SLS General Discussion Thread 8

[Jim]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

No, it was always 5 segments.   The Ares 5 and SLS cores are heavier.

[VSECOTSPE]

Alabamatross?

We have a winner.  Seconded.

[dchenevert]

I know someone posted this before, the ideal name for SLS is Albatross.

Alabamatross?

don't get me started.

NASA == "National Alabama Space Administration"

[Hog]

Time for thread 9 already I see.

[Robotbeat]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

wasn’t this a rather old decision, back in the Ares days? Gotta go look up the threads… it’s SOMEWHERE on this forum!

[shintoo]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

wasn’t this a rather old decision, back in the Ares days? Gotta go look up the threads… it’s SOMEWHERE on this forum!

I figured it was during Ares design as Ares had the 5 segments as well. If only the forum search feature worked a bit better. Luckily there was plenty of NSF coverage during the time, including some ATK quotes in https://www.nasaspaceflight.com/2011/09/sls-finally-announced-nasa-forward-path/

Just trying to get my story straight for the oncoming onslaught of questions from family while waiting around Monday morning 

[woods170]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

wasn’t this a rather old decision, back in the Ares days? Gotta go look up the threads… it’s SOMEWHERE on this forum!

The five segment SRBs came into existence, courtesy of Orion being overweight for the original Ares I design. This effect was worsened when the Ares I upper stage switched from an air-started RS-25 to the J-2X. The result was two things happening: Orion was put on a major diet, including shrinking the capsule diameter back to 5 meters (from 5.5 meters) and shrinking the service module. Additionally, the planned four-segment SRB was changed out for a more powerful five-segment SRB, to make up for performence lost on the upper stage. This all happened in early 2006, shortly after the ESAS had been released.

[dglow]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

wasn’t this a rather old decision, back in the Ares days? Gotta go look up the threads… it’s SOMEWHERE on this forum!

The five segment SRBs came into existence, courtesy of Orion being overweight for the original Ares I design. This effect was worsened when the Ares I upper stage switched from an air-started RS-25 to the J-2X. The result was two things happening: Orion was put on a major diet, including shrinking the capsule diameter back to 5 meters (from 5.5 meters) and shrinking the service module. Additionally, the planned four-segment SRB was changed out for a more powerful five-segment SRB, to make up for performence lost on the upper stage. This all happened in early 2006, shortly after the ESAS had been released.

I’ve wondered to what extent SRB length is tied to core stage dimensions. With Shuttle, the SRBs’ forward mounting point was the inter-tank section of the ET. There’s a large structural crossmember between the LOX and H2 tanks which I had assumed was there to handle the boosters’ thrust load.

Jump ahead to SLS, which needs to carry more core propellant than Shuttle but without the benefit of Ares’ expanded tank diameter. By stretching the 8.4m ET into SLS’s core didn’t NASA *need* to size the SRBs to match?

[DanClemmensen]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

wasn’t this a rather old decision, back in the Ares days? Gotta go look up the threads… it’s SOMEWHERE on this forum!

The five segment SRBs came into existence, courtesy of Orion being overweight for the original Ares I design. This effect was worsened when the Ares I upper stage switched from an air-started RS-25 to the J-2X. The result was two things happening: Orion was put on a major diet, including shrinking the capsule diameter back to 5 meters (from 5.5 meters) and shrinking the service module. Additionally, the planned four-segment SRB was changed out for a more powerful five-segment SRB, to make up for performence lost on the upper stage. This all happened in early 2006, shortly after the ESAS had been released.

I’ve wondered to what extent SRB length is tied to core stage dimensions. With Shuttle, the SRBs’ forward mounting point was the inter-tank section of the ET. There’s a large structural crossmember between the LOX and H2 tanks which I had assumed was there to handle the boosters’ thrust load.

Jump ahead to SLS, which needs to carry more core propellant than Shuttle but without the benefit of Ares’ expanded tank diameter. By stretching the 8.4m ET into SLS’s core didn’t NASA *need* to size the SRBs to match?

Jim reminded me awhile back that the thrust of an SRB increases with the length. This is because the thrust is a function of the exposed area of the fuel, and in these SRBs there is a hollow center and the fuel burns from the inside out, not from the bottom up. These SRBs are longer because the SLS needs more thrust than the shuttle did.

