Author Topic: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3  (Read 807177 times)

Offline biosehnsucht

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1720 on: 02/03/2017 07:56 PM »
On the idea of "Roombas with welders": Why not little robots with big battery packs that are basically weld-down "shoes" with wheels, they drive themselves over the feet, raise their wheels (so they're sitting on the deck for welding), then dump the rest of their stored battery power into welding themselves to the deck? Rather than robot welders, the robots self-weld to the deck. Would still require some effort to remove them, but they could be "modular" such that all the non-shoe parts can be unbolted after they're in port and attached to a fresh shoe, while regular cutting techniques are used to get the welded shoes off...

Online meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1721 on: 02/03/2017 08:26 PM »
On the idea of "Roombas with welders": Why not little robots with big battery packs that are basically weld-down "shoes" with wheels, they drive themselves over the feet, raise their wheels (so they're sitting on the deck for welding), then dump the rest of their stored battery power into welding themselves to the deck? Rather than robot welders, the robots self-weld to the deck. Would still require some effort to remove them, but they could be "modular" such that all the non-shoe parts can be unbolted after they're in port and attached to a fresh shoe, while regular cutting techniques are used to get the welded shoes off...

That's exactly what I had in mind, with the welding being this, and each gun firing only once



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Offline Req

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1722 on: 02/03/2017 11:17 PM »
I know, not likely.

Less than not likely, more like nil of a chance.

Don't tell me, I already expressed my doubts.  Musk is the one you should be informing, he's the one who has expressed intent to do so, with this ASDS design, with consistency multiple times over multiple years, even again fairly recently.
« Last Edit: 02/03/2017 11:20 PM by Req »

Online meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1723 on: 02/04/2017 01:27 AM »
I know, not likely.

Less than not likely, more like nil of a chance.

Don't tell me, I already expressed my doubts.  Musk is the one you should be informing, he's the one who has expressed intent to do so, with this ASDS design, with consistency multiple times over multiple years, even again fairly recently.

Yeah, but it'll take more than some room under a container to pull that off.

The launch back is more than a gentle GH hop.

When you see a barge design that looks like a twin-hull, then we'll know it's getting close...  :)

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Offline Req

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1724 on: 02/04/2017 02:40 AM »
I suggest you review the source material.  He has explicitly said that this design will allow for refuel and hop back, and that these barges will be modified in the future to do so.

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1725 on: 02/04/2017 03:39 AM »
I suggest you review the source material.  He has explicitly said that this design will allow for refuel and hop back, and that these barges will be modified in the future to do so.

Do you have the source?  I remember the statement, something along the lines of "in the future, ... will allow fly back", but I think it left a lot of room for "how much improvement is still needed".

In a positive sense, the things he knows he's going to do two-three-ten years from now, they're in his head, and sometimes it's hard to be sure how many steps are between "now" and "then".

I think regularly flying rockets will happen, but will require quite a bit more hardware.

The barge will need a launch mount, since I don't think the legs will support the launch of a fueled rocket plus fold-up mechanism.  Too heavy, too hot.

The launch mount will need something like a flame duct. (hence the reference to a twin body barge, but that's not the only way to do it)

You'll need a way to get the rocket to the launch mount, fold the legs, refuel, etc -

We're not quite there yet.
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Offline deruch

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1726 on: 02/04/2017 03:42 AM »
I suggest you review the source material.  He has explicitly said that this design will allow for refuel and hop back, and that these barges will be modified in the future to do so.
Musk had also explicitly said that the F9 design would allow for full reuse including U/S.  And that they would eventually be modified to do so.  Now this is no longer in the cards even if it might be theoretically possible to achieve with enough work.  In the same vein, maybe it is theoretically possible to envision some future system of highly altered ASDS that could allow for refuel and hop-back.  And there may even be current, low-level planning to explore these modifications in the future.  But don't be surprised if, in the end, it is dropped for the same reason that U/S reuse of the F9 was dropped  They don't have an inexhaustible supply of engineering and design talent nor bottomless money pockets to fund R&D as well as their other plans.  So, they'll decide that those resources are better spent on other projects.  Or maybe it'll just be overtaken by events--like if the Falcon family of launchers were retired before they got to that point.  etc. 

None of which is to say that Jim's position--that it'll never happen it's not happening--is incompatible with the statements from Elon; there's only apparent contradiction, not actual conflict.  [I think] Jim is talking about what he expects the end result will be based on what he sees as the challenges presented by hop-back from ASDSs and SpaceX's other plans.  And Elon is perfectly happy to plan with very low level ideas (what's possible based on 1st principles analysis and sparse matrix engineering) and then talk about those future plans (because they are usually really cool) as if they are definite, only to postpone them again and again or pivot away from them totally when conditions/priorities have changed. 

