Claim: Supergun could have put satellites into Orbit, if the first customer hadn't been Saddam Hussein. [Status: uncertain]

[SSgt Baloo]

"In 1961, Bull began working on the High Altitude Research Project (Harp), a joint venture between the US and Canadian governments. Using modified ex-Navy guns, Bull and his colleagues fired weather probes into sub-orbit and back down again. The costly and controversial Vietnam War meant the project was canned in 1967 before they could get any objects into orbit, but it teased Bull with the possibility of creating a satellite-launching supergun – a spacegun."

More here: http://www.bbc.com/future/story/20160317-the-man-who-tried-to-make-a-supergun-for-saddam-hussein?utm_source=fark&utm_medium=website&utm_content=link

[kunok]

Uhh very political question.

I like the https://en.wikipedia.org/wiki/Space_gun projects, in my fantasy I will put a huge cannon in the Kilimanjaro, almost in the equator, somewhat close to a important port (mombasa), and with less than half bar pressure in the top

Edited March 18, 2016 by kunok

[SSgt Baloo]

"Space Gun Suborbital tours. Your survival is 100% guaranteed, or your money will cheerfully be returned."*

* All refund requests must be made by the customer, in person.

[sgt_flyer]

a short suborbital hop would be possible, however going orbital from that would be really difficult.

for going orbital, you'd need to accelerate the projectile to at least a high percentage of the orbital speed, in 156m. even if you could make the barrel to be able to resist to the pressure needes (or use a railgun / coilgun design if you don't want to deal with the gas pressures) - i'll let you imagine the G-Forces that it would put on the payload . - after that, your payload will suffer from atmospheric heating & drag as soon as it leaves the gun. on top of that, you need to include something to circularise your orbit once you are nearing your apoapsis .

basically, unless you come up with a way to have vacuum around the payload along the trajectory...

 

you'd need to go much bigger and higher than that if you want to go orbital

here's the more realistic maglev version of this 'spacegun' - but it still has some shortcomings

https://en.wikipedia.org/wiki/StarTram

 

 

[SSgt Baloo]

You may be under the misapprehension that electronics would not survive the gee forces. If you had read the article, you would know that each of your points is addressed, from putting ablative heat shields on the objects being sent into orbit to the ruggedness required of guidance and other electronics that have to be fired from a cannon.

http://www.raytheon.com/news/feature/rms14_precision_projectile.html

It depends on what you're putting in orbit. Small satellites with electronics (communications anyone?) would be easy to launch, possibly requiring a solid rocket motor (or some other solution) to circularize the orbit once sufficient altitude has been gained.

I think the main thing that killed the space cannon as a viable project is that only a very specific type and size of satellite can be launched from a particular cannon, and it's a bugger to aim. If, as Saddam had planned, you build one into the side a mountain, you can only "aim" by varying the propellant charge.

[DerekL1963]

39 minutes ago, SSgt Baloo said:

It depends on what you're putting in orbit. Small satellites with electronics (communications anyone?) would be easy to launch, possibly requiring a solid rocket motor (or some other solution) to circularize the orbit once sufficient altitude has been gained.

No possibly about it - any gun launch system will require something that can circularize the orbit.  This is a consequence of orbital mathematics - all orbits must pass through the point where the orbital velocity was last changed, E.G. the muzzle of the gun.

 

 

[sgt_flyer]

@SSgt Baloo

there's one simple problem with hardening the electronics and various actuators / solenoids / solar panels against the kind of G forces they would have to sustain when launched from such a cannon - it would make the satellites themselves even pricier than what they already are... sure they would pay less launch fees, but needing extensive R&D and materials for the satellites...

it would make such a gun would only be useful for launching very small amounts of raw materials - for which you need to add a container to protect them, a docking system (ideally you'll need a tug to ferry those raw materials) and an access system to enable the transfer of those raw materials.

[Nothalogh]

1 hour ago, DerekL1963 said:

No possibly about it - any gun launch system will require something that can circularize the orbit.  This is a consequence of orbital mathematics - all orbits must pass through the point where the orbital velocity was last changed, E.G. the muzzle of the gun.

