NASA to Brief Media About Ares I Thrust Oscillation Plans

[Antares]

The RoCS loads on the Softride buttresses (these things look Gothic to me) will be small compared to the rest.  The bending loads are far worse.

[bad_astra]

Perhaps if they had went with the lattice type interstage they could have incorporated the isolators into the framework.

[foltster]

Thanks Ross. That's what I was kind of getting at, but I was confused by the paraphrased quote from the live coverage that said TO "occurs at 115 seconds" rather than peaks at it. You clarify it very well.

http://www.nasa.gov/pdf/267605main_TOmitigation.pdf

speakes volumes. No way 100 pounds x 16 is the counter oscillating mass.

By my math, 1600 pounds oscillating sinusoidally at 15 Hz can create a sinusoidal peak-to-peak force of 100,000 pounds if it has a total displacement of 2.7 inches.

I picked that number based on the 100,000 mentioned by kraisee, although now I see that he said the TO force is 100,000 psf, not lbf. That's a discrepancy...is it force or pressure? 5-6 G's would suggest to me its the pressure, but 5-6 G's sounds way out of scale for a booster pulling 3-4 G's RMS (+/- 100% chamber pressure?)...err, I guess I'm forgetting about the 2nd stage resonance.

The required displacement scales linearly with the required force. I'm not entirely sure how the power scales, but I think it's roughly to the square of the required force. It seems to me they're going to need some hefty, high draw batteries.

Maybe they could use those heavy batteries as the oscillating mass???

[robertross]

Batteries normally don't take too well to serious vibrations. If the battery shorts, there goes your TO mitigation method, plus a fire or explosion from the battery bursting. Plus the wiring, which is normally tied to brevent breakage, is whipped around like a skipping rope.

[phred]

Has there been any specific information on how these oscillating mass actuators will work?  I understand batteries will somehow drive mass back and forth, but what's the mechanism?

[kraisee]

An electro-magnetic coil around a moving metal mass inside.

Although Chris has info on L2 right now talking about hydraulics...   But you'll have to be an L2 subscriber to learn about that.

Ross.