Author Topic: A Cannon for Shooting Supplies into Space  (Read 29866 times)

Offline renclod

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Re: A Cannon for Shooting Supplies into Space
« Reply #40 on: 01/17/2010 01:58 PM »
Another question is:

Dr. J.Hunter said, smooth barrel. Now, what keeps the projectile stable from muzzle out ?

One more: In the video, Dr. J.H. said, in response to a question, that H2 embrittlement is manageable due to the very short propulsive event. But, recovering the H2 ? Also short event ? How ?

« Last Edit: 01/17/2010 01:59 PM by renclod »

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #41 on: 01/17/2010 01:59 PM »
That's quite a big peanut. I'd have to disagree.

Depends on how you look at it.
Claimed funds required for a prototype with a 1kg payload capability to orbit: USD 12 million.
That's less than 3% of COTS money.
That's about 1% of the average Shuttle flight cost.
That's about 0.03% of what Ares I/Orion are currently estimated to cost to develop until IOC.

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #42 on: 01/17/2010 02:11 PM »
One more: In the video, Dr. J.H. said, in response to a question, that H2 embrittlement is manageable due to the very short propulsive event. But, recovering the H2 ? Also short event ? How ?

No, recovering wouldn't be a short event. I assume hydrogen embrittlement is dealt with at the upper part of the barrel (the "silencer part" as Dr. Hunter referred to) by using composites instead of steel in this area (the "outer expansion chamber" in the below picture where H2 would flow in behind the projectile and "sucked out" to the side).

I have no answer to your first question. Just the airflow?

Offline khallow

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Re: A Cannon for Shooting Supplies into Space
« Reply #43 on: 01/17/2010 03:09 PM »
Lambda, I was referring to the claim that lopping 200 m/s off of 3km/s or so delta v was "peanuts".
Karl Hallowell

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #44 on: 01/17/2010 03:14 PM »
Lambda, I was referring to the claim that lopping 200 m/s off of 3km/s or so delta v was "peanuts".


Yup, sorry, a misunderstanding on my part (didn't look at the quote very well before posting...).

Anyway, it's not 200m/s of 3km/s, it's an additional 200m/s atmospheric loss between a sea level launch and a launch on a mountain hill for a 1000 pound payload (smaller payloads get you more atmospheric drag). It's 200m/s of 7.6km/s (orbital speed) or 200m/s of 9km/s (delta-v required for circularized orbit including gravity loss and atmospheric loss). That's between 2-3%. Peanuts.
« Last Edit: 01/17/2010 03:16 PM by Lambda-4 »

Offline khallow

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Re: A Cannon for Shooting Supplies into Space
« Reply #45 on: 01/17/2010 05:56 PM »

Anyway, it's not 200m/s of 3km/s,

But it is. The rocket stage has 200 m/s less velocity to make up and originally it was claimed that the rocket stage only had to generate something like 3 km/s. That's more like 6-7% of delta v, which is quite significant.
Karl Hallowell

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #46 on: 01/17/2010 06:20 PM »

Anyway, it's not 200m/s of 3km/s,

But it is. The rocket stage has 200 m/s less velocity to make up and originally it was claimed that the rocket stage only had to generate something like 3 km/s. That's more like 6-7% of delta v, which is quite significant.


That doesn't make sense. It's an integral system. You got a "first stage", which is the gun launcher that provides 6km/s delta-v and a "second stage", which is a conventional single stage kerolox rocket. It doesn't make any sense to apply the 200m/s to only either of one of those. That's like saying the aerodynamic drag loss for a sidemount HLV of x m/s only applies to the booster phase of the assent.

Anyway, to put the gun up on a mountain 10,000 feet high gets you in a lot of serious trouble and takes away all your flexibility to put your payload into any orbit you want. That's not prudent at all.