 

 

Yep, spaceguns sound appealing, until you figure out how orbit works

[sevenperforce]

2 hours ago, DerekL1963 said:

No possibly about it - any gun launch system will require something that can circularize the orbit.  This is a consequence of orbital mathematics - all orbits must pass through the point where the orbital velocity was last changed, E.G. the muzzle of the gun.

Hmm. Strictly speaking, the last point where the orbital velocity changes would be approximately where it crosses the Karman line. Until then, it is highly subject to drag. Is there a way to design a projectile which will passively re-orient such that a significant portion of its radial velocity is converted to tangential velocity?

[Stargate525]

13 minutes ago, sevenperforce said:

Hmm. Strictly speaking, the last point where the orbital velocity changes would be approximately where it crosses the Karman line. Until then, it is highly subject to drag. Is there a way to design a projectile which will passively re-orient such that a significant portion of its radial velocity is converted to tangential velocity?

I can't think of one. Theoretically you might be able to if you could figure out a way to aerodynamically skip against the karman line, but you'd still be touching atmosphere every orbit, and you'd quickly decay.

[sgt_flyer]

40 minutes ago, Stargate525 said:

I can't think of one. Theoretically you might be able to if you could figure out a way to aerodynamically skip against the karman line, but you'd still be touching atmosphere every orbit, and you'd quickly decay.

you could theoritically get your periapsis out of atmosphere without using propulsion, but it would take even more initial velocity (with all that implies for the gun & the payload...) - as in order to raise your periapsis, you'll need either a gravity assist from the moon, or go on an escape trajectory.

and given n-body problems + atmospheric perturbations during launch, you're likely to still need to make some minor corrections to pull that off. 

Edited March 21, 2016 by sgt_flyer

[kiwi1960]

This idea would work.... on the Moon, where they saw it as a means to cheaply get ore pods into Lunar orbit where they could be picked up and shipped back to Earth... or at least, to a space station where they could be refined into what was needed.... TILL they built the smelters etc on the Moon and used the system to get the things into orbit.

Saddam's only desire for this thing was to target Israel, hence, aiming wasn't that important.

This is now a dead duck since they "invented" the working rail gun AND laser gun.... a few ships are now sporting these weapons... the rail gun can hit targets in Afghanistan while the ship sits off the coast of Pakistan....

[sgt_flyer]

3 minutes ago, kiwi1960 said:

This idea would work.... on the Moon, where they saw it as a means to cheaply get ore pods into Lunar orbit where they could be picked up and shipped back to Earth... or at least, to a space station where they could be refined into what was needed.... TILL they built the smelters etc on the Moon and used the system to get the things into orbit.

Saddam's only desire for this thing was to target Israel, hence, aiming wasn't that important.

This is now a dead duck since they "invented" the working rail gun AND laser gun.... a few ships are now sporting these weapons... the rail gun can hit targets in Afghanistan while the ship sits off the coast of Pakistan....

heh  as the moon is tidally locked, you even can place the payload on an aerobrake trajectory back to earth without needing to re aim  (you'd still need some form of propulsion on the payload to circularise once your apoapsis lowered, if your facilities are in LEO)

[sevenperforce]

11 hours ago, Stargate525 said:

I can't think of one. Theoretically you might be able to if you could figure out a way to aerodynamically skip against the karman line, but you'd still be touching atmosphere every orbit, and you'd quickly decay.

I was thinking more of something like a negative lift-to-drag ratio -- having an aeroshell that would passively re-orient after dropping below a certain speed, but do so at an angle that converted a portion of the drag into negative lift and thus circularize. It wouldn't get you entirely out of the atmosphere, but it might be circular enough that a dedicated space tug could match trajectory near apogee, couple with the payload, and then raise perigee. That would avoid needing any sort of correction on the payload itself.

You could use spin-stabilization to keep the payload in a low-drag orientation through the lower atmosphere, designed in such a way that the angular momentum would decay at around 70 km and allow it to tumble into the higher-drag negative-lift orientation.

