SpaceX Falcon Heavy

Discussion in 'Beginners & Educational Programs' started by Switch, Oct 16, 2019.

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  1. Oct 16, 2019 #1

    Switch

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    Every year or so I meet up with an old grad school friend and his boys in Death Valley for Thanksgiving. We've been flying single engine low power rockets and it's time to take it up a level.

    I was inspired by ToneDeafJunior's build of the SpaceX Falcon Heavy:
    https://www.rocketryforum.com/threads/falcon-heavy-spacex-boyce-aerospace-build.149263/

    But I want to try to build it as a cluster so all three engines work. This is my first time trying that so here I am in the beginners forum with my noob questions. And maybe this will help others who want to try this build.

    So for starters I need a plan check:

    Falcon 9:
    https://shop.spacex.com/products/f9-flying-model-rocket-kit

    The SpaceX Falcon Heavy Upgrade Kit from Boyce Aerospace Hobbies:
    https://boyceaerospacehobbies.com/p...heavy-upgrade-kit?_pos=1&_sid=a2da1f624&_ss=r

    18" BT-60 tubes (4)
    https://www.apogeerockets.com/Build...er_Tubes/41mm_x_18_Body_Tube_Estes_BT-60_Size

    Engine parts for 4 engines
    3.75 inch E Motor Mount Tube for 24MM 10 Pack
    Motor Block/Thrust Ring BT50 Package Of 10
    UMRS 24mm to BT60 Engine Mount (2)
    Large E Type Motor Hook 24mm (2)
    http://www.unclemikesrocketshack.com/Motor_Mounts_Accs/Single_MM.html

    Estes EST1693 E12-6 Standard E Engines (24)

    Strap-on Booster Replacement Hooks (8) :
    https://www.apogeerockets.com/Build...ster-Hooks/Strap-on-Booster-Replacement-Hooks
    [edit: Thanks kuririn, I realize now this is the wrong part and there are lots of problems with this option in general. I may opt to not have booster separate if I cannot find a workable alternative]

    18 inch printed nylon parachutes (4)
    https://www.apogeerockets.com/index.php?main_page=shopping_cart&product_id=2353

    Estes Pro Series II Launch Controller
    https://www.apogeerockets.com/Launch-Accessories/Launch-Controllers/Pro-Series-II-Launch-Controller
    [Edit: Thanks boatgeek, I'll look for an alternative]

    So my question at this point is what did I forget?

    Oh yeah, would it be possible to actually fire the second stage? The second stage is above the parachute for the 1st stage. That would be beyond cool.
     
    Last edited: Oct 16, 2019
  2. Oct 16, 2019 #2

    georgegassaway

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    Stability.

    Ultra-reliable cluster ignition.
     
  3. Oct 16, 2019 #3

    boatgeek

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    If you're staging, you'll need at least one E12-0 motor for the first stage of the center core. There's also a lot of stability work needed to make sure that the full stack and the sustainer will fly and stably. You might want to think about having D12 motors in the side boosters so that you're guaranteed that they will have burned out by the time the center core stages.

    I'm not sure a PS2 controller will do the job for igniting 3 motors simultaneously. At minimum, you'll want to swap out the alkaline battery stack with a LiPo. A 12-volt system may work better. I'd probably run a few tests to make sure you'll get reliable ignition. There are a few threads out now on how to improve the Estes igniters by dipping in glue and rolling in black powder.
     
  4. Oct 16, 2019 #4

    kuririn

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    The Falcon 9 core model on which this is based is a single stager. So in addition to clustering and drop off boosters, do you intend to convert to two stages? Where is the separation point? What kind of fins will you be using for the second stage?

    You will need more than the replacement hooks to convert the side boosters to drop off. The Apogee system integrates a rail, slotted tubes and a slotted nose cone to achieve that effect. It also uses 18mm booster motors so that the side boosters drop off while the core is still under power. They also use streamers, don't know if booster motors have enough kick to eject a parachute, especially on a bt60.

    How do you plan to check for stability? I see on the other thread that you are new to sim programs. Fire it and see is not a responsible option. Open Rocket and Rocksim are simulation programs, if you are a fast learner maybe you might be able to use it before Thanksgiving.

    This is an ambitious project, to put it mildly. I applaud your ambition, and leave it to your judgment to decide whether all these modifications are realistically achieveable. Good luck.
     
  5. Oct 16, 2019 #5

    neil_w

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    Cool project, should be moved to a different forum. Scale perhaps?
     
