caffiend666 writes "In order to abate the massive vibration issues of their new Ares I spacecraft, NASA is installing shock absorbers. 'The plan is to install 16 canisters in the bottom of the rocket with 100-pound weights attached to springs. Battery-powered motors will move the weights up and down to stop vibrations. Those are essentially remote-controlled shock absorbers, said Garry Lyles, who headed the team of NASA engineers tackling the shaking problem.' So, when the spaceship is a rocking, don't come a knocking?"
...the weights are almost all at the bottom of the rocket, so they should only affect the first stage.
Still, that's where the most fuel is burned. For an historical example, by the time the Saturn V rocket had traveled its own length--360 feet--it had burned a greater weight in fuel than the weight of the command and service modules it was sending to the moon.
It's been considered. Leave the first stage on the ground. Launch with a cannon or railgun to get the initial acceleration instead of putting the engine and fuel on board. Non-living cargo can take considerable acceleration. You just need a longer railgun if you want to launch pesky humans.
As for this system, it seems like what they are doing is basically the same as noise-canceling headphones. Maybe they need a couple of giant bass speakers. Once in space they can switch them over to play techno.
Altogether, the added equipment would reduce the lift capacity of the Ares I rocket's first stage by up to 1,400 pounds (625 kg), though the booster segment currently has a margin of about 8,000 pounds (3,628 kg) to work with, Cook said.
As someone noted, there's plenty of margin in first stage.
Second point: If you look at the math for a two stage rocket, the effect of adding a pound to the first stage is inconsequential compared to the effect of adding a pound to the second stage. Sadly I'm away from my books (in a job transition at the moment) but the simple way to think of it is this: you only drag first stage with you for the first 2 or so minutes of flight, and then upper stage carries you for the next six minutes or so. So the weight is only with you for a short integrated length of time.
You can see this in effect when you consider the difference between first stage and second stage - first stage is essentially a modified Shuttle solid rocket motor, and second stage is essentially a re-designed external tank (yes, it's different, but the construction is the tank, thin wall aluminum with TPS).
First stage is thick, heavy steel, overdesigned for re-entry.
Second stage is thin, light aluminum.
The first stage is heavier, again, because of reuse and because mass isn't the design driver. Upper stage, however, since it nearly inserts orbit and is drug along the entire time is an incredible mass driver and must be as light as possible.
Sorry for rambling, and apologies for not showing the math, but in short, that's why adding 3/4 a ton to first stage isn't as big a deal as it sounds like. In the long run, it might effect maybe 10% of its weight in payload, if even...
some inefficiencies in other areas (like shock absorbers and weights) might be tolerable provided that such problems are not the result of more fundamental design flaws in the Ares rocket.
Well that's the thing, see. These problems are the result of more fundamental design flaws in the Ares rocket -- specifically, designing the thing with a single solid first stage to start with.
Solids give a notoriously rough ride. Liquid fuel engines are fed a smooth flow of fuel and are fine tuned to keep out any combustion instability or oscillation. Solids are just a big chunk of almost-explosive with a hole drilled down the middle -- once you light it, that's it. Except for ammunition (ICBMs, artillery rockets, etc), traditionally solids have been used in multiples, usually together with a liquid-fueled core. The advantage is that the thrust variations of multiple solids tends to average out -- you still get vibration, but not as bad. But Ares 1 went with a single, huge, solid stage. That's like designing-in a vibration problem.
On top of that, the damn thing is a hammerhead design, wider at the top than at the bottom (look at the picture, it looks like a corn dog). Those are notoriously prone to stability problems of their own. With liquid fueled engines with some throttle range and gimballed for steering, that's a minor issue. With a solid whose idea of throttle control is cutting the right shape hole down the middle so as to expose different amounts of burning surface at different times, and whose gimballing ability is, well, limited at best -- you'd better hope you don't have any unexpected issues with that inherent hammerhead instability -- like wind shear, or oh say unexpected excessive vibration.
The whole thing is a freaking kludge, and adding a ton of active dampening is just yet another kludge. The manned spacecraft division of NASA jumped the shark a long time ago, this is just further proof.
Ares being cheap is a false economy. By trying to essentially throw together a rocket from spare parts, they are now costing more money making it work than if they had just built a launcher with a free hand.
That's great. Use a solid rocket to save a couple bucks, then add 1600 pounds of dead weight (not dead, really, but still needed because the solids vibrate too much) to make the thing work.
This Ares thing is getting more shuttle-ish by the minute.
Would the Apollo survivors please come back from retirement? Looks like the new folks are having some trouble with the problems you already solved.
