totm nov 2023 SpaceX Discussion Thread

[Shpaget]

I'm gone for an hour and suddenly SpaceX gets the biggest gig in 50 years.

[sevenperforce]

Fascinating...

Someone on NSF spotted that the render has a braking burn afterglow on just two engines. 

Insane detail.

[mikegarrison]

Am I missing something, or isn't this just the first downselect gate?

[tater]

1 minute ago, mikegarrison said:

Am I missing something, or isn't this just the first downselect gate?

Yeah, it is. They're not building all three.

BO was expected. Dynetics has looked good from the start as a vehicle (the low profile is great). SpaceX being selected at all is the surprise, really.

[Spaceception]

9 minutes ago, mikegarrison said:

Am I missing something, or isn't this just the first downselect gate?

It is. But if I read the Spaceflight now article right, NASA won't want to go fewer than 2 partners, and would prefer all 3 if given the funding.

But even still, the fact NASA is directly funding Starship development through this year is really amazing.

Edited April 30, 2020 by Spaceception
Wrong site, sorry

[sevenperforce]

How to obviate SLS:

1. Launch uncrewed Orion to LEO on DIVH, NG, Vulcan, or FH.
2. Use an empty ACES, NGUS, or F9US and a docking connector to deliver uncrewed Orion to HLO.
3. Send the lunar Starship to EEO on Superheavy.
4. Refuel the lunar Starship in EEO.
5. Send astronauts on Dragon 2 to rendezvous with the lunar Starship in EEO, transfer, land, mission.
6. Lunar Starship takes astronauts to LLO where they meet Orion, which takes them back to Earth.
7. Lunar Starship slowly aerobrakes down to EEO.

Edited April 30, 2020 by sevenperforce

[CatastrophicFailure]

Minor, but interesting observation on the landing profile:

 

[RCgothic]

It's speculated you need gimballing for control in descent, but RVac can't gimbal. Thus both RVac and the RSL opposite being paired together.

[sevenperforce]

16 minutes ago, RCgothic said:

It's speculated you need gimballing for control in descent, but RVac can't gimbal. Thus both RVac and the RSL opposite being paired together.

RVac would burn at max thrust; RSL would burn at minimum thrust gimbaled toward the RVac to cancel torque.

[magnemoe]

29 minutes ago, sevenperforce said:

They are supposed to be 10-tonne thrusters. Maybe 11-12 with longer nozzles. I spy three banks with three nozzles each, so nine nozzles. That gives you 971 kN.

Let's say that the lighter, streamlined lunar Starship masses 180 tonnes once it gets back to LLO, ballpark. That means it needs to weigh about 300 tonnes on the lunar surface. To hover 300 tonnes on the moon you need 486 kN. Considering cosine losses, I think nine hot-gas RCS thrusters are exactly right for this job. 

No, it's a hot gas-gas meth-GOX thruster using autogenous tapoff.

Yes that sounds right, you can always use an burner to make more hot gas. 
Now you could make this shorter than standard Starship? Yes you need the crew quarter but it could be cut down a bit as its a bit large for an moon landing. Granted you probably stay an lunar day and you might add labs and stuff but still. 
You also want some tools and some rovers, an drill rig  would be very interesting, perhaps one of the tiny excavators. Still its not very heavy and you could burn this dry and refuel in orbit. 
This give you an 14 day lunar base. 

Note you could probably give an cargo Starship the landing engines too, it will eat up a bit of your cargo space and you need doors on the reentry side but still, this is to build an permanent moon base, has to claim Shackleton fast.  

[sevenperforce]

Just now, magnemoe said:

Yes that sounds right, you can always use an burner to make more hot gas. 

Or resistive heating from the battery packs. Also the tanks will be half full on landing, which means a LOT of pressurized gas to tap off.

Just now, magnemoe said:

Now you could make this shorter than standard Starship? Yes you need the crew quarter but it could be cut down a bit as its a bit large for an moon landing. Granted you probably stay an lunar day and you might add labs and stuff but still. 

No, it needs to be full size because it is launching from elliptical earth orbit and it needs to make it all the way back to LLO at least.

Just now, magnemoe said:

Note you could probably give an cargo Starship the landing engines too, it will eat up a bit of your cargo space and you need doors on the reentry side but still, this is to build an permanent moon base, has to claim Shackleton fast.  

SpaceX doesn't intend any lunar Starship to be one-way, so the cargo lunar Starship will look the same. No TPS.

