Thrust
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Space Shuttle External Tank

Hi there. I had a question regarding the external tank. I know there were possible plans to reuse them in earth orbit that never materialized. Could the space shuttle actually have burned into earth orbit with the external tank still attached to it without any modifications, and a full payload in its cargo bay? And if so, would its total LEO payload have surpassed that of the Saturn V?

By several of my calculations, it shows that it would indeed have surpassed the Saturn V. The earlier standard tanks weighed 77,000 lbs dry. Combined with the shuttle's 240,000 pound payload capacity, this would have resulted in a payload to earth orbit of greater than 310,000 pounds, more than Apollo 15's payload. Even with the super-lightweight tanks, this still would've tied the Saturn V.

Now, my calculations are my calculations. I'm trying to get input from others on this forum regarding this question. I was once under the impression the shuttle was not as powerful as the Saturn V. Now I'm not so sure.
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vikkyvik
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RE: Space Shuttle External Tank

 Quoting THrust (Thread starter):Combined with the shuttle's 240,000 pound payload capacity

I think you quoted the wrong figure. The orbiter's Gross Liftoff Weight appears to be 240,000 lbs, while the Max Payload appears to be ~55,000 lbs.
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Thrust
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RE: Space Shuttle External Tank

i'm talking about total weight injected into space.
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kc135topboom
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RE: Space Shuttle External Tank

 Quoting THrust (Thread starter): would its total LEO payload have surpassed that of the Saturn V?
 Quoting vikkyvik (Reply 1):The orbiter's Gross Liftoff Weight appears to be 240,000 lbs, while the Max Payload appears to be ~55,000 lbs.
 Quoting THrust (Reply 2):i'm talking about total weight injected into space.

The Saturn V rocket still holds the records for weight it can send to LEO and to TLI. To LEO (any orbit with an altitude BELOW 2,000 km, or about 1,200 miles) the S-V can lift 260,000 lbs. In other words it could lift the MGW of the fully loaded Shuttle, and then some.

To TLI (Trans Lunar Injection), the S-V could lift 100,000 lbs. In other words, the S-V can lift almost twice the weight the Shuttle can put into Low Earth Orbit, but send it onto Trans Lunar Injection (which is the point after at least one complete orbit of the Earth, so speed can build up, that you begin to leave the Earth Orbit on your way to the Moon).

There has never been a rocket as capable or as reliable as the Saturn V. It 'flew' 11 times (13 if you count the Saturn INT-21), and was successful every time. It did have one partial launch failure, Apollo-6, the rocket experienced severe Pogo Oscillations, due to the attachments of the F-1 engines, then after the 3rd stage was exhausted and jettisoned, the 2nd stage lost 2 of its 5 J-2 engines, but it still made it into a 200 mile high orbit.

Some have suggested the Apollo-13 mission was also an S-V failure, but it was not. The O2 tank explosion aboard the A-13 SM was some 56 hours after the launch, and some 200,000 miles in altitude. This was well after the S-V did its job of the launch and insertion into TLI.

moo
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RE: Space Shuttle External Tank

 Quoting KC135TopBoom (Reply 3):

Apollo 13 is often mentioned as a possible S-V "failure" because there was a centre engine cutout on the second stage due to pogo-ing, in addition to the famous CM issue.

kc135topboom
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RE: Space Shuttle External Tank

I have never heard of a PO event with the A-13 mission, nor a J-2 engine shutdown. But even if this did happen, it would be considered a 'partial failure' as they still got to TLI.

Do you have a link to the event? I'm not saying it didn't happen, just I have not heard of it happening, other than the A-6 mission.

zanl188
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RE: Space Shuttle External Tank

 Quoting KC135TopBoom (Reply 5):Do you have a link to the event? I'm not saying it didn't happen, just I have not heard of it happening, other than the A-6 mission.

Early center engine shutdown on the Apollo 13 S-II is a well known event. Check your own sources. No way it would be considered a failure, glitch yes, failure no.

 Quoting KC135TopBoom (Reply 3):It did have one partial launch failure, Apollo-6, the rocket experienced severe Pogo Oscillations, due to the attachments of the F-1 engines, then after the 3rd stage was exhausted and jettisoned, the 2nd stage lost 2 of its 5 J-2 engines, but it still made it into a 200 mile high orbit.

Your sequence is all wrong... You can't have an exhausted and jettisoned 3rd stage BEFORE 2 engines shutdown early on the 2nd stage. Apollo 6 would have been aborted had there been a crew aboard. I'd call it a successful failure though because many things were learned and there wasn't much if any delay caused by Apollo 6.