  6. Oct 17, 2019 #6

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    FalconHeavy.PNG FalconHeavy_1st_Plot.PNG FalconHeavy_1st_Profile.png

    Well, it turned out to be pretty easy to figure out how to add two boosters. And appears stable using 4 fins. Obviously I'm just getting started.
     
  7. Oct 17, 2019 #7

    kuririn

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    Great start. Per BA it will fly stable with two fins since the outboards act like a pair of fins. With four fins you can reduce nose weight. You might want to sim both configurations.
    Hey, I thought you said you were new to Rocksim?:D
    Laters.

    PS Here's a Falcon 9 .rkt file, it can save you time when drawing up the Falcon Heavy file. Just add the upgrade parts. Downloaded from EMRR.
     

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    Last edited: Oct 17, 2019
  8. Oct 17, 2019 #8

    boatgeek

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    Are you dropping the side boosters at motor burnout? If so, you will need fins to replace that stability once the boosters are gone. I'd suggest 4 fins at 45 degrees to the booster axis, but YMMV.
     
  9. Oct 18, 2019 #9

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    Yeah, I found that rocksim file to do my 1st test flight with the pod option to add side boosters. I was able to
    That is a good point. Just to learn RockSim better, I made this (which works in RockSim)
    Falcon 2nd stage.PNG

    and this Falcon Heavy
    4 engines.PNG

    With the fins at 45 degrees as you suggested.

    But I've been struggling to get this working as a two stage model in RockSim and the Single stage is not stable.

    As I think about this the following progression of test seem appropriate for each level of complexity.
    1) Model in RockSim, 2) Bench Test 3) Fly

    Original F9 kit
    Second stage (if I can figure out the 2nd stage ingnition)
    Original F9 + Second stage
    Original F9 w/ Boosters (ToneDeafJunior' did this)
    Original F9 w/ Boosters + separation + 2nd stage

    I doubt if I will successfully fly a clustered two stage model. The fun is trying to get there. Realistically, I hope to get at least a 3 cluster without separation to fly.
     

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    Last edited: Oct 18, 2019
  10. Oct 18, 2019 #10

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    OK here is a good reference standard for the model
    https://www.spacex.com/falcon-heavy

    https://www.spacex.com/sites/all/th.../falconheavy/falcon-heavy-render.png?tok=FHR2
     
  11. Oct 19, 2019 #11

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    Update:

    Well, I least figured out how to model it. Sort of...

    And some help from Tim at Apogee led me to the solution for 2 stages:
    https://www.apogeerockets.com/education/downloads/Newsletter439.pdf


    FalconHeavy_version_0001.PNG FalconHeavy_version_0001_flight.PNG FalconHeavy_version_0001_flight_graph.PNG
     

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    Last edited: Oct 19, 2019
  12. Oct 23, 2019 #12

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    OK, so parts are in (mostly).
    IMG_1171.JPG

    This is a two stage rocket with two boosters. The main stage will use rear ejection for recovery, hence the 18" engine tube (see https://www.apogeerockets.com/education/downloads/Newsletter439.pdf).

    I updated the (attached) RockSim file with actual weights to the nearest gram. But for redundant parts (engine tubes etc.) I measured all of the parts and divided by the number of parts for accuracy.
    The RockSim model flies better now...

    I did a dry fit of all of the parts (except parachutes, Boyce kit, and fins on the 2nd stage)
    IMG_1167.JPG

    which weighed in at 480g.
    IMG_1168.JPG


    I attempted to do a "swing test" but my tape job was flimsy and it tumbled miserably. My guess is the velocity was too slow for the scale of the model. I'll need to test again with the Boyce kit and final fin design. Basically I'l be adding/removing fin surface area until it is stable.

    I think I'm going to need another launch lug and a longer rod.
     

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    Last edited: Oct 23, 2019
  13. Oct 23, 2019 #13

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    I thought it would be fun to try to design mounts for the boosters and here is what I came up with:

    These are the parts: Nylon washes and bushings, and small magnets.

    IMG_1172.JPG



    The primary stage to booster mount would look like this:
    IMG_1181.JPG

    This is both halves of the mount itself. The thinner washer and bushing would detach (mounted on the primary stage) from the thicker washer (mounted on the booster).
    IMG_1177.JPG


    Here is how the attachment and attachment/detachment would work.

    In the nose cone of each booster, aligned with the magnet in the 1st stage of the primary is a corresponding magnet attracting N/S to the magnet in the primary stage.

    A second magnet with opposite polarity is positioned in the booster nose cone so that when the nose cone ejects, the polarity flips and the booster mount switches from attachment attraction to repulsion (e.g from N/S to N/N).

