Author Topic: SLS: Higher payload without second stage  (Read 14267 times)

Offline sevenperforce

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SLS: Higher payload without second stage
« on: 05/25/2017 09:25 PM »
I was running some numbers today and I came across something that I can only describe as startling.

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.

Why on earth would the SLS use a second stage when it doesn't actually meaningfully increase payload? I mean, I get that the RS-25s can't restart, but still....

Offline ThereIWas3

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Re: SLS: Higher payload without second stage
« Reply #1 on: 05/25/2017 09:50 PM »
Because getting to orbit is only halfway to your final destination?
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Offline sevenperforce

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Re: SLS: Higher payload without second stage
« Reply #2 on: 05/25/2017 10:01 PM »
Because 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.

Offline kkattula

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Re: SLS: Higher payload without second stage
« Reply #3 on: 05/25/2017 10:08 PM »
Because the ICPS is not intended for LEO payloads? 

Re-start aside, trying to push a nearly empty, but still heavy, core through TLI would be grossly inefficient. In fact if that whole 70 tonnes was propellant it wouldn't quite be enough to send the 85 tonne core through TLI.

Offline kkattula

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Re: SLS: Higher payload without second stage
« Reply #4 on: 05/25/2017 10:12 PM »
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.
« Last Edit: 05/25/2017 10:37 PM by kkattula »

Offline sevenperforce

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Re: SLS: Higher payload without second stage
« Reply #5 on: 05/25/2017 10:40 PM »
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.
*ICPS mission

Online envy887

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Re: SLS: Higher payload without second stage
« Reply #6 on: 05/26/2017 01:22 AM »
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...

Offline Patchouli

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Re: SLS: Higher payload without second stage
« Reply #7 on: 05/26/2017 04:38 AM »
Because 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.
« Last Edit: 05/26/2017 04:39 AM by Patchouli »

Offline redliox

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Re: SLS: Higher payload without second stage
« Reply #8 on: 05/26/2017 05:22 AM »
There's always the weight of added equipment that factors in and such, so I'm not completely surprised.  However, the only way I could see anyone benefiting from those numbers is if you create a vehicle akin to SpaceX's ITS design.  Bear in mind, I'm not fanboying SpaceX here, I'm simply stating if you're wanting to create something efficient we're talking incorporating the 2nd stage into the payload you wish to deliver.  I'm certain Blue Origins, ULA, and Orbital ATK, and Sierra Nevada could all do this easily.  Heck, I'd even suggest using this logic as a basis for nixing the Orion and opening up a slot for a better vehicle that still rides the SLS.

I don't think anyone aiming to deliver a straightforward satellite or probe would not utilize a disposable 2nd or 3rd stage, but then again the SLS is meant more for HSF and the sporadic flagship probe.
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Offline hkultala

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Re: SLS: Higher payload without second stage
« Reply #9 on: 05/26/2017 05:45 AM »
Because getting to orbit is only halfway to your final destination?
Not if the SLS core alone could do TLI with Orion.

It could not.

Without the upper stage, the payload capacity drops terribly when going to anything higher than LEO.

The upper stage is like a space tug, for going from almost-LEO to the destination trajectory.

Quote
With expanded tankage on the Orion Service Module and a direct ascent, EM-1 could skip the ICPS entirely. So...why?

To get to the trajectory needed by the mission. The core stage cannot do that,.

Quote
Though I can see why the ICPS will only ever fly once. It's utterly useless for LEO.

Who cares about LEO for SLS?

Online Steven Pietrobon

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Re: SLS: Higher payload without second stage
« Reply #10 on: 05/26/2017 07:48 AM »
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.

Try offloading some propellant from ICPS. That might get you even more payload.
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Offline sevenperforce

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Re: SLS: Higher payload without second stage
« Reply #11 on: 05/26/2017 04:00 PM »
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...
Hmm. Ran the numbers. Looks like the SLS core could send Orion to about 16,500 km, best-case scenario. So yeah, this makes sense.

I think my confusion was because I had erroneously assumed Block 1 would fly ordinary LEO missions. Block 1 with ICPS only has one mission, EM-1, and on that mission the ICPS is essentially part of the payload to LEO (ICPS + Orion + SM is only 57 tonnes). It's just a coincidence that the ICPS's very low TWR (0.2 gees at staging) means it itself could only lift about 70 tonnes to LEO if used as part of the LEO lift vehicle rather than the BLEO injection stage.