Offline khallow

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Re: A Cannon for Shooting Supplies into Space
« Reply #47 on: 01/17/2010 07:22 PM »

That doesn't make sense. It's an integral system. You got a "first stage", which is the gun launcher that provides 6km/s delta-v and a "second stage", which is a conventional single stage kerolox rocket. It doesn't make any sense to apply the 200m/s to only either of one of those. That's like saying the aerodynamic drag loss for a sidemount HLV of x m/s only applies to the booster phase of the assent.

Sure it does. I don't know much about space guns, but I do know a fair amount about rockets. A 200 m/s improvement in delta v improves this component considerably. Now are you going to claim that the best solution for this system is worse than merely restricting your optimization to half of the system?

Anyway, considering kerosene/peroxide (with exhaust velocity of 3.1 km/s in vacuum), I get roughly a 6-7% boost in mass fraction from reducing delta v by 200 m/s (38% mass fraction increases to 40.5% mass fraction). If the engine has a lower ISP than that (say like an SRB), then the gain in mass fraction is even greater. At 2.6 km/s (which is the performance of the engine in atmosphere and probably a hard lower bound for any engine design), the improvement in mass fraction increases to roughly 8%.

Reading some more, I see that the gun stage may be thermally restricted by the material of the barrel. If true, then you can't optimize that stage much more than it has been for reasons completely unrelated to altitude.

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Anyway, to put the gun up on a mountain 10,000 feet high gets you in a lot of serious trouble and takes away all your flexibility to put your payload into any orbit you want. That's not prudent at all.

Unless you don't need the flexibility (for example, serving a propellant depot or other fixed popular orbits). And to be honest, I don't see a logistical advantage to sea launch over high altitude land launch. The former needs to upend the barrel in order to load a new payload, it's exposed to sea water and adverse weather just as bad as anything you'll find on a relatively high mountain, and you have to bring the payload out either by boat or helicopter. A land-based system can load faster (since the beech is never 1600 feet below water), isn't exposed to salt water, and the payloads can come by truck or rail.
« Last Edit: 01/17/2010 07:26 PM by khallow »
Karl Hallowell

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #48 on: 01/17/2010 09:50 PM »
1. There are other reasons for a water based gun launcher. They are listed on the first page of this thread. They alone make a sea based gun launcher far superior to a land based launcher (in the 1000 pound projectile class that we are talking about).

2. A mountain side based gun launcher not only restricts you to a single orbit inclination, it also restricts your launch window for e.g. a depot in the only orbit inclination that you can do from there anyway. Besides, a sea based launcher can be near the equator which provides some delta-v from the Earth's rotation. You could only match that with a land based launcher if you go to e.g. Northern Peru's mountain areas. You got a logistical nightmare there.

3. To reiterate my point about the 200m/s additional drag penalty: Do you think it would have been prudent that the Shuttle is launched from somewhere in the Rockies instead of Florida on sea level? After all, you don't consider atmospheric drag "peanuts" in the total equation, so in your view it should also be a more prudent decision to launch big rockets from high altitudes.

Offline gospacex

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Re: A Cannon for Shooting Supplies into Space
« Reply #49 on: 01/18/2010 12:42 AM »
  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.

Not that hard. Just don't try to make *Iranians or North Koreans* invest in your project, use more respectable people/countries, and you'll be ok.

Offline gospacex

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Re: A Cannon for Shooting Supplies into Space
« Reply #50 on: 01/18/2010 12:49 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.

I'm a bit skeptical on kerolox part. Solids may be easier to coerce into surviving high G loads. In fact, military contractors are working on this problem right now for new 6in naval gun. They plan to shoot rocket-assisted shells - basically rugged solid-fueled rockets - to about 100 miles.

Offline MarsInMyLifetime

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Re: A Cannon for Shooting Supplies into Space
« Reply #51 on: 01/18/2010 04:38 AM »
I've missed or haven't read yet how the proposers plan to deal with the inevitable recoil of this design. What mitigates the tendency of the barrel to plunge backwards into the sea when the masses separate at huge relative velocity? Wouldn't the exhausting muzzle gasses filling that vast barrel also impart a significant backwards thrust for a few seconds?

