Author Topic: Starship On-orbit refueling - Options and Discussion  (Read 665728 times)

Offline edzieba

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2540 on: 05/08/2024 10:34 am »
Or add Ys just inside the ship behind the existing QD port, leading to a 'mirrored' (copy of groundside GSE) port immediately above. Open the 'normal' leg of the Y to the normal QD ports and close the new leg for fill/drain ops for launch, then in orbit close the normal leg and open the new leg to the new port for prop transfer ops. Since the new plumbing runs are a few meters at most, that minimises extra hardware to be added and doesn't interfere with normal ground handling. 

Offline waveney

Re: Starship In-orbit refueling - Options and Discussion
« Reply #2541 on: 05/08/2024 02:28 pm »
One question I have: I think we know that prop transfer will use the same QD port on starship as when it is on the pad, right? But these aren't androgynous. So doesn't that mean the two starships can't be perfectly aligned in their back-to-back configuration, as is depicted in all the artwork? (as this would put two "female" QD ports opposite each other).

They may not be androgynous Currently but things can and do change (frequently).   One androgynous port that works both ways means that there is no need for two ports with the added weight and complications that means.  (The best part is no part etc etc)

Offline Greg Hullender

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2542 on: 05/08/2024 11:04 pm »
One question I have: I think we know that prop transfer will use the same QD port on starship as when it is on the pad, right? But these aren't androgynous. So doesn't that mean the two starships can't be perfectly aligned in their back-to-back configuration, as is depicted in all the artwork? (as this would put two "female" QD ports opposite each other).

Does that mean there will be a "male" QD port present on tanker and depot starships? And if so, where would you put this? You could build it into the existing port, but it might be easier when further forward, in the payload bay area of those starship variants. This could put the chaser starship (active navigation/passive docking/donating propellant) roughly half a length or more behind the target starship (passive navigation/active docking/receiving propellant).
This has been discussed a lot (and more than once) here over the past few years. I suppose asking someone to read all 128 pages of discussion would be unreasonable. :-) The general thinking, as Ed says, is that the depot version will have an extra adaptor that exactly matches the GSE that fuels Starships on the ground. Exactly where that will be placed and how the plumbing will work is a mystery.

In general, the consensus seems to be that it's okay for the depot to have extra mass and complexity if it saves mass and complexity on the tankers and regular Starships.

Offline mikelepage

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2543 on: 05/09/2024 02:56 am »
This has been discussed a lot (and more than once) here over the past few years. I suppose asking someone to read all 128 pages of discussion would be unreasonable. :-) The general thinking, as Ed says, is that the depot version will have an extra adaptor that exactly matches the GSE that fuels Starships on the ground. Exactly where that will be placed and how the plumbing will work is a mystery.

In general, the consensus seems to be that it's okay for the depot to have extra mass and complexity if it saves mass and complexity on the tankers and regular Starships.

For sure, I have been reading, if not contributing to this thread the whole time. But we’re constantly receiving new breadcrumbs of info (placement of new “anti-roll’ valves, etc), so the kremlinology aspect can be fun. 

Where even a year ago I could have believed this thread topic was still in the “future work” box, it’s nice to have confirmation that various subsystems are being actively developed now, as it is to have confirmation they’re planning to have a pressure delta as the driving force for fluid transfer (ie as opposed to pumps - which I suppose may still have a supplementary role).

Somewhere back on this thread TheRadicalModerate produced a spreadsheet showing that if settling accelerations much higher than “x” were required (e.g. 10 -4 g), this was going to waste large amounts of propellant during a refuelling campaign unless each transfer could be done in less than half an hour or so.

With so much ice-shedding/off-gassing happening on oft-3, it’d at least be nice to confirm if some or all of that off-gassing done on purpose for the prop transfer demo? (I’ve not seen this but I could have missed it) That would at least explain why they didn’t cut it off when starship started to roll.   

Offline Twark_Main

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2544 on: 05/13/2024 05:16 am »
Sorry, missed this.

