I want to build an upside down rocket. Any tips?

Discussion in 'Oddrocs' started by JebediahKerman, May 18, 2018.

Help Support The Rocketry Forum by donating:

  1. May 18, 2018 #1

    JebediahKerman

    JebediahKerman

    JebediahKerman

    Member

    Joined:
    May 3, 2018
    Messages:
    7
    Likes Received:
    0
    I was thinking about making a rocket with the fins on the top and the nose cone on the bottom. Actually, it would be a boat tail transition so the motor could poke out the bottom. Instead of a nose cone on the top of the rocket, there would be a cap over the parachute. My question is: could such a design be aerodynamically stable, but still look like an ordinary rocket turned upside down?
     
  2. May 18, 2018 #2

    Exactimator

    Exactimator

    Exactimator

    Well-Known Member

    Joined:
    Feb 17, 2014
    Messages:
    769
    Likes Received:
    67
  3. May 18, 2018 #3

    Bat-mite

    Bat-mite

    Bat-mite

    Rocketeer in MD

    Joined:
    Dec 5, 2013
    Messages:
    10,242
    Likes Received:
    1,117
    Gender:
    Male
    Location:
    Maryland
    The problem is that the CP ends up far forward of the CG; so no, not stable. You could build something that fools the eye into thinking the rocket is upside down, like with invisible plexiglass fins at the bottom.
     
  4. May 18, 2018 #4

    Jdog13

    Jdog13

    Jdog13

    Well-Known Member

    Joined:
    Sep 21, 2017
    Messages:
    56
    Likes Received:
    2
    Maybe if you had massive, clear, polycarbonate fins on the bottom.
     
  5. May 18, 2018 #5

    K'Tesh

    K'Tesh

    K'Tesh

    OpenRocket Chuck Norris

    Joined:
    Mar 27, 2013
    Messages:
    12,901
    Likes Received:
    449
    Of course you could make it a tractor kind of system with multiple motors coming out of the top at an angle and pulling the rest of the rocket behind it.
     
    watheyak likes this.
  6. May 18, 2018 #6

    Reinhard

    Reinhard

    Reinhard

    Well-Known Member

    Joined:
    Jan 18, 2009
    Messages:
    872
    Likes Received:
    37
    Location:
    Austria
    Pivoting fins on the forward end and - as already mentioned - clear fins on the rear end.

    Reinhard
     
  7. May 18, 2018 #7

    JebediahKerman

    JebediahKerman

    JebediahKerman

    Member

    Joined:
    May 3, 2018
    Messages:
    7
    Likes Received:
    0
    I like that idea. Might be a bit difficult to do, but it could work. I’ll run it through rocksim and see what I get.
     
  8. May 18, 2018 #8

    Daddyisabar

    Daddyisabar

    Daddyisabar

    Well-Known Member

    Joined:
    Jan 23, 2009
    Messages:
    4,302
    Likes Received:
    59
    Gender:
    Male
    Location:
    Littleton Colorado
    Super easy to do. You will have the most stable Rocket at the launch but no one except a few crazy oddroc fliers will believe you. Tractor motors are just too funny looking and they put the scare into folks.
     
  9. May 18, 2018 #9

    Daddyisabar

    Daddyisabar

    Daddyisabar

    Well-Known Member

    Joined:
    Jan 23, 2009
    Messages:
    4,302
    Likes Received:
    59
    Gender:
    Male
    Location:
    Littleton Colorado
    Make an inverted mean machine with the launch rod going up the middle center line! Maybe it will fly better than a traditional super roc. Then you to can have stories you can only tell close friends. :)
     
  10. May 18, 2018 #10

    Nytrunner

    Nytrunner

    Nytrunner

    Master of Rivets

    Joined:
    Oct 15, 2016
    Messages:
    5,262
    Likes Received:
    1,143
    Gender:
    Male
    Location:
    Huntsville AL
    If you successfully light a cluster, 3 B's or C's in fin tip pods may be interesting. It'll need three little parachutes in the pods, or ducts running to the central tube volume.
     
  11. May 18, 2018 #11

    Daddyisabar

    Daddyisabar

    Daddyisabar

    Well-Known Member

    Joined:
    Jan 23, 2009
    Messages:
    4,302
    Likes Received:
    59
    Gender:
    Male
    Location:
    Littleton Colorado
    Plugged motors with electronic deployment but would have to be D11P at NAR launch.
     
  12. May 18, 2018 #12

    Daddyisabar

    Daddyisabar

    Daddyisabar

    Well-Known Member

    Joined:
    Jan 23, 2009
    Messages:
    4,302
    Likes Received:
    59
    Gender:
    Male
    Location:
    Littleton Colorado
    Build one with over sized, fixed canards. Obviously unstable then flip it arround in the inspection line. So many very naughty ideas!
     
  13. May 18, 2018 #13

    Daddyisabar

    Daddyisabar

    Daddyisabar

    Well-Known Member

    Joined:
    Jan 23, 2009
    Messages:
    4,302
    Likes Received:
    59
    Gender:
    Male
    Location:
    Littleton Colorado
    Bring the motors down to a three quarter forward can't. Disguise the motors as ram air inlets. Give it a Russian style scale look then flip it in line. Three 24mm to a BT 70 and standard motor deployment. Mindsim nearly complete.
     
  14. May 21, 2018 #14

    BABAR

    BABAR

    BABAR

    Builds Rockets for NASA TRF Lifetime Supporter TRF Supporter

    Joined:
    Aug 27, 2011
    Messages:
    4,455
    Likes Received:
    517
    Interesting idea. SuperRoc rules as follows

    Super-Roc Altitude Competition shall be scored as follows: the length in centimeters of the model, as measured from the tip of the nose cone to the aftmost end of the motor nozzle, up to the maximum length for that category, shall be awarded as static points. If the model has more than one motor, the length shall be measured to the motor nozzle closest to the tip of the nose cone. No additional points are awarded for any length beyond the maximum.

