We're not used to docking spacecraft where over half the mass is loose in the tanks. That's not slosh, that's a couple of independent tsunamis in there.The only predictable way to do this is get the ships on your fractional-g recipe ahead of time, never going into drift. Align courses, and dock sideways, without ever dropping the acceleration. And at that point, start moving fuel until done.So the entire operation from before docking to after separation, is under this slight baseline acceleration (and the docking accelerations are lower)Otherwise the effects of 100 ton propellant blobs hitting the sidewalls at random delays, off center, will be insane.
Quote from: Twark_Main on 11/14/2024 06:23 pmIn no particular orderAtlas demonstrated disconnecting engines in-flight.Why should we expect connecting engines will be easier than disconnecting them?Why separate engines and tankage vs using on-orbit refilling?I guess I wasn't clear. The assemblage of OTV and tanks would be the BEO depot rather than using an SS variation. It saves dry mass for missions to NRHO, LLO, mars and anywhere else a depot is needed other than LEO.
In no particular orderAtlas demonstrated disconnecting engines in-flight.Why should we expect connecting engines will be easier than disconnecting them?Why separate engines and tankage vs using on-orbit refilling?
Quote from: OTV Booster on 11/15/2024 07:41 pmQuote from: Twark_Main on 11/14/2024 06:23 pmIn no particular orderAtlas demonstrated disconnecting engines in-flight.Why should we expect connecting engines will be easier than disconnecting them?Why separate engines and tankage vs using on-orbit refilling?I guess I wasn't clear. The assemblage of OTV and tanks would be the BEO depot rather than using an SS variation. It saves dry mass for missions to NRHO, LLO, mars and anywhere else a depot is needed other than LEO.Okay, but... same questions?At most, the dry mass means you deliver 1-2 tonnes more propellant per engine removed. In reality it will be less, because some of those gains are lost to Oberth.Seems like a lot of non-recurring R&D for a tiny benefit.
Here's the new render for the depot/tanker docking. We probably shouldn't read too much into this, but some things jumped out:1) Kinda looks like the depot might not have RVacs, and they've been covered with some kind of insulation?2) As we've suspected for a while, it looks like the QD is the plumbing connection between depot and tanker. However, also as discussed, there's some kind of a spacer / gender-bender between the two QDs. It's not possible to tell if it's launched that way or not.3) Docking is... interesting. Looks like two pairs of struts with piston shock absorbers, which slide into sockets. I can't tell whether the struts are part of the depot or part of the tanker, although the former would make more sense, but the piston telescoping seems to argue for the other way around. I don't understand the two thinner struts that surround the strut with the piston. Could they be used to deploy the strut?4) It'd be nice to know how long the struts are when undocked. I assume fairly long, because making a perfect 4-point docking seems like it'll be hard without something to take out the inevitable misalignments. Looks like the docking sockets could handle the struts sliding into place from someplace closer to the midline.5) Doesn't seem to be any extra hardware for cryocooling, and it looks like they're going for Solar White on the depot.
All of the docking hardware needs to be on Depot, not tanker, because Depot must be able to transfer propellant to other Ship types, notably HLS.
Depot has a very HLS look to it too, as if it was just missing some HLS leg hardware.
Here's the new render for the depot/tanker docking. We probably shouldn't read too much into this, but some things jumped out:1) Kinda looks like the depot might not have RVacs, and they've been covered with some kind of insulation?2) As we've suspected for a while, it looks like the QD is the plumbing connection between depot and tanker. However, also as discussed, there's some kind of a spacer / gender-bender between the two QDs. It's not possible to tell if it's launched that way or not.3) Docking is... interesting. Looks like two pairs of struts with piston shock absorbers, which slide into sockets. I can't tell whether the struts are part of the depot or part of the tanker, although the former would make more sense, but the piston telescoping seems to argue for the other way around. I don't understand the two thinner struts that surround the strut with the piston. Could they be used to deploy the strut?4) It'd be nice to know how long the struts are when undocked. I assume fairly long, because making a perfect 4-point docking seems like it'll be hard without something to take out the inevitable misalignments. Looks like the docking sockets could handle the struts sliding into place from someplace closer to the midline.5) Doesn't seem to be any extra hardware for cryocooling, and it looks like they're going for Solar White on the depot.Update: Here's the tweet from SpaceX:https://x.com/SpaceX/status/1858991247312212112
The fairings are interesting. The depot side is perfectly set up for a receiving socket and the tanker side fairing has nothing to do with the positioning strut. The strut misses it entirely.Heres my speculation. After disconnect, the strut assembly lays down not quite flat on the tanker pointing aft and then its base joint, riding on a carrier, retracts into the fairing as far as it can. This is also its launch position.One last speculation. Some wires may have been crossed somewhere in the art department. I see no advantage and many disadvantages in putting the struts on the tanker. The depot makes more sense.
