totm nov 2023 SpaceX Discussion Thread

[Spaceception]

Rapter firing

This feels realer than ever, just 6-9 months, and construction will start, they've built and tested hardware, and are busy making facilities. We're getting there, we're going to the planets and beyond.

Edited September 29, 2017 by Spaceception

[sh1pman]

SpaceX Airways. Ride the ICBM!

[RedKraken]

Just now, sh1pman said:

SpaceX Airways. Ride the ICBM!

The wildest ride on the planet.

[insert_name]

1 minute ago, RedKraken said:

How many people ride roller coasters or the g sling-shots?

Similar loads (up to 5-6g).

On your back in a proper seat....not a problem.

Some folks will black out.

Yes I am just discouraging airline economy seating style seats, I get uncomfortable enough with just one g in those already

[Rakaydos]

Just now, insert_name said:

Yes I am just discouraging airline economy seating style seats, I get uncomfortable enough with just one g in those already

What about japaneese pod-hotel beds? Or bunk beds?

[CatastrophicFailure]

Quote

...F9 upper stage recovery...

wha--?

Quote

...nuclear flarping engines...

Guh!!

Quote

...anywhere on earth in an hour...

derrrrr

><twitchtwitch><*poik!*

great holy flarp that thing's as big as the whole space station...

***STACK OVERFLOW ERROR!***

CATFAILR.EXE HAS STOPPED WORKING

ABORT, RETRY, IGNORE?

[sh1pman]

To be honest, I've never thought about the possibility of refuelling in high elliptic orbit. This will be bloody awesome if they can make it work.

[Tw1]

Some images from a friend who's at a space conference in adelaide

[.50calBMG]

Anyone have any idea what the engine layout for the booster is? Dont think they showed it during the presentation, but it looked like there were 2 rings and a center cluster like the old one. The outer ring looked pretty spread out too

[sh1pman]

Also, what about the heatshield? How are they going to restore it on Mars?

[RedKraken]

point to point 1hr

https://www.youtube.com/watch?time_continue=3&v=zqE-ultsWt0

[RedKraken]

13 minutes ago, .50calBMg said:

Anyone have any idea what the engine layout for the booster is? Dont think they showed it during the presentation, but it looked like there were 2 rings and a center cluster like the old one. The outer ring looked pretty spread out too

Check nsf.

One guy (onespeed) suggests 1-6-12-12 :

http://forum.nasaspaceflight.com/index.php?topic=43035.603

entry 603

Edited September 29, 2017 by RedKraken

[NSEP]

Oh my kraken.

Construction begins in less than a year?

We can finally send those Flat Earthers to space soon?

First cargo mission in 2022?

I mean, we thought Elon was crazy when he told us they are going to land a rocket on a barge, so is he crazy now?

I do expect a ton of delays though.

[mikegarrison]

46 minutes ago, tater said:

No one would want to be on a flight from LAX to Dubai for that long... but who cares what the seat is like when the flight is under 30 minutes?

Typical 1 way 1st class is around 12k$. With 800+ seats, that's over 10 million $ a flight at current 1st class rates.

That's the same mistake Concorde made. You can't build your market assuming that everyone is willing to pay as much as the most expensive seats today, no matter how fast you fly. Except for a few people, the money value of their time is simply not high enough. If you want to get coach class numbers of people, you need to have coach class prices. And remember, in this market he is NOT getting any price advantage from reusability. Instead, that advantage will be going the other way, because SpaceX has no experience building vehicles that can be used thousands of times.

[RedKraken]

Full speech

 

[tater]

10 minutes ago, mikegarrison said:

That's the same mistake Concorde made. You can't build your market assuming that everyone is willing to pay as much as the most expensive seats today, no matter how fast you fly. Except for a few people, the money value of their time is simply not high enough. If you want to get coach class numbers of people, you need to have coach class prices. And remember, in this market he is NOT getting any price advantage from reusability. Instead, that advantage will be going the other way, because SpaceX has no experience building vehicles that can be used thousands of times.

Don't get me wrong, I'm highly skeptical of the point to point, I was trying to ballpark the math.

Quote

elonmusk Fly to most places on Earth in under 30 mins and anywhere in under 60. Cost per seat should be about the same as full fare economy in an aircraft. Forgot to mention that.

 

37 minutes ago, sh1pman said:

Also, what about the heatshield? How are they going to restore it on Mars?

I would assume that any ablation is not enough to matter over one flight cycle. So it returns to Earth, and gets refurbished.

With the dv he showed on the chart, there is enough propellant for a return trip from Mars very nearly depending on the orbital mechanics. Some of the rendezvous on trajectory browser ate under 5 km/s total dv 1 way. 

