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Space Technology

CEV Revolutionary Gimballed Thrusters 71

Posted by ScuttleMonkey from the one-of-these-days-alice dept.
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."
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CEV Revolutionary Gimballed Thrusters More

CEV Revolutionary Gimballed Thrusters

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  • Didn't the Soyuz 11A511U have Gimballed Thrusters? [astronautix.com]
    • I share the concerns you mentiond - particularly because just the cost of re-learning the performance of the RCS, in terms of fuel wasted, would be prohibitive and way more dangerous than the risk of impacting something.

      Your analogy with the progress collision with Mir is, however, flawed - it had nothing to do with gimbals, as the capsule DOES NOT have gimballed RCS, the first stage of the rocket does.

      to the original poster, I must note that the soyuz roket variant you pointed to used gimballed vernier thr
    • Didn't the Soyuz 11A511U have Gimballed Thrusters?

      Indeed, as was the Rocketdyne J-2 on the Apollo command module. Both the Soyuz and Apollo thrusters are main engines. These gimballed thrusters are for the Reaction Control System, used for fine positioning and attitude control. RCS thrusters have traditionally been fixed, rather than steerable.

      • Not to be completely anal, but the conical command module was essentially the capsule that returned to earth. The cylindrical service module (where the infamous LOX tank exploded on Apollo 13) had the gimballed J-2. Otherwise, right on.

  • Gimbal? (Score:4, Informative)

    by iopha ( 626985 ) on Saturday January 07, 2006 @01:26PM (#14417434) Homepage
    If you're like me and are wondering what the heck a gimbal is, wikipedia [wikipedia.org] has an article. Not being an engineer, I still only have but the fuzziest idea of what's going on here; blame a liberal arts background.

    • Re:Gimbal? (Score:5, Informative)

      by interiot ( 50685 ) on Saturday January 07, 2006 @01:32PM (#14417454) Homepage
      Better is wikipedia's Gimbaled thrust [wikipedia.org] and the NASA pages it points to.

      (funny, I was just reading that before coming to slashdot... even better is the semi-related water rocket [wikipedia.org] page.... awesome stuff)

      • there's one spot in that article that is in-error, but i don't know enough about rockets to be able to correct it :
        In the case of super-roc or backgliding rockets, the centre of gravity and the centre of gravity are as close as possible, so it spins around, which slows down it's descent.
        not sure how to make note of this on Wikipedia itself, do you just edit the discussion page?
      • "Better is wikipedia's Gimbaled thrust [wikipedia.org] and the NASA pages it points to."

        I just started this page a few hours ago! Must be a new record for wiki-to-slashdot linking.
    • So, it's not what slithy toves do in wabes?
      'Twas brillig, and the slithy toves
      Did gyre and gimble in the wabe:
      All mimsy were the borogoves,
      And the mome raths outgrabe

    • For the most part, you Liberal Arts types need only concern yourselves with one type of joint.

      To be blunt.

    • If you're like me and are wondering what the heck a gimbal is, wikipedia has an article.

      Wikipedia says a Gimbal is "a type of coin-operated arcade game where a player attempts to score points by manipulating one or more metal balls on a playfield inside a glass case. " Well, looks like I've learned something today!
      Excellent!
    • Gee none of the wikipedia articles does a very thorough job of explaining gimbal or gimballed thrust. The joint has two degrees of freedom, like your shoulder joint or hip joint. The thrust of the rocket is directed along a line through the center of the nozzle, or very nearly so. If the line along which the thrust is directed goes through the center of mass of the rocket, the rocket goes straight. If it doesn't go through the center of mass of the rocket, the rocket experiences a torque, which will caus
    • Gimbals have been around since...well, if you believe Needham, at least the 10th Century AD in China. A gimbal is just a way of mounting something so it can rotate relative to something else while still being attached to it and moving linearly with it, and the main application has been on boats where equipment like lamps and compasses is suspended in mounts so it can swing. http://www.sailgb.com/p/captains_cabin_lamp/ [sailgb.com] is a picture of a small gimballed lamp. So long as the centre of gravity of the equipment

    • If you're like me and are wondering what the heck a gimbal is, wikipedia has an article. Not being an engineer, I still only have but the fuzziest idea of what's going on here; blame a liberal arts background.

      Do you know the small motorboats, where the boats direction is controlled by turning the engine so it pushes the back of the boat to the side instead of straight forward ? According to the Wikipedia article, the gimbal is a device that lets a rocket do the same.

      In other words, a gimballed rocket

  • ... MS owns the copyright to the word 'innovative'. They will be releasing this new design in 6 months after copying it.
  • The original CSM had gimballed engines. So they announced they are going to do the same damn thing that they did in the 60's? Snore.
    • The main SM engine was gimballed. The RCS system wasn't.
    • From TFA: "four single RCS thrusters, placed 90 degree apart around the circumference of the service module, with the ability to direct thrust to any direction in a hemispherical motion, replacing - and capable of even more manoeuvres than - the current four groups of four (16 in total) body-fixed thrusters."

