# "Starfire" Space Cannon: Why not to invest in a Kickstarter



## lilhasselhoffer (Feb 5, 2014)

https://www.kickstarter.com/projects/1682852725/the-starfire-space-cannon

The idea is basically to shoot something into orbit, with a howitzer.  Let's walk through the process here, and determine whether this guy is on the level.

The amount of energy in a kg of gunpowder is 3 MJ, according to Wikipedia and other sources: http://www.madsci.org/posts/archives/2007-11/1195506740.Ph.r.html, http://en.wikipedia.org/wiki/Energy_density.

The projectile is assumed to have a mass of 4 kg.  I'm basing this assumption off of the forces it will have to endure, and the payload that it must carry.  This isn't a hard and fast figure, but let's determine this as a starting point.

The amount of energy required to escape Earth's gravity well is 0.5*mass*escape velocity^2.  For this particular body, the energy required to escape Earth's gravity well is 0.5*4*11200^2= 250880000 J=250.88 MJ.

Let's assume that no energy is lost to sound, or heat, or anything else.  That means to propel an object out of Earth's gravity well we'd need 250.88/3 = 83.627 kg of gunpowder.  You're looking at approximately 84 kg of gunpowder to propel this thing.

Gunpowder has a density of 1.7g/cm^3, which means you need 0.0494 m^3 or 3015 in^3 of gunpowder.  You've got an 8 in diameter cannon, so the area of the barrel would be 3.14*4^2 or 12.566 in^2.  This means you'd have to have 3015/12.566=239.9" of gunpowder.  At 240" you'd have an 8" diameter cannon 20' high full of gunpowder.  This isn't a howitzer, it's a pipe bomb.  That sort of combustion would need an insanely thick wall just to not explode upon the first firing.

The energy is only imparted until the end of the barrel.  Let's assume that the barrel is 13.716 m (he cites 45' for mobility) long.  In order to reach the 11200 m/s velocity, assuming that you've got a constant linear acceleration, you're looking at a time in the barrel of 13.716m/5600m/s=0.002451s.  Acceleration could be given as a=(v-v0)/t, or 11200/0.002451= 4569430 m/s^2, or 4600 km/s^2.  To my knowledge, no material could withstand that kind of acceleration.


Now, let's do some creative thinking as to what is actually going to happen here.  You aren't shooting the projectile out of Earth's gravity well.  You might be able to get a propellant with twice the energy density of gunpowder.  Both of these mean you're looking at maybe 8' of explosives in an 8" diameter barrel.

On the opposite side, you aren't getting 100% efficiency in converting gunpowder into linear kinetic energy.  You have energy dissipated due to wind resistance.  Finally, you've got to have a surviving barrel and projectile for multiple launches, which means a reasonable acceleration.  Applying this, you'd basically be back to the 20' of propellant and a barrel an order of magnitude longer than the one cited.


So, is this guy crazy?  Absolutely.  Even if he built a prototype 3 times the quoted 45' size, he'd still not be able to do anything but extremely low Earth orbit.  This is why NASA isn't doing this, and why the thought process of Jules Verne had a miles long track for a rocket to accelerate on in order to get to the moon.  A howitzer just isn't a smart idea, and this is why Kickstarters fail.  Math work.  Science works.  NASA and the government aren't conspiring to keep us on the Earth, the mathematics here only scratch the surface of the proposition and find the idea completely untenable.  All the money in the world wouldn't help this sort of a stupid project survive.




Edit:
Thinking back on all of this, maybe the definition of space is rather pliable.  Assuming that the goal was just to break into the mesosphere, we might be looking at a winner here.  Of course, the difference between the mesosphere and space is rather significant (100-10000 kilometers is...significant).

I'd say this is a reasonable out for the Kickstarter, but I'd have to eat my words.  The author cites instances of thousands of Gs of acceleration, but somehow links his phased combustion idea to significantly less (but more continuous) force.  There is a substantial question of whether we're comparing apples to apples here, and the website linked to doesn't offer much in the way of hard science.

Consider me skeptical, but a gun without some hard science sounds pretty redneck to me.  If you can't produce calculations, that others can verify, you have failed to prove your point.  Requesting tens of thousands of dollars just to shoot a big gun is...not what I'd consider a fruitful endeavor.


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## RCoon (Feb 5, 2014)

The guy needs to stop smoking crack. Won't work.


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## Frick (Feb 5, 2014)

The lost son of Gerald Bull.

It's the american dream come true.

EDIT: It's supremely unfair to hint all kickstarters are like this btw. There are several retarded ones, and some good ones.


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## rtwjunkie (Feb 5, 2014)

@lilhasselhoffer:  I for one am glad for your mathematics ability, because I would have been till next Tuesday figuring that out, lol!  Math has never been my strong suit.  Thank-you for that in-depth analysis!


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## lilhasselhoffer (Feb 5, 2014)

Frick said:


> The lost son of Gerald Bull.
> 
> It's the american dream come true.
> 
> EDIT: It's supremely unfair to hint all kickstarters are like this btw. There are several retarded ones, and some good ones.