I know the whole Ares thing is to reuse shuttle parts, but it seems that there is very little left from the shuttle that's worth saving and even less that's being saved. The Ares V core is wider, the solids are longer... Couldn't they just build an improved Saturn V and pretend the shuttle never happened?
You think the Saturn V didn't have many tons of anti-vibration structure, anti-pogo devices, and other such things? Get real!
Clueless computer types such as yourself might think that a rocket should be fuel tanks and an engine and nothing else, but that's not how it actually works in the real world. There's a reason that "rocket science" is used as an idiom to indicate something that's extremely hard, you know.
How much do you suppose a "small" damper on the fuel line weighs on a 6.7 million pound rocket? I couldn't find any answers, but it would not surprise me if the Saturn V's "small" pogo suppressors weighed over 1600 pounds in total.
That is exactly what I have been saying. Apollo was the heaviest lifter we had, it worked, and it worked great. What's wrong with pulling out the blue prints, updating some components and building a newer improved version of the Apollo system? Why is this so hard to figure out? It's certainly better than wasting 1600+++ pounds on shock absorbers, damn that is just plane stupid. It's not like this is rocket..oh wait...but still!
That is exactly what I have been saying. Apollo was the heaviest lifter we had, it worked, and it worked great. What's wrong with pulling out the blue prints, updating some components and building a newer improved version of the Apollo system? Why is this so hard to figure out? It's certainly better than wasting 1600+++ pounds on shock absorbers, damn that is just plane stupid. It's not like this is rocket..oh wait...but still!
Because the blueprints and designs don't give you everything. There's a ton of additional work such as tools, dies, machinery, etc. needed to make the parts that are no longer around and which would need to be rebuilt and debugged.
Any modern system such as rockets, cpus, chips, etc. have a lot of ancillary things that are needed to build them. And that's ignoring the little tips and experience with what techniques work which is probably only known by the original engineers and builders.
That is exactly what I have been saying. Apollo was the heaviest lifter we had, it worked, and it worked great.
I'd hesitate to say it 'worked great', given the very few flights the Saturn V (to give it it's proper name) flew. They didn't mostly solve the vibration problems until Apollo 14, for example (they never did completely solve them), and they were making significant modifications right up to the last flight. In particular, they fiddled extensively with the retrorockets on the first and second stages to reduce weight while ensuring proper separation and no recontact.
What's wrong with pulling out the blue prints, updating some components and building a newer improved version of the Apollo system?
Mostly because it isn't a matter of updating 'some components'... For one example - the electronics in the Saturn V IU (Instrument Unit) are hopelessly out of date, you can't simply 'update them' because they interconnect with everything else on the booster. Even just updating the electronics on the IU means redoing the cooling system and wiring harness, not to mention that all the vibration, structural, cooling, etc. etc. analysis will have to be redone as well.
When it comes to the Apollo capsule itself, I've seen credible work that indicates that the weight of its power and electronic would shrink by over 90%! Which means the cooling system is now way oversized... The CG of the capsule also moves radically, which means rejiggering the RCS to account for the changed aerodynamic performance... Etc. Etc.
There's a reason why the Soviets update the Soyuz only infrequently.
Why is this so hard to figure out?
It's only easy when you don't understand the issues involved. Very few Slashdotters seem to know much about the history and engineering of the Apollo program beyond the extremely simplified panegyrics [wikipedia.org] they read as kids.
1. First attempt at building a man rated launcher with an entirely solid fueled stage
2. Largest solid rocket booster ever flown
3. First (I believe) aerodynamically unstable man rated launcher
4. And now, first use of shock absorbers to dampen an otherwise lethal vibration in a launcher
Considering how reverting to capsules was seen as a safe bet, and as taking advantage of existing technology and production lines, there is an increasing amount of experimental new technology involved.
With the Shuttles headed towards retirement and the only remaining source of access to the ISS in jeopardy due to chilly relations with Russia, now doesn't seem like the best time to be getting experimental. Functional will do just nicely.
I honestly think that a manned ATV might fly before Orion at this rate.
3. First (I believe) aerodynamically unstable man rated launcher
Dunno about that one... The Gemini program's launch vehicles tended to suffer what was called the "Pogo" effect [everything2.net] once they reached a certain speed and altitude. Tended to scare the shit out of the first astronauts to experience it.
