Author Topic: SLS trades lean towards opening with four RS-25s on the core stage  (Read 143053 times)

Offline Lobo

  • Senior Member
  • *****
  • Posts: 6915
  • Spokane, WA
  • Liked: 672
  • Likes Given: 436

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.

Ahhh, I hadn't really seen this before, just the more evolved full cyro ACES design.   This DTAL concept looks like it uses a Centaur stage with hypergolics for the lateral thrusters.  With the ascender using hypergolics as well.  The ACES design uses cryo for the lateral thrusters, as well as the ascender.  So everything is just those two non toxic propellants, and fuel can be pumped back and forth between the ascender and ACES descent stage.  (ascender tanks filled prior to descent, upon a successful landing, ascender tanks are pumped into the ACES stage for passive cryo storage for minimal boiloff, then pumped back to the ascender prior to ascent.)

That concept probably came along after this.  But I also imagine you could do the ACES DTAL concept with a Centaur or DCSS with modifications.
However, I think ULA really wants an excuse to develop ACES, so they have a common upper stage accorss their whole line, and for future use with AVP2. 
So if we are looking at an upper stage based lander, that's probably the one to look at.  It also lends itself to a lunar orbit depot and propellant transfers for optimum mission capabilities.  As well as reusing the ascender.

Offline Pheogh

  • Full Member
  • ****
  • Posts: 987
  • Liked: 153
  • Likes Given: 39
I have been meaning to ask this for some time now, but I am curious why images of SLS show a non tapered aft section? During DIRECT 2.0 we had looked at tapering the aft to increase airflow around the engines when it looked like the RS-68's were the political favorite, and probably would have trouble surviving the heat of the SRBs. When we went to SSME's the problem seemed to be mitigated by their regen system but I kept the taper in my imagery? airflow is good right?

So the question remains, what is the trade for tapering or not tapering? In short is it needless  structural complexity in the case of the SSME? Are there dynamics associated with airflow that could prove problematic? Can anyone on here share some of the calculus that goes into tapering or not?

Offline mike robel

  • Extreme Veteran
  • Senior Member
  • *****
  • Posts: 2304
  • Merritt Island, FL
  • Liked: 369
  • Likes Given: 260
The most recent rendering do show a tapered aft end.

Offline Pheogh

  • Full Member
  • ****
  • Posts: 987
  • Liked: 153
  • Likes Given: 39
The most recent rendering do show a tapered aft end.

Hey you are right! thank you. It almost looks like the taper matches the SRB skirt perfectly. It also looks like they are using the "squashed" 4/5 engine arrangement.

Offline Ben the Space Brit

  • Senior Member
  • *****
  • Posts: 7206
  • A spaceflight fan
  • London, UK
  • Liked: 806
  • Likes Given: 900
The most recent rendering do show a tapered aft end.

Hey you are right! thank you. It almost looks like the taper matches the SRB skirt perfectly. It also looks like they are using the "squashed" 4/5 engine arrangement.

From what I've seen, the main engines aren't arranged regularly around the circumferance but in two pairs at the 'top' and 'bottom' of the thrust structure, perpendicular to the axis through the boosters.
"Oops! I left the silly thing in reverse!" - Duck Dodgers

~*~*~*~

The Space Shuttle Program - 1981-2011

The time for words has passed; The time has come to put up or shut up!
DON'T PROPAGANDISE, FLY!!!

Offline luke strawwalker

  • Regular
  • Full Member
  • ****
  • Posts: 1032
  • Liked: 9
  • Likes Given: 0
Did I read correctly that the current 5-Seg SRB design will only be used for the first 2 flights ?

After that, ATK has a more "advanced" design, or we switch to LRBs.

So that means we will have fired this design of the 5-Seg SRB more times on the ground than actually used as a booster.

Who pays for the development of this new ATK design ?

Yes, I noticed that too...

Also note that they plan to allow the first sets of SRB's to sink the Atlantic-- not even recover for analysis... (so much for Jim's "manrated SRB's MUST be recovered and inspected for issues"). 

Pretty convenient way to ensure that you MUST get a fat development contract for NEW SRB's using new casings, if all the old reusable casings are in pieces on the bottom of the Atlantic...

And of course with the core being DESIGNED around SRB's, LRB's will never get a fair shot... they'll be found to be "too expensive" to redesign the core and the LRB's versus the costs of SRB's, even a NEW SRB DESIGN, that utilizes the core unchanged...

