totm nov 2023 SpaceX Discussion Thread

[Xd the great]

Waiting to see new changes...

[kerbiloid]

Waiting for stop changing and begin building.

Edited November 18, 2018 by kerbiloid

[Canopus]

They will scale it down again until what was once called „Mars Colonial Transport“ will turn into a bigger falcon with reusable second stage. Something that can actually be accomplished. 

[Xd the great]

11 minutes ago, Canopus said:

They will scale it down again until what was once called „Mars Colonial Transport“ will turn into a bigger falcon with reusable second stage. Something that can actually be accomplished. 

50 tonnes to Mars is more than enough. Or to anywhere for that matter.

[sh1pman]

55 minutes ago, Canopus said:

They will scale it down again until what was once called „Mars Colonial Transport“ will turn into a bigger falcon with reusable second stage. Something that can actually be accomplished. 

If it works, and it’s fully reusable, then it can be scaled up to be more capable. If it can be scaled up, why waste time on a smaller version?

[DDE]

35 minutes ago, sh1pman said:

If it works, and it’s fully reusable, then it can be scaled up to be more capable. If it can be scaled up, why waste time on a smaller version?

Because even the nu-BFR is too big for the actual satellite launch market? SpaceX has finite resources they can invest before winning their money back. And at the current rate BFR risks having the same problem as the SLS - flying ince in a blue moon.

[hms_warrior]

Random idea on BFR rework. Incooperating stuff that was on the SpaceX to-do list(crossfeed) or is allready done (sideboosters) :

The BFS is made longer and has a mixture of ASL and VAC engines.

Two smaller Bosters are sidemounted.

Sideboosters and ASL engines of BFS ignite at launch, where the BFS-ASL engines are feed from the boosters tanks.

BFS ignites VAC engines, shut down ASL engines.

Boosters seperates and do return.

ASL engines engines on BFS are switched to internal tanks (while shut-off) fuel lines are flushed to remove any bubbles and ASL engines reignite.

Edited November 18, 2018 by hms_warrior

[sh1pman]

10 minutes ago, DDE said:

Because even the nu-BFR is too big for the actual satellite launch market?

I don’t get it. It’s supposed to replace F9 in satellite launches, and F9 flies rather frequently these days. BFR doesn’t need to fill its entire cargo capacity for one launch to be profitable, a single 7t GEO commsat is good enough already. 

[DDE]

4 minutes ago, sh1pman said:

I don’t get it. It’s supposed to replace F9 in satellite launches, and F9 flies rather frequently these days. BFR doesn’t need to fill its entire cargo capacity for one launch to be profitable, a single 7t GEO commsat is good enough already. 

F9 apparently has gobbled up most of the market.

And BFR cost projections are very shaky. Nobody's ever processed and refurbished a truly large orbital rocketship; hell, even the third F9 flight is a major milestone for SpaceX.

[RCgothic]

2 hours ago, DDE said:

Because even the nu-BFR is too big for the actual satellite launch market? SpaceX has finite resources they can invest before winning their money back. And at the current rate BFR risks having the same problem as the SLS - flying ince in a blue moon.

The only way BFR doesn't fly more than SLS after it's been built is if they crash it.

[tater]

5 hours ago, kerbiloid said:

Waiting for stop changing and begin building.

They are already building it. Freezing a design is not how they work, if so we'd be watching boring Falcon 9 v 1 launches with no landings, and FH would loft about as much as a single-stick B5.

2 hours ago, DDE said:

Because even the nu-BFR is too big for the actual satellite launch market? SpaceX has finite resources they can invest before winning their money back. And at the current rate BFR risks having the same problem as the SLS - flying ince in a blue moon.

No. Marginal launch costs of the vehicle are supposed to literally be on the order of 10X cheaper than F9, for multiples of the payload mass (and more importantly, volume). SLS can only fly once a year because it takes a long time (and a metric tonne of money) to build, and the entire thing is thrown away every time. If the entire thing is (easily) reused, then launch costs are amortized vehicle costs, plus propellants (practically free), and labor.

 

1 hour ago, DDE said:

And BFR cost projections are very shaky. Nobody's ever processed and refurbished a truly large orbital rocketship; hell, even the third F9 flight is a major milestone for SpaceX.

This is true. Reuse radically reducing cost is predicated on quick (not for timing, but for labor costs) turn around. We have yet to see this happen. Turn around so far has been decreasing (in time), once we see some radical turn around (the 24 hour one they want to demonstrate) of a flown booster, we will know, even without seeing SpaceX's internal costing that reuse is certainly cost effective since there is no possible way to spend more than a booster costs to construct in 24 hours.

[tater]

Counter-intuitive design that is delightful, and also makes BFR faster to build?

General Dynamic Triamese.

You only build one kind of vehicle.

[ThatGuyWithALongUsername]

8 minutes ago, tater said:

Counter-intuitive design that is delightful, and also makes BFR faster to build?

General Dynamic Triamese.

You only build one kind of vehicle.

I'm not kidding, I just had a similar idea,  but you beat me to it

More specifically, why would we need 3 BFS's (?)? One on it's own can SSTO, albeit without much payload, so just strap one tanker BFS to the side and call it a day- that should be enough.

[tater]

NASA (contractors) proposed many variations of the above in the 60s and 70s.

I'm concentrating on counter-intuitive... The booster part has been seen as the easy bit of BFR since it's just F9 writ large. You need ~31 Raptors to get the beast off the ground. BFS 2018 has 7. If it was upped towards 11, then 3 BFS (with crossfeed) could perhaps work. Fewer if the total mass were to drop (boosters are smaller, and stage as used up). With 3 stages, maybe even the 7 shown in the last iteration works (or make it 9, lol).

