CEV Revolutionary Gimballed Thrusters

simonbp writes "A Tennessee Tech Professor has proposed an innovative gimbal mount for 'inclusion to the design of [NASA's] CEV (Crew Exploration Vehicle), revolutionizing the vehicle's RCS (Reaction Control System) and solar panel orientation capabilities.' This will allow for nimble maneuvering and for the solar cells to maximize power production."

Comments

Re:Wow...Old News Is So Exciting!

[georgewilliamherbert]

It's standard practice to gimbal the main engines in a launch vehicle, or an upper stage. That gives you pitch and yaw (and sometimes, if you have 2 or more engines, roll) orientation control while you're under thrust from those main engines, without having to use the smaller RCS engines as well.

Other ways of doing it include using a RCS anyways, with fixed main engines; putting vanes or paddles in the main engine exhaust stream but keeping it fixed; using aerodynamic control fins (only works in an atmosphere during certain speed ranges, useless at liftoff or in space); injecting a liquid or gas into the main rocket engine nozzles on one side but not the other, to give side thrust (LITVC or Liquid Injection Thrust Vector Control, though it can technically use gas as well).

It is not standard practice to gimbal the reaction control system used in space. The assumption to date has been that the four fixed quads approach gives the best reliability under circumstances where part of the system suffers a failure. If you lose one of these oriented thrusters (stuck actuator or thruster fails) then it's like losing a whole standard quad, in terms of the vehicle's remaining dynamics. Lose two, and your maneuverability is severely impaired.

I work in this lab.

[docfreezzzz]

I am a Mechanical Engineering Undergraduate who attends TTU and does research for the department in which this design originated. I work in the lab where the device was first prototyped. Just as an FYI, the device is revolutionary because of the elimination of repetitive structures. Granted the bearing are an issue but the gimble can achieve a full 360 degree spherical change in attitude with only the use of 3 stepper motors. Nothing else does exactly that at this time. That's why the device is interesting to NASA. Think of replacing the current arrangement of 5 motors with just one. Can you say cost savings? Just thought I would post my 2 cents since I have had to demo the device on several occassions and have first hand experience with the mechanism. OUT

Re:I work in this lab.

[docfreezzzz]

It was meant more for small craft travel vector correction. Hence the attachment to CEV. Not main craft repetitive flights like the space shuttle. Sorry I gave that as an example but its something everyone can relate to. I do have to disagree with you in terms of your analysis of engineering economics however. How many space shuttles do you think they mass produce? Most parts are one offs from precision manufacturing facilities. The only parts which are repeat manufactured are SRBs and those are extremely simple. The dies and CNC code is what is costed most in manufacturing. The mass production just makes the profit/cost ratio more favorable to the consumer... aka NASA. If you only make 30 pieces. There really isn't a mass production method in place. And technicians are much faster at servicing one part instead of 4. That's part of the reasoning behind the system. We are talking about replacing multiple pieces with one piece therefore they still have the same learning curve for servicing the system. As for redundancy I do agree with you there. It is far safer to have a backup system. However, even with the multiple booster positioning systems in place today. If one fails entirely, there is still a serious impairment to the craft. They just don't send up unused pieces with a space vehicle. Weight costs money. Several grams can cost on the order of thousands of dollars to reach high earth orbit. Once again the system that weighs less wins especially with funding reductions in the program as of late. Just my 2 cents... ;) OUT