totm nov 2023 SpaceX Discussion Thread

[CBase]

8 hours ago, Codraroll said:

If it works, hey, bonus Starlinks in orbit! And if not, well, they can probably afford to lose a few.

You are absolutely right, the payload costs are not the dicisive factor.  The question is will next flight be orbital or stay suborbital. But thinking of it, maybe you are right: Even on a suborbital flight testing with a real Starlink satelite is probably much faster, realistic and therefore cheaper than trying to mock the satelite.

[Piscator]

If you're building this many satellites you probably get a few rejects you can use to test the dispensing mechanism. I agree though that it wouldn't be very sensible to release operational satellites on a suborbital trajectory and that trajectories will likely remain suborbital until a deorbit burn is demonstrated.

Edited March 15 by Piscator
Typo

[darthgently]

I'm just going to throw this out there as a very strong opinion : 

The number of allocated "likes" per forum user per day should take the number of recent posts into account to some degree. 

Something very likeable occurs when historic things happen.  Common sense really

[AckSed]

4 hours ago, Piscator said:

If you're building this many satellites you probably get a few rejects you can use to test the dispensing mechanism. I agree though that it wouldn't be very sensible to release operational satellites on a suborbital trajectory and that trajectories will likely remain suborbital until a deorbit burn is demonstrated.

They could go Aperture Science and test this test by asking 'are the argon thrusters enough to raise their orbit from a near-orbit parabola?' These will not be small satellites, and perhaps they have space to add extra argon or thrusters.

[darthgently]

Nice rotation corrected video of S28 reentry (relative to surface)

 

[tater]

 

[tater]

 

[Piscator]

1 hour ago, AckSed said:

They could go Aperture Science and test this test by asking 'are the argon thrusters enough to raise their orbit from a near-orbit parabola?' These will not be small satellites, and perhaps they have space to add extra argon or thrusters.

I guess they could try it, but they would end up with a bunch of satellites with reduced life-expectancy (very reduced if they don't dispense properly). I'm not sure that's a good deal.

[tater]

To scale, obviously.

[Spaceception]

59 minutes ago, tater said:

 

So already planning towards V3 of the vehicle? I wonder how it translates to GTO to orbit. The old users guide assumed 100+ mT, and 21 mT to GTO. Could it send a payload to GEO and still return in 1 launch, or is that just beyond its capability?

[tater]

Assuming upper stage (expended) is 50t, expended V3 could throw 145t to TLI in 1 launch, or 115t to NRHO, or put 95t  directly in LLO.

Start with the 95t left in LLO.

Using existing hypergolic engines (Isp = 319), the 95t (wet) lander can round trip to the surface, back to LLO and have a dry mass of 26t. That's a big lander.

Assume Gateway. 3.65 km/s from LEO (3.2 km/s for TLI). 2.75 km/s to the surface.

V3 can send 185t to TLI. Our 26t (dry) lander can go RT from Gateway with a ton and a half margin. This is using Shuttle OMS engines (like Orion SM) for propulsion, obviously better with cryos.

Probably needs a higher dry to wet mass ratio, honestly, from the 14-15% I have to 20-30% would be better. To get in that range lander needs hydrolox engines. I_sp at least 445s.

 

Edited March 15 by tater

[Flavio hc16]

Imho we will see the V3 reach 160 meters of total stack: 90 for superheavy and 70 for Starship, with 5000 gross tons for superheavy and 2500-3000 tons for starship ( in normal and tanker configuration respectively), at 10k tons of thrust that's still a respectable 1.3 of TWR at liftoff.

 

Utter insanity, and we are all here for this.

 

In the end SH will have something like 20x350 tons raptor boost and 13x 300 raptor SL that gimble, and the starship will have 6x350 tons raptor vacuum fixed and 3x300 tons SL gimballing raptors, for a total of 11k tons for SH and 3k tons of thrust for starship. This will give a 1.5 TWR for normal starship stack and 1.2 for Starship in particular, and 1.4 and 1 for the tanker version.

Let's do some math:

So, assumptions: 

 

- Isp avg of raptor 2 sea level during ascent: 350 ( it's 330-360 at sea level and vacuum respectively)

 

- Isp of starship during ascent: 370 ( sea level is at 360, raptor vacuum at 380).

 

- starship empty weight 150 tons

 

- superheavy empty weight: 300 tons

 

- remaining props and deltaV for starship to deorbit and land: 950 m/s aka 50 tons prop at 350 Isp, and I'm being very conservative. (100 meters/seconds for deorbit like Shuttle and 800 m/s for landing)

 

- remaning props and deltaV for superheavy for boost back and landing: 400 tons, good for 2900 Ms/s of DV

 

- payload: 200 tons

 

- so total mass that has to reach orbit: 400 tons (150+50+200)

 

- DV needed to reach orbit : 9.2-9.4 km/s of DV ( probably even lower for starship because it has a lot of thrust so way less gravity losses, but it is a good ballpark).

 

- total mass of 2nd stage: 2700 tons (2350 tons of prop, 150 starship, 200 tons payload)

 

- total mass at stage separation: 3400 tons (2700+ 300 SH +400 SH prop for boost back and landing)

 

Total weight of the stack: 7500 tons, 4500 tons are props for the 1st stage, of witch 4100 will be burnt before staging.

 

So: 1st stage gives the 2nd stage 2700 Ms/s of DV ( if you want to calculate with a DV calculator: full mass 7500 tons, dry mass 3400 tons, Isp 350)

 

2nd stage DV with 400 tons of stuff ( 200+50+150) with 2300 tons of props burnt , 2700 tons full mass and 370 of ISP: 6900 Ms/s of DV

 

Total DV: 9.6 km/s of DV total, way more than needed.