[Northstar1989]

On 9/27/2017 at 10:46 AM, sevenperforce said:

Well, I didn't say that overexpanded thrust columns are never controllable; I said that firing the Merlin 1D Vac with the full nozzle at sea level would cause catastrophic flow separation. Nothing wrong with overexpansion; the problem is severe flow separation.

The SSMEs avoided severe flow separation by bending the nozzle curve back toward parallel at the end, increasing the flow pressure around the edge even though the flow at the center remained overexpanded.

That's *exactly* what I was going to say about how the SSME's achieved it.

 

So why can't they just give the Merlin Vac a new nozzle that does the same thing?

[Nibb31]

The design seems to have matured a bit since last year, especially regarding the windows (I still suspect that it will lose even more as the design matures) and the stubby fins, which now seem to have been replaced by much more sensible winglets. I do like the refueling mode with ullage thrusters, although I can see it consuming a lot thruster fuel.

I'm still not buying the solar arrays or the ground clearance. I don't believe in the viability of P2P suborbital flights either, nor do I think it will ever get certified to visit the ISS before the ISS is decommissioned. And there are still no plans as to how to fund the actual Mars infrastructure.

What impressed me the most is shutting down F9 and FH production lines to fund this thing. F9 is their cash cow, so that is a huge risk. If F9 reusability turns out to be less efficient than expected, or if some fundamental design flaw delays ITS, then the whole company is toast.

Edited September 29, 2017 by Nibb31

[Northstar1989]

On 9/27/2017 at 12:26 PM, sevenperforce said:

Increase in LEO payload would be negligible. The increase in gravity losses due to the lower TWR (recall that the Merlin 1D Vacuum already has a TWR < 1 at separation) would wreck any improvements.

The Merlin 1D Vac doesn't have a TWR < 1.  What do you think it is, an ion engine?  The STAGE has a TWR <1 at ignition.  Give it less fuel and payload, more Merlin 1D Vac engines, or just look at the TWR closer to engine cutoff, and TWR will be >1.

[mikegarrison]

I am highly dubious of his claim that "cost per seat should be about the same as full fare economy". That sounds an awful lot like wishful thinking.

What part of his suborbital flight is cheaper than an airplane? The fuel? The hardware? I can't see it.

[Northstar1989]

On 9/27/2017 at 1:11 PM, IncongruousGoat said:

Anything important is at least 400 km up, if not higher. Yes, the Karman Line is at 100 km, but that doesn't mean there's no drag at that altitude.

Well, a nuclear-powered Propulsive Fluid Accumulator would probably only orbit at 120-150 km, if one were ever built- and I'd call something that caould provide unlimited LOX for orbital refueling until the nuclear reactor ceases functioning pretty darn important... (Solar-powered PFA's would have to orbit at a higher altitude, in order to have enough electricity to have a high enough ISP to counteract drag...)  Of course they would operate at such low altitudes BECAUSE of all the residual atmosphere there...

Edited September 29, 2017 by Northstar1989

[tater]

5 minutes ago, mikegarrison said:

I am highly dubious of his claim that "cost per seat should be about the same as full fare economy". That sounds an awful lot like wishful thinking.

What part of his suborbital flight is cheaper than an airplane? The fuel? The hardware? I can't see it.

Assume that the vehicle can fly many, many times. Propellant costs for this would be a nominal load for the booster, and almost nothing for the spacecraft, it just needs to land, not reach orbit. So the propellant cost could be under 1 million. The craft could carry north of 800 people... It's not impossible $ wise. I'me still super skeptical of it, but they obviously did some math (how you'd amortize the vehicle is another issue, along with lifetime).

I can see one very interested customer for all of it, including point to point, or even nearly single orbit... sounds like what they always wanted. They being the USAF.

[mikegarrison]

2 minutes ago, tater said:

Assume that the vehicle can fly many, many times. Propellant costs for this would be a nominal load for the booster, and almost nothing for the spacecraft, it just needs to land, not reach orbit. So the propellant cost could be under 1 million. The craft could carry north of 800 people... It's not impossible $ wise. I'me still super skeptical of it, but they obviously did some math (how you'd amortize the vehicle is another issue, along with lifetime).

Airplanes can already fly many, many times. Fuel costs to completely fill the tanks of an A380 are about $130,000. Capital costs for an airplane are going to be less than for a giant rocket. Etc. Etc.

About the only possible place I can see him saving money on is in the cabin. Won't need food service or much in the way of in-flight entertainment systems.

[Northstar1989]

4 hours ago, Spaceception said:

Looks like they're making a pit stop at the moon

 

Looks like Elon is bending to practicality again.  And I don't mean that testing on the Moon first is NECESSARY (although it certainly is helpful- and cheaper than testing equipment on Mars), but that some people THINK it is needed.  And sonetimes, perception is all that matters...

[mark7]

Actually I am more curious about the raptors. They are now 50% less powerful and the ISP dropped a bit. Are the scales also changed? I can't remember the previous value.