More thumbs on scales... SSDD...

later!  OL JR :)
NO plan IS the plan...

"His plan had no goals, no timeline, and no budgetary guidelines. Just maybe's, pretty speeches, and smokescreens."

Offline luke strawwalker

  • Regular
  • Full Member
  • ****
  • Posts: 1032
  • Liked: 9
  • Likes Given: 0
That's probably how it will pan out. Lunar and NEO can be done with Block 1A/CPS but any Mars or Martian Moon missions will take Block 2 as the reference hardware and that will be developed along with mission modules in the $3+bn budget. I suppose it's all part of ensuring the use of all the CxP hardware in development, the J-2X will be developed and then parked until the upper stage can be developed in the fixed budget.

Yes.

I predict the Block I will fly more than twice (maybe up to 4 times, since there are apparently about 16 RS-25Ds available, which would allow for 4 flights).

So that already puts us into the 2023 - 2025 timeframe before we get Block IA. Plenty of time for political / mission focus shifts.

As for the block IA, I predict we'll keep that at least until 2035.

Finally, I predict that after the first two Block I flights with the current 5-segs, we will get an evaluation between different "Advanced Booster Options" (as planned), but in the end, they'll most likely stick with the ATK 5 seg boosters, for cost reasons, (unless some very effective and cheap LRBs become available or unless the 5 segs fail completely), with a vague promise of some sort of "improved booster" somewhere down the road. Just like with Shuttle, which was supposed to replace the RSRBs with something new (ASRB, 5-segs, even LRBs) several times during its lifetime...

Exactly... I see that justification shooting down any chance of LRB's...

Later!  OL JR :)
NO plan IS the plan...

"His plan had no goals, no timeline, and no budgetary guidelines. Just maybe's, pretty speeches, and smokescreens."

Offline 93143

  • Senior Member
  • *****
  • Posts: 3054
  • Liked: 312
  • Likes Given: 1
I predict the Block I will fly more than twice (maybe up to 4 times, since there are apparently about 16 RS-25Ds available, which would allow for 4 flights).

So that already puts us into the 2023 - 2025 timeframe

I notice you've got a hidden assumption in there about the flight rate...

Offline Downix

  • Senior Member
  • *****
  • Posts: 7082
  • Liked: 22
  • Likes Given: 1
Did I read correctly that the current 5-Seg SRB design will only be used for the first 2 flights ?

After that, ATK has a more "advanced" design, or we switch to LRBs.

So that means we will have fired this design of the 5-Seg SRB more times on the ground than actually used as a booster.

Who pays for the development of this new ATK design ?

Yes, I noticed that too...

Also note that they plan to allow the first sets of SRB's to sink the Atlantic-- not even recover for analysis... (so much for Jim's "manrated SRB's MUST be recovered and inspected for issues"). 

Pretty convenient way to ensure that you MUST get a fat development contract for NEW SRB's using new casings, if all the old reusable casings are in pieces on the bottom of the Atlantic...

And of course with the core being DESIGNED around SRB's, LRB's will never get a fair shot... they'll be found to be "too expensive" to redesign the core and the LRB's versus the costs of SRB's, even a NEW SRB DESIGN, that utilizes the core unchanged...

More thumbs on scales... SSDD...

later!  OL JR :)
It may be thumbs on scales, but it can and will bite them in the butt badly.  They assume, incorrectly, that they are the only SRB company in the US, ignoring that there is another, and that other has built and fired SRB's which dwarf even the 5-segment of ATK.

And there is a way to build LRB's to beat SRB's even while sticking to the SRB design and load demands, in short, without redesigning the core.  8)
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 Lurker Steve

  • Full Member
  • ****
  • Posts: 1420
  • Liked: 35
  • Likes Given: 9
As a non-rocket scientist, let me ask some questions :
1) The current ATK 5-seg SRBs are designed with the same basic design of reusable casings that the Shuttle SRBs use. There is extra structural weight because the casings need to survive intact. There is a huge amount of labor to refurb the casings, but it is possible to reuse them.

2) If we aren't reusing the SRBs, then some of that extra structral weight can be removed. Since the SRB become lighter by several tons, that extra weight can be translated into extra cargo the SLS could lift.

