
The Nuclear Potato Cannon, Part 2 (2006) - ajarmst
http://nfttu.blogspot.com/2006/01/nuclear-potato-cannon-part-2.html
======
flashdance
Dr. Brownlee himself (the guy who designed the experiment) said that the plate
was vaporized by the atmosphere and never got to space.

Sorry for the buzzkill, folks.

[https://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_...](https://en.wikipedia.org/wiki/Operation_Plumbbob#Propulsion_of_steel_plate_cap)

~~~
paulsutter
You're misquoting the article:

> Dr. Brownlee believes that the plate did not leave the atmosphere, as it may
> even have been vaporized by compression heating of the atmosphere due to its
> high speed.

~~~
mark-r
I'm curious, what speed is necessary for compression heating to be a
significant factor? Obviously a regular rocket doesn't melt on its way into
orbit, while it _does_ need special protection for the trip back.

~~~
GlenTheMachine
Rockets do actually heat in flight. But their launch profile is carefully
chosen to keep the heating to managable levels. Liquid fuel rockets typically
throttle down somewhere around a minute after launch, at a point called
"max-Q", which is the point of maximum aerodynamic pressure. They throttle
back up again once they have gotten above enough of the atmosphere.

As a point of reference, the SR-71 was one of the first major aircraft
programs to use titanium extensively, the reason being that at the speeds the
SR-71 flew, aluminum couldn't maintain structural stability due to the heat.
And the SR-71 was "only" a Mach 3 airplane, flying at "only" 60,000 to 80,000
feet. It's fuselage would reach nearly 600 degrees.

An orbital launch vehicle typically reaches Mach 3 very roughly that same
altitude, or somewhat higher (the figure I can find is Mach 4.5 at 28 nautical
miles, which by interpolation I'm guessing is Mach 3 at between ten to twenty
nautical miles; ten nautical miles is roughly 60,000 feet).

~~~
orclev
Another bit about the SR-71 (and supposedly concordes) is that their
structures are designed with tolerances based around the forces they
experience at speed. The effect of which is that when sitting on the ground
not going anywhere there are gaps between some parts, and others are tightly
compressed together (and then separate while traveling at speed). I don't
remember if it was the last concorde, or one of the SR-71s, but there's a
story out there about the pilot on its final flight sticking his hat into a
gap in the cockpit, which on landing promptly closed up permanently sealing
his hat in place inside of the cockpit (he did it on purpose to commemorate
the last flight). Similarly there are stories out there that claim the SR-71
leaked fuel like a sieve while sitting on the ground because it needed the
atmospheric heating from going supersonic to seal up all the various fittings
in its fuel system.

~~~
lostlogin
Any SR-71 story usually comes with the obligatory story about the Cessna v
navy ground speed check. I'm replacing that story with the story of the time
an SR-71 went very slowly.

[https://www.google.co.nz/amp/foxtrotalpha.jalopnik.com/the-s...](https://www.google.co.nz/amp/foxtrotalpha.jalopnik.com/the-
sr-71-blackbirds-most-spectacular-flyover-was-also-1719654907/amp)

~~~
grzm
Thanks! Tyler Rogoway can certainly relate a story.

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GlenTheMachine
In grad school my advisor (who was teaching "Launch and Entry Systems") told
us this story. A few lectures later he went over rail guns as a launch system,
and mentioned that by his back-of-the-envelope calculations, a slug of
titanium the size of a telephone pole, launched at earth escape velocity by a
rail gun at sea level, would ablate approximately a third of its length away
in the first thousand meters, or something close to that (it's been a long
time).

Actually calculating the heating of a steel plate launched at that speed is a
significantly nontrivial problem, because its aerodynamics are unstable. In
other words, it would almost certainly tumble in flight, in an unpredictable
manner. There's no guarantee that it would even fly in anything approximating
a straight line. Even figuring out the effective coefficient of drag would be
really hard. Figuring out the thermal profile would be even harder.

But, as several other comments have mentioned - no matter how you slice it, it
would be subject to a hell of a lot of heating, and it's a pretty safe bet
that it ablated completely away and did not reach space.

------
mikeash
I'm familiar with this incident, but never saw this article before. I've seen
articles such as
[http://nuclearweaponarchive.org/Usa/Tests/Plumbob.html#Pasca...](http://nuclearweaponarchive.org/Usa/Tests/Plumbob.html#PascalB)
and
[http://nuclearweaponarchive.org/Usa/Tests/Brownlee.html](http://nuclearweaponarchive.org/Usa/Tests/Brownlee.html)
(the latter being written by Dr. Brownlee, the scientist who designed the test
in question).

This article seems like an independent telling of these events, along with an
independent recalculation of the results in the first link, but based on
conversations with the same person, which is kind of interesting.

