LPR Space Shuttle Build - just for neil_w

Discussion in 'Scale' started by Charles_McG, Dec 8, 2017.

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  1. Dec 8, 2017 #1

    Charles_McG

    Charles_McG

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    I'm continuing my 1/100 US manned spaceflight series with the Space Shuttle.

    This will be a little off-scale in several directions. The 3.44" tubing from my 1/35 Titan GLV is about 1/97 for the external tank. Using BT58 for the SRB is about 1/95. Taking inspiration from other threads here on the forum, I'm using a Guillows foam orbiter. The wingspan is right for the tubes - but the body is small for the wings - more like 1/115.

    So I've gathered my parts and am doing some test fitting and prepping.

    IMG_2319.jpg

    IMG_2323.jpg
    Nosecones by Sandman.

    IMG_2324.jpg

    IMG_2330.jpg
     
  2. Dec 9, 2017 #2

    burkefj

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    Nice, the little 2 ch rc linear servo boards are so small and light, with a little 1s lipo shoud be a very easy rc add, I assume you are just going to do elevons?

    Frank
     
  3. Dec 9, 2017 #3

    Charles_McG

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    I was thinking elevator and rudder, but don't have my heart set.
     
  4. Dec 9, 2017 #4

    burkefj

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    Just curious, I know Gassaway likes rudder on his shuttles, I've always flown my shuttles with elevon, in fact I don't have any aircraft with a functional rudder at this time and never had any issue. I just think setup of elevons is easier than tying elevons together and running a separate rudder wire but whever should work.

     
  5. Dec 9, 2017 #5

    neil_w

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    :cheers:
     
  6. Dec 9, 2017 #6

    MaxQ

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    LOL , Where's George? :pop:
     
  7. Dec 9, 2017 #7

    cruzsergio

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    Subscribed! :D
     
  8. Dec 9, 2017 #8

    Charles_McG

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    My boys and I only have RC experience with rudder/elevator. Dual elevon would be easier mechanically. Other folks say it flies fine that way - I've just no practice. Fixable, I suppose.
     
  9. Dec 9, 2017 #9

    Charles_McG

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    Test fitting transitions.
    IMG_2331.jpg
    IMG_2332.jpg
     
  10. Dec 15, 2017 #10

    Andrew_ASC

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    Beautiful. Don't sweat the scaling discrepancies on the wings.
     
  11. Dec 15, 2017 #11

    K'Tesh

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    I'm in... :pop:

    However, do make sure that the motor hasn't undergone any thermal cycling.
     
  12. Dec 15, 2017 #12

    Charles_McG

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    SRB centering rings and aft skirt transition.

    IMG_2335.jpg

    I'm putting in canted 18mm motor mounts. I may never use them - but now is the time to put them in.
     
  13. Dec 15, 2017 #13

    djs

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    Charles_McG- did you determine a method for having the SRBs separate?
     
  14. Dec 15, 2017 #14

    Charles_McG

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    Well, I've got a few ideas Glen. My current Plan A is to have the bottom attachment points be post and lug, like on my Titan IIIe. Possibly hinged to allow the nose to tip out. Posts oriented so they transfer any SRB thrust to the ET.

    For the forward attachment point, I'm looking at a simple shelf/overhang with a piston or movable flap on the ET. Put a Quantum in the ET with small pyro charges ducted to the flaps/pistons so they push the SRB off the shelf and the SRBs fall away by drag.

    My Titan IIIe boosters separate by nose-blow at motor burnout - which works, but you end up with a high speed chute deployment. -That- I don't like, so if I fly with separating SRBs, I want them to deploy recovery at apogee.
     
  15. Dec 15, 2017 #15

    djs

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    What about putting the SRBs on a streamer instead of a chute. They're pretty lightweight, I would imagine?

    The other option is to just fly with Estes E12s in the SRBs. Then when they cato, they're sure to separate the SRBs from the rest of the shuttle/ET. Plus you'll get the added value of the SRBs being shredded into very small pieces that won't need a recovery system!
     
