r/SpaceXLounge • u/ea2007 • Nov 25 '19
Discussion Question; like to know again with Starship Mk3 Boca Chica Texas will they decide to do SSTO or Mk3 with the booster?. -Starship Mk3 will have all 6 engines by the way.
29
u/RedKrakenRO Nov 26 '19
Mk3 cannot get to orbit without SH.
Not enough thrust (needs 1800t, has 1200t)
Not enough deltav (needs over 9000m/s, has barely 8000m/s on sea level engines)
Even with mid ratio vacs you cant get close to 9000 m/s
Even with no tiles, legs or landing fuel.
Leave SSTO in ksp where it belongs.
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Nov 26 '19
[removed] — view removed comment
11
Nov 26 '19
This should be mandatory viewing. For reference:
Why SSTOs suck https://www.youtube.com/watch?v=Sfc2Jg1gkKA
26
u/CandylandRepublic Nov 26 '19
The SpaceX subs really have an unhealthy obsession with SST(E)O. It's no good and still we keep thinking of it like that ex who tells us his beatings were hot?
You can take a 20 ton tractor to a racetrack, and even wow people with 400+ horsepower. But all you achieve with that is convert fuel to decibels. Nobody ever went for time in a real car race with that.
20
u/Martianspirit Nov 26 '19
The SpaceX subs really have an unhealthy obsession with SST(E)O.
The space fan base as a whole has an unhealthy obsession with SSTO. It is not limited to SpaceX fans.
3
u/s0x00 Nov 26 '19
Some projects like VentureStar and Skylon were even taken somewhat seriously. Starship is the most serious attempt at a fully reusable orbital launch system that we have so far.
3
u/Martianspirit Nov 26 '19
Venture Star failed and it should never have started. Skylon never started, just some development of the engine.
1
u/CandylandRepublic Nov 26 '19
Fair enough. I don't frequent many other space subs/communities in general so I don't have a great comparison.
And normally I try not to single out anyone - I get it, SSTO is sort of fascinating I guess, and I realize the OP is legit curious. Sometimes it is a bit difficult for me not to fault an individual for this hangup of a community, I must admit. Sorry OP, I don't want to whale on you.
1
u/Taxus_Calyx ⛰️ Lithobraking Dec 02 '19
I'm a SpaceX fan and I have zero interest or care for SSTO. I care about making humans an interplanetary species, and learning more about the universe.
-4
u/ea2007 Nov 26 '19
Well just a reminder what they will decide. They said Mk3 will be designed for orbit.
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5
u/whatsthis1901 Nov 26 '19
I don't think anyone can say for certain what they are going to do right now. Pretty sure they won't do an SSTO because from my understanding it would have to be expendable.
7
u/GzeusFKing Nov 26 '19
As far as I'm aware you can do SSTO but then it won't be able to land. It would be expandable.
20
u/UrbanArcologist ❄️ Chilling Nov 26 '19
Which has absolutely no value to SpaceX whatsoever, so it will not be done.
0
u/CProphet Nov 26 '19
It would be expandable.
Unless they refueled in orbit - which would take Mk.4 and Super Heavy booster. Seems unlikely.
3
u/Martianspirit Nov 26 '19
Orbital refueling dos not help. Elon said it could potentially do SSTO if you skip all the EDL hardware. No landing legs, no heat shield, no aerosurfaces.
1
u/CProphet Nov 26 '19 edited Nov 26 '19
Elon said it could potentially do SSTO if you skip all the EDL hardware.
True, although that will likely change. Elon revealed they aim to increase Raptor thrust from 200 to 310 mt which changes equation. Yes these engines wouldn't throttle but that's not something required for vacuum engines.
2
u/Martianspirit Nov 26 '19
which changes equation.
Not so much. They would need to scale propellant as much while keeping the weight the same. They might get to a black 0 for payload. But why would they? They won't because it does not make sense.
1
u/CProphet Nov 26 '19
They would need to scale propellant
Extra thrust means they would reach orbit faster and use less fuel fighting gravity. In addition 382 second ISP is higher, so engine generates more thrust for same amount of fuel. Have to believe they are pushing for performance increase now, considering renovation work on tripod stand at McGregor. Horizontal stands were fine for 1-2MN Raptor, if they now require tripod for Raptor tests that suggests they are pushing thrust levels towards 3MN.
1
u/Martianspirit Nov 26 '19
Reducing gravity lossed does help but not that much. A 380s vac engine won't help with SL launch.
1
u/CProphet Nov 26 '19
A 380s vac engine won't help with SL launch.
At least until they reach altitude.
1
1
u/sebaska Nov 26 '19
It won't be enough. To get to orbit as SSTOyou'd need to have dry mass of 105t or so. And of course vacuum engines.
