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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?"
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?
Here's a picture of it.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
Please give these guys a call http://www.directlauncher.com/
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.
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 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.
Quo usque tandem abutere, Nimbus, patientia nostra?
There's a much more informative article on Space.com from yesterday: http://www.space.com/news/080819-nasa-ares1-vibration-update.html
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.
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, 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.
If you mod me Overrated, you are admitting that you have no penis.
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!
gigantino.tv - Heavy but weighs nothing.
http://www.nasaspaceflight.com/content/?cid=5167
Constrained by the Ares I launch vehicle, the SRD lift-off weight target for Orion is set at 64,450 lbs...
2.5% of total weight, to offset "massive vibration issues" sounds worthwhile to me, particularly if something important might come loose (or worse, break).
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!
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2
Does someone have a car analogy?
Because they didn't design their engine very well, it now needs a very large harmonic balancer.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
The blueprints are gone, along with most of the other design paperwork. Many things would have to be re-engineered just to build what once existed.
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 craft until the computer shut it off.
There are lots more...
while (sig==sig) sig=!sig;
The active system may seem overly complicated, but trust me, passive damping was looked at. There were 6 different isolation systems on the table prior to this final down-select. And in fact, the dampers at the mid-stage are entirely passive. They are enhancements to CSA Engineering's Softride system.
The active tuned mass actuators are necessary in the first stage because nothing else would work for the heavy resonant burn effect.
Resonant burn is something seen in all solid-fuel rockets where an axial oscillation occurs as the fuel gets used.
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 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.
That's a different thing. Ares is aerodynamically unstable, because it has a thin and heavy first stage and a large-diameter, light second stage -- that thing will constantly try to turn around while flying through the atmosphere and needs constant control to keep it flying with the engine pointing backwards.
Try to throw a dart with the light and fluffy bit forward and the thin and heavy bit backward and you know what it is like.
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.
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>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.
Also, there is a fallacy in your logic.
it would not surprise me if the Saturn V's "small" pogo suppressors weighed over 1600 pounds in total.
The Saturn V is a much bigger rocket than Aries I.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
Huh? First off, Pogo is experienced to some degree or another by practically ever booster of significant size. The best you can do is dampen it below danger levels, as it is an inherent mode of vibration in booster.
Secondly, Apollo didn't 'solve' it, they merely dampened it below problematic levels. Even so, that was only finally accomplished fairly later in the program - Apollo 13, for example, suffered extremely from Pogo. On that flight, Pogo was bad enough that it came right to the boundary of abort conditions. If Pogo hasn't caused the center engine on the stage to shut down, and thus reduced the vibrations, it's virtually certain the second stage would have disintegrated.
Only the last five flights (14-Skylab 1) didn't suffer from significant and potentially dangerous levels of Pogo vibration. (A fact NASA kept hidden for thirty years.)
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
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, flexing the massive thrust frame by three inches at 16Hz, experiencing 68 gees.
You're greatly exaggerating the Wikipedia entry, which itself exaggerates the actual facts. (What, Wikipedia not accurate? I'm shocked!)
There was a known pogo issue on the center S-II engine, observed at 18 Hz on Apollo 8, apparently limited by non-linearities in the system. On the next flight they increased tank pressure but that didn't eliminate pogo and measurement showed G's getting too close to design limits. On the next few flights they built in an early shutdown of the center engine, but several bursts of pogo showed up on Apollo 12 (which had its own share of excitement, being struck by lightning just after launch).
There was a pogo-suppressor designed to fix the problem, but installing it on Apollo 13 was problematic because the vehicle was already stacked. Early in the second stage flight they observed a couple of rounds of self-limiting 16 Hz pogo as on Apollo 12, but then next round ran away and vibration forces on the center engine built up.
The center engine shutdown was initiated by a pressure sensor - the pogo is related to wild variations in engine pressure (both cause and effect) and the engine pressure sensor sensed low average pressure and shut the engine down before any damage occurred. It was not "a fuel sensor falsely tripped", but a correctly operating pressure sensor that caused the shutdown. The four outboard engines then just burned longer to make up the difference. In no way did the center engine "nearly rip the entire rocket to little pieces".
All later flights had the pogo suppressor installed and had no problems.
-- Alastair
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.
Close but not quite. The materials were also flame-retardant or resistant at 100% oxygen atmosphere at the pressure specified for flight, about 3 psi. (The same as the partial pressure of O2 in normal air.) This they did not change after the accident.
The accident happened because they wanted to run the pad test at a higher pressure than the outside -- to simulate that aspect of flight conditions -- and so ran up the cabin pressure to 16 PSI -- of pure O2. Things that won't burn in 3 PSI O2 can burn quite vigorously at 16 PSI O2. Worse, NASA had been warned by North American about the dangers in a high pressure O2 environment. This procedure they did change after the accident, along with making a number of design changes on the CM.
(Ironically, one of the design issues on the CM was the inward-opening hatch, which Grissom had insisted on after the explosive bolts on his Mercury hatch underwent an uncommanded detonation after splashdown and he almost drowned. The inward-opening hatch meant the astronauts couldn't open it as pressure rose in the capsule because of the fire. The redesign included an easier to open, outward swinging hatch.) (Many years later, the likely cause of the uncommanded detonation of the explosive bolts is believed to be due to static buildup because of the recovery helicopter's downwash.)
-- Alastair
You know, the motors and controls could be *in* the canisters.
And considering the Ares V is such an improvement over older designs, a bit of dead weight is more than made up for by the overall efficiency of the vehicle.
The Ares V weighs 10% more than the Saturn V, but it carries 60% more payload. The Ares V weighs 50% more than the Space Shuttle, but it carries 700% more payload.
I doubt anyone will bemoan the loss of a tenth of a percent of the Ares V's ~200 ton payload capacity.
How can I believe you when you tell me what I don't want to hear?
Unfortunately the 1600lbs+ of kludge is going on Ares I not on Ares V. Saying that however, Ares V hasn't got any spare capacity for TLI either!
$2B OR NOT $2B = $FF
Except that liquid fueled engines weigh more than solid fueld engines...
Funniest, most wrong thing I've read on Slashdot today.
Hints: look up "specific impulse" and "combustion chamber wall thickness", among others. Hell, look at any kid's introductory book on rockets; it will explain in words short enough for you to understand why solids are (for a given delta-vee) so much heavier than liquids.
-- Alastair