Airlock

SpaceX: Current missions and future plans. (Renamed thread.)

7830 posts in this topic

2 hours ago, Gkirmathal said:

Probably an impossible idea: but couldn't they rework the the upper stage, to be able to be robotically refueled? And device a way to make the the Merlin 1D Vac not freeze up so it can be easily restarted.

Launch a refueling craft to GTO (or what is useful) and let the Moon mission rendezvous with it. Robotically refuel it's second stage and progress with the mission.

That would require designing a whole new upper stage, as well as a whole new refueling vehicle. That would take years of development and would side track all their other projects.

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5 minutes ago, Nibb31 said:

That would require designing a whole new upper stage, as well as a whole new refueling vehicle. That would take years of development and would side track all their other projects.

Yea, at that point you might as well make it the Falcon/Raptor Upperstage people have been speculating about since the AF contract was bandied about.

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Posted (edited)

Refueling in space with cryogens hasn't been done; only with N2O4, UDMH, and ethanol. It's going to be doable, and several groups are working on it, but it's not going to be easy to develop.

Edited by Kryten
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5 hours ago, Exoscientist said:

The Isp of the Superdracos is only 240s at sea level. But with just a nozzle extension we can get the vacuum Isp to the 320 s range.

The Superdracos are the Dragon V2's launch escape system. The thing that saves the astronauts life if everything else goes horribly wrong. SpaceX won't start messing around with that lightly.

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33 minutes ago, cantab said:

The Superdracos are the Dragon V2's launch escape system. The thing that saves the astronauts life if everything else goes horribly wrong. SpaceX won't start messing around with that lightly.

At least for any varient that actually launches crew.

A hypothetical lunar lander varient of Dragon 2 (White dragon) that goes up unmanned for a 1-way landing on the moon has less need for a launch abort system.

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1 hour ago, cantab said:

The Superdracos are the Dragon V2's launch escape system. The thing that saves the astronauts life if everything else goes horribly wrong. SpaceX won't start messing around with that lightly.

I'd bet that there's a variant of the dragon trunk sitting somewhere at Hawthorne that has Hypergol tanks and Super-Draco engine mounted in place of cargo capability

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There might be a sketch of one somewhere. But not actual hardware.

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2 minutes ago, sojourner said:

There might be a sketch of one somewhere. But not actual hardware.

Why not, it's a logical thing to test and prove possible

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12 minutes ago, Nothalogh said:

Why not, it's a logical thing to test and prove possible

Because it's very expensive to design and build the hardware just to test that.

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Just now, kunok said:

Because it's very expensive to design and build the hardware just to test that.

They built Grasshopper just to prove it was possible

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Just now, Nothalogh said:

They built Grasshopper just to prove it was possible

That was for a defined goal, that is to develop the landing capabilities of the Falcon9. (And it was already proven what grasshopper did)

You are basically suggesting to design a new service module, that is exactly one thing that SpaceX has opposed to do. You are really oversimplifying the engineering in that.

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I wonder if they could put something in the trunk with a docking ring that could function as added life support/etc? Trunk separation from the upper stage would perhaps have this orbital module attached (in a way that can be separated) to the upper stage. So the vehicle separates, rotates, docks with this section, then has added capability. Obviously this would require actual astronaut pilots, or non-trivial amounts of training with the attitude control system in case automated docking fails.

The trunk volume is after all about like the capsule itself. If not for the current mission, this might be a relatively easy way to increase duration/comfort (say to function as a cislunar taxi vehicle). For a trip that requires a week or two in transit with anything like the total crew capacity, having the orbital module be a dedicated bathroom might alone justify the development of it. :D 

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24 minutes ago, tater said:

Obviously this would require actual astronaut pilots, or non-trivial amounts of training with the attitude control system in case automated docking fails.

And a backup plan in case docking fails entirely...

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47 minutes ago, DerekL1963 said:

And a backup plan in case docking fails entirely...

Yeah, if it were required for the mission, then the maneuver would have to be done before TLI so there would be an abort modality. If it were merely something that increased habitability (from a quality standpoint), then it's not a problem. Has an ISS docking/berthing ever failed?

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45 minutes ago, tater said:

Yeah, if it were required for the mission, then the maneuver would have to be done before TLI so there would be an abort modality. If it were merely something that increased habitability (from a quality standpoint), then it's not a problem. Has an ISS docking/berthing ever failed?

No, they've never failed AFAIK.   But the margins are lower and the risk level greater when you're off to the moon rather than delivering supplies to a station that has a reserve *and* multiple potential routes of supply.

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Dragon would never really be able to go to the ISS in this configuration anyway (unless its was in a really bizarre emergency where it couldn't reenter but could still rendezvous and dock) because while SpaceX may be happy to take paying tourists onboard, NASA an Roscosmos almost certainly aren't.

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2 hours ago, tater said:

I wonder if they could put something in the trunk with a docking ring that could function as added life support/etc? Trunk separation from the upper stage would perhaps have this orbital module attached (in a way that can be separated) to the upper stage. So the vehicle separates, rotates, docks with this section, then has added capability. Obviously this would require actual astronaut pilots, or non-trivial amounts of training with the attitude control system in case automated docking fails.

The trunk volume is after all about like the capsule itself. If not for the current mission, this might be a relatively easy way to increase duration/comfort (say to function as a cislunar taxi vehicle). For a trip that requires a week or two in transit with anything like the total crew capacity, having the orbital module be a dedicated bathroom might alone justify the development of it. :D 

Might as well just stick a BEAM with a docking adapter instead of a berthing adapter at that point.

