ESMD To talk About Ares Thrust Oscillation Problems

NASA To Brief Media About Ares I Thrust Oscillation Plans

"NASA will host a media teleconference on Tuesday, Aug. 19, at 11:30 a.m. EDT, to discuss results and recommendations from the Ares I thrust oscillation focus team."

Editor's note: Last week NASA decided to implement the so called "Option 2B Active Aft Skirt Reaction Mass Actuator (RMA) option" with "damping and isolation at the FS frustum/US region" in order to deal with the thrust oscillation problem with the current design of the Ares 1 launch vehicle. This decision is a hybrid of sorts between two earlier options - one called "Dual Plane Isolation Plus Passive TMAs)" and the other "Active TMAs Plus Single Plane Isolation".

On Telecon

-- Jeff Hanley, manager, Constellation Program, NASA's Johnson Space Center, Houston
-- Steve Cook, manager, Ares Projects, NASA's Marshall Space Flight Center, Huntsville, Ala.
-- Garry Lyles, associate director for technical management, NASA's Marshall Space Flight Center

Notes below

Jeff Hanley

Here to talk about TO problem and decisions we made recently.

Steve Cook

Gary's team came up with a creative set of options to deal with TO. Took that forward to Hanley last week and going to Washington next week with the solution we're working. We have a minimum impact solution on Orion. Allows us to "dial up" to deal with unknown unknowns. Lets us offramp in various stages if data allows.

Thrust Oscillation Focus team work integrated into main design. Conducting PDR now - finishing PDR on 10 Sep. We will have Delta PDR for just this issue no later than next spring - still working on details of that.

Gary Lyles

Smooth ride up to 105-115 seconds. Most of the activity occurs for a few seconds - max vibration - over short period of time.

We are dealing with effects on crew - crew performance read displays and respond to what they see. We found that the crew health issue is easy to mitiagte. We have a goal of getting vibration on crew - longitudinal - at 1/4 G

Discovered that the tune mass absorbers would be best placed in the aft skirt of the first stage. There may be modifications in the inert components of the motor (non-propellant).

Found that a totally passive system became ineffective at lower levels. Active tune mass absorbers were good at dealing with frequency ranges down to 1/4G and below.

Design changes will be made on Ares side only. The active systems allow us to deal with any uncertainties in the system. Still a lot of immaturity in the vehicle at this stage (PDR). We can remove these options as we learn more and we can tune them.

Solution chosen is a combination of a complaint structure between the first and upper stage and an active tune mass - reaction mass actuator - in aft skirt of the first stage.

16 actuators will be in the aft skirt and will be driven by battery power with a redundant control systems We can loose multiple actuators and still cancel the vibration on the crew. Even if we lose all active control in the system - a passive tune mass absorber would still kep things under the health limits for the crew.

This is a low weight solution. The impact on mass to orbit is approx 1200 - 1400 pounds which is within the mass margin on the Ares side.


I asked if there are any studies under way whereby NASA is looking at alternative means whereby Orion could be placed into orbit i.e. EELVs, variants on Ares, etc.

Jeff Hanley replied "No we are committed to Ares 1. We have made tremendous progress to make it a workable system. Options that we have looked at recently are flight test vehicles we might use to gain experience with certain parts of the system. We have looked at concepts for variants that would be transitional vehicles. We have not - nor have we in the 2 1/2 - 3 years since ESAS - looked at alternate launch systems for Ares 1 and Ares 5."

When I asked if any FOIA request, GAO request, or Congressional request to NASA would yield any emails or internal studies ongoing, the response was again no - except that there was an admission that they "get legitimate questions from external stakeholders - did you look at this, did you look at that?" and that internal reviews of alternate launch concepts have "been in response to queries from outside. We reverified to outside stakeholders - and to ourselves - that we have the best architecture."

Rode in the chair - closest thing that it feels like is a low, high vibration rumble. At 1/4G you can read - higher you cannot read as easily.

Dampening crew seats - looked at that - decided that we did to want to put any mass on Orion since it has to go to the moon and back.

DTO on shuttle - this will give us data on shuttle SRBs. There will be a set of accelerometers on the structure - forward skirt and attach points. This will allow us to correlate driving pressures of motor on the vehicle. This will let us make sure that the same modeling technique that we used on Ares 1 is appropriate.

Also have accelerometers that will attach to crew seats to see what shuttle vibration is felt by the crew.

Any problems vetoed by the astronaut office? No. There were no vetoes from the Astronaut office. They had their opinion - as does any other office - they had preferred solutions - this one aligned with their preferred solution. There were others that would have been OK from a crew perspective - some that they preferred less. No veto.

We had a lot of conversations - there are two limits - a crew health limit which is higher so as to not damage anyone - and the operational limit which is lower so that the crew can actually function. A lot of conversations around that operational limit. Is that really the limit or is there an engineering level to tolerate a G level that is higher than that?

Steve Cooke: there is nothing on our list that is a showstopper. Everything is within what you typically associate with a launch vehicle development program.

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This page contains a single entry by Keith Cowing published on August 19, 2008 12:27 PM.

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