SpaceX's Big F'ing Rocket

[Dr Mordrid]

BFR = Big F**king Rocket, or in proper company Big Falcon Rocket. That's what they've been calling it since 3 years ago and now it looks to really be happening. BFR would provide the basis for a new generation of heavy lift rockets.

Word has leaked out that early last year SpaceX licensed the Rocketdyne RS-84 staged combustion re-usable kerosene/LOX engine and the supporting tech, metallurgy etc. Staged combustion engines use a pre-burner to heat the fuel and oxidizer then use them to run the turbopumps before they'e injected into the thrust chamber, increasing the overall efficiency of the engine.

RS-84 has a thrust of over 1,000,000 lb/ft, which is over 2/3 the thrust of the F-1 engine used in the Saturn V and over 2.5 times the thrust of the Space Shuttle Main Engine. EACH.

A BFE (big f**king engine) for the BFR.




What would the BFR look like? This artwork of a purported SpaceX heavy lift roadmap floated around the 'net last year and everyone blew it off as fake, but now I'm not so sure. If this roadmap is real the Griffon engine would be the BFE, aka RS-84

PS: the 36 ton version would likely be upgradable to 50 tons with the liquid hydrogen 2nd stage announced last June. Like wise the 12.5 ton would likely go to almost 20 tons.

[cjolley]

Sorry, it can't be called the BFR untill it bests the F-1

Impressive anyway.

[KRSESQ]

The RS-84 has a dry weight of 8,128 kg, Compared to 8,353 kg for the F1. So the weight/thrust ratio is somewhat lower.

I'm sure the engineers will have that hashed out in a few years.

(Hope they have some robust engine mounts!)

Kevin

[Dr Mordrid]

What was a shame is that the F1A had a thrust of 2 million lf/ft, but then the Apollo program was canceled and it never flew.

The F1 also had a bit of a checkered performance record what with at least 2 failing during launches. The only thing that saved those missions was having 5 engines which allowed engine-out launch; shut down the bad one (and sometimes its opposite if not the center engine) and throttle up the rest for an extended burn.

My understanding is that the SpaceX engine will undergo tests later this year in McGregor, Texas, so I imagine the engine mount is taken care of. Hope those folks in McGregor have their ear plugs at hand. The F9 rattled everything for almost 40 miles when they fired it during a temperature inversion.

[cjolley]

Of course it all comes down to cost.
The F-1 was about what you would expect for an 18,000lb Rolex watch.
Nobody is willing to spend like that on a rocket engine now.

$/lb of thrust would be an interesting comparison if anyone has the time.

[Dr Mordrid]

F-1 specific impulse: 265 sea level/304 vacuum

RS-84 specific impulse: 305 sea level/324 vacuum

[cjolley]

F-1 specific impulse: 265 sea level/304 vacuum

RS-84 specific impulse: 305 sea level/324 vacuum

Each extra pound of fuel required is one less pound of payload at launch.
That specific impulse advantage would take the RS-80 to about 75%, up from >66%, of the effective power of the F-1.

Not bad.

I still wonder about $/lb in orbit adjusted for inflation.
Bet that would make the RS-80 look even better.

[Dr Mordrid]

Try this one;

According to industry experts the real (vs. NASA's figures) cost/lb for a shuttle flight is about $35,000/lb of cargo and crew.

So, it costs around $42,875,000 to launch the 7 person crew at 175lbs each. It costs another $1.925 billion for the 55,000 lbs of cargo it can carry.

Total: $1,967,875,000 per shuttle launch.

NASA's incredibly twisted bookkeeping puts the total cost of a flight at just $1.000 - $1.250 billion because of "recurring costs", but IMO that's hogwash; it costs what it costs.

OTOH SpaceX is quoting <$150 million for a 7 passenger Dragon flight and $100 million for a fully loaded Falcon 9 Heavy, which can loft 64,900 lbs. A Falcon 9 Heavy H could loft almost 99,000 lbs (this being the one with a hydrogen/LOX 2nd stage).

Total: $250 - $300 million for both launches.

Neither of these would be using the RS-84 but their existing Merlin 1C reusable keroLOX engine, and that's getting a power upgrade.