 

I would say that that if they can make the raptor really to 350 tons for the fixed/vacuum ones and 300 tons of thrust of the gimballing ones, we are golden, and 200 tons of payload might be conservative.

 

[tater]

A 50t (dry) upper stage tug (so needs batteries, solar, RCS, etc) can deliver 115 tons to Gateway. If it was props, it could leave 30t with a vehicle at Gateway, and return to LEO propulsively (or drop off a 30t cargo).

This is in 1 launch.

Hmm, assume LSS (HLS, whatever) is 80t.

It can be sent to Gateway in 1 launch, and arrives with 90t of props. Needs 5.5 km/s to do a RT to the surface and back. That's 280t of props, so it needs another 190t delivered. Our tug can do that (they yeet itself into a solar orbit with a few tons of props) in 2 launches (with margin).

So HLS can work with 3 expended flights, doing refilling at the Moon. If the 2 refills are done in LEO instead, it can fly from LEO direct to the lunar surface, and arrive back at Gateway with 35t of residual props.

HLS needs just 135t of props to propulsively return to LEO from Gateway.  Once refilling is a thing, so much is possible, but given the expendable tug is so close to that, it might be possible to do an all Starship lunar surface mission with just a few expendable launches (load crew in LEO with Dragon, meet Dragon upon return to LEO).

 

 

 

[AckSed]

1 hour ago, tater said:

To scale, obviously.

Awesome picture.

Given the Shuttle comparison, it makes me wonder how they're going to configure the payload bay on Starship. Clamshell doors, sliding hatches?

[tater]

 

[KSK]

4 hours ago, tater said:

 

And V5 will have a warp drive on the back, and V7 will usher in world peace and first contact with the Vogons. Or something.

How about getting this rocket consistently pointing in the right direction first, and doing all the other things too, before flapping your everlasting gums about the next one?

More prosaically, I'd prefer bread today than jam at some unspecified Elon Time tomorrow.

 

[Exoscientist]

2 hours ago, tater said:

Assuming upper stage (expended) is 50t, expended V3 could throw 145t to TLI in 1 launch, or 115t to NRHO, or put 95t  directly in LLO.

Start with the 95t left in LLO.

Using existing hypergolic engines (Isp = 319), the 95t (wet) lander can round trip to the surface, back to LLO and have a dry mass of 26t. That's a big lander.

Assume Gateway. 3.65 km/s from LEO (3.2 km/s for TLI). 2.75 km/s to the surface.

V3 can send 185t to TLI. Our 26t (dry) lander can go RT from Gateway with a ton and a half margin. This is using Shuttle OMS engines (like Orion SM) for propulsion, obviously better with cryos.

Probably needs a higher dry to wet mass ratio, honestly, from the 14-15% I have to 20-30% would be better. To get in that range lander needs hydrolox engines. I_sp at least 445s.

 

 Thanks for that. An expendable SH/SS could get in the range of 200 to 250 tons to LEO. That would be well more than enough to do its own single launch mission to the Moon or Mars, no SLS required. Keep in mind such an expendable launch is only in the $90 million cost range. While not at the $10 million aspirational rate Elon wants for full reusability,  considering the amount of payload it could loft, it still would be a major improvement over what we have now, and literally orders of magnitude cheaper than the SLS. 

By the way, suppose as a SpaceX exec once suggested the Starship HLS would need “10ish” orbital refuelings. At the $10 million per launch rate for a fully reusable SH/SS that’s still $100 million. Then the single launch expendable approach would actually be in the same cost range as the fully reusable approach, anyway.

 See the calculations here:

SpaceX should explore a weight-optimized, expendable Starship upper stage.
https://exoscientist.blogspot.com/2024/03/spacex-should-explore-weight-optimized.html

 

  Bob Clark

[PakledHostage]

12 minutes ago, KSK said:

And V5 will have a warp drive on the back, and V7 will usher in world peace and first contact with the Vogons. Or something.

 

So long as they're not Pakleds...

[tater]

3 minutes ago, KSK said:

And V5 will have a warp drive on the back, and V7 will usher in world peace and first contact with the Vogons. Or something.

How about getting this rocket consistently pointing in the right direction first, and doing all the other things too, before flapping your everlasting gums about the next one?

More prosaically, I'd prefer bread today than jam at some unspecified Elon Time tomorrow.

They are always improving everything, same as they have done with F9/Merlin.

As I recall, the V1 (assuming that is current) is already just the remaining ships, then all being worked on are V2 (that was said a few months ago). V3 I think is V2 with a stretch.

[tater]

 

Astronaut approved.

[tater]

 

Someone pointed out the V3 needs to be taller. It does.

[Flavio hc16]

21 minutes ago, tater said:

 

Someone pointed out the V3 needs to be taller. It does.

And probably even the SH will need to get taller

[tater]

14 minutes ago, Flavio hc16 said:

And probably even the SH will need to get taller

I assume some height to each added? Musk's range of 20-30m is 11-16 rings (the ring stock is 1.83m wide (6 feet)).

[cubinator]

1 hour ago, tater said:

 

Someone pointed out the V3 needs to be taller. It does.

I've always wanted to see one of these scale diagrams with both rockets and dinosaurs on it...

[darthgently]

2 hours ago, KSK said:

More prosaically, I'd prefer bread today than jam at some unspecified Elon Time tomorrow.

The bread truck full of bread is the hundreds of successful launches and landings in the books with F9 and FH.  We have our bread today.  Not sure what you mean.  You'd prefer Musk be on Bezo time?

The recipe seems to be working quite well

Edited March 15 by darthgently