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What is the main part of the Shuttle stack we should keep?

What is the main part of the Shuttle stack we should keep?

  • Orbiter

    Votes: 2 22.2%
  • SSMEs

    Votes: 3 33.3%
  • SRBs

    Votes: 2 22.2%
  • ET

    Votes: 2 22.2%

  • Total voters
    9
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RVHM

Guest
With the demise of the Space Shuttle program, and possibly any sort of future Shuttle-Derived Launch Vehicle, a great deal of technological assets are going to be lost to the American space program. Which one do you believe would be most important to keep for future architectures, and why?

I think the most important asset we should keep is the SSME. A very well-know quantity, the SSME has been used, built upon and improved for over three decades, resulting in the finest hydrolox engine ever to exist. It has reached a level of development where its performance is unlikely to be surpassed by any chemical-based rocket engine. Besides, the only American alternative, the RS-68, is much less efficient.

That is why I think we should keep at least the SSME from the Shuttle stack, what do you think we should keep?
 
P

pathfinder_01

Guest
IMHO none.

The SSME are expensive and were built with reuse in mind. If you want to convert the shuttle stack into a heavy lift like Ares V, you will need different engines. The RS-68 is cheaper and develops better thrust.

Large steel cased segmented SRBS are a product of the 70ies. You can get better performance with composite case solid rockets not to mention lox\kerosene engines as well as the RS-68 deliver more thrust than the SSME. There is less need of them and they are expensive to process. They were a 1970’ s answer to a problem(How to get the shuttle off the pad with its great isp, but poor thrust).

The fuel tank is just a tank. It would have to be redesigned no matter what due to different structural loads. The diameter might have to be changed if an engine with less ISP is chosen (RS-68).

I think the ideal heavy lift will be based off the EELV or falcon. It will share facilities and crew with the EELV. That way you don’t need the expense of different crew, different buildings, and different launch pads. I love the shuttle. Think it is one heck of a great craft but if we are to go forward then it’s time is done. The perfect heavy lift is one that can be maintained without NASA bearing its full costs. Only a HSF program needs heavy lift and even then only sometimes (i.e. heavy lift can put up a space station quickly, but I don’t think the crew needs 100tons of supply regularly). If the heavy lift is a completely separate system like shuttle derived then NASA will never be able to afford to put BEO craft atop it.
 
R

RVHM

Guest
pathfinder_01":kqv2ssix said:
IMHO none.

The SSME are expensive and were built with reuse in mind. If you want to convert the shuttle stack into a heavy lift like Ares V, you will need different engines. The RS-68 is cheaper and develops better thrust.
Yeah, but an expendible version of the SSME can be created with lower costs. Besides, the RS-68 has more thrust but also a much lower specific impulse, and its ablative cooling can be a problem when used in great numbers.

pathfinder_01":kqv2ssix said:
Large steel cased segmented SRBS are a product of the 70ies. You can get better performance with composite case solid rockets not to mention lox\kerosene engines as well as the RS-68 deliver more thrust than the SSME. There is less need of them and they are expensive to process. They were a 1970’ s answer to a problem(How to get the shuttle off the pad with its great isp, but poor thrust).
True, composite case solid rockets would be better. At some time, there was talk of changing the SRB casings to composites. But LRBs require many engines if they are going to replace SRBs (SRBs are nearly twice as powerful as the best Kerolox engine ever, and roughly 2.5 times as powerful as the best American Kerolox engine.

pathfinder_01":kqv2ssix said:
The fuel tank is just a tank. It would have to be redesigned no matter what due to different structural loads. The diameter might have to be changed if an engine with less ISP is chosen (RS-68).
That's another reason why RS-68 is bad. Changing the tank structure to accommodate this engine has knock-on costs on tooling, transport, infrastructure, etc., so costs will rocket.

pathfinder_01":kqv2ssix said:
I think the ideal heavy lift will be based off the EELV or falcon. It will share facilities and crew with the EELV. That way you don’t need the expense of different crew, different buildings, and different launch pads. I love the shuttle. Think it is one heck of a great craft but if we are to go forward then it’s time is done. The perfect heavy lift is one that can be maintained without NASA bearing its full costs. Only a HSF program needs heavy lift and even then only sometimes (i.e. heavy lift can put up a space station quickly, but I don’t think the crew needs 100tons of supply regularly). If the heavy lift is a completely separate system like shuttle derived then NASA will never be able to afford to put BEO craft atop it.
How many CCBs would you need to create an HLV?
 
P

PistolPete037

Guest
If Ares had ended up using any components of the Shuttle stack, then it might have not gotten canceled.
 
R

RVHM

Guest
PistolPete037":1hmct7qx said:
If Ares had ended up using any components of the Shuttle stack, then it might have not gotten canceled.
Then why is Obama cancelling all flavors of SDLV?
 
S

stevekk

Guest
pathfinder_01":381s7lex said:
IMHO none.

The SSME are expensive and were built with reuse in mind. If you want to convert the shuttle stack into a heavy lift like Ares V, you will need different engines. The RS-68 is cheaper and develops better thrust.

