In this photo by BocaChicaGal, one of the header tanks appears to have a heat shield section and further mounting assemblies for its place in the outer hull.
Can it be battery that EM was talking about?

Yes, it's a Model S/X battery pack...



Would be funny if they even left the motor on there for the compressor

Looks like it might even be two of them, back to back. Wow.  :o

You're right. It's two back to back for 200kWh of storage. If they attach one set per header tank, that's 400kWh of electrical energy available!

How much power do they actually need for spacecraft operations, I wonder?
« Last Edit: 09/24/2019 05:59 pm by exilon »

Offline OTV Booster

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #978 on: 09/23/2019 06:42 pm »
I think the header tanks were moved up to the nosecone probably just for the prototype since there's so little mass up there. Presumably, in production versions there will be enough forward weight where this doesn't need to be done and the header tanks can be inside the main tanks.
I think move header tanks is design change.
It will give them better center of gravity, shield crew from radiation, easy access to fix it cryogenic device if will not work properly. LOX will could be used also as source of oxygen for crew.

Agreed. That is too big a change to be just for a prototype. At least at the moment they intend that to be the orbital design.


Could be... But then it could be a simple proxy for a later [size=78%]complexity[/size]
We are on the cusp of revolutionary access to space. One hallmark of a revolution is that there is a disjuncture through which projections do not work. The thread must be picked up anew and the tapestry of history woven with a fresh pattern.

Offline uhuznaa

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Re: SpaceX Starship : Texas Prototype(s) Thread 2 : Discussion
« Reply #979 on: 09/23/2019 06:52 pm »

How much power do they actually need for spacecraft operations, I wonder?

Well, it's a big spacecraft after all... The question is if they will use electric actuators for basically everything or not. It certainly would save them lots of complexity at least for the prototypes and they have quite some expertise to borrow from Tesla I guess. Also good for reusability anyway.



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