Quote from: hkultala on 05/26/2017 05:45 am{snip}Who cares about LEO for SLS?Heavy cargo to LEO is probably the SLS's main market.SLS's payload is too small to send people to Mars on a single launch. A ship yard to build Mars Transfer Vehicles is likely to be in LEO.
{snip}Who cares about LEO for SLS?
Quote from: Coastal Ron on 05/26/2017 05:31 pmQuote from: clongton on 05/26/2017 05:06 pmThe SLS flight avionics are not designed to send a payload into orbit. It is designed to get the upper stage to an optimum altitude, speed and trajectory to finish the job of orbital insertion. To attempt to use the core stage as a SSTO vehicle would require a complete re-write of the software.Not that I'm advocating this should be done, but wouldn't re-writing the software just be on the order of $Millions, not $Billions?And I understand that it's not just one system that would have to be rewritten, but multiple that have to be coordinated. It's just that you'd think the ability to adjust the trajectory would have anticipated the full range of possibilities.Of course if the top-level design spec never called out for that possibility it makes sense to not build it in. Just one of those things that you'd think would not be hard in our modern age of computers...Like I said in another post somewhere, it's not the individual software modules that are difficult - it's the system integration that's hard. individual modules may be beautiful and work exceptionally well but put them all together in a sandbox and they may not play well together. The rocket gods have very weird senses of humor. They like things that cause heartburn.
Quote from: clongton on 05/26/2017 05:06 pmThe SLS flight avionics are not designed to send a payload into orbit. It is designed to get the upper stage to an optimum altitude, speed and trajectory to finish the job of orbital insertion. To attempt to use the core stage as a SSTO vehicle would require a complete re-write of the software.Not that I'm advocating this should be done, but wouldn't re-writing the software just be on the order of $Millions, not $Billions?And I understand that it's not just one system that would have to be rewritten, but multiple that have to be coordinated. It's just that you'd think the ability to adjust the trajectory would have anticipated the full range of possibilities.Of course if the top-level design spec never called out for that possibility it makes sense to not build it in. Just one of those things that you'd think would not be hard in our modern age of computers...
The SLS flight avionics are not designed to send a payload into orbit. It is designed to get the upper stage to an optimum altitude, speed and trajectory to finish the job of orbital insertion. To attempt to use the core stage as a SSTO vehicle would require a complete re-write of the software.
Shouldn't be a show stopper as the Saturn V was altered to fly in two stage configuration to launch Skylab when normally the S-IVB did finial orbital insertion.In fact making a stage and a half SLS should be a lot easier.
Quote from: A_M_Swallow on 05/27/2017 03:26 amQuote from: hkultala on 05/26/2017 05:45 am{snip}Who cares about LEO for SLS?Heavy cargo to LEO is probably the SLS's main market.SLS's payload is too small to send people to Mars on a single launch. A ship yard to build Mars Transfer Vehicles is likely to be in LEO. There aren't going to be any shipyards ala Star Trek. The MTV is going to be a single-piece vehicle sent to the Gateway station is the current plan. It also is going to be solar electric meaning even if the SLS can't deliver it the full distance by itself the MTV is going to spiral itself out.However heavy cargo is indeed going to be SLS' market. Missions to Europa or the Ice Giants benefit as do either space telescopes or the Gateway station, perhaps even commercial variants in LEO. The market for heavy payloads won't have any other launcher for 5-10 years which makes it SLS' golden time regardless of opinion of it.
As well as the manned MTV there is the lander and surface equipment. Likely to be too heavy for even a SLS Block 2
Quote from: A_M_Swallow on 05/27/2017 09:07 pmAs well as the manned MTV there is the lander and surface equipment. Likely to be too heavy for even a SLS Block 2Right. So for any kind of human exploration architecture, SLS is *incapable* of doing it in one launch. There will always be assembly, either in LEO or in a higher orbit. So while 'escape payload capability' is cool and all for robotic missions, it matters little in practice.
Not sure that is correct. By the time SLS Block 1 launches (EM-1, late 2019, or 2020), FH (Block 5+) will probably have more lift capacity and will be cheaper by 5x or so. By the time Block 1B launches (EM-2, 2023?), there will likely be a reusable launcher with greater capability. Block 2 is too far into the future (greater than 10 years) to even imagine SLS still being around.SLS may never be Number One... and at its price point, no one will be able to fly on it except NASA flying US Senate dictated payloads. There will be no Golden Age of SLS.
If SLS had gone the route of Direct with plumbing for 5 engines, but use 3 engines on block 1, it would have gotten 70 tons to LEO. Then add the two other engines, with a single engine J2X and get 130 tons. Then add the new Black Knight boosters and get maybe 140-145 tons. I do not understand why they went with 4 engines on the core. I think it was a permanent compromise not using neither 3 or 5. Direct with and evolving future upgrades would already be flying. Any Martian trip will either involve in space assembly, which could be done with cheaper rockets, or like SpaceX's approach, big ship and in orbit refueling. Both involve rendeveau and docking. Cheaper rockets win out.