The fuel tank is just a tank. It would have to be redesigned no matter what due to different structural loads. The diameter might have to be changed if an engine with less ISP is chosen (RS-68).
It sounds like the SSME is only the engine of choice if you are building a re-usable craft. I don't see a case for maintaining the current SRB or external tank stack either.
 
E

EarthlingX

Guest
SSME is not restartable, and enabling it for that would cost too much. Besides there is no need for that, since RS-68 was started as an evolution of SSME, and its simpler design makes it much more appropriate for such a role.
No part of Shuttle, as it is, is worth keeping, except in a museum (or my front lawn), or for use in SDLV, while the stocks last.

Some info to make a bit more informed opinion, and to give starting points for further study :
http://www.nasaspaceflight.com : SD HLV Review Outlines ISS Logistics and Transport

http://www.nasaspaceflight.com : Completed SD HLV assessment highlights low-cost post-shuttle solution

http://www.nasaspaceflight.com : MAF provide positive ET hardware overview for early SD HLV test flight

www.nasaspaceflight.com : Bolden Directs MSFC Special Team to evaluate HLV alternatives

Wiki : Shuttle-Derived Launch Vehicle

http://www.astronautix.com/lvs/shuttle.htm
 
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scottb50

Guest
The SSME could be restarted but is not configured for it, the RS68 isn't either. That they could be made to restart is another thing. The Merlin uses a solid cartridge for starting with three available starts, the J2X uses stored hypergolics to get the turbopumps running.

It's not so much it can't be restarted as there was no need to add that capability to it, though it could be added. One very good reason is not really suitable for in-Space use both because of it's power and nozzle design, purpose built engines make more sense. The RL-10 is a good example, it is sized for prospective payloads and uses a vacuum optimized nozzle.
The Falcon 9 uses the Merlin for both stages with the upper stage using a much bigger nozzle.

Basically there is no real reason to restart an SSME, not that it couldn't be done.

http://yarchive.net/space/shuttle/ssme_ignition.html
 
Z

ZiraldoAerospace

Guest
I personally voted for the orbiter its self, but... WHO IN HELL WOULD VOTE FOR THE SRB'S?????????????????????????????????????????????????? ARE YOU ON CRACK????!!! Why???????????? Pick any of the other three, I don't care, that is personal preference, but doesn't everyone know that the SRB's suck??? Sorry, I was just a little frustrated :shock:
 
V

vulture4

Guest
ZiraldoAerospace":2xr4qhil said:
I personally voted for the orbiter its self, but... WHO IN HELL WOULD VOTE FOR THE SRB'S?????????????????????????????????????????????????? ARE YOU ON CRACK????!!! Why???????????? Pick any of the other three, I don't care, that is personal preference, but doesn't everyone know that the SRB's suck??? Sorry, I was just a little frustrated :shock:
Agree. Using the SRB for Constellation or any future project is an inexplicable choice from the perspective of reliability, operating cost, and reuseability.

But then, a recent NASA conference on reliability reached the astounding conclusion that solids are more reliable than liquids because they have fewer parts. This is an extraordinarily simplistic claim. Having seen Atlas, Titan, and Shuttle all destroyed because of SRB failures, this seems inconsistent with history. It also ignores some basic principles of reliability engineering. Most launch vehicle failures are deterministic, not random, so the preflight testing of liquid engines (which cannot be done with solids) substantially reduces the risk of failure, while it's extremely difficult to exclude defects in the case or fuel grain of solids. Having attended hundreds of NASA safety meetings over more than two decades, I have so far seen no evidence that NASA has a better understanding of safety than a typical private contractor in the aerospace field.

On the operating cost side, you have to watch the process of shipping, inspecting, and stacking the solids. The number of hazardous operations, crane lifts, and total man-hours is much greater than with boosters like the Soyuz and Delta, not to mention the immense weight that requires the MLPs and crawlers. Just compare the cost of the massive Ares infrastructure with that needed for launching the Falcon

The reusability of the SRBs has always been more show than substance.It's been argued that the cost of reuse is less than the cost of manufacture, but just barely, and an expendable SRB would likely be much cheaper. Reprocessing the orbiter, particularly with the improved application of foam post-Columbia, has been cheap by comparison.

The use (and reuse) of the SRB on Constellation, like its original use on the Shuttle, seems to have been a superficial decision by high-level managers, followed rather blindly by those of us in the lower ranks who should have been smart enough to recognize its shortcomings and had the initiative to raise the issue.
 
S

stevekk

Guest
vulture4":4v4i3beb said:
ZiraldoAerospace":4v4i3beb said:
I personally voted for the orbiter its self, but... WHO IN HELL WOULD VOTE FOR THE SRB'S?????????????????????????????????????????????????? ARE YOU ON CRACK????!!! Why???????????? Pick any of the other three, I don't care, that is personal preference, but doesn't everyone know that the SRB's suck??? Sorry, I was just a little frustrated :shock:
Agree. Using the SRB for Constellation or any future project is an inexplicable choice from the perspective of reliability, operating cost, and reuseability.