[Lukaszenko]

Project HARP fired 180 kg to an altitude of 180 km...so apparently the whole atmospheric drag/ heating thing can be worked around, at least to a degree.  

[sgt_flyer]

3 hours ago, Lukaszenko said:

Project HARP fired 180 kg to an altitude of 180 km...so apparently the whole atmospheric drag/ heating thing can be worked around, at least to a degree.  

Suborbital is way easier than orbital  for the 180km launch, Harp fired the test projectiles (martlet-2) with a 7000FPS muzzle velocity (2,1 km/s). orbital velocity is at 7,8 km/s.

the test projectiles they later fired with solid motors in the projectiles - the solid fuel had problems resisting muzzle velocities above 3400 FPS... (martlet 3A, martlet 3B)

they supposedly found a way to make the fuel more resistant to acceleration later, but never fired these versions before HARP was shut down.

Edited March 21, 2016 by sgt_flyer

[fredinno]

15 hours ago, kiwi1960 said:

This idea would work.... on the Moon, where they saw it as a means to cheaply get ore pods into Lunar orbit where they could be picked up and shipped back to Earth... or at least, to a space station where they could be refined into what was needed.... TILL they built the smelters etc on the Moon and used the system to get the things into orbit.

Saddam's only desire for this thing was to target Israel, hence, aiming wasn't that important.

This is now a dead duck since they "invented" the working rail gun AND laser gun.... a few ships are now sporting these weapons... the rail gun can hit targets in Afghanistan while the ship sits off the coast of Pakistan....

Source for the guns?

5 hours ago, sevenperforce said:

I was thinking more of something like a negative lift-to-drag ratio -- having an aeroshell that would passively re-orient after dropping below a certain speed, but do so at an angle that converted a portion of the drag into negative lift and thus circularize. It wouldn't get you entirely out of the atmosphere, but it might be circular enough that a dedicated space tug could match trajectory near apogee, couple with the payload, and then raise perigee. That would avoid needing any sort of correction on the payload itself.

You could use spin-stabilization to keep the payload in a low-drag orientation through the lower atmosphere, designed in such a way that the angular momentum would decay at around 70 km and allow it to tumble into the higher-drag negative-lift orientation.

Why would you risk a space tug by putting it on a suborbital trajectory every time you want to get into orbit. Oh yeah, rendezvous takes 6 hours.

Also, adding the docking port and special lifting body, plus a heat-tolerant aeroshell probably increases costs to make this pointless. What's wrong with a solid apogee motor?

[StrandedonEarth]

Let's see, the shortest path through the atmosphere (least aero drag) would be straight up. Horizontal velocity at apogee would be next to nil (aside from that provided by Earth's rotation). So you'd need a kick motor with around 17,500 mph of dV..

If you want some horizontal velocity at apogee, you'd need to fire at an angle, spending way more dV fighting drag, and experiencing a lot more atmospheric heating. Not insurmountable, but by the time you reach apogee you'd still have lost a lot of horizontal velocity. How much horizontal  velocity would it be reasonably possible to have at apogee?

Now here's a thought for a very low ISP kick motor: there's going to be an awful lot of heating to get an appreciable hV at apogee, right? Have a significant part of the projectile be made of water sealed in a pressure vessel. At apogee open a valve to an exhaust port, and use the steam for thrust. The water would be doing double duty! Of course, I doubt that would be enough...

[wumpus]

20 hours ago, DerekL1963 said:

No possibly about it - any gun launch system will require something that can circularize the orbit.  This is a consequence of orbital mathematics - all orbits must pass through the point where the orbital velocity was last changed, E.G. the muzzle of the gun.