The 2 staged boosters are tanker variants.

[ThatGuyWithALongUsername]

46 minutes ago, tater said:

NASA (contractors) proposed many variations of the above in the 60s and 70s.

I'm concentrating on counter-intuitive... The booster part has been seen as the easy bit of BFR since it's just F9 writ large. You need ~31 Raptors to get the beast off the ground. BFS 2018 has 7. If it was upped towards 11, then 3 BFS (with crossfeed) could perhaps work. Fewer if the total mass were to drop (boosters are smaller, and stage as used up). With 3 stages, maybe even the 7 shown in the last iteration works (or make it 9, lol).

The 2 staged boosters are tanker variants.

That makes a lot of sense. Also, eliminating the BFB would get rid of the need to land back on the launch mount and cramp 30+ engines on a stage the same diameter as the BFS with 7 engines. I can see a lot of development time that can be shaved off here.

In addition, you could dock a full tanker to it in LEO and increase payload capacity to Mars without refueling.

[tater]

The tankers could each have 12 engines. The BFS has 7. 31 at liftoff among the 3.

Crossfeed so that core remains full.

Symmetry of aero surfaces might need to change to allow them to nest together.

Note that all these changes are effectively external. Tooling remains the same for tanks. One entire vehicle never has to be designed. Eventually vacuum raptor is added as planned to BFS for more capability BLEO.

2-stage version by General Dynamics:

http://www.pmview.com/spaceodysseytwo/spacelvs/sld026.htm

[DDE]

1 hour ago, tater said:

SLS can only fly once a year because it takes a long time (and a metric tonne of money) to build, and the entire thing is thrown away every time.

You fail to describe the entire vicious cycle; the SLS is being built at well below the pace it could be 

The high cost reduces frequency of missions. The inferquent missions cause overheads per flight, and therefore cost, to increase. Round and round and round it goes.

It’s also an excellent time to voice my concern over what else Boeing and LockMart write off as SLS expenses. Insiders say that the practice of purposefully misattributed costs is exactly what plagues Angara.

[tater]

1 minute ago, DDE said:

You fail to describe the entire vicious cycle; the SLS is being built at well below the pace it could be 

The high cost reduces frequency of missions. The inferquent missions cause overheads per flight, and therefore cost, to increase. Round and round and round it goes.

SLS is always thrown away. Building faster is never an option, they don't have the facilities to ever build more than perhaps 2 a year.

BFR can take just as long to build, but then it can fly in whatever the turn-around time is. Launch cadence is completely divorced from production time.

[Mad Rocket Scientist]

7 hours ago, Canopus said:

They will scale it down again until what was once called „Mars Colonial Transport“ will turn into a bigger falcon with reusable second stage. Something that can actually be accomplished. 

That doesn't sound counter-intuitive though.

3 hours ago, tater said:

Counter-intuitive design that is delightful, and also makes BFR faster to build?

[...]

General Dynamic Triamese.

[...]

You only build one kind of vehicle.

I like that idea.

I would love to see BFR turn into one of those great very early shuttle concepts. Not because I think they would work better, but because they look great.

[DDE]

3 hours ago, tater said:

Building faster is never an option, they don't have the facilities to ever build more than perhaps 2 a year.

Which is about four times faster than what they have the funding for, and probably commensurate with JPL’s ability to come up with payloads for them.

[tater]

35 minutes ago, DDE said:

Which is about four times faster than what they have the funding for, and probably commensurate with JPL’s ability to come up with payloads for them.

You'll get no disagreement from ME on that end. Assume that only one SLS can possibly be built every 2 years. That's the max launch cadence. If 1 BFR can be built every 2 years, then BFR can fly as often as it can be turned around. If the cost of operating it to LEO is less than F9 cost (even with their internal reuse numbers), then even single payloads can fly in the huge BFR. If it's more than an F9 launch, but you can comanifaxt X payloads such that the per payload cost is cheaper, then you fly BFR. Win-win.

BTW, my idea "works in KSP."

I dumped the core stage tail fin entirely, and used a Falcon 9 landing leg on that side (Musk said it didn't do anything aerodynamically).

[sh1pman]

1 minute ago, tater said:

BTW, my idea "works in KSP."

How well does it work? Crossfeed enabled?

[tater]

7 minutes ago, sh1pman said:

How well does it work? Crossfeed enabled?

Nah, I just reduced the props in the tankers. I didn't even add engines, that mess has 21 instead of 31.

If the tankers each had 9-10 instead of 7 it would work with the core shut down until sep I think.

Crossfeed is needlessly complex I think. Make it work with vehicle commonality, and nothing more.

I threw the core into a very lofted suborbital, then managed to land one of the boosters downrange (next landmass East). The other crashed while I was doing so (don't have the mod to land side boosters, etc). I landed it manually, BTW (first time playing with this mod, too). Then popped to the core, and did a burn for orbit. Have props left to land, actually.

Edited November 18, 2018 by tater

[sh1pman]

BTW, couple of months ago I made a similar thing in stock KSP, but with 2 big boosters around a central winged spaceship (like Shuttle, but with props). Boosters had 7 Vector engines each, spaceship had 3, crossfeed enabled. Worked really well. 

[RedKraken]

I am getting about 60t to leo from my spreadsheets for triamese BFR2018.

Im using 85t dry, 1000t methalox, stage at 33% fuel remaining in center core.

Throttle control for core, no crossfeed.

Not using 1100t since the twr drops to 1.20

It would be about 80t if you could run the engines harder - 115% thrust.

Going to need very strong attachments to keep three 1100 tonne ships together.

The dry mass is going to be more than 85t i think.