Author Topic: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3  (Read 792633 times)

Online meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1840 on: 03/02/2017 07:58 PM »
So out of curiosity..  assuming the robot weighs enough so that welding is not necessary - what will the crew be doing after the stage is latched and secured?

Hopefully not even getting on board.
They could even hook up to the towline without getting on board.
Boarding ships at sea in waves is something that should be avoided if possible.

Might be able to rig up a bosen chair between the ship and ASDS, but it'd still be dangerous as all heck!
From ships to  platforms we'd use cranes. The crane operator would get to Tarzan over on a rope. Managers in dry offices on land came up with lots of brilliant schemes for ship to ship in seas, but it always went back to jumping when the odds looked good.
 Most of us put Bosun's chairs up there with Bangalore torpedoes as the worst inventions in history.

 If you were going to secure the legs in seas with Roombas, electromagnets would be a lot simpler and faster than automated welding. I doubt if the barge would ever be allowed in any port before a crew boarded and took care of a few things.
A central mega-Roomba, as opposed to four foot-grabbers, can be heavy enough that it does not need magnets or stud welders. It just IS, held in place by the power of its own majesty.

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Offline rsdavis9

So I think some kind of "securing" robot is a given.
Spacex loves to kill 2 birds with one stone. Or basically get more than one thing done.
I still think they will have some big improvement with process flow with this robot being on board the barge.
I'm predicting that this robot will secure the stage for transit and when back in port lift the stage enough for leg removal thereby removing 2 of 3 steps so they can got right to make horizontal and load on truck.
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Offline leetdan

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1842 on: 03/02/2017 08:58 PM »
Any sort of remote vehicle like this could be engineered such that it maintains traction in at least the same sea state that a landed stage maintains traction.  Mass, deck vs. tire friction, cross section vs. wave or wind action, all of it is solvable.

My uninformed guess is a low-profile (Roomba-like) crawler that scoots under the landed stage, aligns and rotates a jack stand that engages the launch hold downs, extends outriggers, and then lifts the stage enough to take the load off the legs.  0% autonomous, supported by onboard and on-barge video assets.

Offline Confusador

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1843 on: 03/02/2017 09:01 PM »
So I think some kind of "securing" robot is a given.
....

I'm not actually sold on that, though I grant the possibility.  I'm betting on a fire-fighting robot.

Offline CameronD

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1844 on: 03/02/2017 09:35 PM »
So out of curiosity..  assuming the robot weighs enough so that welding is not necessary - what will the crew be doing after the stage is latched and secured?

Hopefully not even getting on board.
They could even hook up to the towline without getting on board.
Boarding ships at sea in waves is something that should be avoided if possible.

Actually, it's not all that dangerous (with the proper skills and equipment) so long as the vessel being boarded is moving, eg. the ASDS going flat-out for home, at the right angle to the waves.  Sea pilots do this all the time and something fairly low and wide (like a barge) is deliberately designed to be easy to board in all but the roughest of seas.

Believe me, the nervy bit is getting off of the comfy, warm, mother ship into the "dinghy"..
« Last Edit: 03/02/2017 09:37 PM by CameronD »
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline old_sellsword

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1845 on: 03/02/2017 09:41 PM »
eg. the ASDS going flat-out for home, at the right angle to the waves.

Does the ASDS ever do anything but stationkeep under it's own power?

Offline envy887

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1846 on: 03/02/2017 11:02 PM »
So I think some kind of "securing" robot is a given.
....

I'm not actually sold on that, though I grant the possibility.  I'm betting on a fire-fighting robot.

Why not both? Dousing the bottom of the stage with foam is pretty easy if you're already under there grabbing the hold-down points.

Online meekGee

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1847 on: 03/03/2017 01:57 AM »
Any sort of remote vehicle like this could be engineered such that it maintains traction in at least the same sea state that a landed stage maintains traction.  Mass, deck vs. tire friction, cross section vs. wave or wind action, all of it is solvable.

My uninformed guess is a low-profile (Roomba-like) crawler that scoots under the landed stage, aligns and rotates a jack stand that engages the launch hold downs, extends outriggers, and then lifts the stage enough to take the load off the legs.  0% autonomous, supported by onboard and on-barge video assets.

I'm with you until the "lift" part.

I think it pulls down.

