Author Topic: Discussion/Comparison of the new generation of American heavy lift launchers  (Read 15009 times)

Offline Paul451

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[...]

BFR's equivalent of "expendable" would be refuelling with 1, 2, 3, or 4 tugs. It shouldn't be hard to work out payload vs delta-v vs amount of refuelling. What delta-v numbers are you using for TLI/TMI/GTO?

Offline DreamyPickle

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Updated with BFR added, based on the attached chart from Elon's September 29, 2017 presentation.

Yes, BFR without refueling is pointless outside LEO. But it's explicitly designed to refuel in orbit so that should be included. Maybe also add distributed launch with ACES?

In theory BFR might be able to do more in expendable mode (like most other entries) but that's obviously silly and not going to happen. The design doesn't even include an option for detachable fairings.

Using a third stage inside the payload bay is also something that should be very seriously considered. The shuttle actually used this architecture and it would be the best way to launch space probes on BFR.

Offline Paul451

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Using a third stage inside the payload bay is also something that should be very seriously considered.

A single Raptor-vac based upper-stage with a total wet mass, including payload, maxing out the 150t to LEO, gives you 75 tonnes total mass to GTO. If the upper-stage is a lazy 10% dry mass¹, that gives you 60 tonnes to GTO.

Same stage gives 35t payload to 4km/s. 23t to 5km/s. 15t to 6km/s. Etc.


¹ In order to compete with the cost of just refuelling the BFS², any such expendable upper-stage would have to be cheaply built, trading mass for cost. Or you could spend more once for a reusable/refuellable tug.

² Musk's slides gave about 110 tonnes to GTO for a single refuelling.
« Last Edit: 10/07/2017 03:05 PM by Paul451 »

Offline envy887

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I estimate ~73,500 kg per launch to TLI with this architecture (662 tonnes counting lander and ascent stages and propellant over 9 launches). Six tankers stage at 200 km circular LEO, then the last two tankers stage at LEO+550 m/s.
« Last Edit: 10/09/2017 05:47 PM by envy887 »

Offline envy887

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I also estimate ~66,000 kg per launch to TMI with 6 LEO refueling launches (462 tonnes injected for 7 total launches, TMI is LEO+3900 m/s).

Offline envy887

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How I'd display it:

==============================================================
Vehicle          1st Flt   TransLunar   TransMars      GTO   
==============================================================
...
BFR                2022?         0 kg         0 kg  ~20,000 kg
BFR-R              2022?   ~73,500 kg   ~66,000 kg      ??? kg
...
==============================================================
"X" Denotes Expendable Version
"R" Denotes LEO Refueling, per launch basis
« Last Edit: 10/09/2017 05:46 PM by envy887 »

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