 
...The lowest viable SSO is 274 x 274 x 97.7°, and you want to launch from Kodiak.  So our delta-v budget is:

+475m/s to cover launching against Earth's rotation, plus azimuth changes (again, spreadsheet hacking involved)


...That swing from a 408m/s rotational advantage to a 475m/s disadvantage...

Are you sure you're not counting the same penalty twice?  What's the difference between the "launching against Earth's rotation" penalty and the "azimuth" penalty?

At 57.4° latitude, Kodiak's pure eastward velocity is only 250 m/s. Solving for azimuth via cos(inclination) = cos(latitude) × sin(azimuth), the launch azimuth is 194.1°. Sine of 194.1° is -0.24, so the downrange component of that eastward velocity is only 250 m/s × -0.24 = -61 m/s.


That's a far cry from -475 m/s.  Why the discrepancy I wonder?

Crap.  I did indeed double-count, but it's still 474m/s more, which puts the prop to orbit using unstretched tanks at 95.6t.  Spreadsheet screenshot for the azimuths and delta-v attached, and the real sheet's available here.

Two things you have wrong:

1) You left out the fact that, from LC-39A due east, you get 408m/s, so the LC-39A launch site starts with a 408-250=158m/s advantage over Kodiak

But the way you did it, you still have to add in the whole 408m/s advantage you get from the Cape, which takes you to 474m/s more delta-v from Kodiak.

I just thought you covered it quite nicely in your summary. Didn't feel a need to repeat it back to you.  ;)

Besides, you know full well that if I thought it was wrong, I surely would've spoken up. ;D


2) The eastward component is orbitalSpeed*sin(azimuth) - 250, not 250*sin(azimuth).  Then you have the big south/north component, which doesn't exist at all if you're launching to 28.6º from the Cape.

Update:  More accounting problems.  You got the right total answer for how much it costs beyond inertial orbital speed to launch from Kodiak, and I'm too stupid to figure out why.  ...  (We have minor geodetic differences, because I used average radius for equatorial speed, rather than equatorial radius.)

Update to the update:  It may just be a coincidence that you got close the right answer.  Even with our geodetic differences, you're still off by about 5m/s.  There may be an algebraic invariance lurking in here somewhere, but I can't find it.  I had the link up-thread, but here's the algorithm I'm using.

Math checks out for me.   "thumbs up"

The 5 m/s was just deciding not to bother with the rotating frame azimuth, surmising (quite correctly, as you admit) that such a small tertiary effect wasn't nearly big enough to explain a >400 m/s error.  That's all.  No great mystery!

Although I must say "algorithm" is overselling it a tad. No loops, no recursion, nothing fun, just a snippet of arithmetic.  While you can argue 'everything' in math is an algorithm (1 + 1), and I know everyone likes fancy CS terminology, but if I'm honest at best I would call this a "procedure."   8)
« Last Edit: 05/13/2024 09:29 am by Twark_Main »

Offline OTV Booster

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2545 on: 07/05/2024 10:23 pm »
One question I have: I think we know that prop transfer will use the same QD port on starship as when it is on the pad, right? But these aren't androgynous. So doesn't that mean the two starships can't be perfectly aligned in their back-to-back configuration, as is depicted in all the artwork? (as this would put two "female" QD ports opposite each other).

Does that mean there will be a "male" QD port present on tanker and depot starships? And if so, where would you put this? You could build it into the existing port, but it might be easier when further forward, in the payload bay area of those starship variants. This could put the chaser starship (active navigation/passive docking/donating propellant) roughly half a length or more behind the target starship (passive navigation/active docking/receiving propellant).
This has been discussed a lot (and more than once) here over the past few years. I suppose asking someone to read all 128 pages of discussion would be unreasonable. :-) The general thinking, as Ed says, is that the depot version will have an extra adaptor that exactly matches the GSE that fuels Starships on the ground. Exactly where that will be placed and how the plumbing will work is a mystery.