You need the "wide stance" of the original legs, but because the rocket is tall, a stage can "walk" by temporarily losing traction on a 1-2 legs.

The Roomba can weigh as much as the entire rocket.  Have it pull down, so that the normal forces on the legs double (they are rated for a dynamic impact, so they'll be fine with the extra load), and still have traction left over at the Roomba itself.

Sort of like chaining the stage down with a vertical chain.  The chain itself doesn't add lateral holding forces, but the extra load on the legs sure does.
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Offline CameronD

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1848 on: 03/03/2017 04:13 AM »
eg. the ASDS going flat-out for home, at the right angle to the waves.

Does the ASDS ever do anything but stationkeep under it's own power?

IIRC, we've seen video of it cruising around in happy circles after the first successful landing many pages back.. but in any case, there's absolutely no reason why it couldn't, simply by shifting the setpoint to 'back to port'.  With the thrusters they're using, I expect the speed wouldn't be more than a couple of knots, but that's better (and a lot safer for the landed booster!) than lying there beam-on to the waves.
« Last Edit: 03/03/2017 04:15 AM by CameronD »
With sufficient thrust, pigs fly just fine - however, this is not necessarily a good idea. It is hard to be sure where they are
going to land, and it could be dangerous sitting under them as they fly overhead.

Offline Semmel

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1849 on: 03/03/2017 07:58 AM »
First what we know:
* SpaceX stated they want to fly stages back from the barge to land (as unlikely as that seems)
* SpaceX want to land BFR on a launch cradle

Ok, complete, full force speculation mode from here.
Lets take both statements at face value and assume they still want to do this. So we accept the two above statements as axioms and do not question them. Following is a speculation run on what conclusion would follow given the above axioms.

It would make sense for SpaceX to be able to test the landing on launch mounts before doing it with BFR. So that would imply tests with F9.

How can they fly a stage from the barge back to land? Its not possible using the legs. They would have to land folded out, then fold them in again and than launch and land on land. But for folding the legs up before launch, F9 needs to sit on a launch mount on the barge. It cant get there without a large crane. Therefore, the only good option would be to land on the launch mount in the first place, not using the legs.

What about an alternative?
* SpaceX builds a launch/landing mount on the barge (I know I know, its not possible. Remember the full fledged speculation mode, ok?)
* The Roomba Garage olds a robot that brings RP1 and LOX lines to the first stage, hooks it up and refills it partly. The access ports are at the bottom, so it should be possible.
* The stage flies back to land and lands at LZ1

Obviously it would not start like that. The first try to land on a launch/land mount would be at LZ1. Once that works, it might be tried on the barge. It has been pointed out that the barge is not stable enough for a precision landing. However, the landing mount might have a homing beacon that the first stage targets in the last meters of descend instead of the GPS coordinates that are used now. It might be tough but I dont think impossible.

Offline rpapo

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1850 on: 03/03/2017 12:02 PM »
IIRC, we've seen video of it cruising around in happy circles after the first successful landing many pages back..
Are we sure this (the victory lap) wasn't just an artifact of the drone's perhaps circling point of view?  I just looked at that video again, and it didn't seem all that certain the barge was making headway apart from keeping it's nose into the waves.
An Apollo fanboy . . . fifty years ago.

Offline rsdavis9

So  next flight echo wont use the drone. Whats the next flight after that? SES first "flight proven" booster? It will try to land I assume. Maybe we will see roomba in action then.
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Online matthewkantar

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1852 on: 03/03/2017 01:50 PM »
I'm with you until the "lift" part.

I think it pulls down.

You need the "wide stance" of the original legs, but because the rocket is tall, a stage can "walk" by temporarily losing traction on a 1-2 legs.

The Roomba can weigh as much as the entire rocket.  Have it pull down, so that the normal forces on the legs double (they are rated for a dynamic impact, so they'll be fine with the extra load), and still have traction left over at the Roomba itself.

Sort of like chaining the stage down with a vertical chain.  The chain itself doesn't add lateral holding forces, but the extra load on the legs sure does.

That all seems correct to me, except SpaceX practice seems to have been to install jacks and then pull the stage down onto them with binders. The legs are designed for a dynamic load, but maybe not tens of thousands of cycles of waves applying and unapplying a force to the side of the stage. If the new gizmo exists, I think it will follow previous practice. Center under stage, magnetize, grab hold downs, secure mechanically, jack stage up a bit so that the legs are doing the minimum in holding the rocket verticals.