Pogo isn't due to an aerodynamic instability, it's due to feedback cycles in the fuel/engine system. Simply put, the more G's the rocket experiences, the faster the fuel wants to flow into the engine, increasing thrust, increasing G's, etc. Now, the fuel system is designed to limit that for obvious reasons. Pogo happens when the control mechanisms don't react quite as fast as the feedback cycle and overcorrect. Another cause of pogo (serious on Saturn V until they figured it out) is hydraulic effects in
3. Basically all space rockets are aerodynamically unstable. This is absolutely nothing new.
4. Before it was eclipsed by an even worse event, Apollo 13 briefly scared the crap out of everyone involved when the center engine of the second stage nearly ripped the entire rocket to little pieces. It was experiencing pogo oscillation [wikipedia.org], flexing the massive thrust frame by three inches at 16Hz, experiencing 68 gees. Just before this incredible vibration destroyed the entire craft, a fuel sensor was falsely tripped and shut the engine down, saving the ship.
Saturn V and Apollo were full of problems. Rocket science is hard, remember? I suggest that you get a clue before you mindlessly criticize.
The Apollo missions definitely weren't entirely safe... but people didn't really care about it as much as they do today. They were driven to succeed at almost any cost, and to do so before the Russians.
Now we have this culture of protection and safety that's we're too afraid to (accidentally) sacrifice a human even at the prospect of settling on the moon. Not saying it's wrong, but it complicates things more.
Whilst I'm not overly surprised by the decision why have they left it this late, as its a well documented [everything2.net] problem thats been around since the beginning of space flight.
This isn't pogo, which you linked to, which affects only liquid-fueled rockets. This is an "organ pipe" oscillation characteristic of solid rocket boosters.
Still an old problem, but not quite what you describe.
This sounds like more than the shock absorbers found in your car and other mechanical systems. Those are passive spring-mass-damper systems. These sound like active vibration control systems, that try to cancel out one shaking by producing an equal and opposite shaking. It's fairly straightforward, the sort of thing you can learn in an undergraduate control theory class, but getting it to work robustly, even on a test stand, takes a fair bit of tuning. Getting it to work on a complex system like Ares seems to be asking for trouble.
If nothing else, it's certainly a very heavy fix. My rocket science is a little rusty, but the 1600 lbs of active weight in the first stage probably doesn't translate into 1600 lbs of lost payload (if it were in the crew capsule, then yes, but the first stage doesn't go all the way to orbit). Even so, it's some lost payload capacity, and does nothing to tackle the root cause of the problem. Back to the drawing board, guys!
Ever get the feeling they're building a kludge all over again? Space Shuttle II -- Revenge of Thousands of Glued On Tiles and Strapping It to the Side an Ice-Covered Tank.
There was no way to passively dampen the vibrations? A simpler, cheaper solution? So instead they'll introduce another ton of lift weight and 17 additional motors and batteries to fail.
My prediction: in the first 50 launches this system will fail and the rocket will either shake the astronauts and payload apart (failure to dampen) or spectacularly shake the rocket apart (oscillate lopsidedly or out of synch with the vibrations).
With luck Slashdot will archive this long enough. Given that this is a NASA project, that might not be likely.
Fly EELV instead - make Orion a much simpler and more robust capsule. Delta IV Heavy can already lift the ISS-bound version of Orion without trouble. Ares is a joke, a joke played by ATK, Mike Griffin and Scotty Horowitz on the US taxpayer.
The other problem with ESAS/Ares/VSE as currently implemented by NASA is that they choose the launcher (vaporware Ares based on SRBs) and are trying to shoe-horn the payload into it. This is 100% backwards from how most missions are designed, with the payload dictating the launcher.
Between this and the trouble that Orion development is experiencing, it would appear that the Chinese or even US private firms will be on the Moon before NASA. Go Bigelow!
I looked at the title and for a moment was stunned, thinking that NASA was actually working on building Project Orion [wikipedia.org]. Now thers's a spaceship that really needs its shock absorbers.
Chrome rims and a spoiler. We might not be alone, so dress to impress!
Btw, not 16, "a 17th shock absorber will be a ring of weights and springs near the middle of the rocket". Might not have a cannister though, or a switch ; )
Dealing with a vibration problem by adding nearly a ton of lead bouncy weights is not a great solution; especially when your mission is climbing out of a deep gravity well. They need to be looking for and fixing the source of the vibration.
Fortunately, they are. From Wired [wired.com]: "In the long term, Gary Lyles, associate director for technical management at NASA's Marshall Space Flight Center, said they are planning cold flow testing to learn more about the source of the vibration within the motor design itself. The next step would be sub-scale hot flow tests with solid rocket motors. If the tests prove conclusive, NASA will be able to look at doing a block upgrade to the motor and adding design changes to the full scale motor that will result in less vibration being produced. This would solve the problem without adding on extra weight to compensate for the problem."
