Because getting to orbit is only halfway to your final destination?
In contrast, the ICPS will only mass 3.5 tonnes empty, and hold 27 tonnes of propellant.Edit: Which is still not quite enough to send a fully tanked Orion through TLI. That's why the ICPS missions don't go too deep into the Moon's gravity well.
Quote from: ThereIWas3 on 05/25/2017 09:50 pmBecause getting to orbit is only halfway to your final destination?Not if the SLS core alone could do TLI with Orion.
With expanded tankage on the Orion Service Module and a direct ascent, EM-1 could skip the ICPS entirely. So...why?
Though I can see why the ICPS will only ever fly once. It's utterly useless for LEO.
With the current SLS Block 1 configuration, payload to LEO is projected as 70 tonnes. Running the numbers myself with this calculator, I get around 73 tonnes to a standard 185x185, 28.5 degree LEO from the Cape.But if I drop the ICPS entirely, I get 71 tonnes to the same orbit.Apparently, the added mass of the ICPS forces the SLS to climb more slowly, not only increasing gravity drag but keeping the RS-25s in the lower atmosphere and preventing them from reaching full efficiency until later in the ascent.
SLS core carries Orion and ICPS to a 975 nautical miles apogee. ICPS does perigee raise and TLI.Try calculating the highest orbit SLS can bring Orion to without an upper stage...
Quote from: ThereIWas3 on 05/25/2017 09:50 pmBecause getting to orbit is only halfway to your final destination?True as the core stage probably can't even get to escape velocity with no payload as it's dry mass is somewhere around 80 tons. Though I can see SLS being used without an upper stage for some LEO payloads.
Who cares about LEO for SLS?
Try offloading some propellant from ICPS. That might get you even more payload.
I didn't realize that there are literally no planned LEO missions for SLS. All planned missions are BLEO. The 70-130 tonne LEO payload numbers don't actually represent any real missions.
Quote from: sevenperforce on 05/26/2017 04:00 pmI didn't realize that there are literally no planned LEO missions for SLS. All planned missions are BLEO. The 70-130 tonne LEO payload numbers don't actually represent any real missions.Precisely. I would love to see these discussions talk about the real SLS payload number - the payload sent beyond low earth orbit.
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.
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...
{snip}Who cares about LEO for SLS?
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.
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.
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.
Quote from: Lars-J on 05/28/2017 07:38 amQuote 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. No, I think that's what he WAS saying. The SLS was the referent of that pronoun. "Even with (the SLS's) very badly underpowered upper stage, SLS block 1 still has more capacity to LEO."
Quote from: Lars-J on 05/28/2017 07:38 amQuote 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. SLS block 1 uses ICPS, not falcon upper stage. ICPS (with that single 110kN RL-10) is the very badly underpowered upper stage I was talking about.
If I had the SLS budget to play with,
Quote from: sevenperforce on 05/26/2017 04:44 pmIf I had the SLS budget to play with, I have once suggested using SLS cores as space station habitats. Much like the old Space Ilands group.I was told that it won't work for several reasons such as heat management, wet launch complications and performance.But now theres a group that seriously suggests doing that with centaur and got NASA funding to research into that as a possible gateway technology. so maybe it is actually possible with SLS cores?!?Also, there are those who suggest that it is smart to reuse the booster's engine compartment and have suggested applying HIAD and parachute combo to do that.there are those who plan to recover side boosters too (no link needed here)I suggest that there could be a way in which SLS makes sense - that is if it was designed as follows-Two RTLS advanced boostersSMART style reuse for the core's engine compartmentOn orbit recycle of modified O2 and H2 tanks as habitats for a space station.Space station support systems and modules are launched as cargoI don't know if that can eventually become cheaper than full reuse architecture like ITS, but it has a fair chance, if a big space station is one of the goals. That is because a bigger fraction of what is launched to orbit, stays on orbit.
Even if it doesn't wait, the commercial launchers will be flying before SLS.. Really, who's the one waiting here?
Quote from: AncientU on 05/27/2017 11:18 pmConstellation was supposed to have us on the Moon today, too.How's that coming?It was canceled by President Obama. - Ed Kyle
Quote from: hkultala on 05/28/2017 04:05 pmQuote from: Lars-J on 05/28/2017 07:38 amQuote 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. SLS block 1 uses ICPS, not falcon upper stage. ICPS (with that single 110kN RL-10) is the very badly underpowered upper stage I was talking about.Being a big fan of parallel staging, I'd be interested to see the ICPS given an optional 2-engine (or even 4-engine) drop skirt a la Saturn S-1D to increase its payload to LEO. Fixes the underpower problem without increasing dry mass in the BLEO stage.That's if it actually was ever going to be used for LEO. But of course it isn't.
