Author Topic: A Cannon for Shooting Supplies into Space  (Read 29894 times)

Online hop

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Re: A Cannon for Shooting Supplies into Space
« Reply #20 on: 01/16/2010 10:40 PM »
What do you mean? The speed record for a hydrogen gun is 11.6km/s, way more than required to get to orbit.
After you have included drag losses ?
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That was reached back in the 1960s.
That does not equate to a vehicle that can travel through the atmosphere (many of the research gas guns fire into a vacuum chamber) at that speed with a payload and survive.

This is but one of several 800lb gorillas in the room with all these "single initial impulse" schemes (rail guns, cannons, maglev tracks etc). While you may be able to pull it off, mach 25 (+ whatever you lose to drag) at sea level is going to be hard. Far harder than a normal re-entry, since you are going fastest in the densest part of the atmosphere, rather than the reverse.

Another difficulty is that none of these schemes can replace rocket based launchers, or serve any of the existing launch market, so the entire rocket based infrastructure still has to be maintained. Sure, you might be able to launch fuel, air and water cheaper, but you will now be paying for both the gun launch infrastructure and the standing army of rocket support people. If we get to the point that we have enough demand for bulk inert cargo to justify initial investment and infrastructure, we will probably be well into the territory where RLVs make sense.

Offline DiggyCoxwell

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Re: A Cannon for Shooting Supplies into Space
« Reply #21 on: 01/16/2010 11:13 PM »
  I second what Hop has to say about the issue.

But if you seriously want to carry on long-range space cannon
research started by the deceased Canadian scientist, and you succeed
in persuading Mossad that your research agenda is "peaceful",
good luck.

  Money will be an issue.
 The sudden humongous silicon-chip crushing g-forces will be a problem.
 The enormous air compression ahead of the projectile in the barrel will be a problem.
   Gravity loss and air drag loss will have to be accounted for the for the sake of the projectile.
 
  I have a suggestion or two.

You want to do an updated Jules Verne with the cannon and send an unmanned projectile to the moon, with a terminal velocity over
11 km per second above the atmosphere?

Why not do this?

Use a projectile whose shell is lined with reinforced coolant jackets
holding liquid nitrogen.
Liquid nitrogen will serve two purposes.

1) it will keep the skin of the projectile from vaporizing or melting
before leaving the atmosphere.

2) super-heated, vaporized and pressurized, the searing-hot nitrogen gas can serve as a monopropellant to recover velocity lost
by the projectile due to gravity and atmospheric drag.

Submerse the electronics, (both for avionics and science)
in a vessel filled with a harmless fluid or gel to neutralize
the enormous g-forces acting on the components as much as possible.
     
And fit pressure release plugs along the length of the cannon barrel
to mercifully relieve the sudden enormous air-pressure build up moving ahead of the projectile.
« Last Edit: 01/16/2010 11:17 PM by DiggyCoxwell »

Offline A_M_Swallow

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Re: A Cannon for Shooting Supplies into Space
« Reply #22 on: 01/17/2010 02:10 AM »

Submerse the electronics, (both for avionics and science)
in a vessel filled with a harmless fluid or gel to neutralize
the enormous g-forces acting on the components as much as possible.

Proximity shells using radar have been around since the Second World War.  They can take enormous accelerations, for instance the M734 fuse is rated at 395 g.  Others can take more.
http://en.wikipedia.org/wiki/M734

p.s. This means that avionics able to survive being fired from a space cannon can be built.
« Last Edit: 01/17/2010 02:12 AM by A_M_Swallow »

Offline kch

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Re: A Cannon for Shooting Supplies into Space
« Reply #23 on: 01/17/2010 02:53 AM »

Submerse the electronics, (both for avionics and science)
in a vessel filled with a harmless fluid or gel to neutralize
the enormous g-forces acting on the components as much as possible.

Proximity shells using radar have been around since the Second World War.  They can take enormous accelerations, for instance the M734 fuse is rated at 395 g.  Others can take more.
http://en.wikipedia.org/wiki/M734

p.s. This means that avionics able to survive being fired from a space cannon can be built.

Look up "Project HARP" and/or "High Altitude Research Project" on the Web and take a look at what kind of G forces they were successfully dealing with (almost 50 years ago) ...

