Musk has stated many times now that he wants to retire the Falcons and Dragons as soon as possible. Does it make sense for NASA to start a BEO exploration program when the vendor wants to retire their product in 5 or so years? At this point the first question any proposed exploration program needs to ask is will the BRF happen? If the answer is no then the Falcon Heavy and maybe SLS likely do have an important role to play.Lets imagine that BFR is successful and everything that SpaceX is promising with it. It would be better for NASA to wait for that to come online and buy it off the shelf. While a payload meant for the Falcon Heavy could launch on the BFR it would be underutilizing the capability of the BFR. Imagine if NASA contracted to have a Moon lander launched on the Falcon Heavy. I doubt a lander could be made and ready to launch before the BFR, if it shows up when Musk is proposing. It would be a funny situation for the BFR to be launching a moon lander while itself being capable of landing on the moon because NASA contacted another company to build the lander.
Quote from: drunyan8315 on 02/07/2018 09:39 pmHow can one discuss the relative merits of two rocket systems without acknowledging that one is throwaway and the other is reusable? The first SLS is going to go up in 4-5 years and then... it will be vaporized. Then you get to build another one.Any Falcon Heavy lifting a heavy payload is also throwaway. And that'll be most of them, given that F9 can loft most commercial satellites.
How can one discuss the relative merits of two rocket systems without acknowledging that one is throwaway and the other is reusable? The first SLS is going to go up in 4-5 years and then... it will be vaporized. Then you get to build another one.
Quote from: Robotbeat on 02/09/2018 01:06 amYou're relying on figures from the KSC ELV performance page, which has figures that are years out of date. For instance, FH can do about 16 tons through trans Mars insertion, which is about c3= 7km^2/s^2 on an *exceptionally* good opportunity. According to KSC's page, FH can only do 10t. So for high energy trajectories, FH can do about 60% better than the KSC page suggests.No, I didn't use the KSC page. I have expendable Falcon Heavy at 16.8 tonnes TMI. SLS Block 1 would be 19+ tonnes, but of course it is only going to fly one trans-lunar mission. For TLI, I show expendable Falcon Heavy at 20+ tonnes and SLS Block 1 at 24.5 tonnes.The real comparison is with SLS Block 1B, which is expected to be 32 and 39 tonnes to TMI/TLI, respectfully. - Ed Kyle
You're relying on figures from the KSC ELV performance page, which has figures that are years out of date. For instance, FH can do about 16 tons through trans Mars insertion, which is about c3= 7km^2/s^2 on an *exceptionally* good opportunity. According to KSC's page, FH can only do 10t. So for high energy trajectories, FH can do about 60% better than the KSC page suggests.
... so multiple expended Falcon Heavies would be needed. These expendable versions are going to cost substantially more than the numbers everyone sees on the SpaceX web site.
...It doesn't matter what the throw-weight is of the SLS or any other launch system, it only matters how they are used. For instance, there are really two approaches to doing human space exploration:A. Single-launch architectures, which is what Apollo used and what the SLS is.B. Multi-launch architectures, which allows many launch systems to be used.For single-launch architectures the limitation is that you get diminishing returns the farther out you go, so in reality our Moon is the furthest NASA could go with humans. That was how far Apollo went, and the SLS is about the same as the Saturn V.
...The best way forward is to allow many launch vehicles to participate in expanding humanity out into space, and use a launch architecture that embraces that.My $0.02
The Orion Spacecraft would launch on the second Falcon Heavy after the Lander was in Lunar orbit. The Orion would make a rendezvous with the Lander, dock, transfer crew.
Don't go into *Low* lunar orbit but instead an elliptical orbit. Way less delta-V to enter and leave. Solves a whole bunch of problems and makes logistics by a whole range of rockets easier.
Orion SM has enough ΔV only for TEI, not enough for both LOI and TEI. FH-US cannot remain in standby mode for three days waiting to perform a LOI burn. How would you get the Orion into Lunar orbit and still have enough prop for TEI? You need aux tanks on SM or a small kick stage for LOI. Alternately, you use a lighter D2, but then you need a far more robust SM that can provide ΔV for both burns and ECLSS for 3 weeks.
Dr Steve; in a 2x launch scenario where an expendable Falcon 9 launches a 23 ton, hypergolically fueled Lander into LEO, then a Falcon Heavy places an upper stage with a docking collar and plenty of propellants nearby, they dock and go TLI... Would that Lander have enough delta-v to insert itself into low lunar orbit, or would the Falcon upper stage have to do it?
