Author Topic: SLS General Discussion Thread 2  (Read 226126 times)

Offline notsorandom

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Re: SLS General Discussion Thread 2
« Reply #20 on: 08/12/2015 12:55 PM »
Has NASA thought of using aerospike engines for the core stage instead?

No, the whole point of the SLS design is to use derivatives of shuttle propulsion elements (SSME and SRB's).    SLS will fly only one to two times a year.  Not enough to justfiy a new engine development program.

These questions are the same as those on Orion.  SLS and Orion are not designed to push the state of the art or to reduce operational costs.

Interesting, I also read that during the use of the SLS it will be improved, is this true? Why not reduce operational costs? I understand with what you have said Jim, that they are re-using technologies but will that not reduce the costs as well?
SLS is not going to be doing anything very revolutionary. There are some optimizations already being incorporated. An example would be the first new batch of RS-25 engines will have a new engine controller and less person hour intensive manufacturing. I'd expect like the Shuttle and even Saturn V that SLS will be upgraded over its lifetime. There is still likely to be some sort of advanced booster competition in the future where new technologies may be used. Also the EUS is likely to use RL-10 engines at first but may use another engine. It may also use composite tanks. Those things though are not finalized as the priority is getting the first two launched done.

Offline BrightLight

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Re: SLS General Discussion Thread 2
« Reply #21 on: 08/18/2015 01:37 AM »
http://www.nasaspaceflight.com/2015/08/asap-status-sls-orion-red-risks/

Really good article Chris, highly informative and also positive, I'm glad to see SLS is moving past CxP and maybe into flight status!
« Last Edit: 08/18/2015 10:41 AM by Chris Bergin »

Offline clongton

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Re: SLS General Discussion Thread 2
« Reply #22 on: 08/18/2015 02:01 AM »
Good article. Although short it provided a fairly meaty summary of where the SLS is currently on its journey to flight status. You noted that ASAP still has a concern about schedule driving decisions that might be detrimental to crew safety. Personally I don't think that will be a problem. Pressure schedule can result when things are getting tight and there is no sign of any of that happening with the program. If anything SLS seems to be having a fairly easy time of it, which isn't really surprising as this is the evolutionary path that the Shuttle designers envisioned would be taken to field a true HLV based on the STS design. Over the years several designs began this way, only to fall victim to various circumstances. The two most recent were the NLS and DIRECT, both of which followed this pre-determined "path of least resistance" to an operational HLV. Alas it was not to be for either vehicle. But this third attempt may be the charm. SLS has gotten the furthest along of any of them, even passing where CxP was when it was cancelled, and has yet to encounter a single major problem with the design. We just might get to see the evolved STS HLV fly yet. One thing it has going for it, and a very big thing at that, is that there is plenty of budgetary support for this program, dispite the dearth of payloads to date, besides Orion, that would take advantage of its massive capability. But if SLS actually gets to the finish line and flies, I'm pretty sure that payloads won't be too far behind.

Once again - great article. Thank you.
« Last Edit: 08/18/2015 11:39 AM by clongton »
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Offline Rocket Science

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Re: SLS General Discussion Thread 2
« Reply #23 on: 08/18/2015 02:16 AM »
Thanks for the great article Chris. The political will and the funding is there to build it so we should try to get behind it despite its mission uncertainty.  Interesting the free hydrogen is still an issue perhaps some simple blowers to move it from under the vehicle along with the sparklers might do the trick...
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Offline sdsds

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Re: SLS General Discussion Thread 2
« Reply #25 on: 08/20/2015 07:11 AM »
Interesting the free hydrogen is still an issue

Thanks for pointing that out. In truth though has gaseous hydrogen ever been a concern for any group other than ASAP? In what way has the concern ever been quantified? I ask because sure, fireballs around e.g. Delta IV liftoffs have looked frightening, but have they ever had an impact on mission success? In particular for crew safety, suppose some disasterous contingency scenario were to occur -- isn't that what pad abort systems are designed to handle?
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Offline Rocket Science

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Re: SLS General Discussion Thread 2
« Reply #26 on: 08/20/2015 12:46 PM »
Interesting the free hydrogen is still an issue

Thanks for pointing that out. In truth though has gaseous hydrogen ever been a concern for any group other than ASAP? In what way has the concern ever been quantified? I ask because sure, fireballs around e.g. Delta IV liftoffs have looked frightening, but have they ever had an impact on mission success? In particular for crew safety, suppose some disasterous contingency scenario were to occur -- isn't that what pad abort systems are designed to handle?
During the 70ís when the Shuttle was being designed there was concern that one of the SRBs could prematurely ignite causing a disaster. It could be similar thinking and precaution at play here... Agreed, at least they have a pad abort ability now...
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Offline notsorandom