Full disclosure: I've bought in to Kickstarter.  As yet, I've not been burned.

At the same time, the software deliver rates for funded projects is currently below 50%.  The projects are not being tested for feasibility prior to being launched.  No oversight means projects can get posted, which can never get completed.  Kickstarter has not come forward with quality assessment criteria, so I'm rather sketchy on their long term viability.


I've not tried to imply that all Kickstarter projects are worthless, but that the math makes this Kickstarter something not to invest in.  Assuming you took the implication otherwise, I'd like to rectify that error on my part.  Kickstarters aren't inherently bad or good, each needs to be vetted.  The promises of this particular Kickstarter are why people shouldn't blindly invest in Kickstarter.


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## Ahhzz (Feb 5, 2014)

I'm afraid I'm in way too deep to Kickstarter, but all things considered, I'm only down 2 projects to the tune of $20 total, and one is still technically "in progress". But I do try to invest a little effort to ensure that what I'm looking at is not at least on the surface, a complete crock. I wanted to select all three of the top options


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## Divide Overflow (Feb 5, 2014)

He took a couple of science terms and tried to spin it as a complex orbital mechanics model.  Big surprise it's a complete and total failure.

Let the backer beware!


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## FordGT90Concept (Feb 5, 2014)

Let's not forget the part where an enormous amount of force has to be exerted on the object in the space of <50' feet.  The probe, and everything in it, is not likely to survive the brutal acceleration.  The only technology available today that can maybe launch a projectile into space from the ground is electro-magnetic cannons.  None yet exist powerful enough to do it and it would cost billions of dollars to make happen--well outside the realm of Kickstarter.


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## lilhasselhoffer (Feb 5, 2014)

FordGT90Concept said:


> Let's not forget the part where an enormous amount of force has to be exerted on the object in the space of <50' feet.  The probe, and everything in it, is not likely to survive the brutal acceleration.  The only technology available today that can maybe launch a projectile into space from the ground is electro-magnetic cannons.  None yet exist powerful enough to do it and it would cost billions of dollars to make happen--well outside the realm of Kickstarter.





lilhasselhoffer said:


> The energy is only imparted until the end of the barrel.  Let's assume that the barrel is 13.716 m (he cites 45' for mobility) long.  In order to reach the 11200 m/s velocity, assuming that you've got a constant linear acceleration, you're looking at a time in the barrel of 13.716m/5600m/s=0.002451s.  Acceleration could be given as a=(v-v0)/t, or 11200/0.002451= 4569430 m/s^2, or 4600 km/s^2.  To my knowledge, no material could withstand that kind of acceleration.



I didn't forget.


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## Vario (Feb 5, 2014)

What about if the damn thing landed on your house?


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## ste2425 (Feb 5, 2014)

I got so excited when I started reading the op I was thinking of some sort of starship troopers or halo orbital cannon and thought dam that's amazing. Then sadly sense took over and now I'm upset


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## Bo$$ (Feb 5, 2014)

Sounds to me he has ignored air resistance.


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## Kreij (Feb 6, 2014)

This project is awesome! It's like a giant potato gun.
We could lob spuds back and forth between Canada and Wisconsin!!!
I want one.


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## Steevo (Feb 7, 2014)

When dealing with the physics at that power level the rotation of the earth can be used to lessen the actual initial kinetic power required. Already a rail launched rocket has been proposed, and depending on end payload destination either launching against the rotation or with can save total fuel weight. 

http://spaceplace.nasa.gov/launch-windows/en/

http://www.qrg.northwestern.edu/projects/vss/docs /Navigation/2-why-launch-from-equator.html

http://en.wikipedia.org/wiki/Rocket_sled_launch


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## lilhasselhoffer (Feb 7, 2014)

Steevo said:


> When dealing with the physics at that power level the rotation of the earth can be used to lessen the actual initial kinetic power required. Already a rail launched rocket has been proposed, and depending on end payload destination either launching against the rotation or with can save total fuel weight.
> 
> http://spaceplace.nasa.gov/launch-windows/en/
> 
> ...



I'm perplexed here.  You have a point about the rotation of Earth.  The perplexing part is whether you not you know basic geography of our planet.  Canada and the equator are quite a good deal away from one another.


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## Frick (Feb 7, 2014)

lilhasselhoffer said:


> I'm perplexed here.  You have a point about the rotation of Earth.  The perplexing part is whether you not you know basic geography of our planet.  Canada and the equator are quite a good deal away from one another.



I'm pretty sure he's talking about the general concept.


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## lilhasselhoffer (Feb 7, 2014)

Frick said:


> I'm pretty sure he's talking about the general concept.



That makes a lot more sense.  I was assuming that the proposition was that they'd done the math and this would work at the equator.  My bad, and apologies.


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## Steevo (Feb 10, 2014)

Frick said:


> I'm pretty sure he's talking about the general concept.




Wait, they aren't next to each other!!!


Mind = blown!!

I was just in Canada a couple months ago, and I swore I saw some coconuts, palm trees and grass skirts.