Because 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.
Yeah, by my numbers the core stage can manage an apogee of about 105,000 km without payload.

And SLS sans upper stage for LEO was the DIRECT plan, IIRC.

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.

Offline edkyle99

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Re: SLS: Higher payload without second stage
« Reply #12 on: 05/26/2017 04:20 PM »
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.
Precisely.  I would love to see these discussions talk about the real SLS payload number - the payload sent beyond low earth orbit.

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Offline sevenperforce

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Re: SLS: Higher payload without second stage
« Reply #13 on: 05/26/2017 04:44 PM »
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.
Precisely.  I would love to see these discussions talk about the real SLS payload number - the payload sent beyond low earth orbit.
Personally, I loathe the idea of ginormous flagship missions. That was necessary with Apollo, when we lacked the ability to sustain high launch cadence and reliable orbital rendezvous, but those are solved problems now. Assemble in LEO and then go to wherever you want to go.

If I had the SLS budget to play with, I'd say to make it do one thing and one thing only: launch a single-engine high-energy propulsion bus with onboard gaseous biprop RCS and solar-powered cooling system, with side-mounted automated coupling ports. Contract with commercial providers to launch the actual mission spacecraft and then use the SLS bus to send it wherever you want it to go. Your payload too large for one propulsion bus? Launch two of them and couple them side-to-side. In other words, Kerbal the hell out of it.
« Last Edit: 05/26/2017 04:47 PM by sevenperforce »

Offline clongton

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Re: SLS: Higher payload without second stage
« Reply #14 on: 05/26/2017 05:06 PM »
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.
« Last Edit: 05/26/2017 05:07 PM by clongton »
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Re: SLS: Higher payload without second stage
« Reply #15 on: 05/26/2017 05:31 PM »
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.

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...
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Offline sevenperforce

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Re: SLS: Higher payload without second stage
« Reply #16 on: 05/26/2017 05:53 PM »
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.
Presumably, even SSTO launches would leave the perigee low enough that it would re-enter nominally; the payload could self-circularize.

Offline clongton

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Re: SLS: Higher payload without second stage
« Reply #17 on: 05/26/2017 05:54 PM »
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.

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.
« Last Edit: 05/26/2017 05:56 PM by clongton »
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Offline sevenperforce

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Re: SLS: Higher payload without second stage
« Reply #18 on: 05/26/2017 09:07 PM »
I was thinking about the SLS, particularly the high dry mass of the core in comparison to the dry mass of the Space Shuttle External Tank, and it reminded me of the Saturn S-1D proposal. You know, use the Saturn V first stage as an SSTO, but place the four external engines on a jettisonable launch skirt that is dropped at 70% propellant consumption.

Five RS-25s is not enough to get a full SLS core off the ground, but six would do the trick.

If the heavy SLS core thrust structure (which I'm estimating at around 30 tonnes) was redesigned as a toroidal, jettisonable skirt that clamped around two additional RS-25s mounted to the base of the tank, and launched without SRBs, then jettisoning the skirt at 68% propellant consumption would allow the core engines + tank to deliver up to 50.6 tonnes to a nominal low earth orbit. That's pretty respectable, and it would be able to deliver ICPS+Orion+SM to the planned EM-1 staging altitude and velocity without needing any SRBs at all.

With SRBs added back on, it would be able to deliver up to 112 tonnes to LEO, more than SLS Block 1B can deliver with the EUS.
« Last Edit: 05/26/2017 09:08 PM by sevenperforce »

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Re: SLS: Higher payload without second stage
« Reply #19 on: 05/27/2017 03:26 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. Boots and flags to the Moon on an expendable lander is a very small market.

Offline redliox

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Re: SLS: Higher payload without second stage
« Reply #20 on: 05/27/2017 04:00 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.
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Offline Patchouli

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Re: SLS: Higher payload without second stage
« Reply #21 on: 05/27/2017 04:20 AM »
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.