The flammable Apollo Command module was designed by North American Aviation, not by the imported German rocket scientists who worked on the Saturn V booster.
(The Apollo capsule was considered by many to be bloated and technically inferior to the earlier Gemini capsules.)
Their demise wasn't caused by a flaw in the rocket itself, it was because the capsule was using pure oxygen under low pressure in order to save weight.
Unfortunately - materials that were flame-retardant or flameproof in normal air became extremely volatile in the 100% oxygen atmosphere in the capsule. They changed to a different mixture after that accident.
Their accident also happened while on the ground during a test and not in space. Their accident was actually to honor them being designated Apollo 1. (as from what I have understood from at least one source, other sources does claim that it already was designated Apollo 1). So the only in flight accident with the Apollo program was Apollo 13 - and they did survive.
So this actually tells us - beware us from accountants.
Close, but there's a bit more to it than just being a 100% Oxygen environment. One of the things being tested was that the capsule would function properly experiencing the same outward pressure that it would experience in orbit. When the craft was in space, it would be pressurized at about 2-3 psi or pure Oxygen. To simulate that on the ground, the cabin was pressurized to 18 psi, 2 psi more than air pressure at see level.
In the aftermath, they realized just how stupid that was; at that pressure of pure O2, a bar of Aluminum would "burn like wood". Almost anything will burn, and many things will burn spontaneously. To make matters worse, almost every exposed surface of the module was covered in velcro for ease of use in zero-g. The problem is, the velcro was literally explosive at the Oxygen density used during the test.
Actually, the Germans designed the Apollo for us. That worked very well. Then we designed the Shuttle. Two of them blew up, due to inelegant fundamental design flaws. So it was not the 'last time' but 'the time before last' that you refer to. Apart from that - your analysis is spot-on....
Not going to talk about your "Germans" comment, but...
Apollo had at least 2 major incidents, killing 3 astronauts, and endangering 3 others.
Shit happens when you are pushing the envelop. Mercury, Gemini, Apollo, Shuttle, Sal
Oh, it was WAY worse than that... just off the top of my head:
1) When landing on the moon, during the final (and most tricky) phase the computer controlling the LEM effectively turned off - Neil landed manually, with the computer yelling abort all the way.
2) Apollo 15 (I think) they tried decreasing the number of thrusters used to separate the stages - the stages almost collided, nearly killing everyone aboard.
3) Apollo 13, the center engine entered a pogo oscillation on launch that was about to destroy the
The US government oversaw Apollo. US enterprise is currently overseeing a crappy suborbital space plane and an even crappier low payload rocket.
If the current incarnation of NASA has a problem, it is that like many modern government agencies it is trying to emulated private enterprise too much.
Hilariously the apollo program had some pretty serious pogo oscillation problems. Pogo is shaking the rocket up and down makes the propellant flow increase and decrease making the oscillations worse.
In the apollo era, as per http://www.clavius.org/techsvpogo.html [clavius.org] they used plumbing style water hammer chambers to eliminate the fluid surges. Let the vehicle shake but prevent the ability for shaking to cause thrust variations.
The modern solution is apparently dynamic shock absorber technology on the vehicle.
The modern solution eliminates the shaking, the old solution allowed it to shake but patched around it so it didn't have negative effects.
The modern solution is better, which makes the comparisons to Apollo kind of funny to those who know...
Maybe the vibrations are originating from multiple sources. It may be far more effective and cheaper to add active damping than to redesign the engines, the gimbals, the fuel pumps, the launch pad, and whatever else could be contributing to inducing these vibrations.
cost? (Score:5, Insightful)
Re:cost? (Score:5, Interesting)
Just about anything can be a "weight". It's in their best interests to make the weights serve (another) function.
Also, the weights are almost all at the bottom of the rocket, so they should only affect the first stage.
Parent
Re: (Score:3, Informative)
Still, that's where the most fuel is burned. For an historical example, by the time the Saturn V rocket had traveled its own length--360 feet--it had burned a greater weight in fuel than the weight of the command and service modules it was sending to the moon.
Re:cost? (Score:5, Informative)
Parent
Re: (Score:3, Informative)
It's like trying to reduce the vibrations in your Chevette by encasing it in lead: probably effective, but your gas mileage is going to suck.
Re: (Score:3, Informative)
Does someone have a car analogy?
Because they didn't design their engine very well, it now needs a very large harmonic balancer. [wikipedia.org]
Re:cost? (Score:4, Funny)
It's been considered. Leave the first stage on the ground. Launch with a cannon or railgun to get the initial acceleration instead of putting the engine and fuel on board. Non-living cargo can take considerable acceleration. You just need a longer railgun if you want to launch pesky humans.