3) Would these lighter SRBs have an increased thrust and/or ISP over the existing SRBs without reformulating the actual solid fuel ?

4) Without a re-formulation of the solid fuel, does this give ATK any additional advantage, other than being able to manufacture a less expensive SRB, due to the lighter structure / non-reusable design ?

5) If this comes down to purely a cost-based competition, with the vendor paying for all development of the improved booster, who wins: a pair of LRB boosters or a pair of ATK or Aerojet SRBs ?

Offline Mr. Justice

  • Full Member
  • **
  • Posts: 215
  • Liked: 0
  • Likes Given: 0
As a non-rocket scientist, let me ask some questions :
1) The current ATK 5-seg SRBs are designed with the same basic design of reusable casings that the Shuttle SRBs use. There is extra structural weight because the casings need to survive intact. There is a huge amount of labor to refurb the casings, but it is possible to reuse them.

2) If we aren't reusing the SRBs, then some of that extra structral weight can be removed. Since the SRB become lighter by several tons, that extra weight can be translated into extra cargo the SLS could lift.

3) Would these lighter SRBs have an increased thrust and/or ISP over the existing SRBs without reformulating the actual solid fuel ?

4) Without a re-formulation of the solid fuel, does this give ATK any additional advantage, other than being able to manufacture a less expensive SRB, due to the lighter structure / non-reusable design ?

5) If this comes down to purely a cost-based competition, with the vendor paying for all development of the improved booster, who wins: a pair of LRB boosters or a pair of ATK or Aerojet SRBs ?

I was wondering about the same thing. Since STS never flew at a high rate, and SLS will not either how much of an increase in payload capacity can we get by making single use casings and what does that do to the cost of the SRBs?

Offline Mr. Justice

  • Full Member
  • **
  • Posts: 215
  • Liked: 0
  • Likes Given: 0
Did I read correctly that the current 5-Seg SRB design will only be used for the first 2 flights ?

After that, ATK has a more "advanced" design, or we switch to LRBs.

So that means we will have fired this design of the 5-Seg SRB more times on the ground than actually used as a booster.

Who pays for the development of this new ATK design ?

Yes, I noticed that too...

Also note that they plan to allow the first sets of SRB's to sink the Atlantic-- not even recover for analysis... (so much for Jim's "manrated SRB's MUST be recovered and inspected for issues"). 

Pretty convenient way to ensure that you MUST get a fat development contract for NEW SRB's using new casings, if all the old reusable casings are in pieces on the bottom of the Atlantic...

And of course with the core being DESIGNED around SRB's, LRB's will never get a fair shot... they'll be found to be "too expensive" to redesign the core and the LRB's versus the costs of SRB's, even a NEW SRB DESIGN, that utilizes the core unchanged...

More thumbs on scales... SSDD...

later!  OL JR :)
It may be thumbs on scales, but it can and will bite them in the butt badly.  They assume, incorrectly, that they are the only SRB company in the US, ignoring that there is another, and that other has built and fired SRB's which dwarf even the 5-segment of ATK.

And there is a way to build LRB's to beat SRB's even while sticking to the SRB design and load demands, in short, without redesigning the core.  8)

I am not familiar with these other SRBs. Could you please provide some information or, at least the name, as I would like to do a little reading about them? Thanks.

Offline Downix

  • Senior Member
  • *****
  • Posts: 7082
  • Liked: 22
  • Likes Given: 1
Did I read correctly that the current 5-Seg SRB design will only be used for the first 2 flights ?

After that, ATK has a more "advanced" design, or we switch to LRBs.

So that means we will have fired this design of the 5-Seg SRB more times on the ground than actually used as a booster.

Who pays for the development of this new ATK design ?

Yes, I noticed that too...

Also note that they plan to allow the first sets of SRB's to sink the Atlantic-- not even recover for analysis... (so much for Jim's "manrated SRB's MUST be recovered and inspected for issues"). 

Pretty convenient way to ensure that you MUST get a fat development contract for NEW SRB's using new casings, if all the old reusable casings are in pieces on the bottom of the Atlantic...

And of course with the core being DESIGNED around SRB's, LRB's will never get a fair shot... they'll be found to be "too expensive" to redesign the core and the LRB's versus the costs of SRB's, even a NEW SRB DESIGN, that utilizes the core unchanged...

