Wouldn't it make more sense to refuel in lunar orbit
How about this?Fully fuel MCT and a tanker in LEO. Launch them in tandem to a highly elliptic orbit, chosing the orbit so that the tanker has enough fuel left to fully fuel the MCT again. The tanker returns to earth on that orbit. The MCT does its earth departure burn at perigee with max. efficiency. How much delta-v would that gain over starting in LEO? Close to 3km/s?It is operationally less complex than a depot. A depot may become more efficient when many flights go beyond Mars.
Though, the question is that could a single tanker refuel the MCT/ITS after it has already spent 3km/s impulse for acccelerating itself(and the fuel), or would multiple tankers be needed/would the tankers need to be much bigger than the MCT/ITS?When the tanker is returning to LEO it does not need much fuel because it can do aerobraking. Or it could return directly to earth instead of returning to LEO.
Without calculation it seems to me that one tanker could be enough or nearly enough to give the max advantage.
A simulation and analysis of this concept has been in L2 for some time.
It's OK to post an L2 link here as non-members simply can't access it
Would a BFR first stage be able to single-stage-to-orbit without the BFS?I'm wondering how hard it would be to get a BFR into orbit, fuel it, send it to Titan, propulsively land, and use ISRU to use it repeatedly as a Titan launch vehical.
Quote from: rakaydos on 09/20/2016 05:28 pmWould a BFR first stage be able to single-stage-to-orbit without the BFS?I'm wondering how hard it would be to get a BFR into orbit, fuel it, send it to Titan, propulsively land, and use ISRU to use it repeatedly as a Titan launch vehical.Without any payload? Quite possibly.Your idea is impractical (BFR is not designed itself for interplanetary travel) but still very interesting. Should be capable of putting hundreds of tons into Titan orbit IF (big if!!!) fueled up on the surface.
BFR as a system comprises the booster, the pad and the "refurb street". Having only the booster landed on Titan gives you nothing, usability wise.
Heck, you could make a space elevator really easily on Ceres...
Reaching Titan is actually easier then that, it would be 7.3 km/s burn at LEO but you can use friction to do all the deceleration at Titan. Taking off again on Titan would be a nightmare because of the atmospheric thickness, per unit of surface area a column of Titans atmosphere is 7.3 times more massive then Earths and has huge scale height so the launch vehicle must spend a lot of time at low speed plowing through this atmosphere which adds to gravity losses too, finally the density of the atmosphere means rocket engines would yield less then sea-level ISP due to under-expansion in nozzles.So don't expect to get a vehicle back from Titan, the transit times alone means their is little point anyway as the vehicle can't get amortized over enough missions to make reuse attractive.
Point of note, SpaceX has repeatedly stated that what they have in mind for the MCT was a Mars Colonial Transport SYSTEM not simply a stage and lander.
Quote from: Robotbeat on 09/21/2016 05:39 pmHeck, you could make a space elevator really easily on Ceres...I make the Clarke orbit for Ceres to be ~1,200 km from the centre, or about 740 km above the surface. So, a lot easier to build a space elevator for Ceres than Earth!
Taking off again on Titan would be a nightmare because of the atmospheric thickness