Rakaydos
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Posts posted by Rakaydos
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14 minutes ago, sevenperforce said:
Random question, but do turbopumps have transmissions? Obviously there is gearing between the turbine and the impeller but does anything in that ever need to “shift” in some way? I wouldn’t imagine so, but I am curious.
I would imagine they do away with the gearing entirely, and use blade pitch on the impeller for any "gearing" that needs to be done.
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12 minutes ago, zolotiyeruki said:
I have to say that I'm extremely impressed with the packaging, i.e. how small they've been able to make the whole assembly. I say this because at my last job I dealt with moving fluids through pipes, measuring flow, actuating vales, etc. Valve actuators are big, and fast-acting actuators are really big. Accurately measuring steady state fluid flow through a long, straight pipe is more difficult than you'd expect, and measuring rapidly-changing fluid flow through curved pipes in close proximity to pumps and turbines is simply an absurd problem. And doing it in an extremely hot and violently vibrating tail end of a rocket? Fuggetaboutit.
Seriously, my hat is off to those engine designers (and not just SpaceX's!)
You could call it a Pipe dream. :p
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Just now, Shpaget said:
Is that cost to build or to launch?
Build. Not including superheavy, which stays in use on earth, and not including the 2 mil marginal launch costs. And not including the fixed upkeep costs of spaceX facilities and personell.
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21 minutes ago, kerbiloid said:
This SpaceX Martian "plan" reminds me of one thread on a locally well-known survivalists' forum when a guy was seriously planning his post-apocalyptic lair, listing which shower things he should take to feel comfy (a big towel, a small towel, a backup towel; yes, not "a pack of towels"), in addition to the chair to sit outside the house and enjoy the sunsets.
Same easiness in planning.
If both of them were serious, they would start from sending this to Mars before humans.
No Martian bug could gnaw this.
Humans can. Even after decades in a warehouse.I dont think you get it. DRM and mars direct are plans to visit. SpaceX plans an invasion. Complaints like "you need 8 cargo ships of solar panels to refuel a ship to come home" are answered with "ok, we'll do that then." Need food? Bring food for 2 synods, in case something goes wrong, in forms that store well and can make a variety of interesting meals. (a thousand frozen burger paddies is less than a cubic meter.) And you can bet there will be a test greenhouse on the first crewed starship, which in addition to any other projects will include potatoes for the memes.
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"SpaceX plan disadvantages: requires 8 cargo starships to deliver the solar panels to make the fuel to come home. Also requires local resources to make fuel to come home"
Why are these disadvantages? Even taking the number at face value, the marginal cost of constructing 8 new starships is planned to approach 40 million, total. Less than a falcon 9.
Having that much solar power is actually a safety pro- in a 99% dust storm, turn off your fuel plant, and the remaining 1% is plenty for all essential base functions.
Local use of resources is just forward looking. We have enough mars survey data to be sure of having accessable water on hand if we make it a landing target priority.
And if nasa wants to send a cargo ship with enough hydrogen to make a starship"s worth of methalox, and a kilopower for mission assurance power, that's only one extra flight (plus government access to nuclear power).
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8 minutes ago, Blaarkies said:
The re-entry heating hasn't bothered me yet, i just yeet probes back from Minmus to Kerbin with a 30km Pe and they survive just fine. I think a simple heatshield(empty) on a crew capsule will be more than enough protection.
Once you get a Terrier contract to hold on to (and land on Minmus biomes), you will be on a fast pace towards late caveman. The next step seems to be proper crewed landings which needs more than an 18t launch for me
Caveman Orbital rendevous is easy for me, so you saw my 4-launch minmus biome hopper above.
Didnt get to any ladder riding in that run.
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I'm afraid to try NCD. While I enjoy planning extreme missions using caveman limitations, I prefer LATE caveman to early caveman, and NCD seems like it would trap you in the early game for much longer. Plus, different reentry physics or something?
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2 hours ago, Exoscientist said:
Actually, not. This shows why both these advances should be undertaken. By using both, we can reduce the cost of space and improve on the payloads of rockets we have now.
Robert Clark
You haven't shown how ssto will reduce the cost of space, and we've all demonstrated that the same effort will improve the payloads of two-stage to orbit rocket better than ssto. Chemical ssto is an always will be pointless on earth.
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Automated high-output production facility for advanced carbon capture devices.
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Edit:
Here's one way to look at it. The starship, with features required for earth return, can land with just enough header tank fuel to cancel mars terminal velocity, or about 300 m/s, plus gravity drag during the burn. Call it 350 m/s to be generous.