More thumbs on scales... SSDD...

later!  OL JR :)
It may be thumbs on scales, but it can and will bite them in the butt badly.  They assume, incorrectly, that they are the only SRB company in the US, ignoring that there is another, and that other has built and fired SRB's which dwarf even the 5-segment of ATK.

And there is a way to build LRB's to beat SRB's even while sticking to the SRB design and load demands, in short, without redesigning the core.  8)

I am not familiar with these other SRBs. Could you please provide some information or, at least the name, as I would like to do a little reading about them? Thanks.
The Aerojet AJ-260 was designed during the 1960's to be the first stage replacement for the Saturn IB.  There's a thread on the demonstration motor, and its current abandoned state, here:

http://forum.nasaspaceflight.com/index.php?topic=23718.0

The basics however are simple.  It had ~3.9 million lbf peak, while the 5-segment peaks at 3.4 million lbf.
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 Proponent

  • Senior Member
  • *****
  • Posts: 7276
  • Liked: 2781
  • Likes Given: 1461
As a non-rocket scientist, let me ask some questions :
1) The current ATK 5-seg SRBs are designed with the same basic design of reusable casings that the Shuttle SRBs use. There is extra structural weight because the casings need to survive intact. There is a huge amount of labor to refurb the casings, but it is possible to reuse them.

SRB casings need to be heavy because of the large pressures the must withstand.  I doubt that dropping the re-usability requirement by itself would make them much lighter.  That's not to say, however, that SRBs can't be made lighter by building them of different materials.

My understanding is that for the low flight rate that the Shuttle achieved, there was little difference in cost between re-using SRBs and building new ones at the flight rates that were achieved.  Recovery of SRBs was desirable for safety (so they could be inspected after flight).  With the first part of the re-use process -- recovery -- justified on grounds of safety, re-use made sense.

Quote
2) If we aren't reusing the SRBs, then some of that extra structral weight can be removed. Since the SRB become lighter by several tons, that extra weight can be translated into extra cargo the SLS could lift.

Anyway, since the SRBs are attached only for the first couple of minutes anyway, changing their weight doesn't affect payload capability much.  A kilogram saved might add on the order of 100 grams to the payload.

Quote
<snip>

5) If this comes down to purely a cost-based competition, with the vendor paying for all development of the improved booster, who wins: a pair of LRB boosters or a pair of ATK or Aerojet SRBs ?

It strikes me that given the low flight rates foreseen for SLS, it will be hard to justify spending much money up front to reduce operating costs.
« Last Edit: 10/10/2011 05:06 am by Proponent »

Offline Jorge

  • Senior Member
  • *****
  • Posts: 6404
  • Liked: 529
  • Likes Given: 66
As a non-rocket scientist, let me ask some questions :
1) The current ATK 5-seg SRBs are designed with the same basic design of reusable casings that the Shuttle SRBs use. There is extra structural weight because the casings need to survive intact. There is a huge amount of labor to refurb the casings, but it is possible to reuse them.

SRB casings need to be heavy because of the large pressures the must withstand.  I doubt that dropping the re-usability requirement by itself would make them much lighter.

Right. The weight savings would come from deleting the recovery systems (parachutes, etc). The idea that there's extra structural weight is hogwash.

Quote
  That's not to say, however, that SRBs can't be made lighter by building them of different materials.

True (filament-wound casings, etc). But that's completely independent of the reuse/no-reuse decision.
JRF

Offline Ronsmytheiii

  • Moderator
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 23394
  • Liked: 1879
  • Likes Given: 1020
Interesting:

Quote
“Our vision is we’ll have an interface that’s generic, and we’ll be able to carry potentially different boosters and change them out as needed,” Gerstenmaier told a session of the International Astronautical Congress here Thursday. “So we could go compete in the future, maybe downsize if something’s easier for a mission that requires less thrust. We have some variability there, so if we do our job right, we’ll have the ability to change the boosters that sit on the side. That’s our ultimate goal. We’re not going to pick one.”

http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/asd/2011/10/07/01.xml&headline=Booster%20Competition%20For%20New%20NASA%20Heavy%20Lifter
Quote
“It turns out that to get to the 130 metric tons, we’re going to have to redesign the five-segment booster as well,” Gerstenmaier says. “We have to go to potentially a composite case, away from our steel case to save some weight, and we might need to make a propellant change to use the more energetic propellant that sits in the solid rocket motor. So even if we go continuous solids, we’re going to have to make a pretty significant change to the solid-rocket booster segment.”
« Last Edit: 10/10/2011 01:54 pm by Ronsmytheiii »

Offline JohnFornaro

  • Not an expert
  • Senior Member
  • *****
  • Posts: 10972
  • Delta-t is an important metric.
  • Planet Eaarth
    • Design / Program Associates
  • Liked: 1257
  • Likes Given: 724
Quote
Designating the launch vehicle requirements (for a new launch vehicle) before having the mission scope/policy/plan/blah done is bass-ackwards. ...