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.
« Last Edit: 05/27/2017 04:24 AM by Patchouli »

Offline TomH

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Re: SLS: Higher payload without second stage
« Reply #22 on: 05/27/2017 05:30 AM »
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.

IIRC, the controller stayed in the same location, on top of the S-IVB, which in this case had been converted into the Skylab. In the case of flying SLS with no US, the controller has to be relocated.

Online AncientU

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Re: SLS: Higher payload without second stage
« Reply #23 on: 05/27/2017 06:43 PM »
{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.  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.
« Last Edit: 05/27/2017 06:46 PM by AncientU »
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Re: SLS: Higher payload without second stage
« Reply #24 on: 05/27/2017 09:07 PM »
{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

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Re: SLS: Higher payload without second stage
« Reply #25 on: 05/27/2017 09:27 PM »
As well as the manned MTV there is the lander and surface equipment. Likely to be too heavy for even a SLS Block 2

Right. 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.

Offline sevenperforce

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Re: SLS: Higher payload without second stage
« Reply #26 on: 05/27/2017 09:42 PM »
As well as the manned MTV there is the lander and surface equipment. Likely to be too heavy for even a SLS Block 2

Right. 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.
Why not just have SLS launch an autonomous, automatically cooled, rendezvous-and-docking capable hydrolox propulsion bus? Then let it rendezvous with whatever actual mission spacecraft is needed, which can be launched commercially.

Offline spacenut

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Re: SLS: Higher payload without second stage
« Reply #27 on: 05/27/2017 09:49 PM »
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. 

Offline edkyle99

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Re: SLS: Higher payload without second stage
« Reply #28 on: 05/27/2017 10:12 PM »
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.
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
« Last Edit: 05/27/2017 10:21 PM by edkyle99 »

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Re: SLS: Higher payload without second stage
« Reply #29 on: 05/27/2017 11:18 PM »
Constellation was supposed to have us on the Moon today, too.
How's that coming?
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Re: SLS: Higher payload without second stage
« Reply #30 on: 05/28/2017 12:19 AM »
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. 

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.

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Re: SLS: Higher payload without second stage
« Reply #31 on: 05/28/2017 12:33 AM »
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. 

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.

The Russians have been building space stations without EVA for a long time.

ISS was built with EVAs because the Shuttle HAD to have crew and had the capability to support EVA.

It does not follow that using EELV class vehicles with automated assembly would not be cheaper than SLS.
« Last Edit: 05/28/2017 12:34 AM by envy887 »

Offline MATTBLAK

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Re: SLS: Higher payload without second stage
« Reply #32 on: 05/28/2017 12:50 AM »
Constellation was supposed to have us on the Moon today, too.
How's that coming?
No - by 2020 was supposed to be the first landing. But with the low funding it was allocated, it would have been a half-decade or more later than that :(
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Re: SLS: Higher payload without second stage
« Reply #33 on: 05/28/2017 03:25 AM »
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.
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.

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Even if it doesn't wait, the commercial launchers will be flying before SLS..  Really, who's the one waiting here?
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Offline TomH

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Re: SLS: Higher payload without second stage
« Reply #34 on: 05/28/2017 04:14 AM »
As well as the manned MTV there is the lander and surface equipment. Likely to be too heavy for even a SLS Block 2

Right. 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.

B  I  N  G  O! This is part of what disturbs me when SLS is advertised as the most powerful launch vehicle ever. Sure the raw thrust of the boosters is high, but they are heavy with low initial T/W and higher gravity losses. The KeroLox ISP-Density was superior. Taking those factors into consideration, Saturn V was a more capable launcher than SLS. For those who wanted legacy hardware, there was an older legacy that was superior.
« Last Edit: 05/28/2017 04:19 AM by TomH »

Offline hkultala

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Re: SLS: Higher payload without second stage
« Reply #35 on: 05/28/2017 06:43 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.


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.

FH would need quite a long tank stretch to even reach LEO payload of SLS, and for the interesting higher orbits, no tank stretch on FH is going to get it near SLS.

Quote
  By the time Block 1B launches (EM-2, 2023?), there will likely be a reusable launcher with greater capability.

New Glenn? ITS/BFR? New Armstrong

New 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.