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Posted (edited)

36 minutes ago, Steel said:

Dragon would never really be able to go to the ISS in this configuration anyway (unless its was in a really bizarre emergency where it couldn't reenter but could still rendezvous and dock) because while SpaceX may be happy to take paying tourists onboard, NASA an Roscosmos almost certainly aren't.

1. 7 tourists have been on the ISS.

2.  Dragon 2 definitely doesn't have the Dv to change inclination from a lunar flyby to the ISS, and definitely couldn't rondesvous to the ISS from a lunar flyby

Edited by insert_name

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3 hours ago, DerekL1963 said:

No, they've never failed AFAIK.   But the margins are lower and the risk level greater when you're off to the moon rather than delivering supplies to a station that has a reserve *and* multiple potential routes of supply.

Yeah, Agreed. Docking as a single mode of failure would not be a thing without a way to deal with it (astronaut EVA, etc), so not for a "tourist/adventurer" crew.

3 hours ago, sojourner said:

Might as well just stick a BEAM with a docking adapter instead of a berthing adapter at that point.

The point would not be just empty volume, but actual consumables. The volume of the trunk is actually larger than the D2 pressure vessel, so you could add a fair amount of supplies (CO2 scrubbers, O2, water, etc), and still have room for a zero-g toilet. 

I mention the toilet, because... well, listen to the Space Rocket History podcast episode about Apollo 8. In short, yuck. He played a section of a talk by the astronauts, and apparently when the diver came to the capsule after splashdown, and the hatch was opened, he reeled backwards. The astronauts asked, "We look that bad?" His reply? "No, it's the smell."

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37 minutes ago, tater said:

I mention the toilet, because... well, listen to the Space Rocket History podcast episode about Apollo 8. In short, yuck. He played a section of a talk by the astronauts, and apparently when the diver came to the capsule after splashdown, and the hatch was opened, he reeled backwards. The astronauts asked, "We look that bad?" His reply? "No, it's the smell."

That's probably due with the spacecraft being a very small enclosed environment and the occupants thereof having little opportunity for personal hygiene as the lack of a toilet.

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Posted (edited)

So many efforts to keep calling a service module "unpressurized trunk"...

Still interesting about delta-V. As the D-2 inner tanks contain fuel for rocket landing, where is it going to take 300-400 m/s for orbital maneuvers?

9 hours ago, Rakaydos said:

A hypothetical lunar lander varient of Dragon 2 (White dragon) that goes up unmanned for a 1-way landing on the moon has less need for a launch abort system.

It also doesn't need heatshield and side heat protection. As well as the pressurized cabin. And the docking node. And chutes. And a half of antennas.
Wait, oh... It doesn't need the Dragon at all.

5 hours ago, tater said:

Has an ISS docking/berthing ever failed?

Has an ISS docking (rather than berthing) ever attempted?

That's probably due with the spacecraft being a very small enclosed environment and the occupants thereof having little opportunity for personal hygiene as the lack of a toilet.

A tiny Soyuz has a toilet since its birth.

Edited by kerbiloid

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1 hour ago, DerekL1963 said:

That's probably due with the spacecraft being a very small enclosed environment and the occupants thereof having little opportunity for personal hygiene as the lack of a toilet.

Borman got a GI bug, and had diarrhea and was puking. So yeah. But puking is about 50% of the people who first go up, apparently, and even those with previous flights can as well. The GI issue they try to mitigate with food that is very well absorbed with little residual, but it's a non-trivial issue.

1 hour ago, kerbiloid said:

Has an ISS docking (rather than berthing) ever attempted?

Berthing is when they vessel is brought in with the arm, no? Crew vehicles dock, correct?

1 hour ago, kerbiloid said:

A tiny Soyuz has a toilet since its birth.

That's a major feature. Orion is supposed to basically have a portable toilet of some sort, but the real McCoy would be a great addition.

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Posted (edited)

7 minutes ago, tater said:

Berthing is when they vessel is brought in with the arm, no? Crew vehicles dock, correct?

Yes. Yes.

7 minutes ago, tater said:

Crew vehicles dock, correct?

Had a Space X vehicle ever docked?
Say, unmanned Progress and ATV dock, not berth.

Edited by kerbiloid

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Posted (edited)

9 hours ago, tater said:

I wonder if they could put something in the trunk with a docking ring that could function as added life support/etc? Trunk separation from the upper stage would perhaps have this orbital module attached (in a way that can be separated) to the upper stage. So the vehicle separates, rotates, docks with this section, then has added capability. Obviously this would require actual astronaut pilots, or non-trivial amounts of training with the attitude control system in case automated docking fails.

I don't think it's possible to dock with something with such low mass. There needs to be a minimum force applied to the IDS docking rings for them to connect. If the target is too light, you risk bumping it away. It's not like in KSP with magical magnets. At the very least, your orbital module is going to need its own attitude control and batteries to stay steady.

Once you've fitted all that gear into the trunk, I'm not sure that the extra habitable volume is really worth the hassle.

Edited by Nibb31
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12 hours ago, Nothalogh said:

They built Grasshopper just to prove it was possible

Falcon Heavy is just a couple Falcons tie-wrapped together, and yet it's taking the better part of a decade to get it made. Similar story with the SLS. Sometimes aerospace seems to have a way of making seemingly simple things not-so-simple, unless apparently they REALLY REALLY push for it. 

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