  16. Dec 15, 2017 #16

    Charles_McG

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    Already done that with the Titan IIIe.

    1.54" and 14" long is pretty big for a streamer, I think. Besides, I've still got to get the thing out into the airstream. I'll work up to that in steps. First flights will be SRBs unpowered and attached thru flight. Then maybe I'll try SRB separation with a Quark in each SRB. Then an A motor in the SRBs.
     
  17. Dec 15, 2017 #17

    Andrew_ASC

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    If you had a T slot on the sides of the tank, with an end cap on the top and a rail covering that T slot, the rocket SRB thrust would push on the T slot on tank under boost via thrust force. Then after burnout the SRB rail would drag separate from drag forces on the cross sectional area of side mounted SRB boosters in the slipstream. Perhaps that is too complex. You just need something to push on then allow a slider action with ease of sliding no friction issues within the sliding mechanism itself, sorry the stages do drag separate from friction with air, but you want to avoid the slider binding.

    Had similar issue with competition rocket prelim design concepts. We went to series staging because Open Rocket didn't like doing clusters like that at that time and we didn't want a drag force increase from plate area, but I was able to cobble an idea of rails to make it drag separate with side mounted SRB if we needed to go that route similar to how the shuttle was staged.
     
  18. Dec 15, 2017 #18

    Andrew_ASC

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    A micro 1010 sized printed lower profile rail top capped, two on ET, with delrin rail guide buttons on boosters might work. But that might appear ugly from a scale aspect. Sorry man, I'm just tossing some ideas out there, you likely have a better way to do it. That whole blow it apart or let it CATO apart seems iffy.
     
  19. Dec 15, 2017 #19

    Charles_McG

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    If I understand your suggestion properly, it doesn't cover the case of an SRB motor failing to light, or worse, lighting late. My Titan IIIe is made so that the lower attachment point takes the thrust (but not the drag - allowing drag to pull it off), and the upper attachment point can lift the booster along with the core in the event the motor fails to light. In that case, the nose cone blows at burnout, disengaging the upper catch, and the booster is stripped off the core by drag. I have certainly considered a rail and button version - the packaging that the coffee pods come in at my day job just happen to fit the 3d printed Wildman guides beautifully.

    For the STS SRBs, I don't want to do the nose-blow release - since it puts the recovery out at high speed. (Note - that's separation at booster burnout, which looks more awesome than separation after a delay, near apogee.) So I'm going to control the SRB release from inside the ET, as if it were an airstart. I'm thinking of a small pyro to push the SRBs off the upper attachment - but that would be a mechanically fragile attachment method. The Titan method is sturdy- the nose has to go up to lift lugs off posts, not just out. Plan B is to put springs on the ET or SRB to push the SRBs off the shelf - and tie them (the SRB) together with a tensioned line through the body of the ET (to hold them on the shelf so they don't get jostled off), with a hot wire cutter to release the tie line when desired. The more I think of it, the more I like that.

    It's just pleading for a servo mechanism - but while a Quantum can command a servo for deployment, it can't for an airstart. Cris says the loop timing is tighter during boost, and there just isn't enough processor time left to get the PWM to the servo in reliable way.

    The worst case is that the booster is left behind on the launch pad - and lights late. So the design needs to prevent that case entirely.
     