      And I'm pretty sure the orginal CSM did not have a gimbled engine. The Saturn did, but with no where near the same range of motion as being discussed here.

    • 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 atmosph
    • Well you see, it revolves, so naturally "Revolutionary" was quick to come from that, and they kind of just went with the flow to get "innovative".
    • AFAIK the Saturn 5 rocket had gimballed thrusters. Gawd knows why this is revolutionary now. When and why did JPL stop using gimballs?
      • All of the main engines on the three stages of the Saturn V, along with the main engine on the Service Module were mounted on gimbals, as are the three main engines on the Shuttles. I suppose the LEM used similar technology, but I don't feel like checking. Each of the RCS thrusters on the Service Module consisted of four nozzles at 90 angles. For Apollo geeks/modellers, here's a site absolutely loaded with detail shots of the Saturn V, including gimbals; http://www.apollosaturn.com/ [apollosaturn.com]
  • There are a couple of weak links to this solution, but nice design none the less.

    The connecting joints and hoses will be subject to flex failure.
    No doubt they will use appropriate materials to counter repetative wear.

    Also, as with most space equipment, they will most likely make a redundant system.

    • Design is a disaster (Score:4, Insightful)

      by O2H2 ( 891353 ) on Saturday January 07, 2006 @09:30PM (#14419315)
      The design is interesting in a sophomoric way. It is clearly designed by someone who has never had to qualify a device for spaceflight. Highly cantilevered, indeterminate stuctures with eccentric centroids and active mechanisms in the loads paths are terrible. I would give that thing about 60 seconds on a vibe table before it came to pieces. The use of flex hoses with such large motions is also a really bad idea- expecially when they have to flex in multiple axes at once- there is no practical solution to make such a fluid connection last more than a few thousand cycles under cryogenic conditions under the 300 psig pressure conditions that are planned for CEV propulsion. As someone who DOES design such things on a daily basis I give it a D- for practicality, cost and reliability/redundancy.

      Also the control valving is highly decoupled from the combustion chamber which means high dribble volume and terrible min Ibit. Those simple stepper motors also have to operate at 165R for prolonged periods- this denies you most lubricants and requires special resolvers and the like. There is also no way that such a mechanism can deliver the frequency response of multiple small thrusters pointed in multiple directions. There is also the need to interface either a fiber optic or high voltage spark igniter lead to the thruster across large motions- could be a problem for the non-optical approach.

      The issue is : just what problem are we trying to solve? is it cost of the combustion chamber? Number of valves? Weight? Overall complexity? Or is this just an interesting exercise for a kinematics class? The vehicle attitude control function can be performed two active and two standby modules- not four fully active as was used on Apollo. This is highly optimal for cryogenic thrusters since it minimizes the number of lines which must be chilled and pure 6 DOF operations are rare as opposed to simple maneuvers with coupled rotations and translations. This solution was proposed to NASA and rejected as being "just too different from what Apollo did". I cannot imagine them actually flying this contraption.

      • Nice assortment of information.

        When I build my space port, now I know who to call on for preliminary engineering consultation.

        It seems the main concept is to increase exposure of solar cells by allowing the craft to maneuver independantly using gimbles on thrusters.

        Why not use the already battle hardened multi directional thrusters found on a Harrier?


  • Gimball looks to me like a perfectly cromulent word!

  • The original shuttle had gimballed engines, now they're using it for the RCS as well? Big fucking deal. May as well post an article about how the toilet's going to have a different colour of soap.

    The original design with millions of RCS thrusters all over the place was stupid anyway.

  • Link to actual animation (Score:5, Informative)

    by Animats ( 122034 ) on Saturday January 07, 2006 @02:38PM (#14417693) Homepage
    If you don't want to plow through all the blogodreck and registration, here's the animation of the Canfield joint [tntech.edu] (quicktime).

    As a rocket engine gimbal, this doesn't look promising. It's a rather bulky mechanism; the linkage is much larger than the engine bell. It requires fifteen bearings, not including the three motors. The standard solution, a gimbal ring arrangement, only requires four. The bearings also have to handle off-center loads, never a good thing. Bearings in space are headaches; lubrication is tough and temperature changes can jam them.

    The motors are in a weak position from a leverage standpoint; the engine thrust is applied directly to the motor shafts, so they (and their gear trains) must be strong enough to overpower the thruster. In a gimbal ring arrangement, the bearings are usually placed so that the center of thrust is at the center of the gimbal, so that the bearings, not the actuators, take almost all the thrust. Very large engines, like the Space Shuttle and Saturn V main engines, have been successfully gimballed that way.