 Quoting KC135TopBoom (Reply 3):To TLI (Trans Lunar Injection), the S-V could lift 100,000 lbs. In other words, the S-V can lift almost twice the weight the Shuttle can put into Low Earth Orbit, but send it onto Trans Lunar Injection (which is the point after at least one complete orbit of the Earth, so speed can build up, that you begin to leave the Earth Orbit on your way to the Moon).

TLI is not a chance to let "speed build up". TLI is when the 3rd stage is reignited to send the spacecraft to the moon.
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checksixx
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RE: Space Shuttle External Tank

 Quoting THrust (Thread starter):Hi there. I had a question regarding the external tank. I know there were possible plans to reuse them in earth orbit that never materialized. Could the space shuttle actually have burned into earth orbit with the external tank still attached to it without any modifications, and a full payload in its cargo bay?

I'm not aware of any plans, EVER, to reuse the external tanks. They were designed into the program from the start to be one time use. The space shuttle 'burned' into earth orbit EVERY time with the tank attached until MECO.

Stealthz
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RE: Space Shuttle External Tank

 Quoting checksixx (Reply 7):I'm not aware of any plans, EVER, to reuse the external tanks.

I recall articles from the early days of the shuttle program that had concept proposals and artwork for "space stations" assembled from numbers of external tanks, an expansion of the Skylab concept perhaps.

I don't know if these were ever solid engineering proposals or Marketing spin to bolster the concept of STS as an economical and perhaps even a commercially viable concept.
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vzlet
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RE: Space Shuttle External Tank

 Quoting checksixx (Reply 7):The space shuttle 'burned' into earth orbit EVERY time with the tank attached until MECO.

Think about that for a second. If a shuttle (and the still-attached external tank) had orbital velocity at MECO, then the tank itself did too. That obviously wasn't the case. The orbiter required additional velocity from OMS firing(s) to reach orbit.
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zanl188
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RE: Space Shuttle External Tank

 Quoting checksixx (Reply 7):I'm not aware of any plans, EVER, to reuse the external tanks.
 Quoting stealthz (Reply 8):I recall articles from the early days of the shuttle program that had concept proposals and artwork for "space stations" assembled from numbers of external tanks, an expansion of the Skylab concept perhaps. I don't know if these were ever solid engineering proposals or Marketing spin to bolster the concept of STS as an economical and perhaps even a commercially viable concept.

NASA has/had plans for many missions it never actually flew.

 Quoting vzlet (Reply 9):Think about that for a second. If a shuttle (and the still-attached external tank) had orbital velocity at MECO, then the tank itself did too. That obviously wasn't the case. The orbiter required additional velocity from OMS firing(s) to reach orbit.

The ETs were jettisoned from shuttle with almost all the energy needed to go into orbit. They just needed to circularize the orbit and they'd have been in orbit. Further the tanks usually had leftover propellant, add a small engine and voila it's in orbit. Or they may have been able to use a propulsive "vent" (adds velocity) instead of a destructive "vent" (causes tumbling, aids reentry). Not sure if a propulsive vent would have added the required delta-V

 Quoting KC135TopBoom (Reply 3):There has never been a rocket as capable or as reliable as the Saturn V. It 'flew' 11 times (13 if you count the Saturn INT-21), and was successful every time.

Bullhockey. There are a number of launch vehicles that have had a string of successes that long before (or between) failures. Had S-V flown more it would've had a failure. Saturn V was like Concorde in this respect... all it would've taken is one accident to go from first to worst, statistically speaking...
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connies4ever
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RE: Space Shuttle External Tank

 Quoting KC135TopBoom (Reply 3):Some have suggested the Apollo-13 mission was also an S-V failure, but it was not. The O2 tank explosion aboard the A-13 SM was some 56 hours after the launch, and some 200,000 miles in altitude. This was well after the S-V did its job of the launch and insertion into TLI.

Pogo, however, was a more frequent companion on the Apollo missions than most realise:
http://www.pwrengineering.com/articles/pogo.htm

Agreed the centre engine S-II shutdown on Apollo 13 was not a failure but a problem. But it could have been much worse.

 Quoting checksixx (Reply 7):Quoting THrust (Thread starter): Hi there. I had a question regarding the external tank. I know there were possible plans to reuse them in earth orbit that never materialized. Could the space shuttle actually have burned into earth orbit with the external tank still attached to it without any modifications, and a full payload in its cargo bay? I'm not aware of any plans, EVER, to reuse the external tanks. They were designed into the program from the start to be one time use. The space shuttle 'burned' into earth orbit EVERY time with the tank attached until MECO.

