Quote from: JacobLutz7 on 01/20/2018 06:23 pmOrion does not have enough propulsive capability to enter and return from LLO.I actually requested more information on the Orion delta-v front in another thread, the discussion on which starts here.
Orion does not have enough propulsive capability to enter and return from LLO.
This is from memory havn't confirmed it, Orion is about 1800m/s.
The attached NASAfacts sheet from 2011 indicates a delta-V of 4920 ft/s, i.e., 1500 m/s.The mass to orbit is quoted as 50,231 lbm, while the SM's propellant load is 17,433 lbm, giving a mass ratio of 1.5315, assuming negligible propellant residuals. The delta-V of 1500 m/s then in turn implies an effective exhaust velocity of 3518.9 m/s, i.e., a specific impulse of 359 s, which seems unlikely for storable propellants.I think what's missing in this analysis is that some propellant is burned on the way to orbit, since SLS places Orion only into a transfer orbit with a very low perigee.
You're confusing the SLS Core stage with iCPS/EUS. The former stages slightly suborbital, the latter reaches a circular parking orbit first and then performs TLI, and then completes a disposal burn afterwards
Looks like in the budget proposal from a couple weeks back the Deep Space Gateway has been renamed the "Lunar Orbital Platform", the propulsion module now has funding attached to it ($504 million next year, $2.7 billion over five years), and the targeted launch date is actually being moved up to 2022. It is also now is planned for launch on a commercial vehicle instead of on the EM-2 SLS flight.
Quote from: Toast on 02/26/2018 11:27 pmLooks like in the budget proposal from a couple weeks back the Deep Space Gateway has been renamed the "Lunar Orbital Platform", the propulsion module now has funding attached to it ($504 million next year, $2.7 billion over five years), and the targeted launch date is actually being moved up to 2022. It is also now is planned for launch on a commercial vehicle instead of on the EM-2 SLS flight.That's a steep 'initial' price tag for an SEP tug.What part of the technology is so expensive?
Quote from: AncientU on 02/27/2018 10:55 amQuote from: Toast on 02/26/2018 11:27 pmLooks like in the budget proposal from a couple weeks back the Deep Space Gateway has been renamed the "Lunar Orbital Platform", the propulsion module now has funding attached to it ($504 million next year, $2.7 billion over five years), and the targeted launch date is actually being moved up to 2022. It is also now is planned for launch on a commercial vehicle instead of on the EM-2 SLS flight.That's a steep 'initial' price tag for an SEP tug.What part of the technology is so expensive?No part. It's just that it will be done "NASA-style", much like SLS and Orion.Remember: gravy train...
The SLS upper stage is hydrolox, isn't it impossible for it to last 3 days and relight for orbit insertion? I know ULA's ACES claims to be able to do it but that's only after they develop IVF.I also remember reading that NRHO was picked partly because of limited Orion delta-v, is that true?On a related note, isn't it also very difficult to bring a SEP craft to lunar orbit Moon using only its own power? Switching the PPE to a commercial launch brings many new issues.