Author Topic: SLS trades lean towards opening with four RS-25s on the core stage  (Read 143061 times)

Offline gospacex

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Why Block 1 needs the second stage? It'd lift ~70 tons to LEO without it, and we have no payloads even in that class, not to mention heavier ones. Why do we spend $$$ developing something we don't need?

Offline aquanaut99

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Why Block 1 needs the second stage? It'd lift ~70 tons to LEO without it, and we have no payloads even in that class, not to mention heavier ones. Why do we spend $$$ developing something we don't need?

Because the first Orion missions are circumlunar flights. The iCPS is actually an EDS, not a second stage.

You need an EDS for BEO operations, no matter how much your launcher can lift into LEO. Since NASA's HSF goal is BEO flights, we will need an EDS sooner or later. So we might as well develop it now (for Block I, the iCPS is probably not that hard to develop, since it is just a modified and man-rated existing upper-stage...)
« Last Edit: 10/06/2011 02:16 pm by aquanaut99 »

Offline Ben the Space Brit

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Why Block 1 needs the second stage? It'd lift ~70 tons to LEO without it, and we have no payloads even in that class, not to mention heavier ones. Why do we spend $$$ developing something we don't need?

Because the first Orion missions are circumlunar flights. The iCPS is actually an EDS, not a second stage.

Purely speculative at this point but SLS Block-I can throw about 20-30t through escape velocity with the DIVHUS, depending on the target.  This might one day be useful for launching a heavy-weight Galilean Moon or Titan robotic survey mission.
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Offline Chris Bergin

Thread purged of the sandpit fight from at least the mod report standpoint.

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Offline Downix

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Why Block 1 needs the second stage? It'd lift ~70 tons to LEO without it, and we have no payloads even in that class, not to mention heavier ones. Why do we spend $$$ developing something we don't need?

Because the first Orion missions are circumlunar flights. The iCPS is actually an EDS, not a second stage.

Purely speculative at this point but SLS Block-I can throw about 20-30t through escape velocity with the DIVHUS, depending on the target.  This might one day be useful for launching a heavy-weight Galilean Moon or Titan robotic survey mission.
Doing the math, it could push 40 metric tons to escape velocity, or 35 metric tons TLI (including the iCPS performing the final orbital insertion burn).  If you did not need it to perform the final orbital insertion burn, you can increase that to 45 metric tons.  45 Metric Tons, incidentally, would allow the inclusion of a Centaur dual-axis lunar lander along with Orion, using the Centaur for final orbital-insertion burn, and Orion handling the return burn to Earth by itself.

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Offline Proponent

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Quote
Designating the launch vehicle requirements (for a new launch vehicle) before having the mission scope/policy/plan/blah done is bass-ackwards. That I pointed that out is not off-topic; your asking for mission plans for anything without SLS was off-topic.

"Hey guys, I'm going to go order curtains from the store, then I'll measure my windows!"

EDIT:I mean, don't get me wrong, I'm glad we're finally measuring the windows, even if we ordered the curtains already.


The STS had no specific mission really until ISS and it flew for 30 years.  Are not all missions designed around the launch vehicles and not the other way around (Apollo era aside)?

Edit: Meant STS not SLS

STS had a mission: it was sold as a general-purpose space truck that would eliminate the need for any other launch vehicles except perhaps for the very smallest.  By the time of the Challenger accident it had become obvious that STS could not fulfill that role.

Offline mrbliss

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The first escalations occur....soon my pretties, soon we will have ARES V again...

Actually, this is at least the 3rd escalation.

1) 5-seg solids
2) Stretch core to go with the 5-seggers
3) 4 RS-25s to use all that fuel in the stretched core

Offline Jason1701

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So it seems that SLS has its core stretched only because ATK wants it so, not because that's actually required to use 5-segs. Does NASA documentation have any evidence for or against this conclusion?

Offline AlexP

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I don't think it's fair to call any of those things "escalations". 5-seg with a core stretch was the originally released design, and the trade (as Chris called it multiple times in his much appreciated article) to the four-SSME configuration is because

Quote
...using four engines will allow the vehicle to fly fully fueled in all configurations saving the extra calculations/testing for an under-filled three engine core.

So not really an escalation, seems they're just trying to get it ready quicker/with less hassle, and using an extra SSME from the existing stock is deemed a worthwhile trade for it. There doesn't seem anything wrong with that from my perspective.
« Last Edit: 10/06/2011 05:49 pm by AlexP »

Offline BrightLight

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Why Block 1 needs the second stage? It'd lift ~70 tons to LEO without it, and we have no payloads even in that class, not to mention heavier ones. Why do we spend $$$ developing something we don't need?