I guess my position is that you shouldn't trust any Elon promise respecting SpaceX's medium- to long-term future plans, except insofar as you can trust them to actually do whatever they think will get them furthest forward on their path to Mars at that time.  But none of the way-points are actually set in stone, even if Elon has continuously talked about them as essential.  If tomorrow Elon/SpaceX determined that down-range landings on the ASDS weren't beneficial enough and that they would be better off to just use RTLS where possible and expend the rest where not, then I wouldn't be at all surprised if on Monday they got rid of all the ASDSs.  !Poof!  IMO, that has been one of the great strengths of SpaceX.  They're not so wedded to any plan/project that they follow it all the way into a dead-end. 

Sorry for slight digression and back to the original point.  There's pretty much ZERO chance of the changes most recently discussed being for hop-back because, if it was, they would have been talked about in at least a half dozen places and lots of "in-the-know"-type people would have at least heard rumors about it or something with the ASDS.  I include Jim as one of the people who likely would have heard something.  [And if he had, I doubt he would have commented as he did]

edit:altered wording and added [clarifiers] to try to avoid speaking on behalf of others.
« Last Edit: 02/04/2017 05:30 AM by deruch »
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Offline Req

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1727 on: 02/04/2017 03:54 AM »
I suggest you review the source material.  He has explicitly said that this design will allow for refuel and hop back, and that these barges will be modified in the future to do so.

Do you have the source?  I remember the statement, something along the lines of "in the future, ... will allow fly back", but I think it left a lot of room for "how much improvement is still needed".

http://lmgtfy.com/?q=elon+musk+asds+fly+back+refuel

Quote
Musk had also explicitly said that...

Non sequitur, although there's a reason I mentioned that he has been consistently saying this.  And I'm sorry, but I'm not going to theorycraft additional meaning to anything Jim says.  If he wanted to say that he would have heard about it and he hasn't, then I'd be happy to take him at his word.

I don't see why you think you need to argue with me about this.  He said he plans to do it, and some of you think it's outlandish or impossible or whatever.  Apparently some of you didn't even know that he said he plans to do it.  End of discussion, I don't even disagree that it's probably not what's going on right now.  What I don't understand is people jumping to declare what I hope is happening is outlandish to even hope for when it's the only outstanding publicly mentioned upgrade left at present, and people disputing easily available information after being told it exists twice in a row.
« Last Edit: 02/04/2017 04:20 AM by Req »

Online meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1728 on: 02/04/2017 04:57 AM »
Let me put this out there, even though it is not my prediction.

IF, if, somehow F9 gets to "do an BFR" - trade off the legs for side thrusters and a bunch of fuel - and actively homes in on the barge - then the barge can get a landing/launch pad, and there's your futuristic flyback system.

It's absolutely not what I think will happen, but SpaceX is doing a lot of things I didn't see coming, so I don't even try to say "never" anymore.
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Offline Req

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1729 on: 02/04/2017 05:07 AM »
Paging doctor Goldberg...

The legs can't just retract after takeoff and before aero loads get unmanageable?  Grasshopper got plenty high with rigid legs.

Offline deruch

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1730 on: 02/04/2017 05:21 AM »
1. Fair point about not speaking for others. 
My personal wishful-thinking hope on both the deck plates and the raised container is something to do with refuel and hop back to land.  Maybe tanks below, the extra room is for GSE, the deck plates for takeoff impengement and/or holes/ports/etc or something for an at-sea service mast type hookup.  I know, not likely.
2. Not to harp, but this whole jag was spawned not by a comment about potential future developments to the ASDS but about specific changes that have been recently/contemporaneously observed.  Though I do admit that I either missed, forgot, or ignored your inclusion of "wishful-thinking" in that sentence. 

