So, who wants to win 1 million Euro?

[ka9q]

From that he calculates that the Shuttle would need 3 750 tons of fuel to reach LEO.

He's a little off. The launch weight of the shuttle was roughly 2,040 tonnes, which broke down as follows:

Two SRBs: 590 t each (90.7 t structure + 499 t propellant) x 2 = 1180 t
External tank: 762 t (26.5 t structure + 629 t LOX + 106 t LH2)
Orbiter: 79.9 t structure + 16.4 - 25.5 t payload

[nomuse]

Oddly enough, I was talking to a guy last weekend who was electrician for Cameron during The Abyss.  Says Cameron chose to film underwater scenes, well, underwater, because the movements just don't look right if you have actors in air trying to fake it.

I'm pretty sure he'd think it was ludicrous having actors underwater pretending to be floating in air, as well.

(And of all the documented films simulating zero-g, they were done either with wire-work or....well, actually not simulated at all.  Just filmed in very short segments!)

[ka9q]

Says Cameron chose to film underwater scenes, well, underwater, because the movements just don't look right if you have actors in air trying to fake it.

Ah ha! So it was Cameron who took over for Kubrick in the faking-things-for-NASA department!

Somebody tell hunchbacked/inquisitivemind...no doubt he'd do five videos on this new discovery...

[armillary]

Out of curiosity of what kind of loads are imposed on the connections between the tank and the orbiter/SRBs, I did a quick back-of-the envelope calculation here about the forces, at liftoff for simplicity.

The SSME has a thrust of 1.859 MN at liftoff according to wikipedia, for a total thrust of 5.577 MN
The SRBs produce 12 MN each at liftoff, rising to about 14 MN shortly afterwards

Assuming a total orbiter mass of about 100 ton, the gravitational load is:
External tank: 7.482 MN
SRBs: 5.793 MN each
Orbiter: 0.982 MN (give or take)

Subtracting the gravitational loads from the thrust, we have a net contribution to the whole stack:
SRBs: 6.207 MN
Orbiter: 4.595 MN

This shows that the external tank is more or less evenly supported by the SRBs and the SSMEs at that point.
Half the power of the SRBs goes to just lifting their own weight.

Dividing the total force by the mass gives me an acceleration of 6.5 m/s². I wasn't sure how much excess power the shuttle had at liftoff, but this seems in line with what I've seen of the videos.

Before I studied the numbers, I would intuitively have estimated the greatest mass to be the orbiter, and the ET  to be the second heaviest. Mass is deceptive.

[ka9q]

Yeah, those SRB casings are thick steel; no wonder they're so heavy. But they produce a lot of thrust, and that's what you want at liftoff.

The orbiter/ET acceleration peaks at 3 g (and is limited there) just before MECO. The stresses at that point still might not be that high, considering that the tank is nearly empty.

[Noldi400]

I seem to remember reading somewhere that a lot of engineers were opposed to the use of Solid Fuel boosters; they (understandably, I think) weren't comfortable with the idea of strapping a couple of skyrockets to a manned vehicle. i.e., (as you know, Bob) once the SRBs are lit, there's no shutdown until they burn out. IIRC, it seems there was a pretty strong 'lobby' for LRBs, which are more controllable but were rejected, probably because of expense.

Can anyone shed some light on my creaky old memory?:

[ka9q]

I think you're right; I know I didn't like the idea of SRBs, and I even predicted that the first accident with the shuttle would involve them.

[cjameshuff]

I seem to remember reading somewhere that a lot of engineers were opposed to the use of Solid Fuel boosters; they (understandably, I think) weren't comfortable with the idea of strapping a couple of skyrockets to a manned vehicle. i.e., (as you know, Bob) once the SRBs are lit, there's no shutdown until they burn out. IIRC, it seems there was a pretty strong 'lobby' for LRBs, which are more controllable but were rejected, probably because of expense.

Apart from the safety benefits and the removal of the need to ship solid fuel segments around, store and dispose of unused solid fuel, the ability to abort on the pad after ignition or shut down in an abort after liftoff etc, liquids also give substantially better performance, and would have been a big upgrade in cargo capacity. There were various attempts to develop advanced liquid boosters for the Shuttle, but none of them got anywhere. There's a lot of political support for solids, due to the overlap with ballistic missile manufacture and simple pork, hence Congress basically mandating that Constellation and the SLS use them.

[raven]

Engergia (used to launch the Soviet shuttle Buran) used liquid fuel for its strap on boosters, which later formed the basis for the Zenit launch vehicle.

[cjameshuff]

Engergia (used to launch the Soviet shuttle Buran) used liquid fuel for its strap on boosters, which later formed the basis for the Zenit launch vehicle.

Several current launch systems use liquid boosters, including the Soyuz and several of the Long March rockets.

[cjameshuff]

Several current launch systems use liquid boosters, including the Soyuz and several of the Long March rockets.

And on the US side, the Delta IV Heavy and the Atlas V HLV are all-liquid, as is the Falcon Heavy. The last is able to use fuel crossfeed in addition, getting even more of a benefit.

[raven]

Engergia (used to launch the Soviet shuttle Buran) used liquid fuel for its strap on boosters, which later formed the basis for the Zenit launch vehicle.

Several current launch systems use liquid boosters, including the Soyuz and several of the Long March rockets.

Oh, I know. I thought it would be worthwhile mentioning something that was explicitly meant to be comparable to the Shuttle.

[Peter B]

I seem to remember reading somewhere that a lot of engineers were opposed to the use of Solid Fuel boosters; they (understandably, I think) weren't comfortable with the idea of strapping a couple of skyrockets to a manned vehicle. i.e., (as you know, Bob) once the SRBs are lit, there's no shutdown until they burn out. IIRC, it seems there was a pretty strong 'lobby' for LRBs, which are more controllable but were rejected, probably because of expense.

Can anyone shed some light on my creaky old memory?:

My creaky memory is that LRBs were originally planned for the Shuttle, but the cost of developing them would've been a lot higher than the cost of developing SRBs. However, the running costs of the LRBs would've been a lot lower than for the SRBs. Unfortunately for NASA, the time when they didn't have the money was when they were developing the beasts.

It's sort of like the story run on a consumer information TV show in Australia recently - the printer that's cheap to buy requires you to spend large amounts of money on replacement printer cartridges...

[nomuse]

That game became transparent when they started giving the printers themselves away.

[cjameshuff]

My creaky memory is that LRBs were originally planned for the Shuttle, but the cost of developing them would've been a lot higher than the cost of developing SRBs. However, the running costs of the LRBs would've been a lot lower than for the SRBs. Unfortunately for NASA, the time when they didn't have the money was when they were developing the beasts.

That's the argument for the SLS starting with Shuttle-derived SRBs, but they're hoped to be cheaper because we already have something similar to start from, and theoretically require little development to use.

Solids have often been claimed to be cheaper due to their simplicity, but they had to do a huge amount of work to ensure uniform mixing, high quality flawless castings, lots and lots of testing of the finished product, etc, never mind shipping and handling the segments and assembly into the vehicle without damaging them, and the additional expenses of working around giant fully-fueled solid rocket motors. Think of how much money we've poured into just trying to adapt Shuttle boosters for other rockets...

I suspect the justification was political from the start. The Shuttle spread pork all over the country. Even if solids were everything they were advertised as, making huge, massive, delicate, hazardous rocket components in Utah for frequent flights (the Shuttle was supposed to be the cheap, reliable workhorse to replace all expendable launchers, with dozens of flights a year) from Florida just doesn't make sense.