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#120
by
Zappa
on 07 Dec, 2014 01:49
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I am also curious if it is still a go, it's less than a year from now (October last I heard).
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#121
by
Tonioroffo
on 07 Dec, 2014 16:11
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The Astrobotic website has a June 26th press release, so it must still be active?
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#122
by
savuporo
on 07 Dec, 2014 17:40
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#123
by
Zappa
on 07 Dec, 2014 18:03
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Thanks for posting that article.
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#124
by
alang
on 07 Dec, 2014 19:01
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Regarding the battery lifetime of the second stage: has anyone got an idea of the mass penalty of a wraparound solar panel (dragon v2 trunk style) sufficient to prolong falcon second stage battery life?
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#125
by
Prober
on 07 Dec, 2014 21:05
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Regarding the battery lifetime of the second stage: has anyone got an idea of the mass penalty of a wraparound solar panel (dragon v2 trunk style) sufficient to prolong falcon second stage battery life?
you looking for something like a super light solar panel?
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#126
by
guckyfan
on 07 Dec, 2014 21:13
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Regarding the battery lifetime of the second stage: has anyone got an idea of the mass penalty of a wraparound solar panel (dragon v2 trunk style) sufficient to prolong falcon second stage battery life?
How long do you want it to work? For Lunar orbit injection? The bigger problem may be the RP-1 getting too cold.
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#127
by
rpapo
on 07 Dec, 2014 21:26
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I would worry about the LOX getting warm as much as the RP-1 getting cold.
Unless my memory is failing me completely, there has never been a spacecraft with non-hypergolic chemical propulsion that remained usable beyond a few hours after lift-off. I was going to say the Apollo Service Module, but then looked it up and found it had a hypergolic engine too.
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#128
by
savuporo
on 07 Dec, 2014 21:34
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Unless my memory is failing me completely, there has never been a spacecraft with non-hypergolic chemical propulsion that remained usable beyond a few hours after lift-off.
absolutely correct. the record is something like 12 hours, by Centaur.
reigniting a lox/rp rocket after long coast is nontrivial, even if you managed to retain propellants.
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#129
by
nadreck
on 08 Dec, 2014 22:50
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Unless my memory is failing me completely, there has never been a spacecraft with non-hypergolic chemical propulsion that remained usable beyond a few hours after lift-off.
absolutely correct. the record is something like 12 hours, by Centaur.
reigniting a lox/rp rocket after long coast is nontrivial, even if you managed to retain propellants.
It is non-trivial but that or relighting CH
4/LO
2 is needed soon for a variety of reasons and I expect that SpaceX will end up developing that technology before anything bigger than the FH flies.
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#130
by
Danderman
on 08 Dec, 2014 22:58
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FWIW, the original Blok-D had an nominal on orbit lifetime of 30 days, for lunar missions.
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#131
by
ChrisWilson68
on 08 Dec, 2014 23:09
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Unless my memory is failing me completely, there has never been a spacecraft with non-hypergolic chemical propulsion that remained usable beyond a few hours after lift-off.
absolutely correct. the record is something like 12 hours, by Centaur.
reigniting a lox/rp rocket after long coast is nontrivial, even if you managed to retain propellants.
It is non-trivial but that or relighting CH4/LO2 is needed soon for a variety of reasons and I expect that SpaceX will end up developing that technology before anything bigger than the FH flies.
Getting back on topic, this thread is about an Astrobotic mission supposedly launching in 2015. They have to launch in 2015 to have any chance to win the GLXP, which is the whole point of the mission. I think we can all agree SpaceX will not have any engine other than Draco and SuperDraco that will be able to restart to do a lunar insertion burn before the end of 2015, yes? So Falcon 9 itself won't be putting the Astrobotic payload into lunar orbit.
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#132
by
savuporo
on 08 Dec, 2014 23:32
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FWIW, the original Blok-D had an nominal on orbit lifetime of 30 days, for lunar missions.
I would be interesting to know what the actual longest coast time for RD-58 in space has been. Commercial GTO flights take around 6-7 hours max.
Its important to understand though that this is not a single simple engineering issue - battery life, prop boiloff, materials degradation, residuals, electronics robustness etc all drive this variable, and jump from a few hours to a few days carries significant engineering costs and inevitably also mass penalties. So a GTO mass optimized stage would be configured substantially differently from a lunar orbit capable stage.