In my previous comment, I attempted to point out why I think it is a mistake to insist that Elon's comments about future plans are strong evidence for why your "wishful hopes" are reasonable (if doubtful) when, logically, I don't believe they are, Elon's statements notwithstanding.  See the comment below for some logical reasons with which I concur:
Yeah, but it'll take more than some room under a container to pull that off.  The launch back is more than a gentle GH hop.  When you see a barge design that looks like a twin-hull, then we'll know it's getting close...
It certainly wasn't a non-sequitur to point out that Elon has very consistently made public pronouncements about SpaceX's expected path/plans and then later abandoned them many, many times.  Note, I do not include stated goals only paths.  Most specifically, you shouldn't rely on his statements that this design of the ASDS is ready to support refuel and hop-back with only modifications and not major changes (redesign).  Though maybe this is really just a semantic argument about where we each variously draw the lines between redesign, moderate changes, and modifications.  If you think so, feel free to drop it and ignore my attempt to split hairs.
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Offline Req

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1731 on: 02/04/2017 05:40 AM »
2. Not to harp, but this whole jag was spawned not by a comment about potential future developments to the ASDS but about specific changes that have been recently/contemporaneously observed.  Though I do admit that I either missed, forgot, or ignored your inclusion of "wishful-thinking" in that sentence.

But is it really that out of place in time?  Supposedly the "final" major revision to F9, specifically to address reuse, is either finished with design or nearly so, since the plan is to have them flying by the end of the year.  If they have not abandoned the idea of flyback, which I have seen no reason to believe they have, would now not be a reasonable time to begin making those changes?


Quote
It certainly wasn't a non-sequitur
Well you immediately brought up single-stick S2 reuse.  In that case, he came out pretty early and explained what was already obvious to anybody who was doing sims on the rocket regarding second-stage reuse - even with a heroic dry PMF on the S2 with reuse kit, there just wasn't going to be any demand for such small payloads.

In the case of flyback, they have consistently been seriously talking about it as in their plans from 2014(or earlier) until, IIRC, within the last 6 months.  I remember a recent mention at a conference or something that I watched as video.  It's also not immediately obvious that there has to be any kind of flame trench, and in fact, also IIRC, we've gone over that here and the general conclusion was that it could probably take off from it's legs with no problem from a materials perspective, given the GH operations.

So the two don't seem very similar to me as examples.

Edit to add - It doesn't need to worry about optimizing for gravity losses and whatnot because the mission won't even require anything near full tanks to begin with.  Plenty of margin for any kind of staged takeoff profile that's necessary to safely get it off the deck at low throttle and retract the legs before throttling up.  It would be able to ascend, descend, and hover.
« Last Edit: 02/04/2017 06:15 AM by Req »

Offline Herb Schaltegger

Paging doctor Goldberg...

The legs can't just retract after takeoff and before aero loads get unmanageable?  Grasshopper got plenty high with rigid legs.

No. The legs lock in the extended position and have no mechanism to retract, nor does the stage carry an inexhaustible supply of helium to extend them a second time. So keep on dreaming about flyback hops but until you see authorization to do so in FAA and FCC paperwork, you'll be dreaming in fantasyland.
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Offline Req

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1733 on: 02/04/2017 12:48 PM »
Paging doctor Goldberg...

The legs can't just retract after takeoff and before aero loads get unmanageable?  Grasshopper got plenty high with rigid legs.

No. The legs lock in the extended position and have no mechanism to retract, nor does the stage carry an inexhaustible supply of helium to extend them a second time. So keep on dreaming about flyback hops but until you see authorization to do so in FAA and FCC paperwork, you'll be dreaming in fantasyland.

This is common knowledge.  Are you suggesting that making them retract is more complicated and less likely than putting a landing/launching cradle on the ASDS and adding lateral thrusters to the F9 as he was suggesting?  Are you suggesting that if you can refuel RP1 and LOX it would be impossible to reload helium and whatever other expendables the vehicle needs such as fluid for the grid fins and maybe tea/teb?  The fuel/prop is one thing, but those others, that's just a bridge too far?  And again, still wondering why I'm here defending what Musk and SpaceX have repeatedly claimed will happen in no uncertain terms.  Fantasy dreamland indeed.  How disrespectful to them.
« Last Edit: 02/04/2017 01:01 PM by Req »

Online envy887

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1734 on: 02/04/2017 01:23 PM »
The current legs also are very unlikely able to hold the static weight of the rocket once fueled enough to fly back, or take the thermal load of 2 or 3 engines firing on the deck during liftoff. Plus there is no way to do a hold-down, which would be desirable. So it needs a launch stand, either portable to be moved under the rocked after landing, or fixed over the water with a transfer system to move the rocket to it. This can be done with the current hull design though, a double hull is unnecessary.

Flying the Falcon 9 forwards with the interstage open in the lower atmosphere at supersonic speeds is, IMO, entirely infeasible. So it needs a nose cone, and some way to install it while on the barge, likely a crane since the cherry picker isn't tall enough.