In general, the consensus seems to be that it's okay for the depot to have extra mass and complexity if it saves mass and complexity on the tankers and regular Starships.
Another possibility is tricking out the depot QD to exactly mimic the ground QDs, then install a gender bender between the ground and depot QD at launch. The gender bender would stay on the ground and get pulled off before the next launch. This makes the depot 'non standard' but it promises to be so special a build this one detail won't count for much.


A disadvantage is it makes it impossible to refuel a ship directly from a tanker without an on orbit gender bender. Maybe make all tankers a ground QD clone?
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Offline wannamoonbase

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2546 on: 07/06/2024 01:02 am »
One question I have: I think we know that prop transfer will use the same QD port on starship as when it is on the pad, right? But these aren't androgynous. So doesn't that mean the two starships can't be perfectly aligned in their back-to-back configuration, as is depicted in all the artwork? (as this would put two "female" QD ports opposite each other).

Does that mean there will be a "male" QD port present on tanker and depot starships? And if so, where would you put this? You could build it into the existing port, but it might be easier when further forward, in the payload bay area of those starship variants. This could put the chaser starship (active navigation/passive docking/donating propellant) roughly half a length or more behind the target starship (passive navigation/active docking/receiving propellant).
This has been discussed a lot (and more than once) here over the past few years. I suppose asking someone to read all 128 pages of discussion would be unreasonable. :-) The general thinking, as Ed says, is that the depot version will have an extra adaptor that exactly matches the GSE that fuels Starships on the ground. Exactly where that will be placed and how the plumbing will work is a mystery.

In general, the consensus seems to be that it's okay for the depot to have extra mass and complexity if it saves mass and complexity on the tankers and regular Starships.
Another possibility is tricking out the depot QD to exactly mimic the ground QDs, then install a gender bender between the ground and depot QD at launch. The gender bender would stay on the ground and get pulled off before the next launch. This makes the depot 'non standard' but it promises to be so special a build this one detail won't count for much.


A disadvantage is it makes it impossible to refuel a ship directly from a tanker without an on orbit gender bender. Maybe make all tankers a ground QD clone?

100% yes all of this.  An adapter on the ground side of the SQD solves the problem. 

I look forward to the ship to ship demo with the HLS demo not too far afterward. 
Starship, Vulcan and Ariane 6 have all reached orbit.  New Glenn, well we are waiting!

Offline DanClemmensen

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2547 on: 07/06/2024 01:14 am »
One question I have: I think we know that prop transfer will use the same QD port on starship as when it is on the pad, right? But these aren't androgynous. So doesn't that mean the two starships can't be perfectly aligned in their back-to-back configuration, as is depicted in all the artwork? (as this would put two "female" QD ports opposite each other).

Does that mean there will be a "male" QD port present on tanker and depot starships? And if so, where would you put this? You could build it into the existing port, but it might be easier when further forward, in the payload bay area of those starship variants. This could put the chaser starship (active navigation/passive docking/donating propellant) roughly half a length or more behind the target starship (passive navigation/active docking/receiving propellant).
This has been discussed a lot (and more than once) here over the past few years. I suppose asking someone to read all 128 pages of discussion would be unreasonable. :-) The general thinking, as Ed says, is that the depot version will have an extra adaptor that exactly matches the GSE that fuels Starships on the ground. Exactly where that will be placed and how the plumbing will work is a mystery.

In general, the consensus seems to be that it's okay for the depot to have extra mass and complexity if it saves mass and complexity on the tankers and regular Starships.
Another possibility is tricking out the depot QD to exactly mimic the ground QDs, then install a gender bender between the ground and depot QD at launch. The gender bender would stay on the ground and get pulled off before the next launch. This makes the depot 'non standard' but it promises to be so special a build this one detail won't count for much.
That's elegant. The Depot is non-EDL and there will never be very many of them (especially as a percentage of Ships), so would even be reasonable for the gender bender to be single-use, perhaps by discarding it immediately after launch.

