
Build Your Own Thrust Vectored Rockets for Vertical Landings Like SpaceX - gscott
https://makezine.com/2019/10/25/build-your-own-thrust-vectored-rockets-for-vertical-landings-like-spacex/
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Robotbeat
Joe Barnard, who looks a bit like the energy & space entrepreneur, earning him
the title among his friends of “discount Elon Musk,” is one of the very best
channels among tinkerer YouTube. Not annoying or fake enthusiasm like some of
the other channels (but is enthusiastic!), innovative, informative, and fun-
loving. A joy to watch his videos.

Also, I had ice cream with him one time after watching an Antares launch in
Virginia.

Also good to see Make isn’t dead.

~~~
jcims
Totally agree. Very prolific with a mix of software and hardware engineering,
not _at all_ shy about showing failures and setbacks and puts a lot of effort
into the production value of his content. One of my favorites on YouTube for
sure. I do hope he gets into hybrid or liquid propellant to avail himself of
some basic thrust control...his new test stand has me hopeful.

[https://www.youtube.com/channel/UCILl8ozWuxnFYXIe2svjHhg](https://www.youtube.com/channel/UCILl8ozWuxnFYXIe2svjHhg)

~~~
Fiahil
> not at all shy about showing failures and setbacks

This is the same reason why I like Alec Steele, a popular blacksmith channel!
It's much more interesting to learn about all the mistakes, failures and bad
assumptions than to see a perfect, finished product from end to end.

~~~
EvergreenTree
If you haven't found him already, you might like Wintergatan. Martin Molin of
Wintergatan is currently in the process of designing and building a successor
to a marble machine instrument he built a few years ago and is extensively
documenting the process through YouTube. He doesn't shy away from showing
mistakes either and all of his videos are beautifully shot and scored (often
with music by him). If you are interested in engineering of any kind, I would
highly recommend watching the Marble Machine X series from the start. He
learns (and thus teaches) a lot of valuable lessons in the process and it is
really satisfying to see it all finally coming together.

~~~
davefp
I binge-watch the MMX videos over the course of a couple of weeks a year or so
ago in order to get up-to-date and have been following it since. It's been
great to see the thing evolve through the challenges, setbacks, and
breakthroughs. The final machine seems so close now!

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illys
Like SpaceX?

"If you love rockets, you can’t help but notice that real space launch
vehicles lift off the pad slowly, but model rockets zip up like darts."

That reminds me of a common issue with modeling: when you divide sizes by N,
you divide surfaces/light-reflexion/air-resistance/lift by NxN and
volumes/weights by NxNxN.

A 1/10th model is 1/1000th of the original weight with identical materials.
All the dynamics are different and easier at smaller scales. This makes the
real thing an expert work while modeling is reachable by hobbyists - very good
ones in this case.

~~~
tomxor
> All the dynamics are different and easier at smaller scales.

Are you sure about this part? (not rhetoric). Non-linear scaling of surface
and volume are simple to understand, but dynamics doesn't look so straight
forward to me... in my short lived experience trying to fly very small model
helicopters, it was clear that the smaller they are the more unstable they
were. I wasn't sure how much of this was due to limitations in human reaction
time and how much was inherent aerodynamic instability at smaller scales.

In these rocket models the human limitation is clearly removed, the remaining
dynamics look faster at least which may or may not run up against higher
frequency sensor data and processing requirements... are there other dynamics
i'm missing? i guess materials don't bend much at this scale?

~~~
TeMPOraL
Different? Yes. Easier? Depends. One thing you gain with size is _intertia_ ,
which grows with N³, and depending on the design, can be helpful for
stability.

~~~
tomxor
Yes, thanks, this is what I meant but the relationship was not clear to me
before, it seems obvious in retrospect: n^3 * density = mass scales cubed,
which as far as control is concerned is both good (lower impulse
requirements), and bad (lower relative mass requires much finer control)...
happy to be told how to express the later formally :)

~~~
lutorm
The think that makes this scaling "bad" is that moment of inertia is going
down faster than everything else and this means the required control frequency
goes up. A Falcon-sized rocket may only need to correct its course 50 times a
second while a 3-foot scale model would need to do it 10x faster. This means
your sensors need to be faster, your guidance computer has to run faster, and
the actuators have to be able to respond faster.

The hard things on the other side tends to be power requirements, for exactly
the same reason. Mass scales up as the cube of size, including the mass of the
thnigs you have to move. Although you don't have to move them as fast, the net
effect is still that your power requirements become very large for large-scale
vehicles.

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stwr
Been a big fan and supporter of Joe's work for a long time, really amazing
work he is doing and how open he is about it, sharing lots of his knowledge in
the BPS.space discord. Great to see him on the front page!

~~~
Sendotsh
He’s such an inspiration. Zero background in any of this and just went “This
looks cool, I’m going to figure it out”.

His videos are incredibly entertaining and educational too.

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jiofih
The Falcon Heavy model launch is one of the funniest and inspiring things I’ve
seen:
[https://m.youtube.com/watch?v=ff5245EBfis](https://m.youtube.com/watch?v=ff5245EBfis)

~~~
JoeAltmaier
Awesome you mean! Even when it doesn't work, it's doing something amazing.

Somebody buy this guy a Red Button, he deserves it.

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choeger
That is innovation right there in our faces. All that stuff was theoretically
possible ten or twenty years ago. But completely impractical for a single
hobbyist.