Musing further, what would be the acoustic impact to the local oceanic environment at launch?

--
Don
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Offline khallow

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Re: A Cannon for Shooting Supplies into Space
« Reply #52 on: 01/18/2010 04:41 AM »
Ok, the flexibility argument can't be beat. I'll surrender at the end of my post, but first, some belligerent face saving.

1. There are other reasons for a water based gun launcher. They are listed on the first page of this thread. They alone make a sea based gun launcher far superior to a land based launcher (in the 1000 pound projectile class that we are talking about).

Eh, I looked and wasn't impressed. The only remaining issue is gravity sag. The sea launch will have bending from ocean currents and surface wind. The design should be able to handle slight bends in the barrel or it's going to have problems.

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2. A mountain side based gun launcher not only restricts you to a single orbit inclination, it also restricts your launch window for e.g. a depot in the only orbit inclination that you can do from there anyway. Besides, a sea based launcher can be near the equator which provides some delta-v from the Earth's rotation. You could only match that with a land based launcher if you go to e.g. Northern Peru's mountain areas. You got a logistical nightmare there.

For the narrow consideration of launch windows, sea based launcher will have similar constraints on launch windows. It's sole advantage (with respect to the narrow consideration of launch windows) is that if you're not firing nearly straight ahead (that is in the direction of Earth's rotation), you get double the launch windows (once firing northwards and once firing at the same angle southwards). This is countered by the ability of the land based system to launch more payloads during the launch window (though I do mention a fix at the end of this post for sea launch guns).

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3. To reiterate my point about the 200m/s additional drag penalty: Do you think it would have been prudent that the Shuttle is launched from somewhere in the Rockies instead of Florida on sea level? After all, you don't consider atmospheric drag "peanuts" in the total equation, so in your view it should also be a more prudent decision to launch big rockets from high altitudes.

Even if the Shuttle launched in complete vacuum, it would pick up only 107 m/s in air resistance savings. This high air resistance loss is a peculiar feature of space guns (and similar launch systems) due to their high initial velocity. If the space gun has even higher initial velocities, the air resistance saving is even more pronounced.

Further, it's unlikely that the small rockets used in these proposed space guns will use cryogenic propellants (like LOX). That's why I chose relatively low ISP hydrogen peroxide/kerosene and SRB propellant as my two choices for computing mass fraction changes. That means any delta v savings are more significant than they are for the Shuttle (which as I understand uses LOX/LH2 for most of its boost and hence receives less advantage from milking more delta v).

It's worth noting that the infrastructure to support a space gun, whether on land or sea, is going to be far less than that supporting the Shuttle. Hence, it is far less complex logistically to put the space gun on a mountain or in the middle of the ocean.

Having said all that, I think I will throw some olive branches and wave some white flags here. The flexibility argument really is quite strong, pretty much unbeatable in the absence of an obvious high volume customer in a particular orbit. That alone means a sea-based space gun is the better idea (unless you come up with a land-based option with similar flexibility). The low fire rate (if it turns out to matter) can be solved by loading a magazine of payloads rather than one payload at a time (just like a real gun with a magazine can fire many times before reloading instead of just once). Finally, the sea-based design seems to have a more elegant method of handling recoil. The tube merely dips into the ocean, no need to mechanically transmit the recoil to a mountain side or support structure.
« Last Edit: 01/18/2010 04:43 AM by khallow »
Karl Hallowell

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #53 on: 01/18/2010 08:04 AM »
Eh, I looked and wasn't impressed. The only remaining issue is gravity sag. The sea launch will have bending from ocean currents and surface wind. The design should be able to handle slight bends in the barrel or it's going to have problems.