Sorry for OT.
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#133
by
Zappa
on 10 Dec, 2014 01:55
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Getting back on topic, this thread is about an Astrobotic mission supposedly launching in 2015. They have to launch in 2015 to have any chance to win the GLXP, which is the whole point of the mission. I think we can all agree SpaceX will not have any engine other than Draco and SuperDraco that will be able to restart to do a lunar insertion burn before the end of 2015, yes? So Falcon 9 itself won't be putting the Astrobotic payload into lunar orbit.
Could a Falcon 9 just continuously burn it's second stage engine for a TLI burn? Or restart it shortly after entering LEO?
Forgive me if this is a dumb question. It's just that they are offering payload services to the Moon and seem quite confident in accepting money for the job.
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#134
by
ChrisWilson68
on 10 Dec, 2014 01:57
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Getting back on topic, this thread is about an Astrobotic mission supposedly launching in 2015. They have to launch in 2015 to have any chance to win the GLXP, which is the whole point of the mission. I think we can all agree SpaceX will not have any engine other than Draco and SuperDraco that will be able to restart to do a lunar insertion burn before the end of 2015, yes? So Falcon 9 itself won't be putting the Astrobotic payload into lunar orbit.
Could a Falcon 9 just continuously burn it's second stage engine for a TLI burn? Or restart it shortly after entering LEO?
Forgive me if this is a dumb question. It's just that they are offering payload services to the Moon and seem quite confident in accepting money for the job.
I believe it's not the TLI burn that's in question. That's similar to putting a satellite in GTO. The question is how it gets the delta-v to go from there into lunar orbit.
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#135
by
TrevorMonty
on 10 Dec, 2014 07:56
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Getting back on topic, this thread is about an Astrobotic mission supposedly launching in 2015. They have to launch in 2015 to have any chance to win the GLXP, which is the whole point of the mission. I think we can all agree SpaceX will not have any engine other than Draco and SuperDraco that will be able to restart to do a lunar insertion burn before the end of 2015, yes? So Falcon 9 itself won't be putting the Astrobotic payload into lunar orbit.
Could a Falcon 9 just continuously burn it's second stage engine for a TLI burn? Or restart it shortly after entering LEO?
Forgive me if this is a dumb question. It's just that they are offering payload services to the Moon and seem quite confident in accepting money for the job.
I believe it's not the TLI burn that's in question. That's similar to putting a satellite in GTO. The question is how it gets the delta-v to go from there into lunar orbit.
The lander should have enough DV to go from TLI to lunar surface.
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#136
by
ChrisWilson68
on 10 Dec, 2014 08:25
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Getting back on topic, this thread is about an Astrobotic mission supposedly launching in 2015. They have to launch in 2015 to have any chance to win the GLXP, which is the whole point of the mission. I think we can all agree SpaceX will not have any engine other than Draco and SuperDraco that will be able to restart to do a lunar insertion burn before the end of 2015, yes? So Falcon 9 itself won't be putting the Astrobotic payload into lunar orbit.
Could a Falcon 9 just continuously burn it's second stage engine for a TLI burn? Or restart it shortly after entering LEO?
Forgive me if this is a dumb question. It's just that they are offering payload services to the Moon and seem quite confident in accepting money for the job.
I believe it's not the TLI burn that's in question. That's similar to putting a satellite in GTO. The question is how it gets the delta-v to go from there into lunar orbit.
The lander should have enough DV to go from TLI to lunar surface.
Well, it could be made to have enough delta-V, but that would just put that much more burden on the lander. I think someone was asking about it to see if that burden could be removed from the lander. And the answer seems to be no, it can't, so the lander will have to do it.
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#137
by
baldusi
on 10 Dec, 2014 15:11
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Getting back on topic, this thread is about an Astrobotic mission supposedly launching in 2015. They have to launch in 2015 to have any chance to win the GLXP, which is the whole point of the mission. I think we can all agree SpaceX will not have any engine other than Draco and SuperDraco that will be able to restart to do a lunar insertion burn before the end of 2015, yes? So Falcon 9 itself won't be putting the Astrobotic payload into lunar orbit.
Could a Falcon 9 just continuously burn it's second stage engine for a TLI burn? Or restart it shortly after entering LEO?
Forgive me if this is a dumb question. It's just that they are offering payload services to the Moon and seem quite confident in accepting money for the job.