Quote from: spacenut on 05/27/2017 09:49 pmIf SLS had gone the route of Direct with plumbing for 5 engines, but use 3 engines on block 1, it would have gotten 70 tons to LEO. Then add the two other engines, with a single engine J2X and get 130 tons. Then add the new Black Knight boosters and get maybe 140-145 tons. I do not understand why they went with 4 engines on the core. I think it was a permanent compromise not using neither 3 or 5. Direct with and evolving future upgrades would already be flying. Any Martian trip will either involve in space assembly, which could be done with cheaper rockets, or like SpaceX's approach, big ship and in orbit refueling. Both involve rendeveau and docking. Cheaper rockets win out. As the ISS showed constructing spacecraft using say 10 tonne modules requires space walks to join wires and pipes together. I do not know I EVA still cost $1,000,000 an hour but they quickly get expensive. Showing small rockets actually reduces the total price requires a full cost cost trade.
Constellation was supposed to have us on the Moon today, too.How's that coming?
Quote from: AncientU on 05/27/2017 06:43 pmNot sure that is correct. By the time SLS Block 1 launches (EM-1, late 2019, or 2020), FH (Block 5+) will probably have more lift capacity and will be cheaper by 5x or so. By the time Block 1B launches (EM-2, 2023?), there will likely be a reusable launcher with greater capability. Block 2 is too far into the future (greater than 10 years) to even imagine SLS still being around.SLS may never be Number One... and at its price point, no one will be able to fly on it except NASA flying US Senate dictated payloads. There will be no Golden Age of SLS.So, NASA is supposed to just wait for these proposed launch vehicles to finally appear? Falcon Heavy was supposed to fly in 2013. We still haven't seen this rocket and now it seems we won't see it until next year. When we finally do see it, it still won't match SLS. The company developing Falcon Heavy has suffered two big rocket explosions during the past two years. Is NASA supposed to stop what it is doing and simply trust that SpaceX, Blue Origin (which recently suffered an engine test failure), and the like will actually succeed on their announced schedules, even though they are doing everything for the first time? NASA can't wait for promises when it has the propulsion in hand. The others may eventually catch up - I hope they do - but there is no need to wait for them. - Ed Kyle
Quote from: redliox on 05/27/2017 04:00 amQuote from: A_M_Swallow on 05/27/2017 03:26 amQuote from: hkultala on 05/26/2017 05:45 am{snip}Who cares about LEO for SLS?Heavy cargo to LEO is probably the SLS's main market.SLS's payload is too small to send people to Mars on a single launch. A ship yard to build Mars Transfer Vehicles is likely to be in LEO. There aren't going to be any shipyards ala Star Trek. The MTV is going to be a single-piece vehicle sent to the Gateway station is the current plan. It also is going to be solar electric meaning even if the SLS can't deliver it the full distance by itself the MTV is going to spiral itself out.However heavy cargo is indeed going to be SLS' market. Missions to Europa or the Ice Giants benefit as do either space telescopes or the Gateway station, perhaps even commercial variants in LEO. The market for heavy payloads won't have any other launcher for 5-10 years which makes it SLS' golden time regardless of opinion of it.Not sure that is correct. By the time SLS Block 1 launches (EM-1, late 2019, or 2020), FH (Block 5+) will probably have more lift capacity and will be cheaper by 5x or so.
By the time Block 1B launches (EM-2, 2023?), there will likely be a reusable launcher with greater capability.
FH(block 5) has capacity of 63.8 tonnes to LEO, and it's quite LEO optimized-launcher.Even with the very badly underpowered upper stage that makes it very bad for LEO maximum payload, SLS block 1 still has more capacity to LEO, payload to higher orbits where the (lack of) thrust in the US means less is much more than with FH.
Quote from: AncientU on 05/27/2017 06:43 pm By the time Block 1B launches (EM-2, 2023?), there will likely be a reusable launcher with greater capability.New Glenn? ITS/BFR? New ArmstrongNew Glenn won't outperform SLS (block1) to anything higher than LEO.ITS/BFR and New Armstrong will have higher payload than SLS but the question is when they are ready.
Quote from: hkultala on 05/28/2017 06:43 amFH(block 5) has capacity of 63.8 tonnes to LEO, and it's quite LEO optimized-launcher.Even with the very badly underpowered upper stage that makes it very bad for LEO maximum payload, SLS block 1 still has more capacity to LEO, payload to higher orbits where the (lack of) thrust in the US means less is much more than with FH.I get what you mean as far as upper stage efficiency... But very badly underpowered is a very poor choice of words. The M1D-Vac (full thrust) is around 8.5 times more powerful than the most powerful RL-10 ever flown. So even with 4 RL-10 on the EUS, the F9 upper stage has more than twice the thrust.