So it's certainly possible that a vehicle which would be capable of just 100 tons initially could grow to be capable of 200tons after a decade of tweaking and upgrading.
If excess thrust is a problem, perhaps a partly-fueled BFR with only some of the engines lit could work? It would have a lower payload mass fraction to be sure, given the unused engines and tankage, but as long as it can get the payload into the right orbit, who cares? Engine wear and tear would be almost the same in both cases (maybe 10 engines lit instead of 9).
...because it's much more optimized for cheap commercial launch than either FH or BFR, it'd also cement SpaceX's domination of the launch industry. (BFR would leave an opening for a better-optimized RLV which could still compete in the high-revenue Ariane5/Proton market.)
Would it at all be feasible to use the BFR to launch multiple satellites destined for similar orbits? E.g. One yearly launch putting up a dozen satellites in GEO? Additional launches to access other orbits as required.Fuel reserves and delta V capabilities on individual satellites could be increased significantly given the massive payloads on a BFR.
Quote from: Robotbeat on 01/06/2015 11:46 pm...because it's much more optimized for cheap commercial launch than either FH or BFR, it'd also cement SpaceX's domination of the launch industry. (BFR would leave an opening for a better-optimized RLV which could still compete in the high-revenue Ariane5/Proton market.)What do you see as the big differences in op costs (key driver's and guess of their cost difference) between the truly Big FR (aka transorbital railroad), and the smaller rocket you're suggesting? As you know, I lean strongly toward a "millions of colonists sooner" approach; whatever form that may take.
Another issue is reliability-related:Suppose BFR has 30 engines on the first stage alone (FH will have 27). If BFR is developed first, as the very first application of Raptor, that means a huge probability of engine failure occurring at least once on a flight (in fact, I'd probably bet money on it... a little, not a lot) or at very least causing a LOT of aborts during the launch hold-down. You think F9 has a lot of scrubs, just wait until you see the BFR monster trying to spin up 30 new Raptors at once!>
Another issue is reliability-related:Suppose BFR has 30 engines on the first stage alone (FH will have 27). If BFR is developed first, as the very first application of Raptor, that means a huge probability of engine failure occurring at least once on a flight (in fact, I'd probably bet money on it... a little, not a lot) or at very least causing a LOT of aborts during the launch hold-down. You think F9 has a lot of scrubs, just wait until you see the BFR monster trying to spin up 30 new Raptors at once!Going with a smaller 9-engine vehicle initially, however, allows you to increase the reliability of the engine without being bogged down in endless aborts and nearly guaranteed engine failure during flight (which doesn't, of course, mean launch failure). If SpaceX had went straight to the Falcon Heavy, they probably would've folded before they ironed out all of Merlin's little glitches. (This still may be a problem for FH, of course, but by flying Falcon 9 v1.1 at least a dozen times beforehand, it gives Falcon Heavy's first flight a shot of launching without engine failure or endless aborts.) Also, it allows you to improve the performance of Raptor before integrating it on the larger vehicle where more is at stake.