[CatastrophicFailure]

For simplicity’s sake, instead of developing a mostly new thruster based on Raptor, why not just use the powerpack of a Raptor? IIRC they fired these for pretty long durations during development. Not the most efficient, but it doesn’t really need to be if it’s just used for the final few hundred m/s before touchdown, and would need minimal new hardware. 

[tater]

The height is a feature given the landing sites. Sun is grazing angle, solar is way up high. They can use the cargo pods at the bottom for battery packs to survive a lunar night.

1 minute ago, CatastrophicFailure said:

For simplicity’s sake, instead of developing a mostly new thruster based on Raptor, why not just use the powerpack of a Raptor? IIRC they fired these for pretty long durations during development. Not the most efficient, but it doesn’t really need to be if it’s just used for the final few hundred m/s before touchdown, and would need minimal new hardware. 

SS is already going to have methalox RCS, though. Just put proper nozzles on 9 of them, and done. Lower I_sp, but it's literally to kill a few m/s right before touchdown, then to leave the surface (that or they EVA and deploy a blast shield).

[tater]

 

[Ultimate Steve]

3 hours ago, Ultimate Steve said:

Eric Berger is saying on Twitter that SpaceX bid Starship for the Artemis lander program. If true, and I hope I'm wrong, that is a surefire way to not be chosen.

Time to find out what hat tastes like...

[sh1pman]

They’re making a new Starship every 3 weeks, improving the design or manufacturing with every new vehicle. 4 years is more than enough time to land it on the Moon.

Edited April 30, 2020 by sh1pman

[sevenperforce]

Just now, sh1pman said:

 

Clearly talking about tank-pressure-fed hot-gas thrusters.

1 hour ago, CatastrophicFailure said:

For simplicity’s sake, instead of developing a mostly new thruster based on Raptor, why not just use the powerpack of a Raptor? IIRC they fired these for pretty long durations during development. Not the most efficient, but it doesn’t really need to be if it’s just used for the final few hundred m/s before touchdown, and would need minimal new hardware. 

Two problems here. First, the preburners are the heaviest part, so you are basically adding more than a third of the weight of a whole Raptor for each thruster. Second, Raptor is a full-flow staged-combustion engine that uses separate preburners for separate turbopumps. The LOX preburner+turbopump is pushing small amounts of LOX into the CH4 preburner and the CH4 preburner+turbopump is pushing small amounts of CH4 into the LOX preburner. So can't run one without the other unless you have a ground system to do so.

Finally, the new thrusters are being dev'd for RCS to begin with.

[mikegarrison]

1 hour ago, sh1pman said:

They’re making a new Starship every 3 weeks, improving the design or manufacturing with every new vehicle. 4 years is more than enough time to land it on the Moon.

They haven't even got one to leave the pad yet, and you're so sure that the moon in four years is no big deal?

[Flavio hc16]

1 minute ago, mikegarrison said:

They haven't even got one to leave the pad yet, and you're so sure that the moon in four years is no big deal?

4 years ago reusable rocket were basically pipe dream ( 1st landing done), falcon heavy was a paper rocket and noone knew that the starship/bfr project even existed

[mikegarrison]

7 minutes ago, Flavio hc16 said:

4 years ago reusable rocket were basically pipe dream ( 1st landing done), falcon heavy was a paper rocket and noone knew that the starship/bfr project even existed

Four years ago Elon was saying he was going to have ITS flying by now and going to Mars by 2024, too.

Heck, three months ago nobody knew what the world was going to be like today.

I guess we'll see what happens.

Edited April 30, 2020 by mikegarrison

[Flying dutchman]

4 minutes ago, mikegarrison said:

Four years ago Elon was saying he was going to have ITS flying by now and going to Mars by 2024, too.

Heck, three months ago nobody knew what the world was going to be like today.

I guess we'll see what happens.

Well.. you could count starhopper as a prototype of starship.. and since that has already flown you could technically say that "its" has been flying.

 

Just kidding

[tater]

 

[RCgothic]

Lunar demonstration landing in 2022. Hype train!

[tater]

1 hour ago, mikegarrison said:

Four years ago Elon was saying he was going to have ITS flying by now and going to Mars by 2024, too.

To be fair, he said that was his "aspirational" goal. On a less aspirational level, SLS was required by law to fly by Dec 31, 2016.

[mikegarrison]

4 minutes ago, tater said:

To be fair, he said that was his "aspirational" goal. On a less aspirational level, SLS was required by law to fly by Dec 31, 2016.

That doesn't exactly refute my point that schedules tend to slide, especially with designs that are still in the low TRL stages.

Edited April 30, 2020 by mikegarrison