If ULA developed ACES, could this 5.5m upper stage be used on SLS to improve payloads? If so, by how much?
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: edkyle99 on 05/27/2017 10:12 pmSo, 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 KyleNo, NASA should not wait, it should have done the same as with CRS.
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.
Quote from: edkyle99 on 05/27/2017 10:12 pmSo, 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. If SLS was driven by the Cold War or other national imperative, if SLS had a clear exploration goal, deadline, and funding, and if there were not multiple, proven vendors with HLVs coming online in the next half-decade, then yes, NASA should not wait to pursue SLS.But that's not the case. There is no strong exogenous driver for SLS. There is no clear, agreed-to, funded exploration plan. And there are three domestic HLVs from three different vendors close to first flight or under development today (and a fourth ginormous HLV in early design and technology testing). It does not appear that SLS will be operational before or deliver more total tonnage to space over time than these domestic HLVs. But even if that was not the case, the environment is such that a few years of delay or the large opportunity costs imposed by SLS are worth the difference.Good Government 101 tells us that there is a public sector and a private sector and that the government should not try to duplicate in the public sector what industry can deliver from the private sector. National policy should move NASA out of the ETO segment, focus NASA resources on the in-space (transit, EDL, surface) technologies and systems that industry is not pursuing, and leverage and build on the ongoing ETO developments in the private sector.
These are all good points. However, NASA is required by law to build SLS. They are required by law to NOT wait to pursue SLS - it has a specific deadline, which has already passed. And national policy is directed by the President and affirmed and funded by Congress - NASA can only advise both and cannot chose their own way.
National policy should move NASA out of the ETO segment, focus NASA resources on the in-space (transit, EDL, surface) technologies and systems that industry is not pursuing, and leverage and build on the ongoing ETO developments in the private sector.
Good Government 101 tells us that there is a public sector and a private sector and that the government should not try to duplicate in the public sector what industry can deliver from the private sector. National policy should move NASA out of the ETO segment, focus NASA resources on the in-space (transit, EDL, surface) technologies and systems that industry is not pursuing, and leverage and build on the ongoing ETO developments in the private sector.
Quote from: UltraViolet9 on 05/30/2017 08:50 pmGood Government 101 tells us that there is a public sector and a private sector and that the government should not try to duplicate in the public sector what industry can deliver from the private sector. National policy should move NASA out of the ETO segment, focus NASA resources on the in-space (transit, EDL, surface) technologies and systems that industry is not pursuing, and leverage and build on the ongoing ETO developments in the private sector.How long until the same argument is used to say that NASA shouldn't be building any in-space vehicles at all? After all commercial interests might do that on their own as well...
Government helped build the railroads out west by giving land to the railroad companies along the routes.
So, NASA is supposed to just wait for these proposed launch vehicles to finally appear? Falcon Heavy was supposed to fly in 2013. [...] NASA can't wait for promises when it has the propulsion in hand.
Quote from: okan170 on 06/03/2017 03:32 amQuote from: UltraViolet9 on 05/30/2017 08:50 pmGood Government 101 tells us that there is a public sector and a private sector and that the government should not try to duplicate in the public sector what industry can deliver from the private sector. National policy should move NASA out of the ETO segment, focus NASA resources on the in-space (transit, EDL, surface) technologies and systems that industry is not pursuing, and leverage and build on the ongoing ETO developments in the private sector.How long until the same argument is used to say that NASA shouldn't be building any in-space vehicles at all? After all commercial interests might do that on their own as well...Does the US government build cars? Boats? Trains? Aircraft? If not, what makes spacecraft so unique that NASA should build them?(And yes I know that much of the Stuff NASA builds is done through contractors, but for the purposes of this discussion I assume that "NASA builds" means "NASA designs and oversees contractors building it")
The Grumman Long Life Vehicle (LLV) is an American light transport truck. The Grumman LLV was designed as a mail truck for the United States Postal Service, which is its primary user.
Propulsion = SSME of which NASA has 15 in hand. Of course, this is not a significant advantage, since propulsion for at least Falcon Heavy is also in hand. RD-180 and RS-68 are also available, though they and SSME have all outlived their usefulness.
Quote from: envy887 on 06/04/2017 07:21 pmPropulsion = SSME of which NASA has 15 in hand. Of course, this is not a significant advantage, since propulsion for at least Falcon Heavy is also in hand. RD-180 and RS-68 are also available, though they and SSME have all outlived their usefulness.Typo maybe?16 RS25s are available, 14 with flight experience, and 2 new build green engines that haven't even been fired at all, ME2062(built in 2010) ME2063(built in 2015). Both engines are EM-1 contingency engines and are scheduled for primary flight usage on EM-2.