    If you put all your engines up front, and there is only ONE nose cone and it is on the TIP of the rocket at the TAIL end, do you still get the points for the distance? Or are those negative points? Or can you not call it a nose cone if it is at the tail end? What if you mount it pointed forward?
     
  15. May 21, 2018 #15

    tomsteve

    tomsteve

    tomsteve

    Well-Known Member

    Joined:
    Feb 24, 2014
    Messages:
    766
    Likes Received:
    104
  16. May 21, 2018 #16

    Daddyisabar

    Daddyisabar

    Daddyisabar

    Well-Known Member

    Joined:
    Jan 23, 2009
    Messages:
    4,302
    Likes Received:
    59
    Gender:
    Male
    Location:
    Littleton Colorado
    You're a gonna need one of dem fancy NEW YORK PINK BOOK LAWYERS!
     
  17. May 21, 2018 #17

    Daddyisabar

    Daddyisabar

    Daddyisabar

    Well-Known Member

    Joined:
    Jan 23, 2009
    Messages:
    4,302
    Likes Received:
    59
    Gender:
    Male
    Location:
    Littleton Colorado
  18. Jul 16, 2018 #18

    Thundercloud

    Thundercloud

    Thundercloud

    Well-Known Member

    Joined:
    Jul 7, 2017
    Messages:
    135
    Likes Received:
    5
    I think it would be cool to have a fin-can that is on top when the rocket is on the pad, then as soon as the acceleration starts, it slides down to the back of the rocket and locks in place.
     
  19. Jul 17, 2018 #19

    Threemorewishes

    Threemorewishes

    Threemorewishes

    Well-Known Member

    Joined:
    Feb 23, 2009
    Messages:
    408
    Likes Received:
    12
    You could attach the upside down rocket to the top of a long stick.
     
  20. Jul 17, 2018 #20

    prfesser

    prfesser

    prfesser

    Lifetime Supporter TRF Lifetime Supporter

    Joined:
    May 7, 2017
    Messages:
    749
    Likes Received:
    471
    Location:
    Murray, KY
    Putting the motors at the front adds weight to the nose, which is good. Probably still need some fin-age on the tail end, colorless perspex or the like.

    Oh, and remember...even though the pointy end will be down, not up, the flame is supposed to point to the ground. ;)
     
  21. Jul 19, 2018 #21

    the random rocketer

    the random rocketer

    the random rocketer

    Active Member

    Joined:
    May 30, 2013
    Messages:
    33
    Likes Received:
    4
    Gender:
    Male
    I remember seeing an upside down fatboy mounted on a (fake) Estes launch pad that was the fin unit. Might have been on the rocket dungeon site a few years back.
     
  22. Jul 19, 2018 #22

    Daddyisabar

    Daddyisabar

    Daddyisabar

    Well-Known Member

    Joined:
    Jan 23, 2009
    Messages:
    4,302
    Likes Received:
    59
    Gender:
    Male
    Location:
    Littleton Colorado
    DLP 18.jpg



    Rather than having the fins move down you can have the motors move up.
     
  23. Jul 22, 2018 #23

    caveduck

    caveduck

    caveduck

    semi old rocketeer

    Joined:
    Jun 6, 2011
    Messages:
    1,221
    Likes Received:
    68
    Active stabilization using the front fins as control surfaces might give you a fighting chance. Might.

    And I have it on good authority that the leading Pink Book lawyers are concentrated in the Chicago area.
     
  24. Feb 12, 2019 #24

    the random rocketer

    the random rocketer

    the random rocketer

    Active Member

    Joined:
    May 30, 2013
    Messages:
    33
    Likes Received:
    4
    Gender:
    Male
    Look in Sport Rocketry NOV/DEC 2007 page 12 there is an Upside down Fat Boy on a fake launcher that is actually the fin unit. The pink book guys don't seem to have had a problem with it.
     
  25. Feb 13, 2019 #25

    GRIFFIN

    GRIFFIN

    GRIFFIN

    Well-Known Member

    Joined:
    Aug 25, 2009
    Messages:
    3,172
    Likes Received:
    85
    Tip points down
     
  26. Nov 25, 2019 #26

    BeyondEarth

    BeyondEarth

    BeyondEarth

    Active Member

    Joined:
    Sep 25, 2015
    Messages:
    27
    Likes Received:
    2
    Location:
    Los Gatos, CA
    @Threemorewishes the stick idea is good, but in California, if it doesn't have at least a little fin, then the stick makes it a bottle rocket = fireworks = banned.
     
  27. Nov 25, 2019 #27

    Thundercloud

    Thundercloud

    Thundercloud

    Well-Known Member

    Joined:
    Jul 7, 2017
    Messages:
    135
    Likes Received:
    5
    I always wanted to try a fincan that slides down the rocket at liftoff.
     
  28. Nov 26, 2019 #28

    AfterBurners

    AfterBurners

    AfterBurners

    Forum Supporter TRF Supporter

    Joined:
    May 8, 2012
    Messages:
    6,792
    Likes Received:
    108
    Gender:
    Male
    Location:
    Dallas Texas
    stand on your head
     
  29. Nov 26, 2019 #29

    Steve Shannon

    Steve Shannon

    Steve Shannon

    Well-Known Member

    Joined:
    Jul 23, 2011
    Messages:
    5,183
    Likes Received:
    1,431
    Location:
    Butte, Montana
    Study aerodynamics until the feeling goes away?
     
    Dipstick, mpitfield and neil_w like this.

Share This Page