On 10/22/2013 4:09 PM, Rick Jones wrote:
In sci.space.history Robert Clark wrote:
Elon Musk lecture at the Royal Aeronautical Society - YouTube.
http://www.youtube.com/watch?v=wB3R5Xk2gTY

About 30 minutes in, he gave the propellant fraction of the new Falcon 9
v1.1 as around 96%, or perhaps 95.5%. The 96% propellant fraction number
gives a 25 to 1 mass ratio. But at an Isp of 311 s for the Merlin 1D, the
rocket equation gives a delta-v of 311*9.81ln(25) = 9,800 m/s. Since the
delta-v to orbit is only about 9,100 m/s, this would allow a significant
amount of payload.
Then using the 9 engines and the full propellant load on the F9 first stage
would allow in fact not just a VTVL test vehicle, but in fact a fully
reusable and fully orbital vehicle.

Modulo the small matter of a re-entry shield no?

rick jones


Well there is that, but also note that not all that propellant can be
used for uplift. Some has be kept in reserve for the landing. Doesn't
that affect the mass ratio? Using Bob's figures there is a ~700 m/s
leeway in delta-v, but each unit drop of the mass ratio is a 125 m/s
loss in delta-v. Go down ~5 1/2 units and you're not at SSTO any longer.

If 30% of the propellant is kept in reserve how would that effect the
mass ratio?*

Dave

*Aerospace is not my specialty. I could probably spend an hour+
researching the answer for myself, or just ask the group and wait for
the answer. I'm lazy. I'll take option #2. ;-)