Yah, agreed. I think perhaps OP has confused SS ET re-use with early Apollo Application (as it was then called) studies that looked at re-using the S-IVB stage in orbit . In the end of course the whole S-IVB was replaced with a fully-kitted laboratory.
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zanl188
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RE: Space Shuttle External Tank

NASA had studies/plans for a number of ET reuse projects. Reuse as lunar shelters, a source of aluminum in orbit, etc..

I didn't spend a lot of time refining the search at NTRS, but you can search to your hearts content....

But to say that there were no plans/studies would be incorrect...

http://ntrs.nasa.gov/search.jsp?Ntx=...&No=20&Ntt=external%20tank%20reuse
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RE: Space Shuttle External Tank

 Quoting ZANL188 (Reply 10):Bullhockey. There are a number of launch vehicles that have had a string of successes that long before (or between) failures. Had S-V flown more it would've had a failure. Saturn V was like Concorde in this respect... all it would've taken is one accident to go from first to worst, statistically speaking...

Atlas V is at 32 launches without a failure. One Centaur quit a little soon, but the payload still made it to it's intended orbit.
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checksixx
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RE: Space Shuttle External Tank

 Quoting vzlet (Reply 9):Quoting checksixx (Reply 7): The space shuttle 'burned' into earth orbit EVERY time with the tank attached until MECO. Think about that for a second. If a shuttle (and the still-attached external tank) had orbital velocity at MECO, then the tank itself did too. That obviously wasn't the case. The orbiter required additional velocity from OMS firing(s) to reach orbit.

My statement was accurate sir.

moo
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RE: Space Shuttle External Tank

 Quoting ZANL188 (Reply 6):No way it would be considered a failure, glitch yes, failure no.
 Quoting KC135TopBoom (Reply 5):But even if this did happen, it would be considered a 'partial failure' as they still got to TLI.
 Quoting connies4ever (Reply 11):Agreed the centre engine S-II shutdown on Apollo 13 was not a failure but a problem

Thats why I used quotes around the word failure

Areopagus
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RE: Space Shuttle External Tank

The shuttle flew a profile that dumped the ET back into the atmosphere over the Indian Ocean, while the orbiter did an OMS burn to get the delta-V to achieve a stable orbit. But I recall reading, around the time of the first shuttle flight, that it would have been more efficient to use SSME/ET propulsion to get all the way to orbit. The problem with that would be to have a derelict ET in orbit with no control over where its remnants fell. They took a payload hit in order to put it down safely short of orbit. IIRC, the payload penalty was not just due to propellant usage, but also to the depressed trajectory needed to put the ET down in the ocean.

zanl188
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RE: Space Shuttle External Tank

 Quoting checksixx (Reply 14):My statement was accurate sir.

As vzlet & Areopagus correctly point out the tanks were never orbited.. so I'm wondering how your statement " The space shuttle 'burned' into earth orbit EVERY time with the tank attached until MECO" is accurate?

Just so everyone understands the shuttle was not in orbit at MECO & neither was the tank. Shuttle required a burn of the OMS engines, some minutes after MECO, to circularize the trajectory and put shuttle in orbit. Without the OMS burn shuttle would have flown a ballistic trajectory and reentered.
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checksixx
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RE: Space Shuttle External Tank

Again...thanks for any help you think you may be providing, but my statement was accurate. Keep wondering why my statement is accurate or go find out for yourself...its up to you.

zanl188
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RE: Space Shuttle External Tank

 Quoting checksixx (Reply 18):Again...thanks for any help you think you may be providing, but my statement was accurate. Keep wondering why my statement is accurate or go find out for yourself...its up to you.

Your statement was inaccurate using the common and accepted vernacular for "in orbit".
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eksath
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RE: Space Shuttle External Tank

 Quoting vzlet (Reply 9): The orbiter required additional velocity from OMS firing(s) to reach orbit.
 Quoting ZANL188 (Reply 17):Without the OMS burn shuttle would have flown a ballistic trajectory and reentered.

Not necessarily. This internal debate i.e. OMS burn or not hit the public eye when Astronaut Mike Mullane wrote his biography in 2005. In it he goes to great lengths to describe the battle he had with John Young (chief astronaut who fought this). John Young's argument was to save it for latter use in the mission if needed. Eventually, Young lost and it became standard practice.