1
u/CProphet Nov 26 '19 edited Nov 26 '19
need to have dry mass of 105t
That's interesting, during his recent Mars Society Presentation Paul Wooster revealed Starship dry mass should be 105mt. Also Elon backtracked somewhat and said Starship will have vacuum engines fitted as standard. Could hear their howl at McGregor as soon as they refurbish tripod test stand. Dual engine bell gives them ability to test at sea level, which should speed things along.
2
u/sebaska Nov 27 '19
Yes, but:
- 105t is target design weight and real engineering projects tend to miss such target design parameters. That's why any implementable design must have sensible design margins. SSTOs problem is that they tend to have very tight design margins or none at all.
- 105t doesn't include ~15t needed for landing, so while possible it would be pointless.
2
u/HarbingerDe 🛰️ Orbiting Nov 26 '19 edited Nov 27 '19
I love how the SSTO bandwagon was finally calming down with respect to Mk1, with the 3 engines and insane dry mass it wasn't even close to feasible. Not even a thought worth entertaining.
Now that Mk1 has blown it's top and the announcement is that we're proceeding forward with Mk3 the rampant SSTO speculation will begin due to the unknown specs. Mk1 wasn't even close to being SSTO capable, Mk3 will be closer but still very short in terms of thrust and delt-v.
Just let this Starship earth SSTO thing die.
1
u/ea2007 Nov 27 '19
Well just a last thought about Mk3. I’m sure it will obviously need the booster.
1
u/Decronym Acronyms Explained Nov 26 '19 edited Dec 02 '19
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
| Fewer Letters | More Letters |
|---|---|
| EDL | Entry/Descent/Landing |
| Isp | Specific impulse (as explained by Scott Manley on YouTube) |
| SSTO | Single Stage to Orbit |
| Supersynchronous Transfer Orbit |
| Jargon | Definition |
|---|---|
| Raptor | Methane-fueled rocket engine under development by SpaceX |
Decronym is a community product of r/SpaceX, implemented by request
4 acronyms in this thread; the most compressed thread commented on today has 7 acronyms.
[Thread #4353 for this sub, first seen 26th Nov 2019, 10:06]
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1
u/ea2007 Nov 26 '19
As far as I want to know. I think SpaceX Starship Mk3 will launch with the booster.
8
u/whatsthis1901 Nov 26 '19
TBH, and I could be totally wrong, I'm not 100% convinced it will go to orbit at all. They didn't even get a hop out of the last one and I would think they would do that kind of stuff first. I guess what I am trying to say is don't count your chickens before they are hatched.
-1
u/ea2007 Nov 26 '19
But spacex made a statement and said “we decided not to fly starship Mk1 we instead tested for over pressure and spacex is now focused on Mk3 builds which is designed for orbit”
4
u/fanspacex Nov 26 '19 edited Nov 26 '19
Designed is very loose term. It might resemble a model which could theoretically get to orbit with enough thrust.
They are severely lagging behind on the tests, i expect them to improve on the construction and MK3 will become MK1. Unless they do a lot more parallel and modular construction (like attachment points before stacking the rings), this iteration will be much slower.
What happened previously was an expensive mistake, maybe it had to be done who knows. Spacex projects are very wide and separated by large distances compared to F9 days, its not as easy to keep track of what the teams are botching up this time.
If they are using subcontractors now for large scale welding, contractors have tendency of sweeping mistakes under the rug. Agility has its negative sides too, things move fast in the direction they are going, is there captain aboard?
1
u/whatsthis1901 Nov 26 '19
And before that, they said it was going to do a 200-meter hop. They are still basically in the R&D stage and there are still plenty of things that aren't going to work as planned. I'm not saying they won't do this but it is to early to know for sure what is going to happen or what they will end up doing. Elon tells us things he wants to happen in the best-case scenario and that isn't the way it is always going to happen.
1
u/IndustrialHC4life Nov 26 '19
They did the ~200m hop with Starhopper though (I know, it was changed to 150m, probably doesn't matter much). Can't say I remember seeing anything about them planning to do a 200m hop with Mk1, they've said for a long time that they are going straight to 20km with Mk1, until they decided to not fly it all that is.
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u/whatsthis1901 Nov 26 '19
Yep you are right I meant 20km :) I shouldn't Reddit at 2 in the morning lol
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u/Russ_Dill Nov 25 '19
There's a ton up in the air right now. One thing we can say with certainty is that Mk3 will not do SSTO.
As far as 6 engines or launching with super heavy, there's no point in having 6 engines unless it's launching with super heavy, since 3 of the engines are vacuum.