Offline khallow

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Re: A Cannon for Shooting Supplies into Space
« Reply #24 on: 01/17/2010 03:30 AM »
I'm quite repetitive here, since this has been said more than once here, but the thing that makes space gun-propelled rockets a remarkable potential technology is that unlike other similar assisted launch systems (that is, portion of delta v is somehow provided from the ground), it has been tried with great success in the HARP project. That gives it a TRL level of 6 or so. The similar ideas of railgun-boosted rockets or laser-heated propellant engines (with the lasers coming from ground) are nowhere near that in readiness level.
« Last Edit: 01/17/2010 03:31 AM by khallow »
Karl Hallowell

Online hop

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Re: A Cannon for Shooting Supplies into Space
« Reply #25 on: 01/17/2010 05:46 AM »
it has been tried with great success in the HARP project. That gives it a TRL level of 6 or so.
The HARP gun was not was not capable of getting anywhere close to orbital velocity. I've seen different numbers for the peak velocity, but it was something under 2.5 km/s. The remaining 6+ will be significantly more difficult. If you are going to have one or more rocket stages (the HARP orbital concepts used 3 AFAIK), what does a giant gun buy you aside from an extremely harsh ride, a lack of scalability, and numerous additional payload constraints ?

Note, I agree that it is probably possible to make a gun launch system where the gun provides a useful fraction of orbital velocity. If your goal is to build big, loud toys, this is a fine idea and I wholehearted support it. OTOH, if your goal is to reduce the cost of doing stuff in space, the case is significantly less compelling.

edit:
Hey, 2.5 km/s is right about lunar escape velocity, and without an atmosphere, the many of the other problems go away. Aside from minor problem of landing a surplus 16 inch gun on the moon, this might be a nice way to export lunar materials ;)
« Last Edit: 01/17/2010 05:55 AM by hop »

Offline A_M_Swallow

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Re: A Cannon for Shooting Supplies into Space
« Reply #26 on: 01/17/2010 06:41 AM »
Hey, 2.5 km/s is right about lunar escape velocity, and without an atmosphere, the many of the other problems go away. Aside from minor problem of landing a surplus 16 inch gun on the moon, this might be a nice way to export lunar materials ;)

The 16 inch gun could be made on the Moon, regolith contains plenty of iron.  The barrel may need lining if LOX is being exported.

Can locally mined Mg + Al + LOX be made to explode?

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #27 on: 01/17/2010 07:20 AM »
After you have included drag losses ?

Both losses from atmospheric drag and gravity losses are a LOT less for a gun launcher than for a rocket. It's actually pretty straight forward calculations - you require about 9km/s to reach a stable orbit (that's about a 1.5 km/s loss in total).

Again, the 11.6km/s reached in the past is sufficient enough for payloads up to several tons (if the gun is that big) to reach orbit.

Quote
This is but one of several 800lb gorillas in the room with all these "single initial impulse" schemes (rail guns, cannons, maglev tracks etc). While you may be able to pull it off, mach 25 (+ whatever you lose to drag) at sea level is going to be hard. Far harder than a normal re-entry, since you are going fastest in the densest part of the atmosphere, rather than the reverse.

See above. Just for comparison's sake, if you built a gun launcher on some mountain side 10,000 feet above sea level, you end up having about a 200m/s benefit over sea level in drag penalty from atmospheric drag for a 1000 pound payload. That's peanuts in the whole equation.

Quote
Another difficulty is that none of these schemes can replace rocket based launchers,
So? That isn't the point.

Quote
...or serve any of the existing launch market, ... Sure, you might be able to launch fuel, air and water cheaper, but you will now be paying for both the gun launch infrastructure and the standing army of rocket support people. If we get to the point that we have enough demand for bulk inert cargo to justify initial investment and infrastructure, we will probably be well into the territory where RLVs make sense.

I completely disagree with your assertion the existing launch market can't benefit from this proposal. I explained above - think about comsats going up on a much cheaper rocket to LEO, get its upper stage refueled and then placed into GEO.

Anyway, RLVs cannot get as low as the price for a gun launcher, and their development costs have always been anywhere north of several tens of billions of dollars. You couldn't recoup those development costs in the next 100 years. In contrast, this gun launcher proposal has a much more modest development price tag - for NASA it's pretty much "petty cash" when compared to the HLV development budget.

And we are at the point where we need to decide how to get 200, 500 and later 1000mt of fuel into orbit - for exploration missions. Current thinking is that NASA will do that with expensive HLVs, but a cheap provider of fuel to fuel depots might just change that equation quite a lot, allowing for a lot more exploration than envisioned right now.

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #28 on: 01/17/2010 07:25 AM »

Submerse the electronics, (both for avionics and science)
in a vessel filled with a harmless fluid or gel to neutralize
the enormous g-forces acting on the components as much as possible.