[Hog]

Are we not forgetting that originally Ares had the 5.5 segment boosters and 6 RS-68s? 

5.5 segment with recovery systems installed for reuse, downgraded to 5 segments with those systems removed for an expendable booster.  Net thrust is the same for both the 5 and 5.5 segment motor.

There were plans for 5 segment Shuttle boosters, with possible Polar launches from Florida.

[Hog]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

wasn’t this a rather old decision, back in the Ares days? Gotta go look up the threads… it’s SOMEWHERE on this forum!

The five segment SRBs came into existence, courtesy of Orion being overweight for the original Ares I design. This effect was worsened when the Ares I upper stage switched from an air-started RS-25 to the J-2X. The result was two things happening: Orion was put on a major diet, including shrinking the capsule diameter back to 5 meters (from 5.5 meters) and shrinking the service module. Additionally, the planned four-segment SRB was changed out for a more powerful five-segment SRB, to make up for performence lost on the upper stage. This all happened in early 2006, shortly after the ESAS had been released.

I’ve wondered to what extent SRB length is tied to core stage dimensions. With Shuttle, the SRBs’ forward mounting point was the inter-tank section of the ET. There’s a large structural crossmember between the LOX and H2 tanks which I had assumed was there to handle the boosters’ thrust load.

Jump ahead to SLS, which needs to carry more core propellant than Shuttle but without the benefit of Ares’ expanded tank diameter. By stretching the 8.4m ET into SLS’s core didn’t NASA *need* to size the SRBs to match?

Jim reminded me awhile back that the thrust of an SRB increases with the length. This is because the thrust is a function of the exposed area of the fuel, and in these SRBs there is a hollow center and the fuel burns from the inside out, not from the bottom up. These SRBs are longer because the SLS needs more thrust than the shuttle did.

Thrust length, burntime diameter, with further surface area adjustments for throttling, when in the bucket.

[Vahe231991]

I would call SLS, Ares IV.

It kinda does look like Ares IV, except the upper stage is way shorter.

Ares IV never existed. There was an Ares V under Constellation but no Ares IV.

There technically was an Ares IV concept: the Ares V core stage and SRBs merged with the Ares I upper stage and Orion spacecraft.

What elements of the proposed Ares IV were utilized in the final design of the SLS, given the similarities between the SLS Block I and Ares IV? I also should note that the SLS Block II kinda looks like the unbuilt Ares V cargo SLV.

[woods170]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

wasn’t this a rather old decision, back in the Ares days? Gotta go look up the threads… it’s SOMEWHERE on this forum!

The five segment SRBs came into existence, courtesy of Orion being overweight for the original Ares I design. This effect was worsened when the Ares I upper stage switched from an air-started RS-25 to the J-2X. The result was two things happening: Orion was put on a major diet, including shrinking the capsule diameter back to 5 meters (from 5.5 meters) and shrinking the service module. Additionally, the planned four-segment SRB was changed out for a more powerful five-segment SRB, to make up for performence lost on the upper stage. This all happened in early 2006, shortly after the ESAS had been released.

I’ve wondered to what extent SRB length is tied to core stage dimensions. With Shuttle, the SRBs’ forward mounting point was the inter-tank section of the ET. There’s a large structural crossmember between the LOX and H2 tanks which I had assumed was there to handle the boosters’ thrust load.

Jump ahead to SLS, which needs to carry more core propellant than Shuttle but without the benefit of Ares’ expanded tank diameter. By stretching the 8.4m ET into SLS’s core didn’t NASA *need* to size the SRBs to match?

Jim reminded me awhile back that the thrust of an SRB increases with the length. This is because the thrust is a function of the exposed area of the fuel, and in these SRBs there is a hollow center and the fuel burns from the inside out, not from the bottom up. These SRBs are longer because the SLS needs more thrust than the shuttle did.

SLS absolutely did NOT need more thrust than the shuttle did. SLS simply could have been a re-branding of the DIRECT architecture, which used the original 4 segment STS SRBs.