Online Lars-J

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Re: SLS: Higher payload without second stage
« Reply #36 on: 05/28/2017 07:38 AM »
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.

I get what you mean as far as upper stage efficiency... But very badly underpowered is a very poor choice of words.   ;D

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.  8)

Online envy887

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Re: SLS: Higher payload without second stage
« Reply #37 on: 05/28/2017 01:56 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 Armstrong

New 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.
The first heavy lift vehicle with a refuelable upper stage will be able to send more mass to high orbits than SLS.
That could be Vulcan-ACES, or ITS which we know are under development. Or a Raptor upper stage on FH or ITS derived vehicle which could still fly before 2022.
« Last Edit: 05/28/2017 02:29 PM by envy887 »

Offline sevenperforce

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Re: SLS: Higher payload without second stage
« Reply #38 on: 05/28/2017 02:08 PM »
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.

I get what you mean as far as upper stage efficiency... But very badly underpowered is a very poor choice of words.   ;D

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.  8)
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."

Offline hkultala

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Re: SLS: Higher payload without second stage
« Reply #39 on: 05/28/2017 04:05 PM »
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.

I get what you mean as far as upper stage efficiency... But very badly underpowered is a very poor choice of words.   ;D

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.  8)



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.





« Last Edit: 05/28/2017 04:07 PM by hkultala »

Online Lars-J

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Re: SLS: Higher payload without second stage
« Reply #40 on: 05/28/2017 06:28 PM »
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.

I get what you mean as far as upper stage efficiency... But very badly underpowered is a very poor choice of words.   ;D

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.  8)
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."

Yes, you are right, so much for my reading ability. :)

Offline sevenperforce

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Re: SLS: Higher payload without second stage
« Reply #41 on: 05/28/2017 06:34 PM »
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.

I get what you mean as far as upper stage efficiency... But very badly underpowered is a very poor choice of words.   ;D

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.  8)



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.

Offline dror

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Re: SLS: Higher payload without second stage
« Reply #42 on: 05/28/2017 06:52 PM »

If 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 boosters
SMART style reuse for the core's engine compartment
On orbit recycle of modified O2 and H2 tanks as habitats for a space station.
Space station support systems and modules are launched as cargo

I 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.

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Offline Ictogan

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Re: SLS: Higher payload without second stage
« Reply #43 on: 05/28/2017 09:04 PM »

If 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 boosters
SMART style reuse for the core's engine compartment
On orbit recycle of modified O2 and H2 tanks as habitats for a space station.
Space station support systems and modules are launched as cargo

I 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.
Reuse only ever makes sense if high flight rates can be anticipated, which simply isn't the case for SLS. Reusing SLS would probably end up as cost effective as reusing the shuttle was.

Offline edkyle99

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Re: SLS: Higher payload without second stage
« Reply #44 on: 05/30/2017 12:20 AM »
Constellation was supposed to have us on the Moon today, too.
How's that coming?
It was canceled by President Obama.

 - Ed Kyle

Offline edkyle99

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Re: SLS: Higher payload without second stage
« Reply #45 on: 05/30/2017 12:23 AM »
Even if it doesn't wait, the commercial launchers will be flying before SLS..  Really, who's the one waiting here?
Which commercial launchers are you describing?  I can't think of any that will out-lift SLS that will be ready before SLS flies.

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Online Lars-J

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Re: SLS: Higher payload without second stage
« Reply #46 on: 05/30/2017 01:06 AM »
Constellation was supposed to have us on the Moon today, too.
How's that coming?
It was canceled by President Obama.

 - Ed Kyle

I think you missed his point. You write that we cannot rely on SpaceX, because of possible schedule and technical issues. But the same is valid for SLS. We are seeing schedule issues. And technical issues. AND... As you point out, also *political* issues. Trump could easily kill SLS if he point his mind to it. Any future president could so the same.

So we can count on neither. So planning any future human space exploration is fraught with these issues. But they are a fact of life, and are not a reason to dismiss SpaceX (or NASA) in an conversation.
« Last Edit: 05/30/2017 01:07 AM by Lars-J »

Offline hkultala

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Re: SLS: Higher payload without second stage
« Reply #47 on: 05/30/2017 01:44 AM »
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.