    The three motors don't seem to add redundancy; it looks like they all have to be working.

    For comparison, here's a simple gimbal from Amadillo Aerospace [armadilloaerospace.com], Carmack's rocket program.

    In reality, having many fixed reaction thrusters is probably more reliable than have a few steerable ones. Fewer moving parts.

    • Ummm.... the quicktime video you linked to looks nothing like the video they have on the nasaspaceflight.com website.

      The 3 movable arms look more like two sevens (7) that got mashed together along the flat part.

      Here's a screenshot [imagevenue.com] (modified with my crazy mspaint skillz)

      I assume the rest of what you said still stands though.
      • Different animation, and a different version of roughly the same klunky mechanism. Better bearing mounts, though. That one you could actually build.

        The motors seem to be right out of the Maxon [maxonmotorusa.com] catalog, with the planetary gearhead option on one end and the encoder on the other. Those are good motors (we used one to steer our DARPA Grand Challenge vehicle), but they are not rated for spacecraft operation.

        Here's an Aeroflex gimbal [aeroflex.com] that actually is used in space to steer a thruster. Note how the rotationa

      • The basic mechanism shown is basically the same.

        What I don't like about this idea is that the thrust seems to be carried by the actuators holding their position. Come to think of it, they're using 3 actuators to accomplish 2 degree of freedom motion. Great. Armadillo's gimbal doesn't have these problems, but it does have a very limited range of motion in comparison.

        It's not difficult (I just did it) to imagine a gimbal with the same or better range of motion, loads not significanlty carried by motors, no ho
        • trunnion on a swivel base.

          The trouble with a trunnion on a swivel base for this application is that it has a singularity around the straight position. Small changes of direction when pointed nearly straight require big changes in the swivel base position. For a thruster, you need to make small corrections quickly, with minimal actuator motion. (Think WWII antiaircraft guns, forced to slew around frantically when the attackers were overhead, usually missing the target at its point of closest approach.)

    • Is it just me, or does the top left of the gadget bear a passing similiarity to the Napster cat-head logo?
  • If you're just curious about what this new gimbal looks like, tntech.edu [nyud.net] has a video [nyud.net] showing how it works. Or, for those who don't like Coral cache, here's a link to the original site [tntech.edu].
  • I hope this idea is adopted. We're talking major cost and energy savings.
  • The video illustrates exactly how the gimbal works.

    It's quite neat actually.

    Too bad the video is a few MB over 50, otherwise they could have coralized the link.

    I won't post a link here, because they say that they don't want their server to go down in flames.

  • I went to the site, where it says a video of the device in action can be seen at the link on the bottom of the page.

    But guess what friends, when you click on the link, you are rejected because you are not a friggin member.

    It might for all I know, be a great idea, but screw em and the camel that rode in on them.

    Whyinhell does Taco post these stories without checking them out for veracity?

    --
    No Cheers, Gene
  • Most vehicles in space use a combination of thrusters and reaction wheels. Essentually a flywheel on each axis is spun up or down to rotate the vehicle. Eventually the wheel is moving too fast and a thruster is used to spin the vehicle so that the wheel can be slowed down. For moving the vehicle it is important to have the thrust vector point at the CG of the vehicle, else a torque is produced causing spinning which requires an additional thruster to compensate. By the way the solid rocket boosters on t

  • I work in this lab. (Score:3, Interesting)

    by docfreezzzz ( 944082 ) on Saturday January 07, 2006 @06:16PM (#14418600)
    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
    • The nice thing about repetitive structures is that they lead to cost reductions through volume manufacturing and assembly. They're also easier to train technicians to service.

      The nice thing about fixed quads for an RCS system is that their only moving parts are the valves -- pretty simple parts. Moving parts are failure points.

      The nice thing about multiple quads vs just a few gimballed thrusters is that they provide redundancy and backup for each other.

      But then NASA has always been in love with the comple
      • 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 extr
        • The only parts which are repeat manufactured are SRBs and those are extremely simple.

          No, the SRB's are re-used (although "crashed and salvaged" might be more accurate). The ET's are disposed of and manufactured new for each flight.

          The dies and CNC code is what is costed [sic] most in manufacturing.

          Right, so it doesn't cost much more to build 30 than it does to build 5. Even if you're largely hand-building the things (vs using CNC), you still need dies and templates. Besides, with any halfway modern CADD

          • Remanufactured is a more approptiate term. I do apologize once again for my choice of language.

            Right, so it doesn't cost much more to build 30 than it does to build 5. Even if you're largely hand-building the things (vs using CNC), you still need dies and templates. Besides, with any halfway modern CADD system, the CNC codes are just another output.

            The original reply gave benefit to the current setup due to cost reduction through volume. My point was it isn't cost reduction through volume. I was no

  • Mmmmm, gumball thrusters *drool*

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