Quote from: JasonAW3 on 03/02/2017 06:38 pmQuote from: rsdavis9 on 03/02/2017 05:31 pmQuote from: meekGee on 03/02/2017 03:41 pmSo 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.
Quote from: rsdavis9 on 03/02/2017 05:31 pmQuote from: meekGee on 03/02/2017 03:41 pmSo 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!
Quote from: meekGee on 03/02/2017 03:41 pmSo 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.
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?
So I think some kind of "securing" robot is a given.....
eg. the ASDS going flat-out for home, at the right angle to the waves.
Quote from: rsdavis9 on 03/02/2017 08:31 pmSo 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.
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.
Quote from: CameronD on 03/02/2017 09:35 pmeg. 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..
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.
Quote from: meekGee on 03/03/2017 01:57 amI'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
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...
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
Notice the ground clean spots on the beam.Matthew