Why use an ACES? A hydogen upper stage would make integration hugely complex and expensive. An expendable BFR upper stage cannot be that expensive in comparison. But with refuellling in LEO I guess it would be possible to send a spacecraft into a high energy orbit and still return the upper stage. Maybe with a simple storable fuel booster that provides extra kick and/or orbit insertion at the destination.
We've been debating awhile now just how Spacex's BFR & the MCT will get us to Mars and how best to accomplish colonization with them. ... There must be other profitable missions and tasks these vehicles could do for Spacex. ... Aside from possibly transforming space tourism, such vehicles might also make lunar bases and/or lunar tourism a real possibility. Or they might enable asteroid mining on a previously unimagined scale. For purely scientific missions, you might see the BFR enabling things like a Europa orbiter and lander mission, or a Titan orbiter and lander mission, or, my personal favorite, an orbiter and lander mission to Pluto.
So let's sound off and debate just what we think the MCT and BFR will be used for besides going to Mars.
My own preference, and I don't expect it to be widely shared, (in addition to an eventual program of asteroid colonization), would be a solar-system wide constellation of 8m-class optical telescopes networked to form a giant multi-source optical interferometer. Getting a 6 a.u. or so baseline would allow us to map just about every star and planet in the galaxy down to a gnat's butt.
There's the perennial favourite of orbital solar-power; though all studies to date show you get more (even 24-hour) power for the same money with ground-based solar, so far as I know none of these have taken reusable launchers and the concomitant reduction of launch costs into account.
Probably we need an Elon v. 2 to revolutionize production methods for space probes and space telescopes!
Maybe propellant shipments for moving asteroids around for Planetary Resources type operations.Quote from: CuddlyRocket on 09/14/2014 11:46 amThere's the perennial favourite of orbital solar-power; though all studies to date show you get more (even 24-hour) power for the same money with ground-based solar, so far as I know none of these have taken reusable launchers and the concomitant reduction of launch costs into account. Also, the lack of winds etc. may allow thinner solar panels to be used. Has anybody done a solar power satellite study assuming 25 um thick panels (that's what IKAROS uses)? Assuming the density is about 2 g/cm^3 that's about 20,000 square meters per metric ton (for the panels alone, not the power wires/cables or the transmitter...) At 10% efficiency and Earth's distance from the sun that 20,000 square meters would produce about 2.7 megawatts* (though I don't know how efficient the transmission to Earth would be).And you might be able to go even thinner than that.
Without a big enough actual collecting area, a huge aperture size only helps for extremely bright sources, like blackhole accretion disks, etc. Ain't no such thing as a free lunch...