RCgothic Posted October 2, 2020 Share Posted October 2, 2020 (edited) Even if it's 6, 230t of propellant to LEO is a hell of a payload whilst reusing both first and second stages! Edited October 2, 2020 by RCgothic Quote Link to comment Share on other sites More sharing options...
RealKerbal3x Posted October 2, 2020 Share Posted October 2, 2020 31 minutes ago, RCgothic said: Even if it's 6, 230t of propellant to LEO is a hell of a payload whilst reusing both first and second stages! I'm still unsure how they're going to refuel the Lunar Starship when it's in lunar orbit. Are they planning to send tankers to NRHO? Is Lunar Starship somehow going to return to LEO after each lunar sortie? I can't think of any other ideas short of putting a giant propellant depot in lunar orbit. Quote Link to comment Share on other sites More sharing options...
Flying dutchman Posted October 2, 2020 Share Posted October 2, 2020 What upgrade? Did i miss something? Quote Link to comment Share on other sites More sharing options...
RCgothic Posted October 2, 2020 Share Posted October 2, 2020 (edited) Update in three weeks. Edited October 2, 2020 by RCgothic Quote Link to comment Share on other sites More sharing options...
RCgothic Posted October 2, 2020 Share Posted October 2, 2020 A 100t lunar Starship *just* has enough DV to go to the lunar surface from LEO and back to NRHO with 0 payload delivered to the surface. In order to fully unlock the potential it's going to have to refuel in NRHO *and* have a way of trans-shipping significant cargo there. I think a deep-space optimised Starship variant (>80t) could deliver 300t of propellant to NRHO *and return* without aerobraking off a full load in LEO. Which is convenient, because Lunar Starship needs about 580t of propellant for a decent margin to land 150t and return 10t. It'd take about 6 LEO tanker-fulls to reload a deep space tanker @230t to LEO (see my post at the top of the page). A regular cargo starship at 100t, could probably deliver 150t to NRHO and return to earth with 10t and land off 5 LEO tanker-fulls. So on a lunar Starship's first mission with 150t it requires the following launches: Itself. 6x refills. Lunar Tanker. 6 refills. That's 14 launches! For its next mission it needs: Cargo starship. 5x refills. 12x refills for the lunar Tanker. 18 launches! Assuming 6.5 days each way to NRHO that's 13 days per trip. Plus say 1 day per refill operation... That's a period of 27 days for the tanker to complete, which isn't too bad. Quote Link to comment Share on other sites More sharing options...
RCgothic Posted October 2, 2020 Share Posted October 2, 2020 Also even if Starship Superheavy averages at $60m per launch (30x the $2m target) then 18 launches is still less than the *engines* of an SLS. Quote Link to comment Share on other sites More sharing options...
Flying dutchman Posted October 2, 2020 Share Posted October 2, 2020 Quote Link to comment Share on other sites More sharing options...
sh1pman Posted October 2, 2020 Share Posted October 2, 2020 1 hour ago, RCgothic said: Lunar Starship needs about 580t of propellant for a decent margin to land 150t and return 10t 1 hour ago, RCgothic said: Itself. 6x refills. Lunar Tanker. 6 refills. That's 14 launches! That’s a lot of launches for one landing. That’s why I think Starship is a bit excessive for Moon missions. I like Zubrin’s plan with small landers more. One tanker in lunar orbit will be enough for many trips to the surface and back. Quote If it can be refueled in LEO, a Starship tanker could be put in orbit about the moon and serve as an excellent refueling station for much smaller landing and ascent vehicles. Such a standalone orbital propellant depot would not need to be at the Gateway. With its extensive propulsion capability, a tanker Starship could be stationed anywhere, including a much more favorable low polar orbit that would provide ready access to the entire moon. To avail themselves of such support, the smaller landers would need to use LOx/CH4 propellant. The proposed Blue Origin lander is an awkwardly tall, three-stage expendable system employing LOx and liquid hydrogen (LOx/H2) propulsion. This would need serious redesign. The Dynetics configuration is more attractive, as it is a clean single-stage (with drop tanks) system, employing dense propellants, with its hab or other payload delivered close to the ground. This could readily make use of LOx/CH4 propulsion. Let’s assume a three-ton dry mass for the small lander. (This appears to be the case for the Blue Moon system. The Apollo Lunar Module upper stage and cabin had a dry mass of 2 tons.) Employing LOx/CH4 propulsion with an exhaust velocity of 3.7 kilometers per second (or 378 seconds of specific impulse), 12 tons of propellant would be needed to descend, land, and return the small lander to the Gateway. If the tanker placed itself in a low polar orbit, however, only 6 tons of propellant would be needed, and expendable staging or drop tanks would become unnecessary. A tanker carrying 100 tons of propellant as cargo could thus support up to 16 sorties to the Lunar surface. This could be greatly expanded further by producing oxygen on the moon, which can be done at the poles by splitting water ice or nearly anywhere by reducing iron oxide. LOx/CH4 propellant is 78 percent oxygen by mass. If the oxygen required for travel between the surface and orbit is produced locally, then the tanker will only need to supply methane, and the number of sorties flights it could support would more than quadruple. Using such a coherent transportation system, the moon could be thoroughly explored. Sortie missions could be sent to many locations, and landing pads could be prepared at the best. ThenStarships could be landed on the moon, not to use as ascent vehicles — their high mass makes them unattractive for that application — but to stay as bases, for which purpose their large size is a plus. In a short amount of time we could have a network of capable bases around the moon, producing oxygen to support an extremely cost-effective lunar exploration and development program. Quote Link to comment Share on other sites More sharing options...