As for this system, it seems like what they are doing is basically the same as noise-canceling headphones. Maybe they need a couple of giant bass speakers. Once in space they can switch them over to play techno.
Parent
Re: (Score:3, Funny)
Bass and techno in space?
What a perfect way to get intelligent life to come destroy us all.
I wonder how you say get off my lawn in alien ?
The Hell! 1600+ pounds additional weight? (Score:3, Insightful)
So they're loading down the first stage with at _least_ 1600 pounds of weight (plus motors, plus batteries, plus cannisters) to dampen vibration?
That's pretty crazy, I would think. It's not like all that weight is gonna come free.
Funny coincidence... (Score:3, Funny)
In related news, did anyone notice the Oprah ad below the story (down on the left side):
"LOSE WEIGHT IN 2008! THE BESTLIFE DIET - JOIN NOW!"
Talk about context-sensitive advertising ;-))
Re:The Hell! 1600+ pounds additional weight? (Score:4, Interesting)
You forgot "plus the additional fuel needed to haul that 1600 pounds skyward".
That's the bitch about designing spaceships - for every ounce you add, you need at least an additional half-pound of fuel* to shove it upwards.
* depending of course on such details as specific impulse, fuel density, etc etc.
Parent
Re:The Hell! 1600+ pounds additional weight? (Score:5, Informative)
There's a much more informative article on Space.com from yesterday: http://www.space.com/news/080819-nasa-ares1-vibration-update.html [space.com]
Parent
Re:The Hell! 1600+ pounds additional weight? (Score:4, Interesting)
Second point: If you look at the math for a two stage rocket, the effect of adding a pound to the first stage is inconsequential compared to the effect of adding a pound to the second stage. Sadly I'm away from my books (in a job transition at the moment) but the simple way to think of it is this: you only drag first stage with you for the first 2 or so minutes of flight, and then upper stage carries you for the next six minutes or so. So the weight is only with you for a short integrated length of time.
You can see this in effect when you consider the difference between first stage and second stage - first stage is essentially a modified Shuttle solid rocket motor, and second stage is essentially a re-designed external tank (yes, it's different, but the construction is the tank, thin wall aluminum with TPS).
First stage is thick, heavy steel, overdesigned for re-entry.
Second stage is thin, light aluminum.
The first stage is heavier, again, because of reuse and because mass isn't the design driver. Upper stage, however, since it nearly inserts orbit and is drug along the entire time is an incredible mass driver and must be as light as possible.
Sorry for rambling, and apologies for not showing the math, but in short, that's why adding 3/4 a ton to first stage isn't as big a deal as it sounds like. In the long run, it might effect maybe 10% of its weight in payload, if even...
Parent
Re:The Hell! 1600+ pounds additional weight? (Score:5, Interesting)
some inefficiencies in other areas (like shock absorbers and weights) might be tolerable provided that such problems are not the result of more fundamental design flaws in the Ares rocket.
Well that's the thing, see. These problems are the result of more fundamental design flaws in the Ares rocket -- specifically, designing the thing with a single solid first stage to start with.
Solids give a notoriously rough ride. Liquid fuel engines are fed a smooth flow of fuel and are fine tuned to keep out any combustion instability or oscillation. Solids are just a big chunk of almost-explosive with a hole drilled down the middle -- once you light it, that's it. Except for ammunition (ICBMs, artillery rockets, etc), traditionally solids have been used in multiples, usually together with a liquid-fueled core. The advantage is that the thrust variations of multiple solids tends to average out -- you still get vibration, but not as bad. But Ares 1 went with a single, huge, solid stage. That's like designing-in a vibration problem.
On top of that, the damn thing is a hammerhead design, wider at the top than at the bottom (look at the picture, it looks like a corn dog). Those are notoriously prone to stability problems of their own. With liquid fueled engines with some throttle range and gimballed for steering, that's a minor issue. With a solid whose idea of throttle control is cutting the right shape hole down the middle so as to expose different amounts of burning surface at different times, and whose gimballing ability is, well, limited at best -- you'd better hope you don't have any unexpected issues with that inherent hammerhead instability -- like wind shear, or oh say unexpected excessive vibration.
The whole thing is a freaking kludge, and adding a ton of active dampening is just yet another kludge. The manned spacecraft division of NASA jumped the shark a long time ago, this is just further proof.
Parent
Hooray for more weight... (Score:3, Interesting)
Re: (Score:3, Funny)
You're clearly no engineer.