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Re: SLS General Discussion Thread 2
« Reply #27 on: 08/20/2015 01:12 PM »
Interesting the free hydrogen is still an issue

Thanks for pointing that out. In truth though has gaseous hydrogen ever been a concern for any group other than ASAP? In what way has the concern ever been quantified? I ask because sure, fireballs around e.g. Delta IV liftoffs have looked frightening, but have they ever had an impact on mission success? In particular for crew safety, suppose some disastrous contingency scenario were to occur -- isn't that what pad abort systems are designed to handle?
Following STS-41-D's pad abort free hydrogen that leaked from the engine cause a fire. Had the normal evacuation procedure been followed the crew would have encountered the fire. While Orion has a LES and Discovery didn't there are still situations where it would be preferable to get the crew out of the capsule rather than activate the LES.

Online DaveS

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Re: SLS General Discussion Thread 2
« Reply #28 on: 08/20/2015 01:32 PM »
Interesting the free hydrogen is still an issue

Thanks for pointing that out. In truth though has gaseous hydrogen ever been a concern for any group other than ASAP? In what way has the concern ever been quantified? I ask because sure, fireballs around e.g. Delta IV liftoffs have looked frightening, but have they ever had an impact on mission success? In particular for crew safety, suppose some disastrous contingency scenario were to occur -- isn't that what pad abort systems are designed to handle?
Following STS-41-D's pad abort free hydrogen that leaked from the engine cause a fire. Had the normal evacuation procedure been followed the crew would have encountered the fire. While Orion has a LES and Discovery didn't there are still situations where it would be preferable to get the crew out of the capsule rather than activate the LES.
They did change the procedures after the 41D RSLS abort to include the immediate activation of the Base Heat Shield (BHS) water deluge system (this is the water system that showers the engines after a RSLS abort). For 41D and earlier, the procedure was a manual activation and it was only in short bursts. After 41D they made it automatic as well as continues which kept the engines and the aft watered down for a good 15 minutes or so.
« Last Edit: 08/20/2015 01:32 PM by DaveS »
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Offline notsorandom

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Re: SLS General Discussion Thread 2
« Reply #29 on: 08/20/2015 03:10 PM »
Interesting the free hydrogen is still an issue

Thanks for pointing that out. In truth though has gaseous hydrogen ever been a concern for any group other than ASAP? In what way has the concern ever been quantified? I ask because sure, fireballs around e.g. Delta IV liftoffs have looked frightening, but have they ever had an impact on mission success? In particular for crew safety, suppose some disastrous contingency scenario were to occur -- isn't that what pad abort systems are designed to handle?
Following STS-41-D's pad abort free hydrogen that leaked from the engine cause a fire. Had the normal evacuation procedure been followed the crew would have encountered the fire. While Orion has a LES and Discovery didn't there are still situations where it would be preferable to get the crew out of the capsule rather than activate the LES.
They did change the procedures after the 41D RSLS abort to include the immediate activation of the Base Heat Shield (BHS) water deluge system (this is the water system that showers the engines after a RSLS abort). For 41D and earlier, the procedure was a manual activation and it was only in short bursts. After 41D they made it automatic as well as continues which kept the engines and the aft watered down for a good 15 minutes or so.
If I'm not mistaken they also added butcher paper in various places so that the cameras on and around the pad could see if there were a fire.

Online DaveS

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Re: SLS General Discussion Thread 2
« Reply #30 on: 08/20/2015 03:53 PM »
Interesting the free hydrogen is still an issue

Thanks for pointing that out. In truth though has gaseous hydrogen ever been a concern for any group other than ASAP? In what way has the concern ever been quantified? I ask because sure, fireballs around e.g. Delta IV liftoffs have looked frightening, but have they ever had an impact on mission success? In particular for crew safety, suppose some disastrous contingency scenario were to occur -- isn't that what pad abort systems are designed to handle?
Following STS-41-D's pad abort free hydrogen that leaked from the engine cause a fire. Had the normal evacuation procedure been followed the crew would have encountered the fire. While Orion has a LES and Discovery didn't there are still situations where it would be preferable to get the crew out of the capsule rather than activate the LES.
They did change the procedures after the 41D RSLS abort to include the immediate activation of the Base Heat Shield (BHS) water deluge system (this is the water system that showers the engines after a RSLS abort). For 41D and earlier, the procedure was a manual activation and it was only in short bursts. After 41D they made it automatic as well as continues which kept the engines and the aft watered down for a good 15 minutes or so.
If I'm not mistaken they also added butcher paper in various places so that the cameras on and around the pad could see if there were a fire.
That was only on the aft vertical struts of the ET. They also installed alot more IR cameras. Before 41D they only had a few.
"For Sardines, space is no problem!"
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"We're rolling in the wrong direction but for the right reasons"
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Offline Gordon C