But then, a recent NASA conference on reliability reached the astounding conclusion that solids are more reliable than liquids because they have fewer parts. This is an extraordinarily simplistic claim. Having seen Atlas, Titan, and Shuttle all destroyed because of SRB failures, this seems inconsistent with history. It also ignores some basic principles of reliability engineering. Most launch vehicle failures are deterministic, not random, so the preflight testing of liquid engines (which cannot be done with solids) substantially reduces the risk of failure, while it's extremely difficult to exclude defects in the case or fuel grain of solids. Having attended hundreds of NASA safety meetings over more than two decades, I have so far seen no evidence that NASA has a better understanding of safety than a typical private contractor in the aerospace field.

On the operating cost side, you have to watch the process of shipping, inspecting, and stacking the solids. The number of hazardous operations, crane lifts, and total man-hours is much greater than with boosters like the Soyuz and Delta, not to mention the immense weight that requires the MLPs and crawlers. Just compare the cost of the massive Ares infrastructure with that needed for launching the Falcon

The reusability of the SRBs has always been more show than substance.It's been argued that the cost of reuse is less than the cost of manufacture, but just barely, and an expendable SRB would likely be much cheaper. Reprocessing the orbiter, particularly with the improved application of foam post-Columbia, has been cheap by comparison.

The use (and reuse) of the SRB on Constellation, like its original use on the Shuttle, seems to have been a superficial decision by high-level managers, followed rather blindly by those of us in the lower ranks who should have been smart enough to recognize its shortcomings and had the initiative to raise the issue.
How much weight can be saved if the SRBs weren't part of the stack ??

What if the Shuttle design was modified to replace the 2 SRBs with an additional 2 or 3 SSMEs/RS-68 engines. Perhaps these additional engines get mounted at the bottom of a much larger external fuel tank. Since the tank isn't loaded until it gets to the pad, the total stack is lighter than the stack with the SRBs. The stack still gets processed and needs to get transported to the pad using some type of Crawler, right ? Do the SSMEs / RS-68s get less expensive if we start building them in significant volume ?
 
E

EarthlingX

Guest
stevekk":jfde9d4a said:
How much weight can be saved if the SRBs weren't part of the stack ??
Don't know exact numbers, would have to check, but my guess would be 90% of boosters weight, before getting to the pad. Liquid tanks don't require so much mechanical endurance as solid boosters, which are a big combustion chamber.

stevekk":jfde9d4a said:
What if the Shuttle design was modified to replace the 2 SRBs with an additional 2 or 3 SSMEs/RS-68 engines. Perhaps these additional engines get mounted at the bottom of a much larger external fuel tank. Since the tank isn't loaded until it gets to the pad, the total stack is lighter than the stack with the SRBs. The stack still gets processed and needs to get transported to the pad using some type of Crawler, right ?
No need for crawler, if there are no SRBs. Everything can be transported on regular train tracks.

stevekk":jfde9d4a said:
Do the SSMEs / RS-68s get less expensive if we start building them in significant volume ?
I would expect so. Doesn't everything ? I don't have exact numbers though.

Check this couple of links :

ntrs.nasa.gov : DUAL LIQUID FLYBACK BOOSTER FOR THE SPACE SHUTTLE (pdf)
C. Blum, P. Jones, B. Meinders
Lockheed Martin Michoud Space Systems
New Orleans, Louisiana

ABSTRACT
Liquid Flyback Boosters provide an opportunity to improve shuttle safety, increase performance, and reduce operating costs. The objective of the LFBB study is to establish the viability of a LFBB configuration to integrate into the shuttle vehicle and meet the goals of the Space Shuttle upgrades program. The design of a technically viable LFBB must integrate into the shuttle vehicle with acceptable impacts to the vehicle elements, i.e. orbiter and external tank and the shuttle operations infrastructure.
The LFBB must also be capable of autonomous return to the launch site. The smooth integration of the LFBB into the space shuttle vehicle and the ability of the LFBB to fly back to the launch site are not mutually compatible capabilities. LFBB wing configurations optimized for ascent must also provide flight quality during the powered return back to the launch site. This paper will focus on the core booster design and ascent performance.
A companion paper, "Conceptual Design for a Space Shuttle Liquid Flyback Booster" will focus on the flyback system design and performance. The LFBB study developed design and aerodynamic data to demonstrate the viability of a dual booster configuration to meet the shuttle upgrade goals, i.e. enhanced safety, improved performance and reduced operations costs.

Other people also interested in flyback boosters :

Wiki : Baikal booster

http://www.flightglobal.com : USAF seeks reusable booster concepts

http://www.aviationweek.com : USAF Plans For Reusable Booster

buzzaldrin.com : Starbooster
 
E

EarthlingX

Guest
www.nasaspaceflight.com : Lunar/BEO – SD HLV, Commercial and International Architecture Outlined
July 14th, 2010 by Chris Bergin



As the on-going political refinements to the FY2011 budget proposal raise the hope of utilizing “Shuttle’s Legacy” in a Heavy Lift Launch Vehicle (HLV), the third article – based on the findings of the expansive SD (Shuttle Derived) HLV assessment presentation – outlines both the use of the HLV in returning to the Moon, and the joint role of working with commercial and international vehicles in a Beyond Earth Orbit (BEO) architecture.
 
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