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SpaceX BFS project (Patreon)

Published:
2018-11-20 12:29:17
Imported:
2026-06

Content

I'm currently in the process of designing a radio control SpaceX BFS (Big Falcon Ship), which is the second stage of the BFR. Essentially what I'm aiming to do is test how the fins will be used to control the craft on decent. They work similar to how my RC wingsuit guy 'worked', where the fins won't rotate like an aircraft's control surfaces, but instead pivot about the parallel axis of the rocket. Here is a video explaining it better: https://youtu.be/CbevByDvLXI?t=348

So I thought I'd come to you guys to get some opinions! 

First option: I've been working on a version (seen in the photo below) that will use the same thrust vectoring technique as my previous spaceX rocket project to gain altitude. Then when at altitude, it'll attempt to descend belly first (black half of the rocket facing down) by moving the fins. The only issue is that this isn't going to be light weight due to the motor and battery required for thrust, so it might just drop like a rock(et without a parachute).

Second option: Build a much simpler version which has no thrust source, but still has control of the fins. This can then be dropped from a drone and hopefully be controlled for a slow decent.

My personal view is that I'd like to got for the fully thrust vectored design, but I have an odd feeling it has a much lower chance of success haha.


Comments

Anonymous

You can make it work Tom.

Jonathan Charnas

The big issue I see with your first option is how you distribute the weight for all your systems & battery. It would have to have a CG about 1/3 of the way through the median chord of the fins to allow you a gliding curve that is below 45 degrees.

tomstanton
>>17316672

The CG placement should be ok as the upper tube section will mostly be empty. So the battery could be placed anywhere within it to balance out the motor at the bottom. The issue will be finding where the CG needs to be for it to descend horizontally and make sure it doesn't just nose dive.

Jonathan Charnas
>>17316672

That was kind of my point, the cg needs to be somewhere on the fins, preferably 1/3 or to 1/2 back from the leading edge of the MAC (mean aerodynamic chord) got them to generate a fulcrum point you can reasonably balance flight around.

tomstanton
>>17316672

That would be the case if only the rear fins produced drag, however the fuselage and front fins need to be considered. I've estimated the centre of pressure to be where the top marking is (black/white dot on the cad model). However the CG is currently at the position of the bottom marking with the battery at the very top. So in it's current configuration, it should fall tail first. Then maybe with adjustments of the fins, I can increase drag at the rear for pitch control.

Jonathan Charnas
>>17316672

Oh hehe, on the angle of the image I didn't spot the front fins at all. In that case, you're absolutely correct.

Jeff LaHay

I like the thrust vectoring option. I think it will be more challenging and you’ll definitely learn more😊

Anonymous

It’ll make a more fun video to watch too

Anonymous

I think you have a better chance of success with the lighter model.

Gavin Remme

I like the idea of the thrust vectored BFS, yet I share your concern that it might just fall like a rock without enough height to actually be able to start controlling it. You might have to go up really high before you're able to achieve the goal of just essentially a controlled fall. But that being said, I really wanna see it actually land upright and be able to take off again.

Anonymous

you should change the cg of the craft when at altitude and use the motor slow your decent like on the real version.

Charlie Barker

Hey Tom, None of your videos show you printing ABS is this something you’ve not attempted or something you have tried but it didn’t work out?

Anonymous

Are you sure "F" stands for Falcon? ;)

Anonymous

Tom - would it not make sense to go with option 2 first... once you have that functioning and coded then build it into an all singing all dancing Option1. If you go with 1 first there are so many variables that could fail (no offence) that you may never get to see the actual concept in action.

U.S. Water Rockets

How about you build a thrust vectoring first stage that drops off just like the real thing? I like the thrust vector concept the most because it's more of a challenge and more can be learned from this. Also, do you mind if I use short clips (with attribution) from your channel in my videos? Just a few seconds of video to show where some of our project inspiration comes from. I'd like to give you credit for stuff like the air hogs engine, etc.

tomstanton
>>17334350

2 stage electric rocket! That could be interesting. Yeah, no problem at all. I'm still looking forward to the air engine video!

tomstanton
>>17331340

Hi Charlie, I've printed a few things with ABS, such as the air engine V1 and the clear hovercraft. But I choose not to print with ABS on a regular basis because it's a bit of a pain. PETG is my preferred material for parts that require mechanical strength.

Anonymous

could you do the glider first then add the thrust second?

tomstanton
>>17397396

Yes, but I've gone the tricky way first haha. Will most likely try a glider version if it fails