I get what you mean as far as upper stage efficiency... But very badly underpowered is a very poor choice of words.   ;D

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.  8)



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.

2 RL-10' weight about 550 kg's together.

Absolutely no sense at all to add all that complexity and risks of the separation mechanism etc to save this, and have  the extra weigth of the separation mechanism for the first part of the flight.

Instead of adding that drop skirt, just add those two extra engines in fixed installation. But then it also makes sense to have bigger tanks etc.

So, absolutely no point of "trying to improve ICPS", instead switch to much better US totally. Like EUS
« Last Edit: 05/30/2017 01:45 AM by hkultala »

Offline spacenut

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Re: SLS: Higher payload without second stage
« Reply #48 on: 05/30/2017 03:02 AM »
If ULA developed ACES, could this 5.5m upper stage be used on SLS to improve payloads?  If so, by how much?

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Re: SLS: Higher payload without second stage
« Reply #49 on: 05/30/2017 03:23 AM »
If ULA developed ACES, could this 5.5m upper stage be used on SLS to improve payloads?  If so, by how much?

LEO capacity would increase considerably, and might be almost equals to SLS with EUS, as ACES has less fuel but it's lighter.

For BLEO, still considerable increase, but would leave more behind EUS as the amount of propellant would start to matter more.

Offline IRobot

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Re: SLS: Higher payload without second stage
« Reply #50 on: 05/30/2017 09:59 AM »
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
No, NASA should not wait, it should have done the same as with CRS.

Offline woods170

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Re: SLS: Higher payload without second stage
« Reply #51 on: 05/30/2017 11:31 AM »
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
No, NASA should not wait, it should have done the same as with CRS.
More specifically: COTS.
Issue the requirements for the required transportation services thru RPF's and let industry come up with solution-proposals.
As it was however, NASA was not allowed to do so by US Congress. NASA was ordered into using SSME's and SRB's by the folks from the Hill. SLS is not nick-named "Senate Launch System" for nothing.

Offline UltraViolet9

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Re: SLS: Higher payload without second stage
« Reply #52 on: 05/30/2017 08:50 PM »
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.

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.


Online envy887

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Re: SLS: Higher payload without second stage
« Reply #53 on: 05/30/2017 09:23 PM »
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.

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.

Offline UltraViolet9

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Re: SLS: Higher payload without second stage
« Reply #54 on: 05/30/2017 10:31 PM »
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.

Agreed for the most part.  That's why I wrote:

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.

That said, the NASA Administrator has an important role to play in setting Administration policy and informing Congressional law.  At the end of the day, the NASA Administrator works for the White House within the limits set by the Congress.  But with the right leadership, NASA could begin moving the nation in this direction.


Offline okan170

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Re: SLS: Higher payload without second stage
« Reply #55 on: 06/03/2017 03:32 AM »
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.

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...
« Last Edit: 06/03/2017 07:08 AM by okan170 »

Online envy887

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Re: SLS: Higher payload without second stage
« Reply #56 on: 06/03/2017 12:39 PM »
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.

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...

I would already argue NASA should support a commercial vehicle to replace Orion.

Offline spacenut

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Re: SLS: Higher payload without second stage
« Reply #57 on: 06/03/2017 02:00 PM »
Government helped build the railroads out west by giving land to the railroad companies along the routes.  Then the government backed off.  Same with space.  Government once built and developed every rocket (1950's 1960's).  Today building rockets is mostly in private hands.  Now they should develop deep space probes and habitats, fuel depots, etc, and bid the launches of the equipment.  Once an in space commerce has begun, then they can back off that. 

I think they should look at the assets they have, and form a committee of the various space vendors.  This committee should as a group design a Mars colony system, or even a moon colony system that can involve the most vendors, and then let NASA direct it, and begin building it.  If it uses SLS, good, if not, other launchers can participate. 

Offline TomH

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Re: SLS: Higher payload without second stage
« Reply #58 on: 06/03/2017 08:35 PM »
Government helped build the railroads out west by giving land to the railroad companies along the routes.

True, but they also gave cash subsidies.

Online Lars-J

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Re: SLS: Higher payload without second stage
« Reply #59 on: 06/04/2017 06:24 AM »
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.