    In this photo the North South polarity is reversed on each magnet, so that when the position of the first magnet is changed with the second, the polarity is reversed.

    IMG_1173.JPG

    The idea is that when the cone separates, the North magnet is replaced by a South magnet, which ejects and repels the magnet attached to the primary 1 stage rocket. The bench test of this is quite dramatic.

    I need to figure out a way to bench test this in terms of mass and acceration. Either this is dumb or it is just a matter of the strength of the magnets and their proximity.

    In the meantime, while the above works (in theory) for the nose cone, I don't have a solution for the connection at the bottom of the boosters. Will it be enough to eject the top of the booster and then let it fall away and have a passive connection for the bottom? Or will I need a similar ejection technique for the bottom booster mount?
     

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    Last edited: Oct 23, 2019
  14. Oct 24, 2019 #14

    mbeels

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    Very interesting idea with the magnets. I'll be curious to see how it works out. How fast do you think the nose cone will be moving? How long will it spend repelling the booster?
     
  15. Oct 24, 2019 #15

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    With the 6mm magnets, we are talking about the velocity in the travel of the first 6mm to 12mm of nose cone ejection. If I assume the ejection charge is just the rocket firing backwards, then I can use RockSim to get the forward thrust for the weight of the rocket and calculate the backward thrust for the weight of just the nose cone.

    On the falcon9 Rocksim, the acceleration starts at 20 m/s/s and the mass is .177 Kg. So that's .7m/s at 6mm or a fraction of a second of repulsion over a 12mm distance.

    So the magnetic repulsion will occur over a time span of about 4 ms.

    There's probably a math error above or a need for Calculus.

    In practical terms I can stack the N/S (hold) magnets to add attractive force and put the N/N (repulse) magnets in series (or stacked) to achieve reasonable results. Or it is just a bad idea. I need to do some bench testing.

    I can also configure the boosters to use rear ejection so the top and bottom mounts use the same release mechanism. My inclination is to build complexity into the top mounts and have a passive system at the bottom.

    I appreciate the feed back.
     
  16. Oct 24, 2019 #16

    OverTheTop

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    Great idea with the magnets :).
     
  17. Oct 24, 2019 #17

    Nytrunner

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  18. Oct 27, 2019 #18

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    So here is the latest update. Boyce Aerospace parts sanded and stained with India ink. Booster mounts assembled and sanded to form. The magnet protrudes from the finished booster mount, so I'm going to drill into the primary stage tube to recess it (which will only make is stronger). It is an admitted design flaw that the mount post is attached to the first stage rather than the boosters but that is just how it goes.

    I was curious about the strength of the magnets so I measured by suspending weight until it released. 157.5g equates to 1.55N which is a lot (I think). Considering that this is on the order or the weight of the complete rocket.

    I've given up on any kind of finless design for the 2nd stage. High winds in Northern California prevent any testing.

    thumbnail_IMG_1189.jpg thumbnail_IMG_1188.jpg thumbnail_IMG_1190.jpg thumbnail_IMG_1184.jpg thumbnail_IMG_1185.jpg
     
  19. Nov 1, 2019 #19

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    For stability we have to rely on RockSim test. The RockSim models appear stable (attached).

    For reliable cluster ignition we've got a Go Box Launch Controller, tested with three starters. And we will take the extra precaution of using QuickBurst QuickDip for the cluster launches.

    The separation point for the 2nd stage will be between the Payload Transition and the payload tube.

    We plan to test the F9 and Falcon Heavy launches in a progression of complexity:

    1st stage (basically a BT-60 tube with rear ejection) this is where we will tune rear ejection technique.
    2nd stage (tune engine and fin size )
    1st stage and 2nd stage combined (tune 2 stage setup -does it work?)
    1st stage with boosters attached but not powered (repeat of ToneDeafJunior's launch)
    1st stage with boosters attached but not powered plus 2nd stage (tune from prior experience above)
    1st stage with boosters powered (terra incognita)
    1st stage with boosters powered plus 2nd stage (terra incognita)
    1st stage with boosters powered plus 2nd stage with booster separation(terra incognita)

    Each will be run with multiple engine combinations to tune velocity and ejection timing.
    We will test both forward ejection and reverse ejection but plan for reverse ejection for the more advanced stages of the progression.

    We have a 7 day launch window.

    BTW Tim and his team at https://www.apogeerockets.com/ have been amazingly helpful on this project. And RockSim is an amazing tool for planning projects like this.