Because the first Orion missions are circumlunar flights. The iCPS is actually an EDS, not a second stage.

Purely speculative at this point but SLS Block-I can throw about 20-30t through escape velocity with the DIVHUS, depending on the target.  This might one day be useful for launching a heavy-weight Galilean Moon or Titan robotic survey mission.
Doing the math, it could push 40 metric tons to escape velocity, or 35 metric tons TLI (including the iCPS performing the final orbital insertion burn).  If you did not need it to perform the final orbital insertion burn, you can increase that to 45 metric tons.  45 Metric Tons, incidentally, would allow the inclusion of a Centaur dual-axis lunar lander along with Orion, using the Centaur for final orbital-insertion burn, and Orion handling the return burn to Earth by itself.
Just as an aside, in the DTAL white paper
http://www.ulalaunch.com/site/docs/publications/DualThrustAxisLander%28DTAL%292009.pdf
I couldn't find the total mass of the lander plus fuel.  I take it from your post that it is less than 45t (including payload?).

Offline Downix

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Why Block 1 needs the second stage? It'd lift ~70 tons to LEO without it, and we have no payloads even in that class, not to mention heavier ones. Why do we spend $$$ developing something we don't need?

Because the first Orion missions are circumlunar flights. The iCPS is actually an EDS, not a second stage.

Purely speculative at this point but SLS Block-I can throw about 20-30t through escape velocity with the DIVHUS, depending on the target.  This might one day be useful for launching a heavy-weight Galilean Moon or Titan robotic survey mission.
Doing the math, it could push 40 metric tons to escape velocity, or 35 metric tons TLI (including the iCPS performing the final orbital insertion burn).  If you did not need it to perform the final orbital insertion burn, you can increase that to 45 metric tons.  45 Metric Tons, incidentally, would allow the inclusion of a Centaur dual-axis lunar lander along with Orion, using the Centaur for final orbital-insertion burn, and Orion handling the return burn to Earth by itself.
Just as an aside, in the DTAL white paper
http://www.ulalaunch.com/site/docs/publications/DualThrustAxisLander%28DTAL%292009.pdf
I couldn't find the total mass of the lander plus fuel.  I take it from your post that it is less than 45t (including payload?).

That's for the ACES lander, I'm speaking of the older Lockheed centaur lander, which is less than 45t.  The ACES upper stage is around 45 metric tons by my calcs, having twice the fuel load of Centaur, so a lander would be even heavier than that.
« Last Edit: 10/06/2011 10:33 pm by Downix »
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline ciscosdad

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I'm personally very heartened by progress so far.
I agree that an approach more akin to Direct (J130 and J240 eta al) would have been more desirable (cheaper), but we, and more specifically nasa have to work within the achievable political realities.
Once Mr Shannon works his magic with the missions, things should look even more positive.
I certainly prefer to be working on the rocket first then the missions. The other way around seems very pointless. It would be nice to have the funding and the political will to do an Apollo (missions and rocket), but that led to 6 moon landings then nothing, so that approach isn't perfect (unsustainable architecture).
Lets build the rocket within the budget,then put it to use within the budget, keep the industrial base alive and the agency and workforce in place and have a real manned spaceflight program. Even just Block 1 would do fine for a long list of interesting missions.

Offline muomega0

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Why Block 1 needs the second stage? It'd lift ~70 tons to LEO without it, and we have no payloads even in that class, not to mention heavier ones. Why do we spend $$$ developing something we don't need?

Because the first Orion missions are circumlunar flights. The iCPS is actually an EDS, not a second stage.

Purely speculative at this point but SLS Block-I can throw about 20-30t through escape velocity with the DIVHUS, depending on the target.  This might one day be useful for launching a heavy-weight Galilean Moon or Titan robotic survey mission.
Doing the math, it could push 40 metric tons to escape velocity, or 35 metric tons TLI (including the iCPS performing the final orbital insertion burn).  If you did not need it to perform the final orbital insertion burn, you can increase that to 45 metric tons.  45 Metric Tons, incidentally, would allow the inclusion of a Centaur dual-axis lunar lander along with Orion, using the Centaur for final orbital-insertion burn, and Orion handling the return burn to Earth by itself.
Just as an aside, in the DTAL white paper
http://www.ulalaunch.com/site/docs/publications/DualThrustAxisLander%28DTAL%292009.pdf
I couldn't find the total mass of the lander plus fuel.  I take it from your post that it is less than 45t (including payload?).