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)?

STS had a mission: it was sold as a general-purpose space truck ...

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 ... 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 longer life than the rocket with a mission...

That is an excellent rebuttal to the rocket without a mission argument.  SLS is a rocket with a general purpose.

SLS will still have to be built.  From VentureStar to Ares, the rockets were never built, so the missions could never evolve.  Furthermore, there already is a mission:  Go back to the Moon to stay.  To do that, a workhorse LV is needed to build the necessary infrastructure.  There's no physical reason that SLS could not be this workhorse LV, but there's plenty of political, porkical, and corporate insider reasons why that couldn't be.
Sometimes I just flat out don't get it.

Offline MP99

Quote
“It turns out that to get to the 130 metric tons, we’re going to have to redesign the five-segment booster as well,” Gerstenmaier says. “We have to go to potentially a composite case, away from our steel case to save some weight, and we might need to make a propellant change to use the more energetic propellant that sits in the solid rocket motor. So even if we go continuous solids, we’re going to have to make a pretty significant change to the solid-rocket booster segment.”

This was pretty much as per Chris' "4x RS-25 on Block 1" article re performance of Block 1 / 1A / 2. Upgrade to HTPB can be traced all the way back to ESAS LV27.3, and way back on SLS too.

But the direct quote from Mr Gerstenmaier, and it's particular wording was fascinating to see.

cheers, Martin

Offline Proponent

  • Senior Member
  • *****
  • Posts: 7276
  • Liked: 2781
  • Likes Given: 1461
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.

The Shuttle was specifically designed to carry the payloads that were already being boosted by expendable rockets.  There was no doubt that the payloads existed, and no doubt that there would have been many payloads for the Shuttle had it performed as promised.  As we all know, the Shuttle did not perform as promised.  But it continued to fly, because it was the United States' only crew-carrying vehicle.  To stop flying the Shuttle would have meant abandonment of human spaceflight by the US.

As for "any heavy loads that might arise," well, SLS has much the same capabilities as the Saturn V:  60 tonnes to LEO for the INT-20 version (S-IC plus S-IVB; 72 tonnes with strengthening to withstand 6Gs), and and 116 tonnes for the INT-21 (S-IC plus S-II).  There was exactly one payload--Skylab--found for the Saturn V aside from the payload for which it was designed.  No one was willing to pay for payloads large enough to need the Saturn V.  Why would you think it's going to be any different for SLS?

SLS can be used for BEO exploration, but, as Robotbeat said above, it's bass-ackward to design the rocket before figuring out the payloads.

Quote
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...

From Vanguard onward, most rockets have been developed after the payloads they would initially carry were defined, and that's the way it should be.

Offline RyanC

  • Full Member
  • ****
  • Posts: 469
  • SA-506 Launch
  • Liked: 125
  • Likes Given: 18
“It turns out that to get to the 130 metric tons, we’re going to have to redesign the five-segment booster as well,” Gerstenmaier says. “We have to go to potentially a composite case, away from our steel case to save some weight, and we might need to make a propellant change to use the more energetic propellant that sits in the solid rocket motor. So even if we go continuous solids, we’re going to have to make a pretty significant change to the solid-rocket booster segment.”

This is really a very very good bait and switch.

They sold RAC-1 Shuttle Derived Heavy Lift as something that could be cheaply and affordably built using parts left over from Shuttle/Constellation, and now they say they need to do all new advanced new SRBs to meet the 130 ton evolved goal.

At this point, what reason is there to continue with SD-HLV if we keep having to redesign, redesign, redesign things; as opposed to the clean sheet RAC-2 architecture which used F-1A?
« Last Edit: 10/10/2011 08:10 pm by RyanCrierie »

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1