Proximity shells using radar have been around since the Second World War.  They can take enormous accelerations, for instance the M734 fuse is rated at 395 g.  Others can take more.
http://en.wikipedia.org/wiki/M734

p.s. This means that avionics able to survive being fired from a space cannon can be built.

Look up "Project HARP" and/or "High Altitude Research Project" on the Web and take a look at what kind of G forces they were successfully dealing with (almost 50 years ago) ...

I go a step further. People just should look at what mobile phone manufacturers subject their products to in terms of G-load. You will be surprised...

Online hop

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Re: A Cannon for Shooting Supplies into Space
« Reply #29 on: 01/17/2010 07:48 AM »
Both losses from atmospheric drag and gravity losses are a LOT less for a gun launcher than for a rocket. It's actually pretty straight forward calculations - you require about 9km/s to reach a stable orbit (that's about a 1.5 km/s loss in total).
Even granting this, you think 9km/s at sea level is no big deal ? ::)
Quote
Again, the 11.6km/s reached in the past is sufficient enough for payloads up to several tons (if the gun is that big) to reach orbit.
You are are ignoring the actual objection. Getting the muzzle velocity is only a small part of the problem.
Quote
Quote
Another difficulty is that none of these schemes can replace rocket based launchers,
So? That isn't the point.
Like I said, if making big noises is the point, I'm fine with that. But if you are going to claim it is going to reduce the cost of the space activities we want to do, the total cost of maintaining both the gun and rocket systems has to be less than the pure rocket approach. While one can imagine scenarios where this might work out, it's far from a given even if the per launch costs of the gun system are low.

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #30 on: 01/17/2010 08:05 AM »
Even granting this, you think 9km/s at sea level is no big deal ? ::)

It wouldn't be 9km/s for the gun launcher. It would be a combination of gun launched projectile and single-stage to orbit kerolox rocket. 6km/s by gun, 3km/s by rocket.

Quote
You are are ignoring the actual objection. Getting the muzzle velocity is only a small part of the problem.
I am not ignoring the objection, I outlined above why drag isn't the problem. You may also want to read up on the question of heating of the projectile and insulation of the payload. Due to the short time of the projectile within a thick atmosphere, there is a physical limit on how much of your heat shield for the payload can burn away. It turns out, heating and insulation isn't a problem either.

Quote
Like I said, if making big noises is the point, I'm fine with that. But if you are going to claim it is going to reduce the cost of the space activities we want to do, the total cost of maintaining both the gun and rocket systems has to be less than the pure rocket approach. While one can imagine scenarios where this might work out, it's far from a given even if the per launch costs of the gun system are low.

That's the nice thing about hydrogen gun launchers. We have a lot of data from operations on them. We know how many people it takes to operate and maintain a gun, which doesn't change with barrel length. It's actually remarkable cheap compared to practically every other technology related to aerospace. You can operate a 300 feet hydrogen gun for a year with near daily shots with a scientific staff of maybe 10-15 people, practically no maintenance, at sea level, with the projectile entering the atmosphere (not a vacuum chamber) etc. It's all been done for many years, you may read up on SHARP. While the regular velocities have only been 3km/s, there was no fundamental problem at all to increase SHARP's speed alone to 6km/s with the same hardware (except that the Airforce objected, they weren't interested in Mach 20 research).

P.S. I am not saying an orbital gun launcher would work as proposed, but if it did work, it's clear that the costs will be low compared to rockets, that's a fact that doesn't go away and is supported by the SHARP costs.

Online hop

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Re: A Cannon for Shooting Supplies into Space
« Reply #31 on: 01/17/2010 08:15 AM »
It wouldn't be 9km/s for the gun launcher. It would be a combination of gun launched projectile and single-stage to orbit kerolox rocket. 6km/s by gun, 3km/s by rocket.
Err, you never said anything about rocket stages before. Not that 6km/s is anything to sneeze at.
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I am not ignoring the objection, I outlined above why drag isn't the problem.
No you claimed it the drag loss was significant you didn't deal with heating. But now you do...
Quote
You may also want to read up on the question of heating of the projectile and insulation of the payload. Due to the short time of the projectile within a thick atmosphere, there is a physical limit on how much of your heat shield for the payload can burn away. It turns out, heating and insulation isn't a problem either.
Good luck with that.  ;D

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #32 on: 01/17/2010 08:52 AM »
Err, you never said anything about rocket stages before. Not that 6km/s is anything to sneeze at.
I assumed you had read the above posts and informed yourself about the proposal that this thread talks about. I don't have to say anything about how the thing is supposed to work, this thread is about this proposal, so I can assume you have looked at the basic characteristics of it.