  20. Dec 15, 2017 #20

    Charles_McG

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  21. Dec 15, 2017 #21

    Charles_McG

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  22. Dec 15, 2017 #22

    Andrew_ASC

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    If you need to prevent a airstart when the model has exceeded planned flight profile, a raven 3 is hard to beat, but granted I've only had experience with a multistage HPR twice this year, and Raven is limited to lighting one HPR motor in flight. There was a deployment charge channel also user programmable through a menu. The raven takes accelerometer data, barometric pressure. User inputs altitude, velocity, time, or acceleration inputs through a menu. You can keep a series staged multistage within a cone inverted above a launch pad. You can ground test the raven and test ignitors. That's not gonna help on a late light if that does occur. It only prevents something from lighting when a disaster occurs. Had a sustainer stage not light when an airframe imploded this year. Your titan system at least had the other SRB stages traveling upward with break away which was very clever. Maybe you could blow the ET rails off if you went a rail route or maybe a solenoid could react quick enough from a radio channel command. A Altus Metrum Telemega is an FCC gps tracker with flight computer, but it has a user initiated pyro charge through a datalink. TeleGPS has the menu on software, but no output for that pyro charge feature, which I used this year. A radio transmitter for R/C will probably do that task way way cheaper if you need to just command initiate something. A featherweight parrot is smaller than a raven if spacing is hard to compromise. Don't know how you plan on setting your parameters for airstart or deploy charges.

    And maybe all that electronic crap is just way over complex for what this is. You are a clever person. It seems complex to initiate the task required and prevent a late light or maybe I'm stupid at this.
     
  23. Dec 15, 2017 #23

    Andrew_ASC

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    If the SRBs both just air started relatively close using parallel igniters? Perhaps the raven pyro channel has enough amperage for two LPR ignitors. Not certain. Would that be safer as the model would have velocity and not be close to pad or users? It certainly wouldn't look scale. You'd delay a late light situation until the thing was mid flight somewhere along programmed parameters. It still has that off center thrust line and a torque would happen when only one SRB lights. But if it didn't fly right on the central booster, then the raven wouldn't trigger ignition on the other stages. And if central motor doesn't light its staying on the pad. But that's probably not what you want to do. Anyways I'll leave you be.
     
  24. Dec 15, 2017 #24

    Andrew_ASC

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    In an airstart of SRBs mid flight after using the pryo channel on a raven you could use the second deployment channel on the raven to ignite a blow off charge at a certain point to separate it... Beyond that I'm clueless as to solve your issues.
     
  25. Dec 15, 2017 #25

    Charles_McG

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    Andrew, I don't think you're stupid at this. I think you're bright and eager and young. The first two aren't sins and the third is self-correcting with a modicum of patience.

    Now, I do think that you're latching on to words and overreading/overthinking - jumping to conclusions about what I'm trying to accomplish . So let's just lay it out there to look at in the soft backlighting of the screen, shall we?

    My first goal is to make a 1/100 sport scale full shuttle stack, without breaking the bank. I want to use the parts and skills I have. So I'm not going to 3D print a 1/100 space shuttle and use it to make vacuum formed upscales of the Estes #1284 1/184 space shuttle. Thought about it, though. I want to use other people's solutions where I can. So first - read all the George G. STS threads and website - and STS threads he's commented on here.

    Then - parts. Tubing - 3.44" tubing from my 1/35 Atlas cloning project - good enough for the ET. BT58 from erockets - close enough for the SRBs. Shuttle - Guillow's foamy looks great, if not quite scale. Tweak design to be off scale in similar ways for rest of parts. Nothing is quite 1/100. All looks good together. Nosecones and ET aft dome - Sandman, check. Electronics for flight - Eggtimer Quantum and Quarks handy. Electronics for RC - Specktrum microbrick on hand from a Tercel upscale I haven't finished.

    Design - flight goals first.
    Full stack with RC glider.
    Ground lit main motor in ET
    Duck feet fins from ET or SRBs okay.
    Separating SRBs nice to have.
    Separating SRBs with motors - stretch goal.
    For either case, SRBs should separate before ET apogee, during main burn is nice to have.
    If possible, build for stretch goal, even if I don't fly it that way.