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Re: SLS General Discussion Thread 2
« Reply #31 on: 08/22/2015 10:41 PM »
Has NASA thought of using aerospike engines for the core stage instead?

No, the whole point of the SLS design is to use derivatives of shuttle propulsion elements (SSME and SRB's).    SLS will fly only one to two times a year.  Not enough to justfiy a new engine development program.

These questions are the same as those on Orion.  SLS and Orion are not designed to push the state of the art or to reduce operational costs.

If SLS were being built without want for use of STS hardware, would it stage sequentially like Saturn V did?  Or is there benefit to horizontal staging where even in absence of STS hardware it would look like Delta IV with boosters on the side of a big core?

Offline sdsds

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Re: SLS General Discussion Thread 2
« Reply #32 on: 08/23/2015 12:11 AM »
If SLS were being built without want for use of STS hardware, would it stage sequentially like Saturn V did?

In late 2010, NASA engaged in a "Requirements Analysis Cycle" evaluating just this kind of question. See:
http://www.nasaspaceflight.com/2010/12/heft-sls-hlv-design-decision-april-2011/

Ed Kyle wrote more about this:
http://www.spacelaunchreport.com/sls4.html

Of course the decision is now "water under the bridge," but your hypothetical question nonetheless deserves some sort of answer!
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Offline Proponent

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Re: SLS General Discussion Thread 2
« Reply #33 on: 08/24/2015 05:37 AM »
If SLS were being built without want for use of STS hardware, would it stage sequentially like Saturn V did?  Or is there benefit to horizontal staging where even in absence of STS hardware it would look like Delta IV with boosters on the side of a big core?

In addition to sdsds's pointer to the series-staged RAC-2 design, first principles suggest you would use traditional series staging rather than parallel staging for a clean-sheet expendable vehicle.  One of the good things about a traditional first stage is that weight is not critical.  Typically each kilogram added to the first-stage's structure reduces the LEO payload by only about 0.1 kg, because the stage isn't carried very far.  In a core-plus boosters design, on the other hand, the core is carried all the way to orbit, so each kilogram of added mass reduces the payload by 1 kg.  Hence, the whole core is a weight-critical structure, and its cost will tend to reflect that.

Another problem with parallel staging is that the core's engines need to operate at sea-level and, with high efficiency, in a vacuum.  This is perfectly possible, as the SSME proved, but it's not cheap.

A while ago I did a back-of-the-envelope numerical comparison (see the attachment) of series and parallel staging to illustrate these arguments.

« Last Edit: 08/25/2015 03:19 AM by Proponent »

Offline redliox

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Re: SLS General Discussion Thread 2
« Reply #34 on: 09/02/2015 09:32 PM »
Couple of links; first, this appears to be a recent SLS blog:
https://blogs.nasa.gov/Rocketology/

Second, the NASA Advisory Council link was fixed and this PowerPoint deck (presented at the end of July at the JPL meeting) has some good information on development/status and recent schedule forecasts:
http://www.nasa.gov/sites/default/files/files/2-Hill-Exploration-Systems-Development-Status-ESD-Status-NAC_Hill-July-28_Final.pdf

The progress looks encouraging.  Reading into it, it looks like both Orion and SLS will be built and ready by the final quarter of 2017 if all goes well.  They mention mating the capsule with ESA's service module in 2017 but they don't elaborate much further on its progress; that makes me desire details on ESA's progress - the last thing we need is a delay caused by European and American contractors misinterpreting each other's Metric and Imperial/English measurements (which would be the least of more serious issues).  Hopefully minimal delays or issues occur and keep EM-1 ready for summer of '18.  :)
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Offline clongton

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Re: SLS General Discussion Thread 2
« Reply #35 on: 09/03/2015 01:15 AM »
When completed, SLS, NASA's new rocket, will be one of the biggest, most powerful rockets ever built.