Offline OTV Booster

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2548 on: 07/06/2024 04:29 pm »
One question I have: I think we know that prop transfer will use the same QD port on starship as when it is on the pad, right? But these aren't androgynous. So doesn't that mean the two starships can't be perfectly aligned in their back-to-back configuration, as is depicted in all the artwork? (as this would put two "female" QD ports opposite each other).

Does that mean there will be a "male" QD port present on tanker and depot starships? And if so, where would you put this? You could build it into the existing port, but it might be easier when further forward, in the payload bay area of those starship variants. This could put the chaser starship (active navigation/passive docking/donating propellant) roughly half a length or more behind the target starship (passive navigation/active docking/receiving propellant).
This has been discussed a lot (and more than once) here over the past few years. I suppose asking someone to read all 128 pages of discussion would be unreasonable. :-) The general thinking, as Ed says, is that the depot version will have an extra adaptor that exactly matches the GSE that fuels Starships on the ground. Exactly where that will be placed and how the plumbing will work is a mystery.

In general, the consensus seems to be that it's okay for the depot to have extra mass and complexity if it saves mass and complexity on the tankers and regular Starships.
Another possibility is tricking out the depot QD to exactly mimic the ground QDs, then install a gender bender between the ground and depot QD at launch. The gender bender would stay on the ground and get pulled off before the next launch. This makes the depot 'non standard' but it promises to be so special a build this one detail won't count for much.
That's elegant. The Depot is non-EDL and there will never be very many of them (especially as a percentage of Ships), so would even be reasonable for the gender bender to be single-use, perhaps by discarding it immediately after launch.
No need to drop the gender bender in flight. It's quick disconnect on both sides. Release the ship facing side at launch. Release the tower facing side while cycling for the next launch.


Still doesn't address a direct transfer between a ship and a tanker. When would this happen? Emergencies obviously. Other than that, when a ship is not operating near an established depot orbit and/or it only needs less than a depot load.


Some of the Artimus options, discussed elsewhere, call for single(ish) tanker loads to HEO and various lunar orbits. These special purpose tankers could be built gender bent but would then have no other purpose. Speculation on the practicality of this would be so starved of context as to all but useless (but fun).


The idea I threw out there earlier about possibility of making all the tankers gender bent and keeping the depot standard won't work out. It ignores the fact that the depot has to be gender bent to mate to the ship. DuH!


This leaves us with the problem of single tanker transfers. Maybe we need some operational experience before worrying about this.



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Online meekGee

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2549 on: 07/06/2024 04:47 pm »
How come there's even a gender?

The current QD might just be a "get something working ASAP" design - it's pretty easy (in SpaceX world) to change it in some future SS design later on...

A genderless design saves a lot of headaches later, as the preceding posts clearly show...

« Last Edit: 07/06/2024 04:50 pm by meekGee »
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Offline DanClemmensen

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2550 on: 07/06/2024 05:28 pm »
How come there's even a gender?

The current QD might just be a "get something working ASAP" design - it's pretty easy (in SpaceX world) to change it in some future SS design later on...

A genderless design saves a lot of headaches later, as the preceding posts clearly show...
Truly androgenous interfaces are hard. Take a look at IDSS as an example. In general, you must specify an "axis of androgny" and this then restricts the mating to exactly one orientation. For serious fluid transfer connections, It seems that the individual connectors are not androgenous. Instead, they are paired, with each side having both one "male" and one "female" connector, effectively doubling the complexity of the interface.

Online meekGee

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2551 on: 07/06/2024 05:52 pm »
How come there's even a gender?

The current QD might just be a "get something working ASAP" design - it's pretty easy (in SpaceX world) to change it in some future SS design later on...

A genderless design saves a lot of headaches later, as the preceding posts clearly show...
Truly androgenous interfaces are hard. Take a look at IDSS as an example. In general, you must specify an "axis of androgny" and this then restricts the mating to exactly one orientation. For serious fluid transfer connections, It seems that the individual connectors are not androgenous. Instead, they are paired, with each side having both one "male" and one "female" connector, effectively doubling the complexity of the interface.
Even if implemented that way, you're not describing "doubling the complexity".