How did SLS get its 5 segment SRBs then?
Well, SLS inherited the 5 segement SRBs from Constellation. The increased thrust was already needed for Ares I, who's design switched from 4 segments to 5 segments early on, for reasons explained above.
By the time CxP was axed, development of the 5 segment SRBs was well underway. The Congressionally mandated transfer of CxP development contracts to SLS guaranteed that SLS would use the 5 segment booster, not the older shuttle boosters.

[libra]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

wasn’t this a rather old decision, back in the Ares days? Gotta go look up the threads… it’s SOMEWHERE on this forum!

The five segment SRBs came into existence, courtesy of Orion being overweight for the original Ares I design. This effect was worsened when the Ares I upper stage switched from an air-started RS-25 to the J-2X. The result was two things happening: Orion was put on a major diet, including shrinking the capsule diameter back to 5 meters (from 5.5 meters) and shrinking the service module. Additionally, the planned four-segment SRB was changed out for a more powerful five-segment SRB, to make up for performence lost on the upper stage. This all happened in early 2006, shortly after the ESAS had been released.

Now that's what you call: a train wreck.

[woods170]

Speaking of old designs - at what point did the decision to move to 5 segment SRB's take place? Was it related to the move to RS-25s over RS-68s?

I know the RS-68s were decided against because of their ablative heat shielding being affected by SRB exhaust heat, and with that engine having a higher thrust, I can see the change to RS-25s and adding a segment to each of the SRBs to make up for the lost thrust happening hand in hand. That is my guess for the story, at least.

wasn’t this a rather old decision, back in the Ares days? Gotta go look up the threads… it’s SOMEWHERE on this forum!

The five segment SRBs came into existence, courtesy of Orion being overweight for the original Ares I design. This effect was worsened when the Ares I upper stage switched from an air-started RS-25 to the J-2X. The result was two things happening: Orion was put on a major diet, including shrinking the capsule diameter back to 5 meters (from 5.5 meters) and shrinking the service module. Additionally, the planned four-segment SRB was changed out for a more powerful five-segment SRB, to make up for performence lost on the upper stage. This all happened in early 2006, shortly after the ESAS had been released.

Now that's what you call: a train wreck.

Agreed. And I have been fortunate to watch that trainwreck unfold in slow-motion, ever since I became a member here in late December 2006. By that time the soap-opera that was Constellation had only just begun. And courtesy of L2 AND the public forum I had a front row seat (@ Chris Bergin: see what I did there?) when CxP met its natural end. Also: DIRECT pretty much had its home here on NSF. So, watching it rise and get into direct conflict with the established forces in the aerospace industry was truly a "bring popcorn" event. The first six years I spent here was well worth the money invested in L2.

Pardon the blatant L2 plug.

[clongton]

SLS absolutely did NOT need more thrust than the shuttle did. SLS simply could have been a re-branding of the DIRECT architecture, which used the original 4 segment STS SRBs.

The vehicle family enjoyed multiple configurations and was the equal - in every way - to the SLS. Additionally, in some configurations it absolutely was superior to SLS, able to put more tonnes into LEO as well as send more tonnes thru TLI. These are not light statements. We spent considerable time with the engineers at the Aerospace Corp in Los Angles, Ca., and the vehicle's performance data was completely verified and was so reported to the Augustine Commission in 2009. SLS did not have to be the boondoggle that it became. A certain NASA Administrator who declared himself to be "the greatest rocket scientist in history", was bound and determined to push thru his personal design (Ares-I and Ares-V) and led NASA down the golden path to HLV catastrophe. SLS was the result of back room politics, political incompetence and arrogance. And here we are.

[yg1968]

SLS absolutely did NOT need more thrust than the shuttle did. SLS simply could have been a re-branding of the DIRECT architecture, which used the original 4 segment STS SRBs.

The vehicle family enjoyed multiple configurations and was the equal - in every way - to the SLS. Additionally, in some configurations it absolutely was superior to SLS, able to put more tonnes into LEO as well as send more tonnes thru TLI. These are not light statements. We spent considerable time with the engineers at the Aerospace Corp in Los Angles, Ca., and the vehicle's performance data was completely verified and was so reported to the Augustine Commission in 2009. SLS did not have to be the boondoggle that it became. A certain NASA Administrator who declared himself to be "the greatest rocket scientist in history", was bound and determined to push thru his personal design (Ares-I and Ares-V) and led NASA down the golden path to HLV catastrophe. SLS was the result of back room politics, political incompetence and arrogance. And here we are.

