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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?"
...and is a mechanical fudge. It looks to be typical American engineering, big, clunky, and with no regard for elegance.
Why don't we outsource the design to some German scientists, like we did the last time? European engineering is at least two grades above ours. We might as well get the best we can for the dollars we're paying...
...that's 1600lbs that could have been used to lift more fun stuff in to space.
"False hope is why we'll never run out of natural resources!" - Lewis Black
Surely the addition of that much hardware would have a significant negative effect on the max possible payload?
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
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?
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.
How can I believe you when you tell me what I don't want to hear?
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?
I worked on vibration testing for the shuttle, before even Enterprise was drop-tested. We were told to spec for x max level, tested to pass, and then 4 months later were told to re-test for 4x level. The whole damned thing had to be re-designed to include a big backbone, which made a major reduction in cargo bay. Well, it passed again, with the upgrade. Then the next year we were told that the actual levels were about x/2. Let's hope they have better cad and get it about right this time around.
But let's be clear: at launch there's a whole lot of shakin' goin' on.
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
The William H Zimmer nuclear plant was 97% complete when it became apparent that the plant owner and construction contractor had so screwed up the construction documentation that it would have taken as much money to recreate the documentation as it took to build the plant. From Wikipedia:
"Originally expected to cost $230 million, when the cost estimate soared to at least $3.4 billion the decision was made in 1984 to convert the plant. (Regulatory delays and high interest rates also contributed to the cost increase.)
The constructor, the Henry J. Kaiser Company, had never built a nuclear power plant before (or since). And the primary owner, Cincinnati Gas and Electric, did its own procurement, awarding contracts for equipment, e.g., for hundreds of valves, with inadequate specifications or QA requirements. Piping welds were not adequately radiographed.
Sargent & Lundy was the Architect/Engineering firm.
An ex-Navy admiral was hired to bring the plant on-line, and Bechtel was retained to nuclear-qualify the plant. However, Bechtel came in with an estimate of over $1.5 billion (to add to $ 1.7 billion already spent) to adequately complete the plant.
The conversion to coal-fired generation cost just over $1 billion, starting in 1987 and completed in 1991. It was the world's first nuclear-to-coal power plant conversion."
Just because the blueprints for Apollo exist doesn't mean that you can recreate the Apollo program. Lets just talk computers alone - where are you going to get flight control computers from 1969? Answer: nowhere - they don't exist. It doesn't matter if my TI calculator has more computing power; the cost to convert my calculator to recreate the function of the flight computer, test it, and rate it, would likely be far more expensive than just building a new one.
"As God is my witness, I thought turkeys could fly." A. Carlson
I remember reading about Apollo astronauts being amazed at how much they shook/vibrated - so much that they joked about not being able to make out controls (no one complained though for fear of loosing the missions)
Its not just the vibrations of the propellant exploding under their pants but the gimble of the engines to keep its trajectory that causes oscillations in the craft.. all being better absorbed by this awesome contraption.
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...