Having two of the same connector is in fact nice, since it adds symmetry to things like mating/separation forces.  So you have two LOx, two LNG, etc, balancing each other.

Much better than gender adapters that are just lose-lose arrangements.

Additionally, if you can do surface seals, you don't even need to do that. It'll take more real estate of course but remember that these ships are huge compared to your everyday ISS visiting capsule, so there are options. (Compare the size of the current quick disconnect to an entire Dragon)
« Last Edit: 07/06/2024 06:14 pm by meekGee »
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Offline OTV Booster

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2552 on: 07/06/2024 10:04 pm »
How come there's even a gender?

The current QD might just be a "get something working ASAP" design - it's pretty easy (in SpaceX world) to change it in some future SS design later on...

A genderless design saves a lot of headaches later, as the preceding posts clearly show...
Truly androgenous interfaces are hard. Take a look at IDSS as an example. In general, you must specify an "axis of androgny" and this then restricts the mating to exactly one orientation. For serious fluid transfer connections, It seems that the individual connectors are not androgenous. Instead, they are paired, with each side having both one "male" and one "female" connector, effectively doubling the complexity of the interface.
Even if implemented that way, you're not describing "doubling the complexity".

Having two of the same connector is in fact nice, since it adds symmetry to things like mating/separation forces.  So you have two LOx, two LNG, etc, balancing each other.

Much better than gender adapters that are just lose-lose arrangements.

Additionally, if you can do surface seals, you don't even need to do that. It'll take more real estate of course but remember that these ships are huge compared to your everyday ISS visiting capsule, so there are options. (Compare the size of the current quick disconnect to an entire Dragon)
You've got a good point. Let's keep an eye on what they do for the GSE when they prep for v2.


Taking a slightly OT tangent, what are the chances they'll temporarily keep v2 booster at the same length as v1 until the second tower is ready for use. Need to know which tower to watch for ship GSE changes. It would be great to see v2 testing before the second tower is finished.
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Offline TheRadicalModerate

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2553 on: 07/06/2024 11:03 pm »
Another possibility is tricking out the depot QD to exactly mimic the ground QDs, then install a gender bender between the ground and depot QD at launch. The gender bender would stay on the ground and get pulled off before the next launch. This makes the depot 'non standard' but it promises to be so special a build this one detail won't count for much.

A disadvantage is it makes it impossible to refuel a ship directly from a tanker without an on orbit gender bender. Maybe make all tankers a ground QD clone?

It's not just getting the guzintas and guzoutas to line up; there has to be some amount of standoff between the two ships.  Something needs to fill that standoff gap.

So even if you built gender-bent tankers and then had a jettisonable (or retrievable) gender-bender to take care of the launch GSE, you'd still be stuck with two QDs that were both flush to the fairing.

I still like the depot kit idea:

1) All Starships would have a series of FRGFs¹ on their dorsal side.

2) The depot kit is a plain-ol' payload.  (If they're clever, it can be stowed as a series of Pez-deployable modules.

3) On orbit, the depot kit component(s) climb out of the Pez door, make their way, FRGF-by-FRGF, to their proper location, attach themselves, and then deploy.

4) The depot kit includes the gender-bender, along with extra power and/or sunshades, cryocoolers, radiators, and grappling gear to assist docking the client Starships.

5) The depot keeps the kit deployed forever.  A tanker/quickie depot could simply jettison the depot kit before EDL, or it can get fancy and stow itself.

I'm pretty skeptical of Elon's statement about tankers individually filling the HLS, if for no other reason than risk reduction.  Tankers and depots are cheap compared to an HLS Starship.  Unless refueling RPODs are incredibly reliable, doing 15 of them against the depot and one against the HLS is a lot less risky than doing 15 straight against the HLS.

However, a depot kit for a tanker still makes a lot of sense if you want to refuel an HLS Starship in NRHO.  If the tanker can return straight to EDL, it can deliver about 70% more prop to the HLS, which should be able to limit things to a single refueling in NRHO.


