Quote from: TheTraveller on 09/30/2016 09:11 amCan the ITS tanker version of the spaceship do SSTO to allow orbital testing before the ITS booster files?From the attached maybe it can do so and even carry a small test crew, assuming 91t of fuel in LEO is enough to deorbit and land.The SL Raptor has 3,050 kN of thrust at sea level, or 311 mT. If there are only 3 SL Raptors on the tanker, that is 933 mT of thrust, which from earth is not sufficient to launch a 2590 mT ship.
Can the ITS tanker version of the spaceship do SSTO to allow orbital testing before the ITS booster files?From the attached maybe it can do so and even carry a small test crew, assuming 91t of fuel in LEO is enough to deorbit and land.
Interesting the atmo Raptors have a 361 Isp on the BFS spec sheet, which is higher than the stated atmo Isp of 334 and lower than the Vac Isp of 382 on the Raptor engine spec sheet.
Here is how it works. 1. SL Raptor with 40:1 ratio nozzle SL Isp: 334sVac Isp: 361s2. Vac Raptor with 200:1 ratio nozzleVac Isp 382sBoth the booster and the spaceship use the same SL Raptors (in the Booster, the inner 7 have gimbals, and in the spaceship all three).The booster has an additional 35 SL Raptors that cannot gimbal, and the spaceship has six Vac Raptors that cannot gimbal.
Quote from: MP99 on 09/30/2016 10:45 amQuote from: Jim on 09/30/2016 03:48 amQuote from: Nathan2go on 09/30/2016 03:46 am I would assume for the propellant refrigeration system?What propellant refrigeration system?Elon seemed to say that they relied on subcooled prop to avoid various issues, including cavitation. Is it possible for prop to remain sub-cooled over a multi month Mars transit? ISTM the alternative is to let the prop reach boiling point, then manage boiloff? Cheers, Martin Use the boil off for attitude control and electrical power production
Quote from: Jim on 09/30/2016 03:48 amQuote from: Nathan2go on 09/30/2016 03:46 am I would assume for the propellant refrigeration system?What propellant refrigeration system?Elon seemed to say that they relied on subcooled prop to avoid various issues, including cavitation. Is it possible for prop to remain sub-cooled over a multi month Mars transit? ISTM the alternative is to let the prop reach boiling point, then manage boiloff? Cheers, Martin
Quote from: Nathan2go on 09/30/2016 03:46 am I would assume for the propellant refrigeration system?What propellant refrigeration system?
I would assume for the propellant refrigeration system?
Look at shipping technology in Europe. When all you had to do was cross the Mediterranean, the ships were pretty lame—they couldn’t cross the Atlantic. So commerce basically had short-range vessels. Without the forcing function, shipping technology didn’t improve that much—you could do the same things with ships, pretty much, around the time of Julius Caesar as you could around the time of Columbus. 1,500 years later, you could still just cross the Mediterranean. But as soon as there was a reason to cross the Atlantic, shipping technology improved dramatically. There needed to be the American colonies in order for that to happen.
The BFS spec sheet shows atmo Raptor Isp of 361 which as all 9 BFS Raptors need to fire up to do Earth side LAS, would suggest that 361 is the averaged Isp of 3 atmo bell and 6 Vac bell Raptors running at the same time.
Quote from: TheTraveller on 09/30/2016 05:02 pmThe BFS spec sheet shows atmo Raptor Isp of 361 which as all 9 BFS Raptors need to fire up to do Earth side LAS, would suggest that 361 is the averaged Isp of 3 atmo bell and 6 Vac bell Raptors running at the same time.If SpaceX added two lines in the second slide for sea level nozzle Raptor thrust and Isp performance in vacuum, this confusion would be averted.
And the sea level Isp for the vac Raptor nozzle would be?
Quote from: TheTraveller on 09/30/2016 05:26 pmAnd the sea level Isp for the vac Raptor nozzle would be?Irrelevant? Do you get an SL isp for RL-10 orJ-2X?The vacuum Raptors are going to work in vacuum.
Quote from: TheTraveller on 09/30/2016 05:26 pmAnd the sea level Isp for the vac Raptor nozzle would be?Irrelevant? Do you get an SL Isp for RL-10 or J-2X?The vacuum Raptors are going to work strictly in vacuum, or near vacuum.Nowhere near Earth sea level with that huge nozzle.
Quote from: Dante80 on 09/30/2016 06:02 pmQuote from: TheTraveller on 09/30/2016 05:26 pmAnd the sea level Isp for the vac Raptor nozzle would be?Irrelevant? Do you get an SL isp for RL-10 orJ-2X?The vacuum Raptors are going to work in vacuum.The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.
Quote from: Snake on 09/30/2016 06:06 pmQuote from: Dante80 on 09/30/2016 06:02 pmQuote from: TheTraveller on 09/30/2016 05:26 pmAnd the sea level Isp for the vac Raptor nozzle would be?Irrelevant? Do you get an SL isp for RL-10 orJ-2X?The vacuum Raptors are going to work in vacuum.The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.Nope, you get flow separation issues on the 200 expanded nozzle, which might even created burn troughs. No SL ignition of vacuum optimized nozzles.
Quote from: HVM on 09/29/2016 10:03 pmComparing sizes again:Also excluding panorama window, shuttle orbiter have bigger individual windows than ITS.Made myself one also. Sea Dragon for fun.
Comparing sizes again:Also excluding panorama window, shuttle orbiter have bigger individual windows than ITS.
Wouldn't you be quite happy to trash the nozzles for an abort?
Quote from: Barrie on 09/30/2016 06:25 pmWouldn't you be quite happy to trash the nozzles for an abort?Not if it creates asymmetric thrust that cannot be compensated for.
Quote from: baldusi on 09/30/2016 06:14 pmQuote from: Snake on 09/30/2016 06:06 pmQuote from: Dante80 on 09/30/2016 06:02 pmQuote from: TheTraveller on 09/30/2016 05:26 pmAnd the sea level Isp for the vac Raptor nozzle would be?Irrelevant? Do you get an SL isp for RL-10 orJ-2X?The vacuum Raptors are going to work in vacuum.The vacuum Raptors will work at or near sea level for some launch abort/escape sequences. I would like to know the engine's Isp at sea level for this reason alone.Nope, you get flow separation issues on the 200 expanded nozzle, which might even created burn troughs. No SL ignition of vacuum optimized nozzles.If so then how can the BFS engines work as LAS as Elon stated? The 3 atmo nozzled Raptors don't have enough lift for LAS.