A raptor is pushing 378 seconds of ISP at mars landing and 2.21x6= 13.26 meganewtons, divided over 220 tons (120 ton starship + 100 tons payload) is 66m/s^2. A suicide burn is about 5 ish seconds, call it 10 for easy math, times the mass flow of 6 raptors (650 kg/s each) gives a conservitive landing fuel load of... 39 tons of landing fuel.
That's a little less than 2/3 the mass of a https://en.wikipedia.org/wiki/Lockheed_Martin_Lunar_Lander (which isnt even rated for 100 tons payload on mars)
What are you stripping out of Starship (that wont cripple it on earth return) to make up that kind of mass deficit, so that Initial Mass in LEO isnt made worse with the addition of a lander?
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15 hours ago, Exoscientist said:
A fair point. One way would be to shorten the nozzles then place them around a central spike, as is planned for the Firefly rocket:
Robert Clark
I suggest you watch this video: https://everydayastronaut.com/aerospikes/
Rocketlab already uses gimbal to get some aerospike-like effects out of electron. But actual aerospikes are just not worth the effort.
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12 hours ago, GoSlash27 said:
To clarify: 6 Raptor engines plus associated thrust puck/ plumbing. Tankage and structure necessary for a fully fueled transit. Drag fins, thermal tiles, crew quarters, life support, and all the associated plumbing/ wiring/ etc.
That all doesn't need to go down to the surface just to turn around and relaunch.
I'm talking about doing something closer to Mars Direct 3.0.
Best,
-Slashy
I dont have access to the video at work, but doesnt your lander need drag fins, thermal tiles, crew quarters, life support, landing engines, and tankage and structure? Plus associated plumbing/wiring, AND the lift capacity and plumbing to refuel the mothership?
Perhaps it's explained better in the video, but you've got duplication of effort all across that archetecture. Earth is the wrong planet for SSTO, but Mars is the right one, and Starship is designed to take advantage of that fact.
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2 minutes ago, Deddly said:
RO might not be necessary to get meaningful results. Stock KSP could give us a good indication too.
The key point, IMO, is that any orbiter with empty tanks requires multiple refueling flights , which adds significant complication to conops. My assertion is that, unlike LEO, there are not any gains to be made from this archetecture, because while it would reduce the departure DV requirement relative to the POR (Starship single stage earth return), this reduction is rendered moot by the fact that the vehical configuration during mars departure is the same as the vehical configuration during earth departure, minus whatever payload is left on mars. You cannot reduce the performance of the mars departure stage without crippling the earth departure stage.
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18 minutes ago, Exoscientist said:
Yes, the payload of the TSTO that also does use them will be higher than the SSTO. But still the SSTO will be more efficient than the current rockets that do not.
Robert Clark
so what are you trying to accomplish?
Because it looks like you want to build a rocket with next gen tech, but aiming for numbers where real next gen launchers will crush it, just for the claim to fame of being SSTO.
Sure. You can do that, if you have a few billion lying around that you dont need anymore. But you're not going to get any investers on board, because there's no return on that investment. 9 engine starship SSPTP is as close as you are going to get, and even that requires commonality with a heavy lift upper stage to make the buisness case close.
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1 minute ago, sevenperforce said:
Going to nine Raptors instead of just six would also nearly solve the pad abort problem. That’s a T/W ratio of 1.4 instead of barely 1.
It could also make single-stage ballistic hops feasible.
Note that vacuum raptors, while cunningly designed to not explode at sea level, are going to lose some thrust to over expansion. So it's probably slightly less than that.
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4 minutes ago, dvader said:
Refueling the jetpack that way should probably not be allowed in my humble opinion. It would allow for infinite fuel exploits by just pushing your space craft with the jet pack. It could also be used/abused for visiting all biomes at no cost of any planet/moon where you can land and take off on less than 600 m/s. Landing on a moon by jetpack alone is of course awesome and encouraged but it should not be for free.
What about conops that track "depleted" jetpacks, even though the game does not, and sends replacements up to manage a particular mission?
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4 minutes ago, GoSlash27 said:
Habitat: Nobody's talking about using the Starship as a habitat, not even Elon.
ISRU: The Starship can be refueled in Martian orbit just as easily as in Earth orbit.
Efficiency: The most efficient profiles are those where you don't land and launch anything that doesn't need to be there.
...that doesnt actually answer the question. What are you leaving in orbit "that doesnt need to be be there", that doesnt require an additional copy on the lander anyway?
What needs to be lifted from mars:
Unitary starship- A complete starship, any return payload, and the fuel for mars departure burn.