Quote from: OTV Booster on 11/20/2024 08:12 pmThe fairings are interesting. The depot side is perfectly set up for a receiving socket and the tanker side fairing has nothing to do with the positioning strut. The strut misses it entirely.Heres my speculation. After disconnect, the strut assembly lays down not quite flat on the tanker pointing aft and then its base joint, riding on a carrier, retracts into the fairing as far as it can. This is also its launch position.One last speculation. Some wires may have been crossed somewhere in the art department. I see no advantage and many disadvantages in putting the struts on the tanker. The depot makes more sense.I've been wondering if maybe the struts are depot equipment that's designed to drag along the dorsal side of the tanker/LSS, until they're captured by the sockets behind the fairings on the tanker. That doesn't explain the two thin struts, though. Maybe they're sensors?
Quote from: DanClemmensen on 11/20/2024 04:34 amAll of the docking hardware needs to be on Depot, not tanker, because Depot must be able to transfer propellant to other Ship types, notably HLS.Yup, that's my reasoning as well. But it doesn't look like that's what's happening.
Quote from: TheRadicalModerate on 11/20/2024 04:35 amQuote from: DanClemmensen on 11/20/2024 04:34 amAll of the docking hardware needs to be on Depot, not tanker, because Depot must be able to transfer propellant to other Ship types, notably HLS.Yup, that's my reasoning as well. But it doesn't look like that's what's happening.This isn't our first rodeo. Old-timers like us should be well aware that when a render looks egregiously dumb like that, what inevitably happens is that Elon says."That? Oh yeah, that's dumb, we just do <thing that made sense all along>."I trust that this pattern will prevail in this instance too.
Quote from: Twark_Main on 11/22/2024 04:29 amQuote from: TheRadicalModerate on 11/20/2024 04:35 amQuote from: DanClemmensen on 11/20/2024 04:34 amAll of the docking hardware needs to be on Depot, not tanker, because Depot must be able to transfer propellant to other Ship types, notably HLS.Yup, that's my reasoning as well. But it doesn't look like that's what's happening.This isn't our first rodeo. Old-timers like us should be well aware that when a render looks egregiously dumb like that, what inevitably happens is that Elon says."That? Oh yeah, that's dumb, we just do <thing that made sense all along>."I trust that this pattern will prevail in this instance too.Why would any graphic artist generate something that fanciful? The fact that this stuff changes from concept to concept--and the level of detail increases--implies that somebody's basing the render off of some particular CAD model. That doesn't mean that the CAD drawing isn't dumb and will be disavowed later on, but I doubt the art department is using the Rectal Extraction Technique to produce these.
Quote from: Twark_Main on 11/22/2024 04:29 amQuote from: TheRadicalModerate on 11/20/2024 04:35 amQuote from: DanClemmensen on 11/20/2024 04:34 amAll of the docking hardware needs to be on Depot, not tanker, because Depot must be able to transfer propellant to other Ship types, notably HLS.Yup, that's my reasoning as well. But it doesn't look like that's what's happening.This isn't our first rodeo. Old-timers like us should be well aware that when a render looks egregiously dumb like that, what inevitably happens is that Elon says."That? Oh yeah, that's dumb, we just do <thing that made sense all along>."I trust that this pattern will prevail in this instance too.Why would any graphic artist generate something that fanciful? The fact that this stuff changes from concept to concept--and the level of detail increases--implies that somebody's basing the render off of some particular CAD model. That doesn't mean that the CAD drawing isn't dumb and will be disavowed later on, but I doubt the art department is using the Rectal Extraction Technique to produce these.
Quote from: TheRadicalModerate on 11/20/2024 04:35 amQuote from: DanClemmensen on 11/20/2024 04:34 amAll of the docking hardware needs to be on Depot, not tanker, because Depot must be able to transfer propellant to other Ship types, notably HLS.Yup, that's my reasoning as well. But it doesn't look like that's what's happening.This isn't our first rodeo. Old-timers like us should be well aware that when a render looks egregiously dumb like that, what inevitably happens is that Elon says."That? Oh yeah, that's dumb, we just do <thing that made sense all along>."I trust that this pattern will prevail in this instance too.