kerbiloid Posted October 2, 2020 Share Posted October 2, 2020 (edited) Korolev: Original plan of lunar landing: 4 dockings, several tankers. SpaceX: 6 (?) dockings, 6 (?) flights of tankers. Korolev: ~30 engines per stage. SpaceX: ~40 engines per stage. Wut kan g0 wяong? Edited October 2, 2020 by kerbiloid Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted October 2, 2020 Share Posted October 2, 2020 4 hours ago, Flying dutchman said: What upgrade? Did i miss something? Yeah I’m lost too Quote Link to comment Share on other sites More sharing options...
tater Posted October 2, 2020 Share Posted October 2, 2020 The first tweet in that series matters: The upgrade is engine performance. 1 hour ago, sh1pman said: That’s a lot of launches for one landing. That’s why I think Starship is a bit excessive for Moon missions. I like Zubrin’s plan with small landers more. One tanker in lunar orbit will be enough for many trips to the surface and back. All that matters is cost. If the goal is operational reusable rockets (like aircraft), the number of flights is a feature, not a problem. Quote Link to comment Share on other sites More sharing options...
RCgothic Posted October 2, 2020 Share Posted October 2, 2020 (edited) It's 18 launches landing 150t of cargo and 100t of spacecraft on the moon and then returning 10t of samples for less price than the *engines* of an expendable SLS (admittedly astronauts delivered to NRHO separately). If the target goal of $2m is met them that's all that for about twice the marginal "at cost" price of a Falcon 9 reused mission. If we want offworld bases then this is absolutely what is needed to make that happen. Edited October 2, 2020 by RCgothic Quote Link to comment Share on other sites More sharing options...
tater Posted October 2, 2020 Share Posted October 2, 2020 Live in 12 hours: Quote Link to comment Share on other sites More sharing options...
tater Posted October 2, 2020 Share Posted October 2, 2020 Quote Link to comment Share on other sites More sharing options...
RealKerbal3x Posted October 2, 2020 Share Posted October 2, 2020 (edited) 37 minutes ago, tater said: I won't be able to watch because it's at 3AM for me but...please...no...scrub... Edited October 2, 2020 by RealKerbal3x Quote Link to comment Share on other sites More sharing options...
magnemoe Posted October 2, 2020 Share Posted October 2, 2020 1 hour ago, RCgothic said: A 100t lunar Starship *just* has enough DV to go to the lunar surface from LEO and back to NRHO with 0 payload delivered to the surface. In order to fully unlock the potential it's going to have to refuel in NRHO *and* have a way of trans-shipping significant cargo there. I think a deep-space optimised Starship variant (>80t) could deliver 300t of propellant to NRHO *and return* without aerobraking off a full load in LEO. Which is convenient, because Lunar Starship needs about 580t of propellant for a decent margin to land 150t and return 10t. It'd take about 6 LEO tanker-fulls to reload a deep space tanker @230t to LEO (see my post at the top of the page). A regular cargo starship at 100t, could probably deliver 150t to NRHO and return to earth with 10t and land off 5 LEO tanker-fulls. So on a lunar Starship's first mission with 150t it requires the following launches: Itself. 6x refills. Lunar Tanker. 6 refills. That's 14 launches! For its next mission it needs: Cargo starship. 5x refills. 12x refills for the lunar Tanker. 18 launches! Assuming 6.5 days each way to NRHO that's 13 days per trip. Plus say 1 day per refill operation... That's a period of 27 days for the tanker to complete, which isn't too bad. I assume moonship will stay in moon orbit, it can not aerobrake down to LEO, smarter to fuel up an tanker in LEO launch this to moon orbit refuel the moonship before it aerobrake down into LEO or direct landing. SpaceX can take much higher risks with the tankers than an manned ship. Quote Link to comment Share on other sites More sharing options...