__________
¹Flight-releasable grapple fixtures--used on ISS for years.  The most elementary version isn't much more than a post with a knob on it, which a grapple can snare.  Having a few of them sticking into the slipstream shouldn't be an issue.

Offline DanClemmensen

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2554 on: 07/06/2024 11:42 pm »
Another possibility is tricking out the depot QD to exactly mimic the ground QDs, then install a gender bender between the ground and depot QD at launch. The gender bender would stay on the ground and get pulled off before the next launch. This makes the depot 'non standard' but it promises to be so special a build this one detail won't count for much.

A disadvantage is it makes it impossible to refuel a ship directly from a tanker without an on orbit gender bender. Maybe make all tankers a ground QD clone?

It's not just getting the guzintas and guzoutas to line up; there has to be some amount of standoff between the two ships.  Something needs to fill that standoff gap.

So even if you built gender-bent tankers and then had a jettisonable (or retrievable) gender-bender to take care of the launch GSE, you'd still be stuck with two QDs that were both flush to the fairing.

I still like the depot kit idea:

1) All Starships would have a series of FRGFs¹ on their dorsal side.

2) The depot kit is a plain-ol' payload.  (If they're clever, it can be stowed as a series of Pez-deployable modules.

3) On orbit, the depot kit component(s) climb out of the Pez door, make their way, FRGF-by-FRGF, to their proper location, attach themselves, and then deploy.

4) The depot kit includes the gender-bender, along with extra power and/or sunshades, cryocoolers, radiators, and grappling gear to assist docking the client Starships.

5) The depot keeps the kit deployed forever.  A tanker/quickie depot could simply jettison the depot kit before EDL, or it can get fancy and stow itself.

I'm pretty skeptical of Elon's statement about tankers individually filling the HLS, if for no other reason than risk reduction.  Tankers and depots are cheap compared to an HLS Starship.  Unless refueling RPODs are incredibly reliable, doing 15 of them against the depot and one against the HLS is a lot less risky than doing 15 straight against the HLS.

However, a depot kit for a tanker still makes a lot of sense if you want to refuel an HLS Starship in NRHO.  If the tanker can return straight to EDL, it can deliver about 70% more prop to the HLS, which should be able to limit things to a single refueling in NRHO.


__________
¹Flight-releasable grapple fixtures--used on ISS for years.  The most elementary version isn't much more than a post with a knob on it, which a grapple can snare.  Having a few of them sticking into the slipstream shouldn't be an issue.
That would work, but I think the idea can be refined somewhat.

First, Depot does not EDL, so no need for a Pez door and its constraints. Instead, the pointy end is just a disposable fairing, covering whatever elaborate deployable mechanism is needed.

Next, forget using a tanker as a mini-depot. As you say, a depot is fairly cheap to begin with. If you want refuel anything in NRHO, send a Depot instead of a tanker.

Offline TheRadicalModerate

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2555 on: 07/06/2024 11:59 pm »
Next, forget using a tanker as a mini-depot. As you say, a depot is fairly cheap to begin with. If you want refuel anything in NRHO, send a Depot instead of a tanker.

Then you have to dispose of the depot. In addition, the tanker gives you experience with high-speed EDL.
« Last Edit: 07/07/2024 04:33 am by TheRadicalModerate »

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2556 on: 07/07/2024 04:09 am »
Next, forget using a tanker as a mini-depot. As you say, a depot is fairly cheap to begin with. If you want refuel anything in NRHO, send a Depot instead of a tanker.

Then you have to dispose of depot. In addition, the tanker gives you experience with high-speed EDL.
OK, simple depot and tanker for Artemis III. Then create the retriever tanker when it's time to refuel in NRHO, perhaps for Artemis VI, since I doubt the Artemis IV HLS will be worth recovering. Retriever tanker cannot carry as much propellant as simple tanker because it has all the extra mass of the prop transfer hardware.

Offline TheRadicalModerate

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2557 on: 07/07/2024 04:35 am »
Next, forget using a tanker as a mini-depot. As you say, a depot is fairly cheap to begin with. If you want refuel anything in NRHO, send a Depot instead of a tanker.