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## AsRock (Feb 10, 2014)

Kreij said:


> This project is awesome! It's like a giant potato gun.
> We could lob spuds back and forth between Canada and Wisconsin!!!
> I want one.




And that's how it should of been advertised lol.


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## 4ghz (Feb 10, 2014)

Worked for Georges Melies: http://en.wikipedia.org/wiki/A_Trip_to_the_Moon


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## qubit (Feb 10, 2014)

Sounds like a scam designed to dupe those who have no idea what it takes to fire something into space and too stupid to do a quick google to find out.


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## Drone (Feb 10, 2014)

E-begging is getting so popular these days. Kickstarter this, kickstarter that. What an eyeroller!


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## lilhasselhoffer (Mar 27, 2014)

I'm just done with some of the people on Kickstarter.  They seem to not have a grasp on reality, and not understand some very basic concepts in mechanics before making any sort of a prototype:
https://www.kickstarter.com/projects/367465572/chi-eer-a-real-efficient-engine-motor?ref=discovery

The big problem here is the fact that they don't seem to understand the idea of friction, or even accurate measurement.

First, the one way gear box is a great idea, assuming that gears don't run on a fricative interface.  Each gear tooth exerts a surface friction on the rack tooth, transferring linear motion into rotary motion.  The difference is that those gear surfaces need to mesh very well, and they are extremely sensitive to breakdown at high operational speeds.  Assuming that you had infinite funding the gears could be made to run,  but you'd still experience substantial losses from friction.

The claims of the Kickstarter are either bogus, or they aren't measuring anything reasonable.  Let's, for just a second, assume that the gears worked without friction.  The input energy source would be pressurized and incompressible water, and the output would be water at ambient pressure.  If you had a tube with cross sectional area 1 square inch, you'd functionally be putting in 60 pounds of pressure into the piston head.  That means, with a 100% conversion into rotary force the only available remaining force would be due to gravitational acceleration.  The demonstrations in the video show water jetting out of the other end, demonstrably showing that 100% force conversion isn't happening.

Now, let's assume this person is completing the exercise in earnest.  They aren't intentionally obscuring data, and they aren't intentionally obscuring facts.  You've got a 60 lbf linear force, converted into a rotational force.  How does one get a 60 lbf rotational measurement?  You aren't expressing this force as torque, so there's no relationship between force and direction.  Measuring that the wheel takes 60 lbf braking applied to prevent motion, at a distance of 5" from the disc center, is not generating a torque of 60 lbf.  Whether intentionally misleading, or immensely incapable of expressing ideas clearly, this is a rather substantial failure of concept.

Finally, everything else wrong with this design.  You can run a compressor or pump at about 35%, from a power source that might be 40% efficient , in order to run a motor at about 85-90% efficiency ideally.  This is adding extra steps to the process of an engine, which functionally can pull maybe 35% efficiency from the combustion cycle.  If the proposal is to convert this transmission into a functional engine design, then best of luck.  Gears don't exactly like massive changes in force and direction, not to mention the wear from a relatively small surface area being pounded constantly by these huge (functionally instantaneous) forces.



Kickstarter.  Where you can propose any stupid idea, and get somebody to give you money.  I wish more projects existed that had reasonable goals and scopes, but the allure of getting "free" money to complete your dreams is too much.  I've watched several projects (some of which I did fund) succeed, and even more artsy types (read: no business acumen) crash and burn when they were forced to cope with being unable to defy the laws of physics.  I'm hoping that crowd funding gets its act together, but there's too much money involved right now for anyone to propose some strict quality controls.


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## ste2425 (Mar 27, 2014)

lilhasselhoffer said:


> I'm just done with some of the people on Kickstarter.  They seem to not have a grasp on reality, and not understand some very basic concepts in mechanics before making any sort of a prototype:
> https://www.kickstarter.com/projects/367465572/chi-eer-a-real-efficient-engine-motor?ref=discovery
> 
> The big problem here is the fact that they don't seem to understand the idea of friction, or even accurate measurement..........



I don't like the idea of yet more chains to replace and time up...


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## Sasqui (Mar 27, 2014)

ste2425 said:


> I just don't like the idea of yet more chains to replace and time up...



That and what LH says.  Claiming 100% efficiency?  I wonder if there are any perpetual motion machines on KS...  I'll have to look.


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## Easy Rhino (Mar 27, 2014)

I would rather have the opportunity to become an early investor so as to not get screwed when Facebook buys the startup I want to back.


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## lilhasselhoffer (Mar 27, 2014)

Easy Rhino said:


> I would rather have the opportunity to become an early investor so as to not get screwed when Facebook buys the startup I want to back.



Ooooh.  Props for a sick burn.  

I wonder what legal obligations Occulus still has to the Kickstarter backers?


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## Easy Rhino (Mar 27, 2014)

lilhasselhoffer said:


> Ooooh.  Props for a sick burn.
> 
> I wonder what legal obligations Occulus still has to the Kickstarter backers?



I read somewhere that Occulus has zero obligation to kickstarters since the people who backed the project all received what they signed up for, a tee shirt of a dev kit, etc. I would rather have tens of thousands of dollars instead.


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