Calculated the Isp for Raptor engine at 320s SL, 356s vac. Any objections?

Quote from: dante2308 on 11/18/2013 06:14 pmCalculated the Isp for Raptor engine at 320s SL, 356s vac. Any objections?What sort of nozzle, first stage or vacuum?

Sorry about the roughness. Here is my first calculated orbit:Launch from Florida:The initial acceleration is 2.65101426361 m/s^2The initial thrust percent is 100The initial number of engines cut off are 0 out of 5Main Engine Cut OFFThe time is 348.21 secondsVelocity is 7.87330442438 km/sAltitude is 134.127262879 kmThe final acceleration is 9.44607675087 m/s^2The final thrust percent is 99The final number of engines cut off are 0 out of 5Orbit Achieved!! Circular orbit velocity was 7.83321791163 km/sCurrent mass is 18.2961705186 tonsThe apogee (max Earth radius) is 524.819854367 kmThe perigee (max Earth radius) is 117.608332424 kmThe inclination is 27.8052772316 degreesObviously this isn't optimal yet and I can get a little more mass to an even higher orbit if i play with it a bit. What do you think about the numbers?

Quote from: dante2308 on 11/19/2013 06:40 amSorry about the roughness. Here is my first calculated orbit:Launch from Florida:The initial acceleration is 2.65101426361 m/s^2The initial thrust percent is 100The initial number of engines cut off are 0 out of 5Main Engine Cut OFFThe time is 348.21 secondsVelocity is 7.87330442438 km/sAltitude is 134.127262879 kmThe final acceleration is 9.44607675087 m/s^2The final thrust percent is 99The final number of engines cut off are 0 out of 5Orbit Achieved!! Circular orbit velocity was 7.83321791163 km/sCurrent mass is 18.2961705186 tonsThe apogee (max Earth radius) is 524.819854367 kmThe perigee (max Earth radius) is 117.608332424 kmThe inclination is 27.8052772316 degreesObviously this isn't optimal yet and I can get a little more mass to an even higher orbit if i play with it a bit. What do you think about the numbers?117 km perigee sound like it's going to drop after couple of orbits due atmospheric drag, not very good orbit.

How would you get sea level Isp that high?

So the final mass placed into orbit is 18.3 tons, out of...how many? Back calculating from your earlier-stated ISp of 320 SL and 356 vac (which I assume you used here) and the initial 5 engines at (300,000 kgf) * (320/356), I got that to have the initial acceleration of (9.81+2.65) m/s^2 you note, the vehicle would be about 400,000 kg on the pad. That means about 4.6% of the gross mass is tanks, engines, structure, TPS, and payload. That seems, in my opinion, to be more aggressive a target than is reasonable.

It's too aggressive. It's within Spacex's current architecture, but no, I don't support SSTO. F = Isp*Veff*mdot so keeping mdot the same, you get a non-linear relationship between force and Isp.

Quote from: dante2308 on 11/19/2013 10:06 pmIt's too aggressive. It's within Spacex's current architecture, but no, I don't support SSTO. F = Isp*Veff*mdot so keeping mdot the same, you get a non-linear relationship between force and Isp... but your turnaround time for the entire vehicle is vastly faster, possibly even just gas-and-go, and your ground infrastructure requirements are vastly less, possibly even just a refueling truck.The question of fully reusable SSTO is one of plausibility, not utility. If you could get a reusable SSTO to work, with even a marginal payload, someone would find a use for it.If you could build a first stage of a reusable TSTO that could also operate in reusable SSTO mode, you'd have the best of both worlds.

Or something else efficient (and more plausible like a crane and click-in connections).

Quote from: go4mars on 11/19/2013 10:36 pmOr something else efficient (and more plausible like a crane and click-in connections).We shall call it "click and go" TSTO reusability. Spread the word.*cough*LEGO*cough*

Or first stage lands, someone throws an ablative tarp on top, second stage lands on the first. Or something else efficient (and more plausible like a crane and click-in connections).

Quote from: go4mars on 11/19/2013 10:36 pmOr first stage lands, someone throws an ablative tarp on top, second stage lands on the first. Or something else efficient (and more plausible like a crane and click-in connections).Land on top? And if the second stage thrusters get wonky on landing, it potentially takes the first stage with it.Besides, I would have thought that the time-consuming parts of setting up the stack would be managing the connections between the stages, and between both and the support structure (electrical and fuel lines, etc.). The crane is a whole lot more plausible.