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Good luck with that.  ;D

I am not involved in the project. However, if you think heating is an unsolvable problem, you might want to contact the Sandia National Laboratories. They did the calculations of the effects of atmospheric heating of a 6km/s fired projectile at sea level and came up with a result - at 6km/s you burn off about 5 inches of your carbon-carbon heatshield on the nosecone (less on the side of course) until you are completely clear of the atmosphere after 70-80s. That isn't bad at all.

Offline Robotbeat

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Re: A Cannon for Shooting Supplies into Space
« Reply #33 on: 01/17/2010 09:43 AM »
If he can build a (demonstration) cannon capable of achieving orbit (with a small boost rocket) for only $12 million, then I would be very surprised, but delighted. It seems to me, though, that this is not an order of magnitude cheaper than a fully reusable rocket, since you can't easily recover the upper stage.

Oh, and add Lockheed Martin to the list of companies working on a reusable first stage (they are working on a fly-back booster).

The nice thing about using propellant depots that are commercially refueled is that crazy ideas like this can be tried. The cheapest method wins! Cheap propellant in LEO (or L2) will change a lot of the trades people make when designing an exploration architecture.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #34 on: 01/17/2010 10:48 AM »
It seems to me, though, that this is not an order of magnitude cheaper than a fully reusable rocket, since you can't easily recover the upper stage.

I don't follow. We are talking a "sounding rocket" class rocket here. Why would anybody want to go into all the trouble to reuse that? It's not very expensive to begin with.

Offline renclod

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Re: A Cannon for Shooting Supplies into Space
« Reply #35 on: 01/17/2010 01:33 PM »
Jan 15 2010 TheSpaceShow with guest Dr. John Hunter
http://archived.thespaceshow.com/shows/1290-BWB-2010-01-15.mp3

If the H2 was really recovered, a gas gun like this, with much reduced muzzle velocity and no atmospheric issues and reduced pipe sag issues, would do great things for lunar based launch needs.

For Earth launch, I have 1E+3 questions. Listening to the show now...


Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #36 on: 01/17/2010 01:45 PM »
For Earth launch, I have 1E+3 questions.

What would those be?

Offline renclod

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Re: A Cannon for Shooting Supplies into Space
« Reply #37 on: 01/17/2010 01:52 PM »
Many. One crazy thing is this:
(not credible... no KISS principle in there)

Offline khallow

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Re: A Cannon for Shooting Supplies into Space
« Reply #38 on: 01/17/2010 01:55 PM »

The HARP gun was not was not capable of getting anywhere close to orbital velocity. I've seen different numbers for the peak velocity, but it was something under 2.5 km/s. The remaining 6+ will be significantly more difficult. If you are going to have one or more rocket stages (the HARP orbital concepts used 3 AFAIK), what does a giant gun buy you aside from an extremely harsh ride, a lack of scalability, and numerous additional payload constraints ?

It buys you delta v, scalability, lower payload costs, and much higher launch frequency. The delta v is an obvious consequence and results in far better mass fraction. Scalability is also fairly obvious. If you want to launch more things, you use more barrels. Lower payload costs are mainly a consequence of the delta v boost (resulting in vastly simpler and better engineering margin launch systems), but also of launch frequency. You basically can keep launching as long as you don't exceed the thermal or wear limits of the barrel.

As far as I can tell, the fact that HARP didn't reach orbital velocities doesn't really change the TRL. It was a working prototype tested in a "relevant environment" (which is what you need to qualify for TRL 6). But I don't know the nuances of the TRL model so I can't say for sure.


See above. Just for comparison's sake, if you built a gun launcher on some mountain side 10,000 feet above sea level, you end up having about a 200m/s benefit over sea level in drag penalty from atmospheric drag for a 1000 pound payload. That's peanuts in the whole equation.

That's quite a big peanut. I'd have to disagree.
Karl Hallowell

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #39 on: 01/17/2010 01:56 PM »
Many. One crazy thing is this:
(not credible... no KISS principle in there)

True, their depot design isn't credible. Does that matter? It's not their field of expertise. Is there a fundamental problem here? Not really, fuel depots are possible and rendezvous is possible as well. It would of course look different than their artist impression, but hey, at this moment it really doesn't matter.

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