Not to mention that propulsive rocket landing is a thing for -what? Six
years?- in the real world now.

~~~
ballooney
There were hobbyists making thrust-vectored rockets at this scale twenty-ish
years ago.

e.g. [http://michael.sdf-eu.org/Gyroc/](http://michael.sdf-eu.org/Gyroc/)

~~~
perfectphase
Gyroc was amazing at the time and is still spoken about in hushed tones in the
UK HPR community. While it was using ADXL50 devices for acceleration, the main
gyro was an entirely custom built mechanical rotating gyro, wish I still had
some pictures of it. Now that's all on a single chip you hardly even notice on
the board :) Some pictures of it are here
[http://ukrocketman.com/rocketry/gimbal.shtml](http://ukrocketman.com/rocketry/gimbal.shtml)

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gridspy
If you want a quick video overview:

"BPS.Space - Channel Trailer - 2019"
[https://www.youtube.com/watch?v=OE0_-g7YV1M](https://www.youtube.com/watch?v=OE0_-g7YV1M)

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andreareina
Fun fact, the landing method described is called a "suicide burn"[1].

[1] [https://space.stackexchange.com/questions/10307/what-is-a-
su...](https://space.stackexchange.com/questions/10307/what-is-a-suicide-
burn#10308)

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chasd00
I highly suggest doing some digging into the rocketry hobby (especially high
power rocketry). Or, as my wife would say, "go down the rabbit hole".

It's like software development, there's some heavy duty stuff being done by
incredibly skilled and talented people outside of work hours.

For example, this guy put a rocket over 200k feet altitude on COTS motors
[https://mach5lowdown.com/2018/11/07/phx4-rocket-launch-
to-20...](https://mach5lowdown.com/2018/11/07/phx4-rocket-launch-to-200000ft/)

Also, check out the engine this guy is building
[http://www.watzlavick.com/robert/rocket/regenChamber3/photos...](http://www.watzlavick.com/robert/rocket/regenChamber3/photos/index.html)

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anovikov
Trick of SpaceX success wasn't in vertically landing rockets - with mass being
concentrated in the bottom in form of engines, thrust structure, and legs,
it's not all that hard.

What was extremely hard, is havigation and control to enable return back to
launch site optimally, going through narrow corridors of acceptable parameters
(go too shallow and you risk being unable to correct your position in the end
as precision drops, go too steep and rocket breaks up due to aerodynamic
forces, and so on), while burning minimum fuel. That was an insanely difficult
GNC task which took so many iterations to perfect out...

Plus yes, on landing they didn't have a second chance as rocket couldn't hover
- minimum engine thrust was bigger than it's mass so if it missed, it either
crashed, or flew back up until running out of fuel and crashing, too.

~~~
taneq
Mass distribution isn’t part of it as long as things are symmetrical
([https://en.m.wikipedia.org/wiki/Pendulum_rocket_fallacy](https://en.m.wikipedia.org/wiki/Pendulum_rocket_fallacy))
but yeah, threading the needle like SpaceX does is not easy.

~~~
TeMPOraL
Got to say, I don't understand how the argument in that article works. If
Goddard's rocket that's on the photo had a canvas stretched between the
wires/pipes that form its body (I assume it's a part of the rocket, and not a
launch platform), then I'd expect aerodynamic forces to act on them,
countering the tilt. Conversely, if such surfaces were above of the engine,
I'd expect them to make the construction unstable.

~~~
taneq
You're right that any canvas stretched around the frame could act as
aerodynamic stabilizer fins. The pendulum rocket fallacy is the assumption
that a higher mounted engine will stabilize the rocket's direction _due to it
'hanging' from the engine,_ by analogy with a pendulum (where the higher a
point you 'hang it from' the more stable it is). The fallacy lies in the fact
that the pendulum is hung from a fixed point which can apply forces to
generate a stabilizing torque, whereas there are no such outside forces
generated by the rocket engine (other than the thrust it produces).

Fins totally work and that's why almost all rockets use them to some degree
for stabilisation while in the atmosphere.

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JoeAltmaier
I showed my wife the video, and she remarked "You know, we went to the moon
with less than that".

So, puts it in context! So much possible now that was unthinkable back then.

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davefp
After seeing the headline I thought "If this is by anyone other than Joe
Barnard they've really missed an opportunity here". Glad to see it's him! His
videos are always in-depth and don't hand-wave or gloss over the various
technical problems he encounters/fixes. He also does detailed breakdowns on
the successes and failures of his launches which I really enjoy.

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lnsru
In my eyes it’s amazing business using affordable hardware components. Respect
for the creator! I dream finding similar niche.

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georgeecollins
I have been launching rockets with my son the last few years, but it was kind
of boring after a while because you I thought you can't (legally) introduce
any controls. I thought! This has taught me that you can introduce controls
for stability. That sounds pretty exciting.

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stuff4ben
We've gone from Elon Musk doing cutting edge stuff as a billionaire to a guy
doing the same thing in his backyard within a decade. What an amazing time to
be alive!

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monocasa
I thought vectorable thrust could run you afoul of ITAR, and pushed you into a
much higher realm of scrutiny, since you've basically designed a missile.

~~~
robotresearcher
In the article he declares he is doing stability control as opposed to
guidance control, and only the latter is regulated.

~~~
monocasa
How do you land without doing guidance control?

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fotbr
He's not landing it back at the pad or anything like that, just wherever it
happens to be coming down at. Then keep it vertical(ish), keep it from moving
too fast sideways or it'll tip over (again, stability, not guidance), and
wherever it touches down, it touches down.

~~~
monocasa
So by design, the rocket motor is going to be active, and pointing at
something he doesn't control?

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nategri
After all the dire news in May I'm very happy so see good content on a Make
domain :)

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protomikron
Cool project, but ... that website gave my browser cancer (if you scroll down
too far, your history is messed up and back button does not work).