RCgothic Posted October 2, 2020 Share Posted October 2, 2020 I was working the deep space tanker as a lightweight variant with maybe no heat shield and fewer engines, not aerobraking. But yeah, if a regular tanker can aerobrake from TLI that's definitely cheaper on the mass budget than saving propellant for LEO insertion. Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted October 2, 2020 Share Posted October 2, 2020 1 hour ago, RCgothic said: I was working the deep space tanker as a lightweight variant with maybe no heat shield and fewer engines, not aerobraking. But yeah, if a regular tanker can aerobrake from TLI that's definitely cheaper on the mass budget than saving propellant for LEO insertion. It does make me wonder if a lunar Tankship could aerobrake into LEO without a heat shield. It is stainless steel after all, and should slow quickly when nearly empty, so it shouldn’t need a very deep pass. Maybe multiple shallow passes? Quote Link to comment Share on other sites More sharing options...
tater Posted October 2, 2020 Share Posted October 2, 2020 4 minutes ago, StrandedonEarth said: It does make me wonder if a lunar Tankship could aerobrake into LEO without a heat shield. It is stainless steel after all, and should slow quickly when nearly empty, so it shouldn’t need a very deep pass. Maybe multiple shallow passes? Works in KSP Quote Link to comment Share on other sites More sharing options...
sh1pman Posted October 2, 2020 Share Posted October 2, 2020 (edited) 8 minutes ago, StrandedonEarth said: It does make me wonder if a lunar Tankship could aerobrake into LEO without a heat shield. It is stainless steel after all, and should slow quickly when nearly empty, so it shouldn’t need a very deep pass. Maybe multiple shallow passes? May take a lot of time, but otherwise I think it’s very possible. OTOH Tankship will then need a set of flaps to orient itself during reentry aerobraking, reducing its fuel capacity somewhat. Edited October 2, 2020 by sh1pman Quote Link to comment Share on other sites More sharing options...
tater Posted October 2, 2020 Share Posted October 2, 2020 Scrubbed Starlink moved to Monday. 3 minutes ago, sh1pman said: May take a lot of time, but otherwise I think it’s very possible. OTOH Tankship will then need a set of flaps to orient itself during reentry aerobraking, reducing its fuel capacity somewhat. It might not need them. Quote Link to comment Share on other sites More sharing options...
sh1pman Posted October 2, 2020 Share Posted October 2, 2020 1 minute ago, tater said: It might not need them. Well, going engines-first works in KSP. Most of the time. Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted October 2, 2020 Share Posted October 2, 2020 (edited) 37 minutes ago, tater said: Works in KSP Works for NASA too... https://mars.nasa.gov/mro/mission/timeline/mtaerobraking/ At the rate Boca Chica is going, SpaceX can easily have a fleet of Tankships in various stages of aerobraking down to a refilling orbit. "Flying" broadside would lower the Ap faster, and protect the engine bells. Maybe some smaller vanes for orientation (passively stable would allow for fixed vanes) would be helpful instead of relying solely on RCS E: it would be interesting to see how how deep into the soup an unshielded Tankship could go, and therefore how much Ap it could shave in a single pass. Maybe some shielding would be useful to keep all the residual props from boiling off and needing to be vented. Edited October 2, 2020 by StrandedonEarth Quote Link to comment Share on other sites More sharing options...
tater Posted October 2, 2020 Share Posted October 2, 2020 Musk said that there was a decent chance SS could do EDL from LEO with no TPS. Quote Link to comment Share on other sites More sharing options...
Commodore_32 Posted October 3, 2020 Share Posted October 3, 2020 Stream Live! T- 9:20 minutes Quote Link to comment Share on other sites More sharing options...
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