Direct was still a government owned HLV. It would have been ready sooner but it still would have suffered the same high cost during operations than any other government program does. I didn't support Direct at the time for that reason and I still don't think that it was a good idea.

[libra]

In the other thread I put it the following way.
DIRECT, Constellation and SLS all used the SD-HLV idea straight out of Mars Direct.
In Constellation case however it was unbalanced because of Ares 1.
In SLS, it is unbalanced because of Congressional pork barrel.
In stark contrast with the above, DIRECT tried to get the best possible architecture out of SD-HLV.

Clongton, what kind of annual flight rate could DIRECT have achieved ? I'm asking this because, in comparison with 1996 and its 8 Shuttle flights, SLS can't do better than 2 annual flights - even if large amounts of dollars and NASA budget were thrown at it. Seems that Boeing and Michoud are bottlenecks. But back in the Shuttle E.T days, Michoud was not limited to 2 per year !

[libra]

SLS absolutely did NOT need more thrust than the shuttle did. SLS simply could have been a re-branding of the DIRECT architecture, which used the original 4 segment STS SRBs.

The vehicle family enjoyed multiple configurations and was the equal - in every way - to the SLS. Additionally, in some configurations it absolutely was superior to SLS, able to put more tonnes into LEO as well as send more tonnes thru TLI. These are not light statements. We spent considerable time with the engineers at the Aerospace Corp in Los Angles, Ca., and the vehicle's performance data was completely verified and was so reported to the Augustine Commission in 2009. SLS did not have to be the boondoggle that it became. A certain NASA Administrator who declared himself to be "the greatest rocket scientist in history", was bound and determined to push thru his personal design (Ares-I and Ares-V) and led NASA down the golden path to HLV catastrophe. SLS was the result of back room politics, political incompetence and arrogance. And here we are.

Direct was still a government owned and operated HLV. It would have been ready sooner but it still would have suffered the same high cost during operations than any other government program does. I didn't support Direct at the time for that reason and I still don't think that it was a good idea.

I get your point of view, but if 2010 taught us something, is that Congress interest for SD-HLV could not be ignored. As much as I hate to say that, make no mistake.
It is the proverbial "making lemons into lemonade". Congress SD-HLV pork barrel & lobby was a pretty strong and entrenched one. Just ask Lori Garver, how the 2010-2011 decision was made, and what it cost to COTS & CCDEV. Don't forget that Congress was ready to nix COTS & CCDEV if nothing replaced at least Ares V (hint: SLS).

So if a bone has to be thrown to goddam SD-HLV entrenched lobby in Congress - then why no pick DIRECT ? (no disrespect to Clongton or the team - oh please). They were more flexible and less expensive SD-HLV that either Ares V or SLS.

That's how I see it. Imagine Jupiter 130 / 232 and Falcon 9 Heavy side by side at The Cape.

[woods170]

SLS absolutely did NOT need more thrust than the shuttle did. SLS simply could have been a re-branding of the DIRECT architecture, which used the original 4 segment STS SRBs.

The vehicle family enjoyed multiple configurations and was the equal - in every way - to the SLS. Additionally, in some configurations it absolutely was superior to SLS, able to put more tonnes into LEO as well as send more tonnes thru TLI. These are not light statements. We spent considerable time with the engineers at the Aerospace Corp in Los Angles, Ca., and the vehicle's performance data was completely verified and was so reported to the Augustine Commission in 2009. SLS did not have to be the boondoggle that it became. A certain NASA Administrator who declared himself to be "the greatest rocket scientist in history", was bound and determined to push thru his personal design (Ares-I and Ares-V) and led NASA down the golden path to HLV catastrophe. SLS was the result of back room politics, political incompetence and arrogance. And here we are.

Chuck, it is okay to say his name out loud: Mike Griffin. Aka the worst NASA administrator ever. The only thing he ever did right IMO, as NASA administrator, was allowing the COTS program to move forward.