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")

Offline spacenut

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Re: SLS: Higher payload without second stage
« Reply #60 on: 06/04/2017 02:47 PM »
Yes, NASA builds means NASA designs and oversees contractors.  However, highways, ports, canals, airports, etc are built by the government (overseeing contractors).  They do not build the trucks, cars, ships (except navy vessels, then with contractors), nor railroad locomotives, cargo cars, or planes. 

Notice, it is the transportation infrastructure they build and maintain.  Ok, so NASA should concentrate on communication satellites between Earth and Mars, Earth and the moon.  They should build in space fuel depots, maybe even Mars cyclers like a bus route between Earth and Mars.  Private companies and/or other earth nations can take advantage of this and build moon mining bases, Mars colonies, in space manufacturing.  NASA should also construct an artificial gravity space station (maybe in conjunction with a fuel depot) in order to experiment with long term effects of moon or Mars gravity. 

If SLS can help build these, good, but it will be expensive.  Hopefully they can do something to get SLS costs down.  Otherwise, they should pay or partly pay for others to build, like COTS.  They do however need to standardize all connections, fuel, docking, etc.  All railroads are standard guage.  All home building materials are standard sizes like doors, windows, studs, joists, plumbing, etc. 
« Last Edit: 06/04/2017 02:48 PM by spacenut »

Offline Paul451

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Re: SLS: Higher payload without second stage
« Reply #61 on: 06/04/2017 06:55 PM »
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.

{sigh} These threads wouldn't keep getting swamped with SpaceX arguments if people wouldn't keep repeating the same nonsense.

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"?
« Last Edit: 06/04/2017 06:56 PM by Paul451 »

Offline spacenut

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Re: SLS: Higher payload without second stage
« Reply #62 on: 06/04/2017 07:04 PM »
This is why I think with FH coming on line and BO with New Glenn in a couple of years.  Both doing 40 tons reusable.  IF NASA concentrated on building a fuel depot.  Both their 2nd or 3rd stages could do a lot of tonnage to deep space.

Online envy887

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Re: SLS: Higher payload without second stage
« Reply #63 on: 06/04/2017 07:21 PM »
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.

Offline ncb1397

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Re: SLS: Higher payload without second stage
« Reply #64 on: 06/04/2017 07:45 PM »
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.

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")

https://en.wikipedia.org/wiki/List_of_currently_active_United_States_military_land_vehicles
https://en.wikipedia.org/wiki/List_of_active_United_States_military_aircraft
https://en.wikipedia.org/wiki/List_of_current_ships_of_the_United_States_Navy

Quote
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.
https://en.wikipedia.org/wiki/Grumman_LLV

NASA owns some RQ-4 globalhawks, full list here:

https://en.wikipedia.org/wiki/List_of_NASA_aircraft

Really, the argument is that the U.S. government can't design, build, own or operate space vehicles since SLS is not exactly built by NASA..they just had input into design and have ownership and control of the completed vehicles. They could only pay United Airlines for tickets to transport people for example and not own a 747 or other transport plane because that is competing with commercial services. If space actually opens up, this structure would represent a pretty extreme inversion of the power structure between corporate and government entities that exist today where corporations are ultimately under control and subservient to governments.

The same argument could be used to ask why NASA owns any fixed wing aircraft or employs any pilots when they could just charter flights from private companies.
« Last Edit: 06/04/2017 08:17 PM by ncb1397 »

Offline Hog

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Re: SLS: Higher payload without second stage
« Reply #65 on: 06/05/2017 01:29 PM »
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.
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.
Paul

Online envy887

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Re: SLS: Higher payload without second stage
« Reply #66 on: 06/05/2017 02:58 PM »
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.
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.

Offline okan170

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Re: SLS: Higher payload without second stage
« Reply #67 on: 06/05/2017 03:19 PM »
(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")

If people keep expanding out into space, eventually I imagine NASA moving to buying and operating designs from others for certain tasks- but not simply buying seats and space forever.  At least unless we start having US armed forces aircraft and ships owned and operated by their manufacturers, and not government personnel as well.

Online RonM

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Re: SLS: Higher payload without second stage
« Reply #68 on: 06/05/2017 03:22 PM »
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.
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.