If you were, you'd realize that all we need to do is starve them for a few months and, bam, double the capacity for hurtling lawyers into space.
I'm not a rocket scientist (Score:5, Interesting)
But adding 1600 lbs plus weight of electric motors to the weight of a space craft, seems like a last resort option.
Nothing else worked?
Re: (Score:3, Insightful)
Interesting tweak (Score:4, Interesting)
That's great. Use a solid rocket to save a couple bucks, then add 1600 pounds of dead weight (not dead, really, but still needed because the solids vibrate too much) to make the thing work.
This Ares thing is getting more shuttle-ish by the minute.
Would the Apollo survivors please come back from retirement? Looks like the new folks are having some trouble with the problems you already solved.
I know the whole Ares thing is to reuse shuttle parts, but it seems that there is very little left from the shuttle that's worth saving and even less that's being saved. The Ares V core is wider, the solids are longer... Couldn't they just build an improved Saturn V and pretend the shuttle never happened?
I bet Kerosene/LOX would be cheaper too.
Re:Interesting tweak (Score:5, Insightful)
You think the Saturn V didn't have many tons of anti-vibration structure, anti-pogo devices, and other such things? Get real!
Clueless computer types such as yourself might think that a rocket should be fuel tanks and an engine and nothing else, but that's not how it actually works in the real world. There's a reason that "rocket science" is used as an idiom to indicate something that's extremely hard, you know.
Parent
Re:Interesting tweak (Score:5, Interesting)
How much do you suppose a "small" damper on the fuel line weighs on a 6.7 million pound rocket? I couldn't find any answers, but it would not surprise me if the Saturn V's "small" pogo suppressors weighed over 1600 pounds in total.
Parent
Re: (Score:3, Informative)
Re: (Score:3, Insightful)
That is exactly what I have been saying. Apollo was the heaviest lifter we had, it worked, and it worked great. What's wrong with pulling out the blue prints, updating some components and building a newer improved version of the Apollo system? Why is this so hard to figure out? It's certainly better than wasting 1600+++ pounds on shock absorbers, damn that is just plane stupid. It's not like this is rocket..oh wait...but still!
Because the blueprints and designs don't give you everything. There's a ton of additional work such as tools, dies, machinery, etc. needed to make the parts that are no longer around and which would need to be rebuilt and debugged.
Any modern system such as rockets, cpus, chips, etc. have a lot of ancillary things that are needed to build them. And that's ignoring the little tips and experience with what techniques work which is probably only known by the original engineers and builders.
Even today, if
Re:Interesting tweak (Score:4, Insightful)
I'd hesitate to say it 'worked great', given the very few flights the Saturn V (to give it it's proper name) flew. They didn't mostly solve the vibration problems until Apollo 14, for example (they never did completely solve them), and they were making significant modifications right up to the last flight. In particular, they fiddled extensively with the retrorockets on the first and second stages to reduce weight while ensuring proper separation and no recontact.
Mostly because it isn't a matter of updating 'some components'... For one example - the electronics in the Saturn V IU (Instrument Unit) are hopelessly out of date, you can't simply 'update them' because they interconnect with everything else on the booster. Even just updating the electronics on the IU means redoing the cooling system and wiring harness, not to mention that all the vibration, structural, cooling, etc. etc. analysis will have to be redone as well.
When it comes to the Apollo capsule itself, I've seen credible work that indicates that the weight of its power and electronic would shrink by over 90%! Which means the cooling system is now way oversized... The CG of the capsule also moves radically, which means rejiggering the RCS to account for the changed aerodynamic performance... Etc. Etc.
There's a reason why the Soviets update the Soyuz only infrequently.
It's only easy when you don't understand the issues involved. Very few Slashdotters seem to know much about the history and engineering of the Apollo program beyond the extremely simplified panegyrics [wikipedia.org] they read as kids.
Parent
More untested principles (Score:5, Interesting)
Lets review what we have so far:
1. First attempt at building a man rated launcher with an entirely solid fueled stage
2. Largest solid rocket booster ever flown
3. First (I believe) aerodynamically unstable man rated launcher
4. And now, first use of shock absorbers to dampen an otherwise lethal vibration in a launcher
Considering how reverting to capsules was seen as a safe bet, and as taking advantage of existing technology and production lines, there is an increasing amount of experimental new technology involved.
With the Shuttles headed towards retirement and the only remaining source of access to the ISS in jeopardy due to chilly relations with Russia, now doesn't seem like the best time to be getting experimental. Functional will do just nicely.