I am reciting from memory hence besides the debate, i don't remember the other details. I can always talk to guys about it as this was SOP after the first few years.

By the way, i highly recommend Mike's book: "Riding Rockets". John Young's image takes a dent in it though. I always liked Young though. He was very friendly and with his strong southern accent, it was easy to forget who he was.

EDIT: did some research (quick), OMS engines NOT used during nominal ascent until STS-90 (1998). I can look up the detailed data files for this mission to see the rationale however I probably wont get to it until Endeavour leaves KSC.

[Edited 2012-09-08 13:28:19]

[Edited 2012-09-08 13:29:33]

[Edited 2012-09-08 13:30:20]
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zanl188
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RE: Space Shuttle External Tank

 Quoting eksath (Reply 20):Not necessarily. This internal debate i.e. OMS burn or not hit the public eye when Astronaut Mike Mullane wrote his biography in 2005. In it he goes to great lengths to describe the battle he had with John Young (chief astronaut who fought this). John Young's argument was to save it for latter use in the mission if needed. Eventually, Young lost and it became standard practice.

Mullane butted heads with Young on the OMS assist manuever which occured pre-MECO, not post.

Use of the OMS to provide orbit insertion, both standard and direct ascent, are well explained at this link:

http://spaceflight.nasa.gov/shuttle/.../shutref/orbiter/oms/overview.html

[Edited 2012-09-08 14:22:22]

[Edited 2012-09-08 14:30:23]
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JBirdAV8r
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RE: Space Shuttle External Tank

 Quoting checksixx (Reply 18):Again...thanks for any help you think you may be providing, but my statement was accurate. Keep wondering why my statement is accurate or go find out for yourself...its up to you.

What a petty game of semantics.

Sure it "goes into orbit." But with orbital parameters that take the perigee into the Earth's atmosphere, it's quite useless, isn't it?
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Thrust
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RE: Space Shuttle External Tank

The question remains....could the external tank have been counted as payload to LEO, since it was attached to the shuttle all the way to MECO? And if the external tank were counted, would the shuttle surpass the Saturn V in payload?
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zanl188
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RE: Space Shuttle External Tank

 Quoting THrust (Reply 23):

Getting the tank all the way to MECO doesn't buy you much - it's still going to reenter before it completes the first orbit. Are you willing to trade off mass from elsewhere in the system? If so then maybe a way could be found to give the tank the extra delta-v to insert it into orbit..

The answer to your question? It depends...
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RE: Space Shuttle External Tank

 Quoting THrust (Reply 23):The question remains....could the external tank have been counted as payload to LEO,

Last stage of many rockets orbits Earth for a while after the satellite separation, and is not treated as a payload. Noone actually willing to pay for that part to stay in orbit, so it is not payload

PW100
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RE: Space Shuttle External Tank

I guess the (theoretical) question THrust really means is as follows: what would be the Shuttle's payload hit, if the ET was NOT detached from the Shuttle prior to the OMS burn. Or, how much mass would the total system have in orbit, including ET if it was not jettisoned?
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rwessel
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RE: Space Shuttle External Tank

 Quoting PW100 (Reply 26):guess the (theoretical) question THrust really means is as follows: what would be the Shuttle's payload hit, if the ET was NOT detached from the Shuttle prior to the OMS burn. Or, how much mass would the total system have in orbit, including ET if it was not jettisoned?

The question is how much delta-V you need to circularize the orbit. 200ft/s is probably a reasonable estimate for a low-ish orbit. Taking a 60,000lb empty tank weight (this is probably low, because of residual propellants), and an OMS engine ISP of 316, you'd need about 1200lbs of additional OMS/RCS propellant (for reference, the system carries just under 48,000lbs of fuel).

The higher you wanted the orbit, and the more unvented propellant left on board the ET, the more you'll need.

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RE: Space Shuttle External Tank

 Quoting PW100 (Reply 26):I guess the (theoretical) question THrust really means is as follows: what would be the Shuttle's payload hit, if the ET was NOT detached from the Shuttle prior to the OMS burn.

Shuttle carried around 22 tons of hypergolic fuel for the OMS and zero-fuel weight of orbiter was about 100 tons, let's call it 1/5 of dry weight.
External tank weight went down from 35 to 26.5 tons - so full trip fuel cost would be 7 to 5 tons.
Tank would not need deorbit burn, so total is a bit lower, but 3-5 tons of fuel/payload hit probably is about right.

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