    I'm sure the veterans of this site know this but I thought I should call that out for what it is.
     
    Last edited: Nov 1, 2019
  20. Nov 1, 2019 #20

    scadaman29325

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    This is fun to watch!
     
  21. Nov 1, 2019 #21

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    Thanks for this and you will see noted in the latest build.
     
  22. Nov 1, 2019 #22

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    Hopefully it will fail in unpredictable ways. I've already gotten great advice from multiple sourc
    Also thanks for this advise and changes noted in the current plan.
     
  23. Nov 1, 2019 #23

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    Thanks for this advise and changes noted in the current plan.
     
  24. Nov 1, 2019 #24

    scadaman29325

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    Sort of like the local dirt track races. You go to watch the fights in the pit area, and a race might break out.
     
  25. Nov 12, 2019 #25

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    Last weekend was bench testing. Lots of fails with reverse deployment as we dialed in the right length of Kevlar string. Also tested the magnetic booster release.
    I'm struggling with the 2nd stage design. With a BT-50 tube inside a BT-60, how do I size the vent holes and still have enough reverse thrust to do the reverse deployment?

    see https://www.apogeerockets.com/education/downloads/Newsletter99.pdf
    and
    https://www.apogeerockets.com/education/downloads/Newsletter439.pdf
     
  26. Nov 18, 2019 #26

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    Well, we are almost out of time. We leave for Death Valley next Friday. Here's the current state of the build. We have two boosters with attachments to the primary stage built . We still need to finish the second stage motor and fins and build two more booster tubes with attachments. We plan to have N+2 redundancy for all major parts so we should be able to learn from any failures and get the whole Falcon Heavy to fly. We hope...

    The venting of air from the ejection of the primary stage is still a concern. We found we can reliably ignite the 2nd stage but reverse recovery deployment has not been reliable.
     

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  27. Nov 20, 2019 #27

    Phillip Weeks

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  28. Nov 20, 2019 #28

    Phillip Weeks

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    Let's hope this works
     
  29. Nov 20, 2019 #29

    SteveNeill

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    It will.
     
  30. Dec 1, 2019 #30

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    DSCN2647.JPG Saline Valley FalconHeavy Launch.png \



    Well here is it on the launch pad in Death Valley on 11/27/2019. A video failure prevented capturing the actual launch
    :-(

    Meanwhile, the day before we launched the Falcon Heavy, we worked on the fine tuning of the ignition of the 2nd stage and the size of the holes needed in the 1st stage to allow the cold air to exit the 1st stage while allowing enough force and heat to eject the reverse recovery motor and still ignite the 2nd stage. We used used D12-3 for the F9 primary and A8-3 for the secondary because we didn't have D12-0 motors and wanted to save our E12-0 motors for the next day. The 3 second delay in the 1st stage meant that the 2nd stage would ignite at apogee or worse leading to the almost complete destruction of our scratch built 2nd stage test rocket. But we got successful 2nd stage ignition on every launch (3) and reverse motor recovery (2) out of three launches. So we considered the day a success.

    The next day we did "rocket surgery" on all of our previous broken rockets and flew them again to get a sense for the wind (5-10 mph) and practice launch safety. We lost our altimeter and misjudged one launch angle, which owing to the wind, worked more like a guided missile...

    Then, with the wind picking up, it was "now or never" for our first Falcon Heavy test flight. We used C6-0 motors in the boosters and E12-0 in the primary stage with an A8-3 in the second stage. Just for fun, we added a red Tesla Roadster to the payload. We planned to do larger motors in the boosters and second stage but ran out of time.

    The total Falcon Heavy with motors and payload weighed 525g. The 48", 1/8" launch rod bent under the strain of the wind, it was literally a balancing act to get it ready to fly.

    Result of the first test flight:

    All three motors ignited! The magnetic booster separation worked! The second stage also ignited! And the Roadster was successfully deployed and recovered with some minor body damage due to the fact that it is not actually in orbit. The reverse ejection of the motors for recovery mostly worked with one booster parachute damaged by the ejection charge. With the exception of one parachute and a lost fin on the 2nd stage, all components were recovered intact and can be launched again. It was friggin awesome!

    A friend took this video which only followed the booster separation, ignition of the 2nd stage, and payload release of the Roadster.


    In the first frame or two you can see the booster has already separated.
    booster separation.PNG
    A special thanks to Apogee Rockets (https://www.apogeerockets.com/) for their amazing library of how-to articles and videos and great technical support, without which this project simply would not have happened.
     
    Last edited: Dec 2, 2019
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