I've been wondering if the Falcon stage would need extensive modifications to last a three day coast to the Moon, or would the Lander have to use 6-to-8 tons of it's propellant load for lunar orbit insertion?
Quote from: Robotbeat on 02/10/2018 03:52 amDon't go into *Low* lunar orbit but instead an elliptical orbit. Way less delta-V to enter and leave. Solves a whole bunch of problems and makes logistics by a whole range of rockets easier.Does an elliptical orbit result in spacecraft having to use instantaneous launches due to tiny windows?
Quote from: edkyle99 on 02/09/2018 02:22 pmQuote from: Robotbeat on 02/09/2018 01:06 amYou're relying on figures from the KSC ELV performance page, which has figures that are years out of date. For instance, FH can do about 16 tons through trans Mars insertion, which is about c3= 7km^2/s^2 on an *exceptionally* good opportunity. According to KSC's page, FH can only do 10t. So for high energy trajectories, FH can do about 60% better than the KSC page suggests.No, I didn't use the KSC page. I have expendable Falcon Heavy at 16.8 tonnes TMI. SLS Block 1 would be 19+ tonnes, but of course it is only going to fly one trans-lunar mission. For TLI, I show expendable Falcon Heavy at 20+ tonnes and SLS Block 1 at 24.5 tonnes.The real comparison is with SLS Block 1B, which is expected to be 32 and 39 tonnes to TMI/TLI, respectfully. - Ed KyleYour FHR payloads for TLI/TMI are probably a bit underestimated. Musk said they could possibly recover all three boosters after sending Red Dragon (which between Dragon itself and the landing propellants would be at least 10 tonnes) to TMI. That is equivalent to nearly triple the 5500 kg you have for TLI.https://twitter.com/elonmusk/status/726820238361120768
On this occasion, as I have suggested recently, this would be 1x Falcon 9 and 1x Falcon Heavy used to transport a 20+plus ton spacecraft to lunar orbit. Sort of like the '1.5 launch' Constellation architecture. I was also recently curious about whether 2x Falcon 9s could accomplish the circumlunar tourist flight - I wondered if the expendable F9 block 5 would place enough propellants into LEO for a Dragon 2 to come long, dock with it and be on its way.
Quote from: A_M_Swallow on 02/10/2018 05:54 amQuote from: Robotbeat on 02/10/2018 03:52 amDon't go into *Low* lunar orbit but instead an elliptical orbit. Way less delta-V to enter and leave. Solves a whole bunch of problems and makes logistics by a whole range of rockets easier.Does an elliptical orbit result in spacecraft having to use instantaneous launches due to tiny windows?I don't think the windows are excessively short. The problem I see is that an efficient TEI burn must take place at perilune and on the far side of the moon. So it seems to me that an elliptical orbit leaves you with departure windows only once a month. You could move perilune, but that takes delta-V. Am I missing something?
Quote from: envy887 on 02/09/2018 08:05 pmQuote from: edkyle99 on 02/09/2018 02:22 pmQuote from: Robotbeat on 02/09/2018 01:06 amYou're relying on figures from the KSC ELV performance page, which has figures that are years out of date. For instance, FH can do about 16 tons through trans Mars insertion, which is about c3= 7km^2/s^2 on an *exceptionally* good opportunity. According to KSC's page, FH can only do 10t. So for high energy trajectories, FH can do about 60% better than the KSC page suggests.No, I didn't use the KSC page. I have expendable Falcon Heavy at 16.8 tonnes TMI. SLS Block 1 would be 19+ tonnes, but of course it is only going to fly one trans-lunar mission. For TLI, I show expendable Falcon Heavy at 20+ tonnes and SLS Block 1 at 24.5 tonnes.The real comparison is with SLS Block 1B, which is expected to be 32 and 39 tonnes to TMI/TLI, respectfully. - Ed KyleYour FHR payloads for TLI/TMI are probably a bit underestimated. Musk said they could possibly recover all three boosters after sending Red Dragon (which between Dragon itself and the landing propellants would be at least 10 tonnes) to TMI. That is equivalent to nearly triple the 5500 kg you have for TLI.https://twitter.com/elonmusk/status/726820238361120768With Reuse, FH is listed as 8 mT to GTO. How does it send 10 mT to Mars?see:http://www.spacex.com/about/capabilitiesFalcon 9 price is listed as 5.5 mT which lines up with stage re-use. The line for FH right next to it is likely the same.
How does it work in NASA - does the top mandate the launch vehicle for every mission?