Then you have to dispose of depot. In addition, the tanker gives you experience with high-speed EDL.
OK, simple depot and tanker for Artemis III. Then create the retriever tanker when it's time to refuel in NRHO, perhaps for Artemis VI, since I doubt the Artemis IV HLS will be worth recovering. Retriever tanker cannot carry as much propellant as simple tanker because it has all the extra mass of the prop transfer hardware.

I'd be surprised if the prop management and transfer hardware were more than a couple of tonnes.

Offline OTV Booster

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2558 on: 07/07/2024 06:48 pm »
Another possibility is tricking out the depot QD to exactly mimic the ground QDs, then install a gender bender between the ground and depot QD at launch. The gender bender would stay on the ground and get pulled off before the next launch. This makes the depot 'non standard' but it promises to be so special a build this one detail won't count for much.

A disadvantage is it makes it impossible to refuel a ship directly from a tanker without an on orbit gender bender. Maybe make all tankers a ground QD clone?

It's not just getting the guzintas and guzoutas to line up; there has to be some amount of standoff between the two ships.  Something needs to fill that standoff gap.

So even if you built gender-bent tankers and then had a jettisonable (or retrievable) gender-bender to take care of the launch GSE, you'd still be stuck with two QDs that were both flush to the fairing.

I still like the depot kit idea:

1) All Starships would have a series of FRGFs¹ on their dorsal side.

2) The depot kit is a plain-ol' payload.  (If they're clever, it can be stowed as a series of Pez-deployable modules.

3) On orbit, the depot kit component(s) climb out of the Pez door, make their way, FRGF-by-FRGF, to their proper location, attach themselves, and then deploy.

4) The depot kit includes the gender-bender, along with extra power and/or sunshades, cryocoolers, radiators, and grappling gear to assist docking the client Starships.

5) The depot keeps the kit deployed forever.  A tanker/quickie depot could simply jettison the depot kit before EDL, or it can get fancy and stow itself.

I'm pretty skeptical of Elon's statement about tankers individually filling the HLS, if for no other reason than risk reduction.  Tankers and depots are cheap compared to an HLS Starship.  Unless refueling RPODs are incredibly reliable, doing 15 of them against the depot and one against the HLS is a lot less risky than doing 15 straight against the HLS.

However, a depot kit for a tanker still makes a lot of sense if you want to refuel an HLS Starship in NRHO.  If the tanker can return straight to EDL, it can deliver about 70% more prop to the HLS, which should be able to limit things to a single refueling in NRHO.


__________
¹Flight-releasable grapple fixtures--used on ISS for years.  The most elementary version isn't much more than a post with a knob on it, which a grapple can snare.  Having a few of them sticking into the slipstream shouldn't be an issue.
The FRGS hitching posts make good sense. Background for those scratching their heads: these are what robot arms attach to. Two or more short simple (a relative statement) robot arms could grapple a tanker to the depot for final positioning and act as standoffs.

For the 'not quite connecting' QDs, the options are an on orbit add on as you suggest, a pantograph behind the depot QD to extend it outward or a depot QD doghouse that extends to the desired height. Keep in mind, an add on QD has to be deep enough to allow crossover plumbing unless one of meekGee's ideas work out. IMO, a depot doghouse would be the lowest mass and functionally the simplest. It could also conceivably limit the standoff arms to two.

A cryo cooler needs to be near power and propellant plumbing. There should be plenty of room above the tanks where there is a battery and plumbing for the header tanks. Convert each propellant pipe to a smaller diameter and double the pipes for a loop. Put the cooler where it's needed. No deployment necessary.

Radiators, sun shields and PV are a tough one. My inclination is to stow them as near to where they'll be deployed as possible. Unfortunately, we know nada about their design. Fan or panel? Double duty as PV and sunshield? Stowing locally shouldn't be all that much of a problem. The nominally windward side is well away from the refueling side and mostly unblemished by doodads. A few equipment blisters won't hurt anything. As Dan pointed out, the nose will also be available.