(And yes I know that much of the Stuff NASA builds is done through contractors, but for the purposes of this discussion I assume that "NASA builds" means "NASA designs and oversees contractors building it")
Quote from: Hog on 06/05/2017 01:29 pmQuote from: envy887 on 06/04/2017 07:21 pmPropulsion = SSME of which NASA has 15 in hand. Of course, this is not a significant advantage, since propulsion for at least Falcon Heavy is also in hand. RD-180 and RS-68 are also available, though they and SSME have all outlived their usefulness.Typo maybe?16 RS25s are available, 14 with flight experience, and 2 new build green engines that haven't even been fired at all, ME2062(built in 2010) ME2063(built in 2015). Both engines are EM-1 contingency engines and are scheduled for primary flight usage on EM-2.I thought it was 15, without going to check. Regardless, NASA has sufficient available, but I disagree with NASA's assessment that they are the most expedient propulsion for a new SHLV.
Quote from: envy887 on 06/04/2017 07:21 pmPropulsion = SSME of which NASA has 15 in hand. Of course, this is not a significant advantage, since propulsion for at least Falcon Heavy is also in hand. RD-180 and RS-68 are also available, though they and SSME have all outlived their usefulness.Actually, it is costing them $1.15B for the next 6 engines... not hardly 'in hand' when you have to pay $200M for the next one.
Quote from: edkyle99 on 05/27/2017 10:12 pmSo, NASA is supposed to just wait for these proposed launch vehicles to finally appear? Falcon Heavy was supposed to fly in 2013. [...] NASA can't wait for promises when it has the propulsion in hand.What "propulsion" does NASA have "in hand"? They haven't even figured out how to weld the tanks.Meanwhile, for FH, the actual flight-hardware is in test-firing before final vehicle assembly. It's likely that they'll have at least three FH flights under their belt before SLS flies. And a dozen FH flights before SLS flies a second time. So in what way would NASA be "waiting" for FH, but have SLS "in hand"?
Quote from: Paul451 on 06/04/2017 06:55 pmQuote from: edkyle99 on 05/27/2017 10:12 pmSo, NASA is supposed to just wait for these proposed launch vehicles to finally appear? Falcon Heavy was supposed to fly in 2013. [...] NASA can't wait for promises when it has the propulsion in hand.What "propulsion" does NASA have "in hand"? They haven't even figured out how to weld the tanks.Meanwhile, for FH, the actual flight-hardware is in test-firing before final vehicle assembly. It's likely that they'll have at least three FH flights under their belt before SLS flies. And a dozen FH flights before SLS flies a second time. So in what way would NASA be "waiting" for FH, but have SLS "in hand"?NASA has RS-25 and five-segment booster and RL10 and, for Orion, AJ-10. In-hand.As for Falcon Heavy, there is no waiting. It is not an SLS replacement. The way SpaceX wants to fly it (recovering boosters and first stage) it will barely boost 5.5 tonnes toward the Moon, compared to SLS Block 1's 24.5 tonnes. Even if the entire rocket was thrown away it would not match even SLS Block 1, and would only lift a bit more than half as much as Block 1B's 39 tonnes. The engines for rockets that might one day be SLS class are still in development. - Ed Kyle
The way SpaceX wants to fly it (recovering boosters and first stage) it will barely boost 5.5 tonnes toward the Moon...
As for Falcon Heavy, there is no waiting. It is not an SLS replacement. The way SpaceX wants to fly it (recovering boosters and first stage) it will barely boost 5.5 tonnes toward the Moon, compared to SLS Block 1's 24.5 tonnes. Even if the entire rocket was thrown away it would not match even SLS Block 1, and would only lift a bit more than half as much as Block 1B's 39 tonnes.
Back on topic: With this 'no second stage' SLS, would the first stage then arrive in a stable orbit?
If it does, would it be possible to use it in the same fashion as proposed for Shuttle external tanks -collect them up in orbit and use them as building bricks for a large space station?
Taking a huge assumption that the technical problems of cryogenic on-orbit refueling could be conquered, would there be any advantage to using these things to send hefty payloads around the solar system?
Quote from: tea monster on 06/07/2017 06:58 amBack on topic: With this 'no second stage' SLS, would the first stage then arrive in a stable orbit?It wouldn't arrive in orbit at all. The RS-25's can't restart, so you can't do a circularisation burn. You'd need to add OMS engines to the core to perform the circularisation.
Then there are core disposal issues then
Quote from: Jim on 06/07/2017 03:30 pmThen there are core disposal issues thenIf the payload is capable of doing a circularisation burn then just set it up so the core comes down in the Indian Ocean like the Shuttle ET used to.
Wouldn't that mean the "payload" is the second stage?