I honestly think that a manned ATV might fly before Orion at this rate.
Re:More untested principles (Score:4, Informative)
3. First (I believe) aerodynamically unstable man rated launcher
Dunno about that one... The Gemini program's launch vehicles tended to suffer what was called the "Pogo" effect [everything2.net] once they reached a certain speed and altitude. Tended to scare the shit out of the first astronauts to experience it.
The Apollo program had solved that.
Parent
Re: (Score:3, Interesting)
Pogo isn't due to an aerodynamic instability, it's due to feedback cycles in the fuel/engine system. Simply put, the more G's the rocket experiences, the faster the fuel wants to flow into the engine, increasing thrust, increasing G's, etc. Now, the fuel system is designed to limit that for obvious reasons. Pogo happens when the control mechanisms don't react quite as fast as the feedback cycle and overcorrect. Another cause of pogo (serious on Saturn V until they figured it out) is hydraulic effects in
Re:More untested principles (Score:5, Informative)
3. Basically all space rockets are aerodynamically unstable. This is absolutely nothing new.
4. Before it was eclipsed by an even worse event, Apollo 13 briefly scared the crap out of everyone involved when the center engine of the second stage nearly ripped the entire rocket to little pieces. It was experiencing pogo oscillation [wikipedia.org], flexing the massive thrust frame by three inches at 16Hz, experiencing 68 gees. Just before this incredible vibration destroyed the entire craft, a fuel sensor was falsely tripped and shut the engine down, saving the ship.
Saturn V and Apollo were full of problems. Rocket science is hard, remember? I suggest that you get a clue before you mindlessly criticize.
Parent
Re:More untested principles (Score:5, Insightful)
The Apollo missions definitely weren't entirely safe... but people didn't really care about it as much as they do today. They were driven to succeed at almost any cost, and to do so before the Russians.
Now we have this culture of protection and safety that's we're too afraid to (accidentally) sacrifice a human even at the prospect of settling on the moon. Not saying it's wrong, but it complicates things more.
Parent
Why have they left it this late? (Score:4, Informative)
Re: (Score:3, Informative)
This isn't pogo, which you linked to, which affects only liquid-fueled rockets. This is an "organ pipe" oscillation characteristic of solid rocket boosters.
Still an old problem, but not quite what you describe.
Can someone at NASA... (Score:3, Informative)
Active Control System (Score:3, Insightful)
If nothing else, it's certainly a very heavy fix. My rocket science is a little rusty, but the 1600 lbs of active weight in the first stage probably doesn't translate into 1600 lbs of lost payload (if it were in the crew capsule, then yes, but the first stage doesn't go all the way to orbit). Even so, it's some lost payload capacity, and does nothing to tackle the root cause of the problem. Back to the drawing board, guys!
Overcomplicated! (Score:4, Insightful)
Ever get the feeling they're building a kludge all over again? Space Shuttle II -- Revenge of Thousands of Glued On Tiles and Strapping It to the Side an Ice-Covered Tank.
There was no way to passively dampen the vibrations? A simpler, cheaper solution? So instead they'll introduce another ton of lift weight and 17 additional motors and batteries to fail.
My prediction: in the first 50 launches this system will fail and the rocket will either shake the astronauts and payload apart (failure to dampen) or spectacularly shake the rocket apart (oscillate lopsidedly or out of synch with the vibrations).
With luck Slashdot will archive this long enough. Given that this is a NASA project, that might not be likely.
save the 1600lbs (Score:3, Informative)
Fly EELV instead - make Orion a much simpler and more robust capsule. Delta IV Heavy can already lift the ISS-bound version of Orion without trouble. Ares is a joke, a joke played by ATK, Mike Griffin and Scotty Horowitz on the US taxpayer.
The other problem with ESAS/Ares/VSE as currently implemented by NASA is that they choose the launcher (vaporware Ares based on SRBs) and are trying to shoe-horn the payload into it. This is 100% backwards from how most missions are designed, with the payload dictating the launcher.
Between this and the trouble that Orion development is experiencing, it would appear that the Chinese or even US private firms will be on the Moon before NASA. Go Bigelow!
Orion? NASA? Shock absorbers? (Score:3, Funny)
Read that dyslexically (Score:3, Funny)
I read that headline dyslexically and thought it said "NASA Installing Shocks on Arse"
I thought it was about some new kind of employee training program involving electrified chairs so that managers could BZZZT someone not working :P
Next : (Score:5, Funny)
Chrome rims and a spoiler. We might not be alone, so dress to impress!
Btw, not 16, "a 17th shock absorber will be a ring of weights and springs near the middle of the rocket".
