Quote from: ugordan on 03/14/2019 07:23 pmQuote from: jongoff on 03/14/2019 07:19 pmWikipedia says the SpaceX PUG says MVac can currently throttle down to 39% (~360kN/81klbf). The MVac throttle range listed in the latest F9 User Guide is 220,500 lbf to 140,679 lbf FWIW.That does not match up with the 6 g maximum axial acceleration for a sub 4 klb payload shown in the same guide. Burnout acceleration with that minimum throttle would be 8.7 g assuming a 5.5 t stage mass. And I'm pretty sure either Musk or SpaceX confirmed the 35% throttle, though I can't find it right now.
Quote from: jongoff on 03/14/2019 07:19 pmWikipedia says the SpaceX PUG says MVac can currently throttle down to 39% (~360kN/81klbf). The MVac throttle range listed in the latest F9 User Guide is 220,500 lbf to 140,679 lbf FWIW.
Wikipedia says the SpaceX PUG says MVac can currently throttle down to 39% (~360kN/81klbf).
Quote from: jongoff on 03/14/2019 07:03 pmIt may be possible to either rate the MVac for lower thrust operations, or add in some sort of reinforcement structure so that all of the thrust loads from the MVac aren't taken just through the docking adapter.What about G loads on the unfurled solar arrays? At the current MVac throttleability levels, at burnout the entire stack would experience around 2G acceleration, are the arrays sturdy enough to cope with that?
It may be possible to either rate the MVac for lower thrust operations, or add in some sort of reinforcement structure so that all of the thrust loads from the MVac aren't taken just through the docking adapter.
I have some questions. Does Orion have to be vertically integrated?Can a Delta IV heavy upper stage with Orion replace a FH upper stage? I know it is rocket lego, but NASA did it with Centaur upper stage on different Atlas rockets. They did something like this with Saturn I. Would it be faster to stretch or widen FH upper stage? Or build a 5m Raptor upper stage? In the next year? Just wondering how they are going to handle this. Loop the moon and come back, or go into moon orbit, stay awhile, then come back.
I agree and I really would like to know if anyone within NSF or the NSF reporter team can answer this question: Can ULA even produce two DIVH vehicles between the time this might be approved and a 2020 NET date ?
Quote from: FinalFrontier on 03/14/2019 07:29 pmI agree and I really would like to know if anyone within NSF or the NSF reporter team can answer this question: Can ULA even produce two DIVH vehicles between the time this might be approved and a 2020 NET date ?I suspect the bigger problem would be launching two DIVH's so close together: Could LC-37B at CCAFS be turned around in time? Maybe ULA could manage closely spaced launches if one went from VAFB, but I wouldn't guess it feasible to launch to the same orbit.
Quote from: mlindner on 03/14/2019 12:06 amI'm tired of people repeating the idea that a craft that's meant to withstand launch and reentry and heavy vibrational side loading in both cases can't withstand some static loading while horizontal. It just doesn't make sense from a physics perspective. Well too bad, because it is true. Spacecraft designed for vertical integration can only support their weight when fully fueled in the velocity direction, not any other way. Just because you don’t want to hear that doesn’t make it true. Any rocket lifting Orion must integrate it vertically, no getting around it.
I'm tired of people repeating the idea that a craft that's meant to withstand launch and reentry and heavy vibrational side loading in both cases can't withstand some static loading while horizontal. It just doesn't make sense from a physics perspective.
Lots of great posts! Thanks, everybody!! Brindenstine's announcement is the most exciting thing that's happened in space policy for a long time. My wife and I just closed the deal on our dream home yesterday, but I'm actually more excited about a commercially launched EM-1!
SADM of the ESM has a unique design incorporating a two axis gimbal. An inner axis provides rotation of the SAW about an axis perpendicular to the ESM longitudinal axis, and an outer axis which rotates the SAW about its own longitudinal axis. The two-axis capability is necessary for two reasons:1) allow maximum sun tracking to meet the power requirements for particular vehicle attitudes of certain mission phases. Insufficient power is generated by the SAW with a single (roll) axis SADM not providing the avoidance capability of the shadowing effect of both the Orion vehicle on the SAW and the SAWs on each other2) insure the structural integrity of the SAWs under injection maneuvers. For the trans-lunar injection performed with the upper stage of the Space Launch System rocket, actually the iCPS (interim Cryogenic Propulsion Stage), the arrays are canted backwards to sustain in deployed configuration the 1 g acceleration load. For the trans-earth injection performed with the ESM main engine, the acceleration is less severe and the arrays have to be canted forwards to prevent damages from the OMS-E engine plume while minimizing the load on the SAWs.
Quote from: spacenut on 03/14/2019 08:10 pmI have some questions. Does Orion have to be vertically integrated?Can a Delta IV heavy upper stage with Orion replace a FH upper stage? I know it is rocket lego, but NASA did it with Centaur upper stage on different Atlas rockets. They did something like this with Saturn I. Would it be faster to stretch or widen FH upper stage? Or build a 5m Raptor upper stage? In the next year? Just wondering how they are going to handle this. Loop the moon and come back, or go into moon orbit, stay awhile, then come back. As for putting a stage as a payload it has to be integrated and the pad and tower has to be equipped to handle to propellants.Does 39a even still have hydrogen plumbing?
Is FH upper stage engine too powerful and would put too many g's on Orion to work unless it can be throttled down?Can FH launch a Centaur upper stage with docking adapter to dock with Orion to push it to lunar location? Would boil off be a problem waiting to dock?
Quote from: spacenut on 03/14/2019 02:55 pmIs FH upper stage engine too powerful and would put too many g's on Orion to work unless it can be throttled down?Can FH launch a Centaur upper stage with docking adapter to dock with Orion to push it to lunar location? Would boil off be a problem waiting to dock? Centaur upper stage might be a pain to integrate. SpaceX does have a very simple, low thrust rocket engine they could use - the Kestrel. Not nearly as efficient as the RL-10, or even the as Merlin Vac, but it's dead simple, and uses the same fuel as the Falcon stack.
Both sites can do a 51 degree orbit but it's sub optimal for lunar missions.
Draco has slightly worse ISP at 300 vs 317 for Kestrel, but seems much easier and a lot lighter. You don't need high thrust for a kick-stage do you? Could gang together as many as you needed. No worries about boil-off or long duration loiter.
SpaceX does have a very simple, low thrust rocket engine they could use - the Kestrel. Not nearly as efficient as the RL-10, or even the as Merlin Vac, but it's dead simple, and uses the same fuel as the Falcon stack.