That's for the ACES lander, I'm speaking of the older Lockheed centaur lander, which is less than 45t.  The ACES upper stage is around 45 metric tons by my calcs, having twice the fuel load of Centaur, so a lander would be even heavier than that.

The DTAL in Figure 9 (attached) has a mass fraction of ~ 0.87 and Propellant Mass of 42 mT, so the lander dry mass weights 6.2 mT and the total mass is ~48 mT. 

It is hard, if not impossible, to justify why the DTAL lander cannot be lofted on a small LV and filled up on orbit with a depot, along with all the other mission hardware for BEO exploration.  With the depot, many more missions will be flown for the same total price. 

It is time to move away from SLS, and the time is now.


Offline Lobo

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That's for the ACES lander, I'm speaking of the older Lockheed centaur lander, which is less than 45t.  The ACES upper stage is around 45 metric tons by my calcs, having twice the fuel load of Centaur, so a lander would be even heavier than that.

Yea, the ACES DTAL was based on the ACES-41 stage, which is named that because it holds 41mt of propellant.  The dry weigh of the ACES-41 stage is about 5mt.  This article has some numbers on that.

http://www.ulalaunch.com/site/docs/publications/AffordableExplorationArchitecture2009.pdf

The DTAL ascender has about 4mt of propellant needed too for ascent.  So, the fully fueled ACES DTAL with ascender would be about 52mt.

I don't think I've ever seen the Centaur lander.  Downix, do you have any info on that?

Offline Starlab90

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This is just a great disappointment. There are no missions of any substance in the planning: flying by and waving at the Moon is not a real mission. It is 51 years after the Apollo 8 mission proving that we cannot match that mission's abilities.


It's been noted more times than I can remember that the mission planning is in work, via Mr Shannon :)
It shows where the real priorities are when the actual mission planning (and hardware, etc) is practically an afterthought compared to the launch vehicle.

To be fair they had it, with the flexible path, which replaced the VSE, with a nice amount of flexibility on the LV (I think they mainly used an Ares V for that....and we're not a million miles off with SLS on that score).

I'm as frustrated with the next man on mission content, but I think the big problem is if they had designed the missions say two years ago, then they'd probably be redoing them now based on the latest budget cycles and such. Not sure, but I bet there would be some people saying "HA, you've created missions and you don't even have a LV yet".

We're not launching SLS any time soon, so Mr Shannon has everything he needs, the LV design, the crew capsule design, the latest budget projects and the time to - I'm sure - work his magic, as he's (Dr Evil voice) "a fricking genius" ;D

Also, people need to remember that there is a plan, of sorts, laid out in full-blown legalese in the 2010 NASA Authorization Bill. The plan is to:

1. Begin development of SLS, MPCV, and the supporting facilities at KSC and elsewhere in Fiscal Years 2011, 2012, and 2013.

2. In 2012, NASA is to ask the NRC to conduct a study on what the next steps in BEO system development should be.

3. Based on the results of the NRC study, Congress will develop the 2013 NASA Authorization Bill, covering FY 2014 through 2016. Hopefully, the study results will also influence a decision by the Administration as to what new start to request in the FY 2014 President's Budget Request, which will come out in early 2013.

It's not as fast a plan as I would like to see, but it's better than no plan at all. At least there is a political consensus that we should have a BEO program. We haven't always had that.

And don't forget, the lack of a manifest beyond the first 2 missions will have no effect on MPCV and SLS development for the next 2 years, except to make us all feel better.

Offline BrightLight

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Why Block 1 needs the second stage? It'd lift ~70 tons to LEO without it, and we have no payloads even in that class, not to mention heavier ones. Why do we spend $$$ developing something we don't need?

Because the first Orion missions are circumlunar flights. The iCPS is actually an EDS, not a second stage.

Purely speculative at this point but SLS Block-I can throw about 20-30t through escape velocity with the DIVHUS, depending on the target.  This might one day be useful for launching a heavy-weight Galilean Moon or Titan robotic survey mission.
Doing the math, it could push 40 metric tons to escape velocity, or 35 metric tons TLI (including the iCPS performing the final orbital insertion burn).  If you did not need it to perform the final orbital insertion burn, you can increase that to 45 metric tons.  45 Metric Tons, incidentally, would allow the inclusion of a Centaur dual-axis lunar lander along with Orion, using the Centaur for final orbital-insertion burn, and Orion handling the return burn to Earth by itself.
Just as an aside, in the DTAL white paper
http://www.ulalaunch.com/site/docs/publications/DualThrustAxisLander%28DTAL%292009.pdf
I couldn't find the total mass of the lander plus fuel.  I take it from your post that it is less than 45t (including payload?).