I believe you are not quite clear on the terms. Falcon 9 would make a single burn of its upper stage, until the upperstage and payload are on TLI. For reasons of efficiency that's done as fast as possible on the opposite side of the Earth as is the Moon. After that, the whole stack will take a few days of coasting until they are close to the Moon. During those days, a couple of adjustment maneuvers might be required.
Once they reach the gravity field of the Moon, they are still going too fast to be captured by the Moons gravity. Depending on initial conditions, without some serious retropropulsion at that time you either crash the moon, get deviated to some Earth orbit or you return to Earth (the famous Free Return Trajectory that saved Apollo 13).
Having a stage that can do a burn four or five days after initial launch is not something easy, and certainly nothing that's usual since even the most complicated missions to Earth orbit are 9hrs top. Thus, the Falcon 9 upper stage would be probably dead by that time and the Astrobotic lander would have to do the retropropulsion by itself. Since the upper stage would be dead mass for the trajectory correction maneuvers, the logical thing would be that the payload separates from the upper stage as soon as it shuts down.
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#138
by
thydusk666
on 10 Dec, 2014 15:22
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Getting back on topic, this thread is about an Astrobotic mission supposedly launching in 2015. They have to launch in 2015 to have any chance to win the GLXP, which is the whole point of the mission. I think we can all agree SpaceX will not have any engine other than Draco and SuperDraco that will be able to restart to do a lunar insertion burn before the end of 2015, yes? So Falcon 9 itself won't be putting the Astrobotic payload into lunar orbit.
Could a Falcon 9 just continuously burn it's second stage engine for a TLI burn? Or restart it shortly after entering LEO?
Forgive me if this is a dumb question. It's just that they are offering payload services to the Moon and seem quite confident in accepting money for the job.
I believe you are not quite clear on the terms. Falcon 9 would make a single burn of its upper stage, until the upperstage and payload are on TLI. For reasons of efficiency that's done as fast as possible on the opposite side of the Earth as is the Moon. After that, the whole stack will take a few days of coasting until they are close to the Moon. During those days, a couple of adjustment maneuvers might be required.
Once they reach the gravity field of the Moon, they are still going too fast to be captured by the Moons gravity. Depending on initial conditions, without some serious retropropulsion at that time you either crash the moon, get deviated to some Earth orbit or you return to Earth (the famous Free Return Trajectory that saved Apollo 13).
Having a stage that can do a burn four or five days after initial launch is not something easy, and certainly nothing that's usual since even the most complicated missions to Earth orbit are 9hrs top. Thus, the Falcon 9 upper stage would be probably dead by that time and the Astrobotic lander would have to do the retropropulsion by itself. Since the upper stage would be dead mass for the trajectory correction maneuvers, the logical thing would be that the payload separates from the upper stage as soon as it shuts down.
Hi Baldusi, I don't believe that is correct (emphasis mine).
You would do your TLI roughly when the Moon rises above horizon.
You need to set your apogee to where the Moon will be when you get there, not where it is at the time of the burn. Hence TLI burn is not done at spacecraft/Moon opposition, but rather at 90-120-ish degrees.
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#139
by
savuporo
on 10 Dec, 2014 16:42
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There are many strategies to get to Moon and land there, even recent orbiter probes have used a bunch of different trajectories. For example see
LADEE trajectory,
LRO and
ArtemisHere is a one of comparison papers between using WSBs, phasing orbits, direct injection etc:
http://www.agi.com/downloads/resources/white-papers/a-comparison-of-lunar-landing-trajectory-strategies-using-numerical-simulations.pdfHop's always colorful illustrations about how to get to the moon here:
http://hopsblog-hop.blogspot.com/2013/08/lunar-ice-vs-neo-ice.htmlBottom line, at the bare minimum you need 700m/s, normally quite a bit more for the LOI, and then you need to add trajectory corrections, margins and whatnot. And of course the landing itself.
The lander would have to have a very substantial Delta-V reserve, and all burns starting with trajectory correction would have to be hypergolic, none of the existing rocket upper stages can help you there. ( EDIT: Well. Briz and Fregat would - if and when they work )
EDIT: another nice paper dissecting all options for GLXP-type vehicles to actually burn themselves to the moon
https://upcommons.upc.edu/pfc/bitstream/2099.1/9666/1/memoria.pdfStart from chapter 1.1.2 or so.