The barge also needs tanks for LOX, RP-1, nitrogen, and helium, and transfer systems to move at least some of those from a support ship to the tanks and from the tanks to the rocket.

So we will see a lot of changes if they decide to actually implement flyback.

Offline Req

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1735 on: 02/04/2017 01:28 PM »
All of the above is known and has been discussed at length on this forum, along with the fact that block 5 has new legs and other reuse improvements.  There have been suggestions made about interstage designs that do not need to be capped, although that problem doesn't seem intractable even if they do.

On the topic of needing hold downs, desirable is the right term.  Remember that the mission is already completed at this point.  Although it wouldn't surprise me if we end up seeing something along the lines of the GH launch structure roll out in 4 segments to both fold up the legs and provide hold-downs(also as previously discussed.)
« Last Edit: 02/04/2017 01:43 PM by Req »

Offline Herb Schaltegger

Paging doctor Goldberg...

The legs can't just retract after takeoff and before aero loads get unmanageable?  Grasshopper got plenty high with rigid legs.

No. The legs lock in the extended position and have no mechanism to retract, nor does the stage carry an inexhaustible supply of helium to extend them a second time. So keep on dreaming about flyback hops but until you see authorization to do so in FAA and FCC paperwork, you'll be dreaming in fantasyland.

This is common knowledge.  Are you suggesting that making them retract is more complicated and less likely than putting a landing/launching cradle on the ASDS and adding lateral thrusters to the F9 as he was suggesting?  Are you suggesting that if you can refuel RP1 and LOX it would be impossible to reload helium and whatever other expendables the vehicle needs such as fluid for the grid fins and maybe tea/teb?  The fuel/prop is one thing, but those others, that's just a bridge too far?  And again, still wondering why I'm here defending what Musk and SpaceX have repeatedly claimed will happen in no uncertain terms.  Fantasy dreamland indeed.  How disrespectful to them.

Of course it is common knowledge. So why do you persist in discussing this concept in the absence of any fact whatsoever to support the idea that it is happening any time in the foreseeable future?

And as for your questions: False dichotomy. The entire first stage of the F9 would have to be substantially redesigned to support retractable legs and/or landing onto a launch mount with thrusters. It would de facto cease being a "Falcon 9" as we know it, or least not a F9 1.1FT/F9 1.2 (which is what the FAA launch licenses call it now).

And yes, until we've seen any evidence whatsoever of the ability to refuel and provide fluids service in situ on a rolling/pitching barge at sea, yes, it's still a fantasy dreamland.

But hey, keep dreaming. Someday these things might happen. But this thread probably isn't the place to do so. In the absence of evidence as to what that small protected space under an elevated container might be used for (and there has already been more plausible speculation up-thread), you're just dreaming if you think SpaceX could fit robotic servicing equipment to support fly-back. Take a look at cryogenic and high-pressure fluid systems design sometime. When you see evidence of any of that being installed on one of the barges, THEN you'll have a basis to keep talking about it. In the meantime you're just arguing to argue.
« Last Edit: 02/04/2017 01:42 PM by Herb Schaltegger »
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Offline Req

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1737 on: 02/04/2017 01:47 PM »
And in the meantime SpaceX obviously just spouts fantasyland dreams off without looking into any of this.  Got it.  And arguing now = replying to people arguing with me after making a statement that couldn't have been interpreted as contradicting anything anybody was saying.

BTW, to your second paragraph, are you aware of F9 block 5 and what it is?  This is already taking place.
« Last Edit: 02/04/2017 01:58 PM by Req »

Offline Herb Schaltegger

And in the meantime SpaceX obviously just spouts fantasyland dreams off without looking into any of this.  Got it.  And arguing now = replying to people arguing with me after making a statement that couldn't have been interpreted as contradicting anything anybody was saying.

I have no doubt SpaceX "looks into" many things - including many things that don't happen in practical reality. That's the nature of their jobs. You can speculate all you want in the threads about that. In the meantime, running off into frenzied imaginings based on one elevated cargo container on the deck of the barge - in the absence of any physical evidence to support said imaginings - is more than a bit tiresome to people who actually understand engineering and physics.
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Offline douglas100

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1739 on: 02/04/2017 01:59 PM »
The only reason to do fly back is to save time. Of course it could be done, with a substantial redesign and engineering effort. But the real question is whether it is needed.

And that depends on flight rate. Is it worthwhile doing at the current projected flight rate? I don't think so. Of course that could change in the future...

Edit: took out the nose cone reference, since it was already posted.
« Last Edit: 02/04/2017 02:05 PM by douglas100 »
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