That's for the ACES lander, I'm speaking of the older Lockheed centaur lander, which is less than 45t.  The ACES upper stage is around 45 metric tons by my calcs, having twice the fuel load of Centaur, so a lander would be even heavier than that.

The DTAL in Figure 9 (attached) has a mass fraction of ~ 0.87 and Propellant Mass of 42 mT, so the lander dry mass weights 6.2 mT and the total mass is ~48 mT. 

It is hard, if not impossible, to justify why the DTAL lander cannot be lofted on a small LV and filled up on orbit with a depot, along with all the other mission hardware for BEO exploration.  With the depot, many more missions will be flown for the same total price. 

It is time to move away from SLS, and the time is now.


That's for the ACES lander, I'm speaking of the older Lockheed centaur lander, which is less than 45t.  The ACES upper stage is around 45 metric tons by my calcs, having twice the fuel load of Centaur, so a lander would be even heavier than that.

Yea, the ACES DTAL was based on the ACES-41 stage, which is named that because it holds 41mt of propellant.  The dry weigh of the ACES-41 stage is about 5mt.  This article has some numbers on that.

http://www.ulalaunch.com/site/docs/publications/AffordableExplorationArchitecture2009.pdf

The DTAL ascender has about 4mt of propellant needed too for ascent.  So, the fully fueled ACES DTAL with ascender would be about 52mt.

I don't think I've ever seen the Centaur lander.  Downix, do you have any info on that?
Here is a white paper from ULA on lander options including the Centaur based system
http://www.ulalaunch.com/site/docs/publications/LunarLanderConfigurationsIncorporatingAccessibility20067284.pdf
It appears that the crew section was adapted from the Centaur lander to the DTAL.

Offline Downix

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Why Block 1 needs the second stage? It'd lift ~70 tons to LEO without it, and we have no payloads even in that class, not to mention heavier ones. Why do we spend $$$ developing something we don't need?

Because the first Orion missions are circumlunar flights. The iCPS is actually an EDS, not a second stage.

Purely speculative at this point but SLS Block-I can throw about 20-30t through escape velocity with the DIVHUS, depending on the target.  This might one day be useful for launching a heavy-weight Galilean Moon or Titan robotic survey mission.
Doing the math, it could push 40 metric tons to escape velocity, or 35 metric tons TLI (including the iCPS performing the final orbital insertion burn).  If you did not need it to perform the final orbital insertion burn, you can increase that to 45 metric tons.  45 Metric Tons, incidentally, would allow the inclusion of a Centaur dual-axis lunar lander along with Orion, using the Centaur for final orbital-insertion burn, and Orion handling the return burn to Earth by itself.
Just as an aside, in the DTAL white paper
http://www.ulalaunch.com/site/docs/publications/DualThrustAxisLander%28DTAL%292009.pdf
I couldn't find the total mass of the lander plus fuel.  I take it from your post that it is less than 45t (including payload?).

That's for the ACES lander, I'm speaking of the older Lockheed centaur lander, which is less than 45t.  The ACES upper stage is around 45 metric tons by my calcs, having twice the fuel load of Centaur, so a lander would be even heavier than that.

The DTAL in Figure 9 (attached) has a mass fraction of ~ 0.87 and Propellant Mass of 42 mT, so the lander dry mass weights 6.2 mT and the total mass is ~48 mT. 

It is hard, if not impossible, to justify why the DTAL lander cannot be lofted on a small LV and filled up on orbit with a depot, along with all the other mission hardware for BEO exploration.  With the depot, many more missions will be flown for the same total price. 

It is time to move away from SLS, and the time is now.


That's for the ACES lander, I'm speaking of the older Lockheed centaur lander, which is less than 45t.  The ACES upper stage is around 45 metric tons by my calcs, having twice the fuel load of Centaur, so a lander would be even heavier than that.

Yea, the ACES DTAL was based on the ACES-41 stage, which is named that because it holds 41mt of propellant.  The dry weigh of the ACES-41 stage is about 5mt.  This article has some numbers on that.

http://www.ulalaunch.com/site/docs/publications/AffordableExplorationArchitecture2009.pdf

The DTAL ascender has about 4mt of propellant needed too for ascent.  So, the fully fueled ACES DTAL with ascender would be about 52mt.

