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NASA Installing Shocks On Ares
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?"
Will they then have to haul nearly a ton into space? That sounds like a very costly improvement to the shuttle.
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.
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?
Think Deeply.
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.
http://www.dieblinkenlights.com
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 ; )
"Kill 'em all and let Root sort 'em out"
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.
If we can put a man on the moon, why can't we shoot people for Apollo-related non-sequiturs?
In related news, did anyone notice the Oprah ad below the story (down on the left side):
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Talk about context-sensitive advertising ;-))
Tell Gus Grissom, Ed White and Roger Chaffee how well the original Apollo design worked for them. Oh wait you can't - they're dead.
No mod points, no meta-moderating/Firehose/all the other free work Slashdot wants me to do.
Whilst I'm not overly surprised by the decision why have they left it this late, as its a well documented problem thats been around since the beginning of space flight.
No, they are dampening the vibrations because vibrations from SRBs are too unpredictable to be canceled out in the way you describe.
If we can put a man on the moon, why can't we shoot people for Apollo-related non-sequiturs?
Yeah, where do you find living Nazi-Era German Rocket Scientists these days?
Tsukasa: All I really want, is to be left alone...
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.
If builders built buildings the way programmers wrote programs, then the first woodpecker would destroy civilization.
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.
Quo usque tandem abutere, Nimbus, patientia nostra?
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.
Get off my lawn.
There's a much more informative article on Space.com from yesterday: http://www.space.com/news/080819-nasa-ares1-vibration-update.html
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.
-- Alastair
>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: "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."
Some mornings it's hardly worth chewing through the restraints to get out of bed.
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.
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 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...
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
It's how much that weight has to be accelerated that matters. If you have to have dead weight, it's better to put it on the first stage than on a later one--you only have to accelerate that dead weight to first-stage burnout, rather than all the way to orbit.
The end effect is that a pound of dead weight in the last stage costs you a pound of payload... but a pound of dead weight on the first stage might only cost you a quarter of a pound in payload.
That's why many people propose making the first stage of a launcher reusable, and throwing away the upper stage (rather than the other way around, like the shuttle). All the reusability adds weight (thermal protection, landing gear, recovery systems)... make it the first stage, and you can make it beefier and more robust. And there's less of a thermal problem to deal with.
That said, 1600 pounds of deadweight mass dampers is a piss-poor engineering solution. But that's what you get when you have a politically-dictated design that's being rushed out the door; shit gets kludged together to make it work now instead of doing it right to begin with. This could be seen as the equivalent of using a GOTO in complicated code (instead of fixing it correctly), or fixing misaligned teeth by pulling them all out (to be replaced by dentures) instead of getting braces. It works, yeah, but it's not a good solution.
The meek may inherit the earth, but the strong shall take the stars.
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...