    Safety considerations (remember, the hierarchy is design to avoid hazards, then engineer to control/mitigate, then procedure/education to manage remainder)
    Overall stack stability - hands off RC boost. Forward weight and aft fins. Watch Cg/Cp, thrust to weight and speed off rail. Duck foot fin choice makes this easier than clear fins on the SRBs, or no fins. (Which have been done by others.)
    Recovery deployment (ET and SRB both) - should be at low speeds, either by delay or flight computer. Quantum and quarks give me lots of flexibility.
    - leaving the SRBs on and recovering with ET - easy, but not aesthetically pleasing.
    - using an ET deployment event to separate SRBs. If I'm going to do it, I still want the separation during boost look.
    - using SRB deployment events to separate - would need to be dual deploy in BT58 - possible, but heavy, or uses motor deploy - either at apogee or at burnout, not preferred.
    - use a Flight Computer (in the ET) event during boost. Superficially like an airstart (same time in profile). Quantum can do this - for a pyro, not a servo. Also, means I'm not forced to fly with motors in boosters to provide motor deploy.
    - by RC - required second RC that I don't have.

    So, use the Quantum airstart ability to do -something- to cut the SRBs loose during ET boost.

    Stretch goal - motors in SRBs - 'cause it's awesome.
    More motors mean more failure modes.
    For cluster with separable pods, worst failure is to lift core and leave behind a pod on the pad. Drag separation on the pad, as it were. So design to avoid possibility entirely. If SRB motor doesn't light, then core has to loft the booster with it. Solution known and practiced.
    This would also allow me to airstart the SRBs - except I'm planning on using that channel for SRB separation.
    Next failure mode is failure to light/late light/uneven thrust causing uneven thrust. Well, the STS stack has the SRB motors way out there compared to the length to the Cg. Lots of moment arm. So I'm going to cant the SRB motor mounts. And use good ignition practice. That, along with a stable design (helped by the aft fins) is about as good as I can do. Since I'm only doing SRBs for show, if at all, I'll start with A3s and see how it goes.

    And I think that gets me to the current design ideas. I've got a couple plans to have a pyro event from the ET separate the SRBs - I just need to pick one to build. Other than that, build light and stable and simple. Pad light everything. Use devices I'm familiar with (like using Quarks as hotwire cutters.) Try to make the grim faced TWA RSO smile when he sees this beast.
     
  26. Dec 17, 2017 #26

    Charles_McG

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    Well Frank, I hope you have quote notification turned on. I think I might end up with rudder/elevator as the only option to me. I've got a Spektrum AR6410L rx with servos (channels 3-4, elevator/rudder) and I have a Spektrum DXe TX. I can't for the life of me figure out how to make it mix the channels properly. It (The TX) has 2 delta elevon configurations available, but neither seem to mix the rudder/elevator properly. I expect it to wiggle both servos in opposite directions for left/right and it just does one. The TX setup through the PC just doesn't seem to have cross channel mixing options (for the DXe)

    I can use it in normal mode, but if you have any thoughts on options I'm overlooking, I'm open to suggestion.

    C.
     
  27. Dec 17, 2017 #27

    burkefj

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    For Delta config it should use aileron and elevator channels, not rudder/elevator, does it have a v tail mix, that would mix elevator and rudder...since you can't change the servo connections, or mix rudder with aileron then mix rudder stick out...
     
    Last edited: Dec 17, 2017
  28. Dec 19, 2017 #28

    Charles_McG

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    SRB canted motor mounts. I failed to use my trig, so the ellipsis were too big for the angle.

    I tacked one point with no run-no drip, set the angle inside the body tube and let it dry. Now I'm going back, adding shock cord anchors and more glue

    IMG_2337.jpg
    IMG_2338.jpg
    IMG_2341.jpg
     
  29. Dec 19, 2017 #29

    djs

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    This is probably the hardest part of the build... "There he is again.. what sort of contraption does he have this time?"

    or bring it to a WOOSH launch and I'll RSO it for ya :)
     
  30. Dec 19, 2017 #30

    neil_w

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    Those look good. Hope to see you launch the full cluster sometime (well, to see video of it, anyway...)
     

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