Not only do you need circularization, you also will have extraordinary difficulties trying to do anything resembling a pitchover (typically called a gravity turn in KSP, especially before 1.0).  Presumably this could be done mostly by control fins (letting you convert vertical velocity to horizontal in a reasonably efficient manner).  Once you leave the atmosphere, you better be going [nearly] horizontal (and obviously, you will need a bit more delta-v to avoid coming back to the atmosphere.  Plus all the standard issues:

• full orbital velocity inside the atmosphere (I'm guessing that over 4,000m elevation is as good as you can hope for).
• Mind boggling g forces: 1 1km gun would hit 6400gs (best possible case).
• Basic guns are limited to Ve (the Ve of the Rocket Equation).  Expect weird multi-combustion guns to get near orbital speed (Bull certainly wasn't stopped by this, but it makes things hard).

Scott Manley has one of his science videos on this: 

 

[fredinno]

40 minutes ago, StrandedonEarth said:

Let's see, the shortest path through the atmosphere (least aero drag) would be straight up. Horizontal velocity at apogee would be next to nil (aside from that provided by Earth's rotation). So you'd need a kick motor with around 17,500 mph of dV..

If you want some horizontal velocity at apogee, you'd need to fire at an angle, spending way more dV fighting drag, and experiencing a lot more atmospheric heating. Not insurmountable, but by the time you reach apogee you'd still have lost a lot of horizontal velocity. How much horizontal  velocity would it be reasonably possible to have at apogee?

Now here's a thought for a very low ISP kick motor: there's going to be an awful lot of heating to get an appreciable hV at apogee, right? Have a significant part of the projectile be made of water sealed in a pressure vessel. At apogee open a valve to an exhaust port, and use the steam for thrust. The water would be doing double duty! Of course, I doubt that would be enough...

Very hot water is corrosive, so that's probably a bad idea. They also have bad isp.

[kiwi1960]

1 hour ago, fredinno said:

Source for the guns?

Oh ye of so very little faith....

https://www.youtube.com/watch?v=o4ZqfEJTGzw
 

The Laser gun....
 

Just because you never heard of it doesn't mean others haven't....

 

[Mazon Del]

Technically only the laser is on a ship at the moment. The USS Ponce, and it is a test system, though testing is proceeding rapidly. I believe the laser is a 30,000 KW beam, and by the end of the year they intend to be testing something like a 150,000 KW beam.

The railgun is not just yet on a ship, though that is supposed to happen this year, again it is a test system and not ready for combat though if the schedule holds they should start arming ships with production railguns on or about 2020.

[fredinno]

11 minutes ago, Mazon Del said:

Technically only the laser is on a ship at the moment. The USS Ponce, and it is a test system, though testing is proceeding rapidly. I believe the laser is a 30,000 KW beam, and by the end of the year they intend to be testing something like a 150,000 KW beam.

The railgun is not just yet on a ship, though that is supposed to happen this year, again it is a test system and not ready for combat though if the schedule holds they should start arming ships with production railguns on or about 2020.

But the railgun is FAR too small for use for space....

[Mazon Del]

11 minutes ago, fredinno said:

But the railgun is FAR too small for use for space....

For a satellite launch, yes, but it is most certainly capable of suborbital shots as evidenced by their desire to use it as an anti-ICBM weapon.

[DerekL1963]

4 hours ago, wumpus said:

On 3/21/2016 at 5:03 PM, DerekL1963 said:

No possibly about it - any gun launch system will require something that can circularize the orbit.  This is a consequence of orbital mathematics - all orbits must pass through the point where the orbital velocity was last changed, E.G. the muzzle of the gun.

Not only do you need circularization, you also will have extraordinary difficulties trying to do anything resembling a pitchover (typically called a gravity turn in KSP, especially before 1.0).

0.o   A gun fired projectile doesn't need to perform a pitch maneuver/gravity turn in the first place, it's not a powered vehicle and doesn't fly like a powered vehicle does.   It needs an attitude control system for the circularization burn.
 

4 hours ago, wumpus said:

Once you leave the atmosphere, you better be going [nearly] horizontal (and obviously, you will need a bit more delta-v to avoid coming back to the atmosphere.

o.0  No, you don't need to be going horizontal or nearly so.  (Though that does minimize the size of your circularization burn.)