As far as the first man-made object in space, there's no real question that
this was not it. There are two major problems: one is that the steel plate
pretty much certainly vaporized in the atmosphere before it reached space. The
second, even bigger problem is that the first man-made object in space was a
V-2 rocket launched in 1944.

~~~
flashdance
That V-2 rocket was indeed the first thing in space, but there's a distinction
to be made: it only went suborbital. If our big steel friend wasn't tragically
vaporized in the atmosphere, it might just have left the earth's gravity well
--maybe even the solar system's well (escape velocity of 44km/s), which is in
part why that incident is so cool!

Fun fact: the first ever picture taken from space was from a v-2 rocket
launched in 1946. This is what it looked like: [https://thumbs-prod.si-
cdn.com/nnJLv8axPAJI3nScxyDExEeTQLk=/...](https://thumbs-prod.si-
cdn.com/nnJLv8axPAJI3nScxyDExEeTQLk=/800x600/filters:no_upscale\(\)/https://public-
media.smithsonianmag.com/filer/33/d1/33d15156-47cd-4307-9c23-e3c8498539f5/1stphotofromspacejpg__600x0_q85_upscale.jpg)

~~~
mikeash
Sure, but the phrasing used here was "...the first man made object shot into
space."

This whole story is awesome, no doubt. That's just not quite the right
question to ask.

In any case, sweet picture.

~~~
flashdance
Totally, I was just trying to be extra pedantic.

~~~
mikeash
No problem, that's what the internet was built for, after all.

------
lord_jim
With the nuke mania of the early Cold War, I'm surprised that the military
never tried creating a nuclear version of Project HARP:
[https://en.m.wikipedia.org/wiki/Project_HARP](https://en.m.wikipedia.org/wiki/Project_HARP)

(I've also always enjoyed the parallels of this story with "From the Earth to
the Moon")

~~~
DanielBMarkham
This -- or a rail gun similar to this concept -- in my mind is the key to true
low-cost LEO cargo. The investment wouldn't be that great in comparitive
terms, and it promises to bring an order of magnitude more cargo to space at
an order of magnitude less cost.

~~~
ChuckMcM
All of the 'all impulse at the start' ideas for putting things into orbit die
on the fact that air is a fluid. Further that fluid is very dense at the
surface of the earth.

What that means in practical terms is that the harder you push something to go
through the air, the harder the air pushes back. If you plot the air
resistance as a function of energy applied, you see that the long before your
payload has achieved orbital velocity + the amount you expect to slow down
going up through additional air, you are dumping so much energy into the air
that your payload vaporizes.

"But we'll shoot it straight up to minimize the time in the air!" Now you'll
have an orbit who's perigee intercepts the earth again (aka highly
elliptical).

The ideal trajectory can be calculated, (easiest at the equator but there are
solutions for latitudes above and below the equator, to accelerate into an
orbital plane such that on your first orbit you can "bounce" (trade excess
velocity for altitude) into something that is lies entirely out of the
atmosphere. But in that trajectory you spend _more_ time at lower altitudes
and that means more energy to get past that air and that makes you vaporize
that much more quickly.

"We'll start from a higher altitude!" is another avenue to explore, the ideal
altitude to start from is > 65,000' (20 km) which is defined as 'near space'
but still 80km from the Kármán line. And we're still unable to build a 20km
tall tower.

~~~
DanielBMarkham
Good points, but anybody's who spent any time at all modeling the problem has
probably worked through them.

Lots of various solutions to various problems. Sabot-type rounds, ablative
coatings, small rockets to add the horizontal element of orbit, longer, mass-
driver-like launchers, and so forth.

The thing is, none of this, pardon the expression, is rocket science. (It's
tough, but there's not a huge amount of new ground to be covered and/or new
technologies to develop). If you can accidentally shoot something outward at
multiples of escape velocity, you can certainly do so on purpose.

ADD: In reference to GP's comment, with the right trajectory it's completely
feasible to shoot something into lunar orbit. Maybe Verne wasn't so far off!

~~~
curtis
I have wondered if it might be feasible to deliver certain kinds of supplies
all the way to the lunar surface using a light gas gun. In fact, you could
take the idea to absurd levels by using lithobraking [1] to "land" stuff on
the surface. One way to do this might be to explode the shell just above the
lunar surface so that the contents will embed only a few centimeters into the
regolith, so it can easily be recovered using very simple technology. Kind of
like mining really rich ore.