Matthew
« Last Edit: 03/03/2017 01:52 PM by matthewkantar »

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1853 on: 03/03/2017 02:06 PM »
I'm with you until the "lift" part.

I think it pulls down.

You need the "wide stance" of the original legs, but because the rocket is tall, a stage can "walk" by temporarily losing traction on a 1-2 legs.

The Roomba can weigh as much as the entire rocket.  Have it pull down, so that the normal forces on the legs double (they are rated for a dynamic impact, so they'll be fine with the extra load), and still have traction left over at the Roomba itself.

Sort of like chaining the stage down with a vertical chain.  The chain itself doesn't add lateral holding forces, but the extra load on the legs sure does.

That all seems correct to me, except SpaceX practice seems to have been to install jacks and then pull the stage down onto them with binders. The legs are designed for a dynamic load, but maybe not tens of thousands of cycles of waves applying and unapplying a force to the side of the stage. If the new gizmo exists, I think it will follow previous practice. Center under stage, magnetize, grab hold downs, secure mechanically, jack stage up a bit so that the legs are doing the minimum in holding the rocket verticals.

Matthew
Yes, there are two ways to do it.

Jack up: Offload the legs and carry the overturning torque using the thrust structure and a much smaller footprint (requires a strong connection to the deck) or,

Winch down: Add load to the legs and rely on them.

The first method requires a magnet, a weld-down, or a much much heavier robot (heavy enough to stabilize the rocket using only  12' base)

The second method requires the legs to work till they reach shore.
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Offline rsdavis9

I "vote" for method 1.
Spacex is always trying to push the envelope and do more than what meets the eye.

EDIT:

BTW what is the mechanism of the TEL? The hold downs are on the pad Correct? How does the TEL line up the booster with the hold downs? Before the booster is on the launch pad what supports the vertical weight of the booster?

I am envisioning something like driving the TEL on to the barge and picking it up...
« Last Edit: 03/03/2017 02:12 PM by rsdavis9 »
With ELV best efficiency was the paradigm. The new paradigm is reusable, good enough, and commonality of design.
Same engines. Design once. Same vehicle. Design once. Reusable. Build once.

Offline old_sellsword

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1855 on: 03/03/2017 02:19 PM »
BTW what is the mechanism of the TEL? The hold downs are on the pad Correct? How does the TEL line up the booster with the hold downs? Before the booster is on the launch pad what supports the vertical weight of the booster?

I am envisioning something like driving the TEL on to the barge and picking it up...

The holddowns are attached in four places to the octaweb, there's a passive cradle around the interstage area, and there's a clamp that goes around the second stage, right underneath the fairing.

A full pad deck + TE combo seems really overkill for transportation, especially since they just modified the old Shuttle transporter for that purpose.

Online matthewkantar

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1856 on: 03/03/2017 02:54 PM »
For automated securing, I think self drilling/tapping bolts would be the way to go. Would require a motorized spindle for each bolt, just rotate the fastener until the torque spikes, and it is set. I have not seen off the shelf bolts like this that are large enough to do the job, they might need to be custom made. The hole can be plugged and welded over after the stage is removed. Designing a bot to do reliable welding in that environment would be much more difficult.

Matthew

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1857 on: 03/03/2017 04:24 PM »
For automated securing, I think self drilling/tapping bolts would be the way to go. Would require a motorized spindle for each bolt, just rotate the fastener until the torque spikes, and it is set. I have not seen off the shelf bolts like this that are large enough to do the job, they might need to be custom made. The hole can be plugged and welded over after the stage is removed. Designing a bot to do reliable welding in that environment would be much more difficult.

Matthew
Stud welds are easy...

Space is not Highlander.  There can, and will, be more than one.

Online matthewkantar

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1858 on: 03/03/2017 05:37 PM »
Notice the ground clean spots on the beam.

Matthew

Offline Lar

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Re: SpaceX's Autonomous Spaceport Drone Ship Discussion Thread 3
« Reply #1859 on: 03/03/2017 07:09 PM »
Notice the ground clean spots on the beam.

Matthew
And of course a robot  could not POSSIBLY be set up to first do a bit of grinding before it fired the stud welder.

(sorry, couldn't resist, that was sarcasm... more seriously if the deck can take these studs it can take some grinding)
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