Might not have a cannister though, or a switch ; )
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Major Kludge (Score:4, Informative)
>big, clunky, and with no regard for elegance.
Dealing with a vibration problem by adding nearly a ton of lead bouncy weights is not a great solution; especially when your mission is climbing out of a deep gravity well. They need to be looking for and fixing the source of the vibration.
Fortunately, they are. From Wired [wired.com]: "In the long term, Gary Lyles, associate director for technical management at NASA's Marshall Space Flight Center, said they are planning cold flow testing to learn more about the source of the vibration within the motor design itself. The next step would be sub-scale hot flow tests with solid rocket motors. If the tests prove conclusive, NASA will be able to look at doing a block upgrade to the motor and adding design changes to the full scale motor that will result in less vibration being produced. This would solve the problem without adding on extra weight to compensate for the problem."
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Re:This is not going to increase efficiency.... (Score:4, Insightful)
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Re: (Score:3, Interesting)
The flammable Apollo Command module was designed by North American Aviation, not by the imported German rocket scientists who worked on the Saturn V booster.
(The Apollo capsule was considered by many to be bloated and technically inferior to the earlier Gemini capsules.)
Re:This is not going to increase efficiency.... (Score:5, Informative)
Their demise wasn't caused by a flaw in the rocket itself, it was because the capsule was using pure oxygen under low pressure in order to save weight.
Unfortunately - materials that were flame-retardant or flameproof in normal air became extremely volatile in the 100% oxygen atmosphere in the capsule. They changed to a different mixture after that accident.
Their accident also happened while on the ground during a test and not in space. Their accident was actually to honor them being designated Apollo 1. (as from what I have understood from at least one source, other sources does claim that it already was designated Apollo 1). So the only in flight accident with the Apollo program was Apollo 13 - and they did survive.
So this actually tells us - beware us from accountants.
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Re:This is not going to increase efficiency.... (Score:5, Interesting)
Close, but there's a bit more to it than just being a 100% Oxygen environment. One of the things being tested was that the capsule would function properly experiencing the same outward pressure that it would experience in orbit. When the craft was in space, it would be pressurized at about 2-3 psi or pure Oxygen. To simulate that on the ground, the cabin was pressurized to 18 psi, 2 psi more than air pressure at see level.
In the aftermath, they realized just how stupid that was; at that pressure of pure O2, a bar of Aluminum would "burn like wood". Almost anything will burn, and many things will burn spontaneously. To make matters worse, almost every exposed surface of the module was covered in velcro for ease of use in zero-g. The problem is, the velcro was literally explosive at the Oxygen density used during the test.
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Re: (Score:3, Funny)
Yeah, where do you find living Nazi-Era German Rocket Scientists these days?
Re: (Score:3, Insightful)
Not going to talk about your "Germans" comment, but...
Apollo had at least 2 major incidents, killing 3 astronauts, and endangering 3 others.
Shit happens when you are pushing the envelop. Mercury, Gemini, Apollo, Shuttle, Sal
Re: (Score:3, Informative)
Oh, it was WAY worse than that... just off the top of my head:
1) When landing on the moon, during the final (and most tricky) phase the computer controlling the LEM effectively turned off - Neil landed manually, with the computer yelling abort all the way.
2) Apollo 15 (I think) they tried decreasing the number of thrusters used to separate the stages - the stages almost collided, nearly killing everyone aboard.
3) Apollo 13, the center engine entered a pogo oscillation on launch that was about to destroy the
Re: (Score:3, Insightful)
The US government oversaw Apollo. US enterprise is currently overseeing a crappy suborbital space plane and an even crappier low payload rocket.
If the current incarnation of NASA has a problem, it is that like many modern government agencies it is trying to emulated private enterprise too much.
Re:Hey there! (Score:4, Informative)
Hilariously the apollo program had some pretty serious pogo oscillation problems. Pogo is shaking the rocket up and down makes the propellant flow increase and decrease making the oscillations worse.
In the apollo era, as per http://www.clavius.org/techsvpogo.html [clavius.org] they used plumbing style water hammer chambers to eliminate the fluid surges. Let the vehicle shake but prevent the ability for shaking to cause thrust variations.
The modern solution is apparently dynamic shock absorber technology on the vehicle.
The modern solution eliminates the shaking, the old solution allowed it to shake but patched around it so it didn't have negative effects.
The modern solution is better, which makes the comparisons to Apollo kind of funny to those who know...
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Re: (Score:3, Insightful)
Re:Not absorbing vibrations (Score:4, Informative)
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