Having been around when the Saturn-V was flying I am constantly irritated when I see statements like this. Everybody is always insisting that we compare apples to apples rather than apples to oranges, EXCEPT when it comes to showcasing the SLS - as if there is nothing else out there that compares favorably. Here's where us "old-timers" step in to set the record straight and keep the SLS proponents honest.

The configuration of SLS above includes two (2) solid side boosters, and then they compare it to the Saturn-V without side boosters. Well for everyone's information there were side booster versions of the Saturn-V being developed that used a pair of 120 inch diameter solids strapped to the side of the core. This vehicle would deliver in excess of 180 tonnes to LEO. If one wants to compare the SLS to Saturn, then compare it to this side-boosted variant. If one does not want to compare to this Saturn variant then delete the SLS solids and compare core to core. Keep it apples to apples. Either way SLS will always come out less than the Saturn.

For those who would say that the solid-boosted Saturn never actually existed I would say that neither does an actual SLS. But I would say that both vehicles were at a similar stage of development, with metal being bent for bothedit. That makes them completely comparable.

I'm not bashing the SLS by any means. What I am bashing is misleading statements about the SLS.

Edit: added clarifying phrase
« Last Edit: 09/03/2015 11:58 AM by clongton »
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Offline RonM

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Re: SLS General Discussion Thread 2
« Reply #36 on: 09/03/2015 02:27 AM »
When completed, SLS, NASA's new rocket, will be one of the biggest, most powerful rockets ever built.

Having been around when the Saturn-V was flying I am constantly irritated when I see statements like this. Everybody is always insisting that we compare apples to apples rather than apples to oranges, EXCEPT when it comes to showcasing the SLS - as if there is nothing else out there that compares favorably. Here's where us "old-timers" step in to set the record straight and keep the SLS proponents honest.

The configuration of SLS above includes two (2) solid side boosters, and then they compare it to the Saturn-V without side boosters. Well for everyone's information there were side booster versions of the Saturn-V being developed that used a pair of 120 inch diameter solids strapped to the side of the core. This vehicle would deliver in excess of 180 tonnes to LEO. If one wants to compare the SLS to Saturn, then compare it to this side-boosted variant. If one does not want to compare to this Saturn variant then delete the SLS solids and compare core to core. Keep it apples to apples. Either way SLS will always come out less than the Saturn.

For those who would say that the solid-boosted Saturn never actually existed I would say that neither does an actual SLS. But I would say that both vehicles were at a similar stage of development. That makes them completely comparable.

I'm not bashing the SLS by any means. What I am bashing is misleading statements about the SLS.

While I see your point, it's not valid under these circumstances.

Metal is being bent, the boosters and engines are real, SLS will launch in less than three years. You can't say SLS doesn't exist.

Online Steven Pietrobon

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Re: SLS General Discussion Thread 2
« Reply #37 on: 09/03/2015 10:20 AM »
For those who would say that the solid-boosted Saturn never actually existed I would say that neither does an actual SLS. But I would say that both vehicles were at a similar stage of development. That makes them completely comparable.

There is no need to compare with a solid boosted version of Saturn V. The Block I (70 t) and Block IB (93 t) versions of SLS are both below the Saturn V (118 t). These two versions are the only ones that NASA is currently planning on building. If NASA does decide to build the full Block II version of SLS (130 t), then that will indeed be the most powerful, but for now, they are definitely not building the world's most powerful rocket.
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Offline woods170

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Re: SLS General Discussion Thread 2
« Reply #38 on: 09/03/2015 11:49 AM »
When completed, SLS, NASA's new rocket, will be one of the biggest, most powerful rockets ever built.

Having been around when the Saturn-V was flying I am constantly irritated when I see statements like this.
<snip>
I'm not bashing the SLS by any means. What I am bashing is misleading statements about the SLS.
Emphasis mine.

There is nothing misleading about the SLS statement. It does not say that SLS is THE most powerful rocket ever build. It specifically states that SLS is ONE of the most powerful rockets ever build. And that is correct. SLS in it's 70 mT and 93 mT incarnations stands among the most powerful rockets in the world, surpassed only by N-1, Energia and Saturn V.
« Last Edit: 09/03/2015 11:56 AM by woods170 »

Offline MarcAlain

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Re: SLS General Discussion Thread 2
« Reply #39 on: 09/03/2015 04:05 PM »
KSC shopping for Liquid Hydrogen solution ahead of SLS debut
http://www.nasaspaceflight.com/2015/03/ksc-shopping-lh2-ahead-sls-launch/

They should just replace the entire first stage with a RP1 fueled, F1 engine cluster.

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