Zubrin-style MEM- enough refueling flights to refill the departure stage, (plus deorbit burns for the lander), and a separate flight for any returning cargo, plus the mass of the lander multiplied by the number of flights required.
The number of refueling flights will quickly eliminate any fuel savings from using a smaller lander, while introducing many more failure points in the conops related to rendevous, docking, and precision relanding.
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13 hours ago, GoSlash27 said:
swjr-swis,
No, not at all. The Starship should be fully reusable, it should just remain in orbit. It's like the lunar orbit rendezvous question back in the Apollo days; it makes no sense to send the entire CM down to the surface only to launch it again.
Conversely, if they want to send it down to the surface it should remain there as infrastructure rather than using it as a return vehicle.
HTHs,
-Slashy
Staging events are usually benificial, of course. But you need a habitat on the surface big enough for the crew that used the ship habitat to get there. And you are using ISRU, unlike apollo, so you need to fill the departure tanks on the CSM, whether it be on the ground, or shipped to orbit. (and in general, larger launches are more efficent, and an additional fuel transfer is extra equipment you need to bring. best part is no part.) And you also need landing engines big enough to lift the refueling flights, which might as well be part of your departure burn.
SpaceX is using the whole buffalo here. So what exactly are you leaving in orbit?
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1 hour ago, Spacescifi said:
Little use arguing semantics when the meaning is clear.
So why are you arguing for any other definition than... single stage, into orbit?
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9 minutes ago, JoeSchmuckatelli said:
Why is there an enormous seam? I thought SH was a single booster - so why the obvious break between sections?
Because they cant weld internal stringers where they weld the common dome in place. They need external stringers JUST to cover that small area.
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4th and final day of main caveman:
Spoiler
A nifty minmus lander with separate ascent stage.
Getting it into orbit might be a bit difficult, though, given it's mass and part count. 1 solar panel, 1 parachute.
this really shouldnt work. But I dont have the part budget for a second one.
took a few tries, but Jeb was able to follow prograde softly enough to avoid plume impingment and off-axis roll.
orbit
fuel pods are much simpler, and give me the part budget for a third booster engine. I didnt bother duplicating the solar panel, though
launch one
rendevour 1 (with launches 2 and 3 visible)
who needs RCS?
Who needs a second solar panel? this guy... fast foward to the 3rd rendevous...
lets check back in with the last fuel pod...
...good enough to get control back.
not good enough to avoid making the same mistake again.
Operation rocket boot 2 is a go.
rocketboot 2 successful in setting the remaining fuel pod into a spin, restoring power and control, before the rendevous window is over.
so, not quite as well balanced as planned.
But nothing a bit of spin-stabilization cant help with...
rendevous boosters depleted
counterweight had a little fuel left in it as well, but from here I needed to activate the main tanks.
found my shadow!
What is that? it cant be! (It isnt)
detuned my engine a bit for more control on langing. Got plenty of fuel, might as well check out that object
Just a rock. (first time playing since they were added)
Lets get some highland science.
forgot about the detuned engine. Landing was a bit rough,
Still have plenty of fuel
Now the main tank fuel is getting low.
Activating departure tanks and engine
why not?
And one more for the road.
That's all I'm going to need.
Proof of completion
Spoiler
Not my first caveman run, but the first time I've bothered to document it. a nice warmup to get back into kerbal after a long hiatus.
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last night and this morning before work (day 3)
Spoiler
Spoiler
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Day 2
Spoiler
A tandem launcher, to get expenience for my engineer, and any potential tourist contract
made it to orbit
and landed
a more scientific variant of the tandem. I really should have put bob in here, but I forgot.
probe time
Standard probe
Easy orbit
oops. but I know how to fix this. kinda my specialty.
Alignment lock disrupted via kinetic adjustment. Operation "Bump it into a spin to get solar power" successful.
the one that did the rendevous goes for some high over kerbin science
The other goes for minmus flyby
This wasnt planned...
some emergency course corrections to avoid a kerbin dive
no good.
the other one has fuel to circularize before entry.
So the minmus window is lost now. doing something easier first.
low, but not low enough for low science.
This also required course corrections to avoid flying off into space,
end of day 2
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1 hour ago, RCgothic said:
Trans-shipping of Cargo is going to be important if they're going to reuse LSS for lunar downmass. Got to restock it somehow.
Imagining something like canadarm plucking a rover out of a Chomper and transferring it to LSS, in orbit.
Real SSTO challenge.
in KSP1 Challenges & Mission ideas
Posted
Noone is arguing it isnt POSSIBLE. We are all saying it's stupid, and that all the technologies you would use for it would make a better TSTO.