I don't think I've ever seen the Centaur lander.  Downix, do you have any info on that?
Here is a white paper from ULA on lander options including the Centaur based system
http://www.ulalaunch.com/site/docs/publications/LunarLanderConfigurationsIncorporatingAccessibility20067284.pdf
It appears that the crew section was adapted from the Centaur lander to the DTAL.
You can also use that paper to calculate out in reverse the dry weight of the lander, as it posts the total delta-v available with a 20 metric ton CEV.  Using those details, you reverse calculate that, to hit the 1911m/s total delta-v available with the 20.8 metric tons of fuel, of roughly 18.4 metric tons, or 39.2 metric tons fully loaded.  This with MPCV would bring the total payload to 60.5 metric tons, too much for Delta IV's upper stage.

*unless*

You use the Centaur for both the final piece of the outgoing *and* the TLI.  Having 1911 m/s, you find that it has ample delta-v for the need.  ACES would further improve this, with it's better fuel fraction and fuel load.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Ben the Space Brit

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Also, people need to remember that there is a plan, of sorts, laid out in full-blown legalese in the 2010 NASA Authorization Bill. The plan is to:

1. Begin development of SLS, MPCV, and the supporting facilities at KSC and elsewhere in Fiscal Years 2011, 2012, and 2013.

2. In 2012, NASA is to ask the NRC to conduct a study on what the next steps in BEO system development should be.

3. Based on the results of the NRC study, Congress will develop the 2013 NASA Authorization Bill, covering FY 2014 through 2016. Hopefully, the study results will also influence a decision by the Administration as to what new start to request in the FY 2014 President's Budget Request, which will come out in early 2013.

It's nice to know that there is a plan of sorts, even if lots of aspects, such as targets, is still TBD.
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Offline JohnFornaro

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Sorry, this just looks like the same old MSFC gigantism fetish all over again. And a lot of responsibility for that lies with the Senate and House, who both had plenty of opportunities to clarify...

Dammit!  There, it would seem, they go again.

There are no missions of any substance in the planning: flying by and waving at the Moon is not a real mission. It is 51 years after the Apollo 8 mission proving that we cannot match that mission's abilities.

Yes, Apollo 8 redux is a mission, and it should be the second mission of SLS, well before December of 2018 if I had my way.  The first flight should be manned, and to the ISS with a boatload of supplies and experiments.  This launch system needs to get up and running ASAP.  The third mission probably should be a polar lunar landing and prospecting mission.  These programs are taking too long, and past work is seen as useless and is not used.  They are redesigning to no end purpose and much talent and effort is simply wasted.

It will be interesting to see what Mr. Shannon concludes.  Which means, I guess, that we're waiting for him to call, right?  The mission plan should be a return to the Moon for good, and we'll practice for Mars.  We don't need to make any plans for Mars other than robotic plans for the moment.  If the story line of "new technologies" has any truth to it, we will design the martian missions with that tech in hand.  The effort is wasted otherwise, or the story line is simply false.

The mission, return to stay, simply does not need to change at all.  Focus on designing the lander to fit on the rocket with no mass creep or function creep.

The wait for missions is not a month long.  It is more nearly four decades long.  You can have a mission without a rocket.  The rocket can support the mission.
Sometimes I just flat out don't get it.

Offline Lobo

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Quote
Designating the launch vehicle requirements (for a new launch vehicle) before having the mission scope/policy/plan/blah done is bass-ackwards. That I pointed that out is not off-topic; your asking for mission plans for anything without SLS was off-topic.

"Hey guys, I'm going to go order curtains from the store, then I'll measure my windows!"

EDIT:I mean, don't get me wrong, I'm glad we're finally measuring the windows, even if we ordered the curtains already.


The STS had no specific mission really until ISS and it flew for 30 years.  Are not all missions designed around the launch vehicles and not the other way around (Apollo era aside)?

Edit: Meant STS not SLS

STS had a mission: it was sold as a general-purpose space truck that would eliminate the need for any other launch vehicles except perhaps for the very smallest.  By the time of the Challenger accident it had become obvious that STS could not fulfill that role.

If that qualifies as a "mission", then SLS has a mission.  It's being sold as a general-purpose space heavly lifter that will be large enough to handle all possible BLEO manned missions that may come up in the next 3 decades, as well as any heavy loads that would go up to LEO during that time.

It's as much of a mission as STS had up front, and STS flew for 30 years.

As I've warned people on the forum before, be careful with this "we can't have a rocket without a defined mission" argument.  Saturn had a defined mission from it's inception, STS did not.  STS had multiple purposes, but not a definate mission it was developed for.  Saturn was developed for a single mission.  And once that mission was achieved, it went on the scrap heap (unfortunately) because it was [perceived] to expensive for any other mission. 
Since STS didn't have a singular "mission", but rather a "purpose", it continued to function in that purpose for 30 years.

I'm just saying given the history of rockets with missions and rockets without, then rocket without a mission had a much long lift than the rocket with a mission...

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