Congress is funding a Shuttle-derived SHLV, so RS25 is what NASA will use.

Online AncientU

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Re: SLS: Higher payload without second stage
« Reply #69 on: 06/06/2017 12:28 AM »
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.

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.
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline ncb1397

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Re: SLS: Higher payload without second stage
« Reply #70 on: 06/06/2017 12:31 AM »
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.

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.

It is $1.15B for RS-25E. $350 million for 6 engines.

Offline edkyle99

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Re: SLS: Higher payload without second stage
« Reply #71 on: 06/06/2017 03:27 AM »
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.

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
« Last Edit: 06/06/2017 03:36 AM by edkyle99 »

Offline woods170

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Re: SLS: Higher payload without second stage
« Reply #72 on: 06/06/2017 06:05 AM »
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.

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
This entire discussion about FH being able to replace SLS (or not) is entirely moot. SLS is a political pork barrel and will not be going away any time soon. So there is no need whatsoever to have it's capabilities replaced by whatever other rocket.
FH will serve it's own market, regardless of SLS being there or not.
« Last Edit: 06/06/2017 06:05 AM by woods170 »

Online envy887

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Re: SLS: Higher payload without second stage
« Reply #73 on: 06/06/2017 02:41 PM »
The way SpaceX wants to fly it (recovering boosters and first stage) it will barely boost 5.5 tonnes toward the Moon...


Edit: reply moved here: https://forum.nasaspaceflight.com/index.php?topic=43073.0
« Last Edit: 06/06/2017 02:43 PM by envy887 »

Offline UltraViolet9

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Re: SLS: Higher payload without second stage
« Reply #74 on: 06/06/2017 07:21 PM »
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.

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...

There are always technology and capability frontiers appropriate for government risk-taking that are beyond private investment. 

We can take all the current commercial plans at face value, and there are still many, large, unfilled, and unfunded gaps to enable human space exploration and activities beyond LEO:  nuclear power sources (space and surface), long-term cryogenic storage, reusable propulsion and subsystems for transit stages and landers, non-chemical propulsion for fast crew transit, high-power electric propulsion for efficient cargo transit, non-propulsive EDL techniques for large landers, surface habitation, surface mobility, ISRU, etc.

And even if we hypothetically reject a NASA role in developing new in-space systems, there are many, promising, advanced, but largely unfunded ETO techniques that promise efficiencies beyond current private heavy lift and reusability efforts:  more efficient/powerful upper stage engines, air-breathing engines, microwave thermal, laser thermal, etc. 

The point is that the bulk of NASA's talents and resources should be focused on the tip of the spear in space exploration and technology, however you define that (ETO versus in-space, existing versus advanced technologies, etc.).  We have three private entities covering the HLV haft.

Offline UltraViolet9

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Re: SLS: Higher payload without second stage
« Reply #75 on: 06/06/2017 08:15 PM »
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. 

Unfortunately, TLI (or mass to any destination) is not the only, or most important, metric, especially when considering a human space exploration campaign or research base.

Payload mass per launch may be the right metric for packing the most transponders on a GEO comsat or for a one-off mission.  But total payload delivered over time (per year or over years) matters more when establishing a base or supporting a campaign. 

Reliability when launching crew or critical assets is also crucial, as the in-space, EDL, and surface segments will be riskier than the launch.  If just leaving the Earth's atmosphere is too risky, it can drive unacceptable LOM/LOC figures for the entire mission or campaign.

Resiliency of the launch effort can be important -- the ability to recover quickly from a launch failure and/or field an alternate launch when crew or critical assets are waiting in space.

And development cost, development schedule, and operational costs are obviously big.  They have to leave enough in the kitty for developing and operating all the other elements in the mission or campaign on a reasonable timeframe.


Offline TomH

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Re: SLS: Higher payload without second stage
« Reply #76 on: 06/07/2017 01:31 AM »
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.
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.

I thought there were 15 left over from STS , but they had enough spare parts to assemble a 16th. With engines changing from reusable to expendable, it was no longer necessary to keep a collection of spare parts on hand.

Offline AS-503

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Re: SLS: Higher payload without second stage
« Reply #77 on: 06/07/2017 02:02 AM »
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.