The idea of StarLink style deployment is interesting (cue up 'Blue Danube') but complex. It might be something to look at for a direct tanker refueling but still, very complex.

By the time a tanker is tricked out to be a depot it has become a depot - but with fins, tiles and an overweight gender bender. Early on and long term have different solutions.

Early on, if a single or maybe even a two tanker load needs transferred somewhere above LEO, bite the bullet and send a special build throwaway tanker(s). Have the target waiting for the tanker so boiloff is not an issue and all hardware associated with it can be skipped. This would also work in the long term for special rare or one off missions.

Long term, spot depots in the high traffic areas that will need them.


Edit: got rid of those double damned double spaces. Been driving me crazy for years.
« Last Edit: 07/07/2024 06:50 pm by OTV Booster »
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Offline TheRadicalModerate

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Re: Starship On-orbit refueling - Options and Discussion
« Reply #2559 on: 07/08/2024 07:58 pm »
For the 'not quite connecting' QDs, the options are an on orbit add on as you suggest, a pantograph behind the depot QD to extend it outward or a depot QD doghouse that extends to the desired height. Keep in mind, an add on QD has to be deep enough to allow crossover plumbing unless one of meekGee's ideas work out. IMO, a depot doghouse would be the lowest mass and functionally the simplest. It could also conceivably limit the standoff arms to two.

You have to deploy something, because the depot-like vehicles all need to launch with an ordinary QD, so the GSE works, and they need to work gender-bent in space.  I can only think of two ways to do that:

1) You have two different sets of connectors.
2) You add the gender-bender on-orbit.

Quote
A cryo cooler needs to be near power and propellant plumbing. There should be plenty of room above the tanks where there is a battery and plumbing for the header tanks. Convert each propellant pipe to a smaller diameter and double the pipes for a loop. Put the cooler where it's needed. No deployment necessary.

Assuming they're going to cryo-cool (which is far from certain), the easiest way to do that is to leverage the gas lines on the QD, feed them into the cryocooler, and then feed the liquified prop back through the fill lines.

The big problem here is keeping the fill lines cold and/or insulated, so the newly-liquified prop doesn't just flash back to gas when its pushed down the warm fill line.

This configuration strongly militates toward having the cryocooler as close to the QD as possible, to reduce the runs of plumbing that needs to stay chilled down.

Quote
Radiators, sun shields and PV are a tough one. My inclination is to stow them as near to where they'll be deployed as possible. Unfortunately, we know nada about their design. Fan or panel? Double duty as PV and sunshield? Stowing locally shouldn't be all that much of a problem. The nominally windward side is well away from the refueling side and mostly unblemished by doodads. A few equipment blisters won't hurt anything. As Dan pointed out, the nose will also be available.

I'm very skeptical of sun shields in LEO, because you also need to shield from Earth  There are ways to do it, but I wouldn't be surprised if brute-force cryocooling turned out to be a better solution.

Quote
The idea of StarLink style deployment is interesting (cue up 'Blue Danube') but complex. It might be something to look at for a direct tanker refueling but still, very complex.

By the time a tanker is tricked out to be a depot it has become a depot - but with fins, tiles and an overweight gender bender. Early on and long term have different solutions.

Early on, if a single or maybe even a two tanker load needs transferred somewhere above LEO, bite the bullet and send a special build throwaway tanker(s). Have the target waiting for the tanker so boiloff is not an issue and all hardware associated with it can be skipped. This would also work in the long term for special rare or one off missions.

Long term, spot depots in the high traffic areas that will need them.

This is why I like the depot kit so much:  A depot may be bigger, lack TPS, be painted solar white, etc., but everything else is the same--except you add the kit, which is literally just a payload.

I think I attached the following slides way up-thread, but this is what I was thinking back then.  You'll notice that this could be segmented so that it was a series of flat packs that got pezzed out of the vehicle, then crawled (or were pushed/dragged) into place.


Tags: HLS 
 

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