[1]
[https://en.wikipedia.org/wiki/Lithobraking](https://en.wikipedia.org/wiki/Lithobraking)

~~~
DanielBMarkham
This entire line of thinking is very reminiscent of the Air Force's X-Plane
program in the 50s.

The Air Force was heading down the road of airplane-to-orbit back in the 50s,
but everybody decided that rockets were the way to go so the X-Plane (at least
in terms of rocket-planes pushing the envelope of manned flight) program was
abandoned.

Who knows where we would be had we kept going? If nothing else, we could have
seen major improvements in heat management.

------
gene-h
It has been proposed that we could construct one of these nuclear potato guns
to launch things into space[1]. One digs a multi-kilometer deep borehole in
say a salt dome(easy to drill), lines that with steel, puts a bomb at the
bottom, some reaction mass(essentially trash that will vaporize in the
explosion), and a projectile we wish to launch into space.

So this solves several problems over other nuclear bomb based propulsion
methods like Project Orion[0]. Foremost, we can contain almost all of the
fallout. Second, we aren't accidentally triggering nuclear war by lobbing a
bunch of nuclear bombs into orbit. In addition, if the nuclear charge is 150
kilotons or less and that charge is detonated underground then it's in full
compliance with certain treaties.

So aside from the shear political impalatibility of using nuclear bombs, there
are a couple problems. Namely, even if we use a very long shaft, the
acceleration is still on the order of thousands of Gs. So no launching humans.
Second, it's impossible to get into earth orbit purely with a cannon launch.
And because it's difficult to make stuff that can withstand thousands of Gs of
acceleration, orbital circularization will be difficult.

So one suggested use case is to literally shoot the moon. One fills the
projectile with things that can withstand the high acceleration like water,
construction materials, MREs, propellant, and carbon(extremely rare on the
moon, but extremely useful for refining silicon for solar cells). We launch
this projectile, which should mass ~3000 tons or so, to the Moon and then
harvest everything we need to bootstrap a Moon base from the impact site.
Perhaps we can even save money on our MREs by letting the acceleration do the
food processing. For example, for apple sauce, all we need to is put cored
apples in a plastic bag. The thousand G acceleration of the launch and lunar
impact should be more than enough to reduce them to pulp.

Now, while we can't get into Earth orbit easily, if the projectile velocity is
sufficiently high we can put the projectile into solar orbit.

It is a questionable proposal, but interesting nonetheless.

[0][https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...](https://en.wikipedia.org/wiki/Project_Orion_\(nuclear_propulsion\))
[1][https://www.nextbigfuture.com/2010/03/150-kiloton-nuclear-
ve...](https://www.nextbigfuture.com/2010/03/150-kiloton-nuclear-verne-
gun.html) [2][https://www.nextbigfuture.com/2010/12/sea-based-launch-
optio...](https://www.nextbigfuture.com/2010/12/sea-based-launch-option-for-
nuclear.html)

~~~
NegativeLatency
I saw a talk about something similar (non nuclear) a few years ago. Could have
made building up a supply of fuel in orbit cheaper.
[https://en.wikipedia.org/wiki/Quicklaunch](https://en.wikipedia.org/wiki/Quicklaunch)

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xiphmont
During my time at MIT, we referred to several explosions in the service and
steam tunnels (caused by aging infrastructure) that launched street-level
manhole covers into the air as the 'People's Republic of Cambridge Unmanned
Space Program'.

Seems the PRoCUSP got several-upped.

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SOLAR_FIELDS
The term potato cannon got me interested enough to look up the Wikipedia page
for it, where I learned that they are also amusingly colloquially referred to
as "spud guns". There's also a vacuum variant known as the "vacuum bazooka".

~~~
anfractuosity
I always thought 'spud gun' referred to this kind of toy gun -
[https://en.wikipedia.org/wiki/Spud_gun#/media/File:Spud_Gun....](https://en.wikipedia.org/wiki/Spud_gun#/media/File:Spud_Gun.jpg)
which fires small parts of a potato.

The vacuum bazooka, looks really neat, I'm surprised that according to wiki,
they can apparently project the potato at 650mph.

~~~
SOLAR_FIELDS
Apparently according to Wikipedia the term is used in both contexts: to
specifically refer to the toy, and more generally as another term for potato
cannons.

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damnfine
If the fov was a 1/4 mile, and the plate near the center, wouldnt that halve
the calculated velocity? I feel like I am missing the actual data here.

~~~
NegativeLatency
There isn't enough data to know the real velocity of it.

Since the plate only appeared in one frame, only a lower bound for it's speed
can be given with observational data. A minimum of 2 frames with the plate
visible would be required for determining its speed.

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BartSaM
For me, this story, showing up here and there, is to discredit Russian Space
Program in some part.

There are so many unknowns...

Do we even know if Russian had a situation like this with their nuclear tests?
Most data is classified anyway, so how can we know?

This is not science, this is just "we cannot find a part that could have to
reach the space".

~~~
ajmurmann
Why do you assume this is a anti Russia story? To me this really was just a
cute story that someone wants to believe in because it's fun and fascinating.

~~~
BartSaM
This story is surfacing every few months on many major outlets. The story
itself is fun, but the fact that it often tries to "prove" that the US was
first in space without any proof is misinformation. A lot of non-technical
people will take this story and pass it as a fact.