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

If SLS is ever tasked with boosting mass to the moon it would be a precursor to (or even including) a manned flight, right?
Are there any plans to fly any lunar-centric missions on SLS?
Hasn't it been proven (even on this very forum) that the Orion LAS can not "outrun" a failed SRB on any mission?
ICPS or Block X second stage, or no second stage, how can the tonnage matter when SLS can't fly humans without black zones on ascent with the shuttle derived 150+ foot SRB?

If you recall back to the 2005 ESAS (Remember Mike Griffin's thumb-on-the-scale architecture study), there was an overwhelming emphasis on astronaut safety for next-gen space craft and LV while at the same time a "mandate" that any new system be developed with shuttle derived hardware. While there were/are developmental short term cost savings with shuttle-derived LV, in other ways it was/is the literal definition of insanity in terms of operational cost savings and crew safety.

You're a fan of aerospace history Ed, do you remember Burt Rutan's assessment of ESAS from 2005?
BTW this is not a provoking question, I love your website and most of your observations.

Offline tea monster

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Re: SLS: Higher payload without second stage
« Reply #78 on: 06/07/2017 06:58 AM »
There has been talk of a 'Lunar Gateway' Lagrange station: https://www.nasaspaceflight.com/2016/05/orbital-atk-cislunar-habitat-missions-sls-orion/
Nasa are looking at this, but nothing has been funded or mandated by The Hill yet. http://www.space.com/14518-nasa-moon-deep-space-station-astronauts.html

Debating the pros and cons of the SLS is kind of pointless as it seems that political considerations drove most of the design decisions. If you accept the brief of "Fly something derived from Shuttle components to save time and development cost" then we would have been several years into a Shuttle C flight program by now and probably had enough money left over to develop a Mars transfer vehicle and a lander.

Even I'm getting fed up with bashing the SLS at this point - only because thinking of where we would be if other choices had been made is way too depressing.

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?

Offline Paul451

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Re: SLS: Higher payload without second stage
« Reply #79 on: 06/07/2017 01:21 PM »
Back 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.

The OP's question presumes the circularisation is performed by the payload. (So, I guess it would be better to say 70 tonnes to LEI, rather than 70 tonnes to LEO.)

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?

If you built a module whose shell mimicked the size (and aerodynamic performance) of the largest possible SLS payload fairing (10x30m?), you'd have a monster space station placed in orbit in a single launch. Skylab II Trump Station Gold.

[However, this suffers from the usual problem with SLS: there's no way to afford SLS development/operations and the development of such a station. Nor is there any real point, except giggles.]

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?

A) The core will hold over 800 tonnes of propellant. Seemed a bit overkill. What payload could you launch that would require such a transfer stage? You could assemble a giant ship from several launches, but then you could have also assembled a modular propulsion system, making reusing the core redundant.

2) The RS-25's restart problem.

iii) Being LH fuelled, the time it would take to refuel the core (ie, the number of launches required) would make leakage-rate a significant loss. You'd need a major redesign to make the tanks near enough to ZBO to make the idea useful.

Online envy887

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Re: SLS: Higher payload without second stage
« Reply #80 on: 06/07/2017 02:10 PM »
Back 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.

Restart isn't necessary to insert into a stable LEO, as it's straightforward to do a direct launch to orbit.

Offline Jim

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Re: SLS: Higher payload without second stage
« Reply #81 on: 06/07/2017 03:30 PM »
Then there are core disposal issues then

Offline Patchouli

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Re: SLS: Higher payload without second stage
« Reply #82 on: 06/07/2017 05:56 PM »
Then there are core disposal issues then

If 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.
« Last Edit: 06/07/2017 05:56 PM by Patchouli »

Offline Jimmy_C

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Re: SLS: Higher payload without second stage
« Reply #83 on: 06/08/2017 08:44 AM »
Then there are core disposal issues then

If 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?

Offline Patchouli

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Re: SLS: Higher payload without second stage
« Reply #84 on: 06/16/2017 03:51 PM »


Wouldn't that mean the "payload" is the second stage?

Sorta but it pretty much just means means the payload would have a RCS/OMS system like the Russian ISS modules.
« Last Edit: 06/16/2017 03:51 PM by Patchouli »

Tags: SLS ICPS Orion