Quote from: clongton on 04/04/2014 08:53 pmAnd they can't "malfunction" inside the VAB. Malfunction means operating incorrectly and inside the VAB they are not operating at all. They are not even "functioning". They are just sitting there doing nothing.Your story does not seem to mesh with the safety precautions taken in the VAB when dealing with solids. Perhaps the precautions were excessive, but the point remains that an element that comes pre-packaged with the propellant *and* oxidizer is always going to be more risky than one that contains neither at the time of handling.
And they can't "malfunction" inside the VAB. Malfunction means operating incorrectly and inside the VAB they are not operating at all. They are not even "functioning". They are just sitting there doing nothing.
enough solids have their place, look at Orbital and their use in Antares.
reduce the risk and improve technical maturation of a liquid oxygen and kerosene oxidizer-rich staged-combustion engine. The company will fabricate a representative full-scale 550,000-pound thrust class main injector and thrust chamber, and prepare to conduct a number of tests measuring performance and demonstrating combustion stability.
These are good questions, questions I'd like to have answered as well. Maybe something that Chris might want to pursue in an update article.I doubt SpaceX is interested, but a Raptor entry would be interesting. It could at least give them some extra research money.
But let's be frank, if SpaceX demonstrates just reusable boosters, the Advanced Booster competition will have a taste of obsolete.
Look. SpaceX has two cards that depend on demonstrating usability. The big one is designing a reusable BFR and thus making SLS obsolete after the four initial launches.
There is one reason I doubt Raptor boosters could be used on SLS: ISP Density of CH4 in relation to VAB door width. With the core having only 4 main engines, and with EUS being smaller than the J-2X LUS, the difference in the 130mt payload must come from potent boosters. 5.5m is the max width for boosters in relation to the VAB doors. I don't know if that volume of CH4 at its ISP density would be enough total thrust. Then subtract prop needed for RTLS, and 130mt seems exceedingly difficult.
Agreed. Which would mean that the program failed not for the reasons so many critics posit, but because superior technology was developed by someone else and thus the fabled heritage technology was swept away by the tide of progress. I would not at all be surprised if your scenario is exactly the way history unfolds.
CH4 is only like 19% less dense than RP-1, and that applies to only the fuel tank. The LOX tank would be the same size.
Quote from: Lobo on 04/25/2014 11:02 pmCH4 is only like 19% less dense than RP-1, and that applies to only the fuel tank. The LOX tank would be the same size.LCH4 has a density of 0.4239 kg/L while RP-1 has a density of 0.8 kg/L. Thus, LCH4 is 47% less dense than RP-1. However, methalox at a 3.6 to 1 oxidiser to fuel mixture ratio (MR) is 19% less dense than kerolox at a 2.8 MR.
Quote from: Steven Pietrobon on 04/28/2014 07:37 amQuote from: Lobo on 04/25/2014 11:02 pmCH4 is only like 19% less dense than RP-1, and that applies to only the fuel tank. The LOX tank would be the same size.LCH4 has a density of 0.4239 kg/L while RP-1 has a density of 0.8 kg/L. Thus, LCH4 is 47% less dense than RP-1. However, methalox at a 3.6 to 1 oxidiser to fuel mixture ratio (MR) is 19% less dense than kerolox at a 2.8 MR.Rule of thumb, for staged combustion, CH4 requires 30% more volume than RP-1. Which if you scale a tank in 3D mean an 9% longer dimensions. And the general 10extra seconds or so of isp usually mean very similar performance. Of course Russians and SpaceX appear to calculate that if you design the SC CH4 cycle taking advantage of the characteristics, like using the expander cycle for something, and thinking in terms of reusability, the CH4 is superior.BTW rocket engine with more restarts lowers development and certifications cost. You might need as little a 10 engines for development vs 100s.
Interesting. So do you mean a Raptor methalox booster would be about 9% longer than a comparitive RP-1 staged combustion booster like an RD-180 powered booster or an AJ-1E6 powered booster? Or that given Raptor's extra performance, it would mean the boosters would be similar in size?Also, roughly, assuming 5.5m diameter for both, how would a Raptor powered booster compare lengthwise to the Dynetics F-1B booster?
What I mean is that the F-1B is less efficient than a SC engine, but can have more thrust.