The remaining reasons (beside orbital flexibility) are gravity sag, mitigation of recoil issues on land for a 1km long gun (as both mentioned by you), range safety issues (none over sea, a lot over land), construction issues on a mountain side (you need to find a smooth, right angle mountain side for a 1km long gun, that doesn't have any geological issues shockwave wise etc.), financial issues for construction at an equatorial mountain side over 10,000 feet over sea level, logistics issues for a high-altitude launch side vs. a sea based launch side that can be supplied by a cargo ship etc.

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Further, it's unlikely that the small rockets used in these proposed space guns will use cryogenic propellants (like LOX).

If you are concerned about the heating effect during ascent, don't be. If insulation wasn't possible, you could forget about the whole thing in the first place, as your cargo would heat up as well, making fuel launches impossible either. After all LOX and hydrocarbon fuels shall be the main payloads.

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Having said all that, I think I will throw some olive branches and wave some white flags here. The flexibility argument really is quite strong, pretty much unbeatable in the absence of an obvious high volume customer in a particular orbit.

Good. Olive branch from my side too (we weren't really fighting, were we?). Anyway, I think I really hope they get to their orbital prototype stage (1kg to orbit). If they manage that, people will acknowledge it is possible and they might just find investors for a bigger version of their gun.

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The low fire rate (if it turns out to matter) can be solved by loading a magazine of payloads rather than one payload at a time (just like a real gun with a magazine can fire many times before reloading instead of just once).

The low fire rate (only 2-3 times per day, not more) is due to the peculiar features of a hydrogen gun, not so much because you need to reload it. I doubt a "magazine of payloads" will help here much.

Offline gospacex

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Re: A Cannon for Shooting Supplies into Space
« Reply #54 on: 01/18/2010 11:38 AM »
Ok, the flexibility argument can't be beat. I'll surrender at the end of my post, but first, some belligerent face saving.

1. There are other reasons for a water based gun launcher. They are listed on the first page of this thread. They alone make a sea based gun launcher far superior to a land based launcher (in the 1000 pound projectile class that we are talking about).

Eh, I looked and wasn't impressed. The only remaining issue is gravity sag. The sea launch will have bending from ocean currents and surface wind. The design should be able to handle slight bends in the barrel or it's going to have problems.

From the picture (all those rings and cables) it seems they plan for active control - cables are tensioned or loosened to slightly bend the barrel as required.

Offline Downix

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Re: A Cannon for Shooting Supplies into Space
« Reply #55 on: 01/18/2010 12:06 PM »
You know, the cannon-launcher and the rocket-launcher do not need to be mutually exclusive.  If you make a projectile with a solid rocket booster embedded inside of it, designed to fire once it hits the optimum point of its parabolic arc, (solid due to being less likely to break due to the gun firing itself) could solve the limits of the cannon launcher, while still saving a fortune compared to the classical rocket, for small loads.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline Lambda-4

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Re: A Cannon for Shooting Supplies into Space
« Reply #56 on: 01/18/2010 12:10 PM »
You know, the cannon-launcher and the rocket-launcher do not need to be mutually exclusive.  If you make a projectile with a solid rocket booster embedded inside of it, designed to fire once it hits the optimum point of its parabolic arc, (solid due to being less likely to break due to the gun firing itself) could solve the limits of the cannon launcher, while still saving a fortune compared to the classical rocket, for small loads.

That's what this proposal is about. 6km/s gas gun launch of a single stage rocket providing an additional 3km/s which gets you to a circularized lower Earth orbit.

Offline Downix

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Re: A Cannon for Shooting Supplies into Space
« Reply #57 on: 01/18/2010 12:20 PM »
You know, the cannon-launcher and the rocket-launcher do not need to be mutually exclusive.  If you make a projectile with a solid rocket booster embedded inside of it, designed to fire once it hits the optimum point of its parabolic arc, (solid due to being less likely to break due to the gun firing itself) could solve the limits of the cannon launcher, while still saving a fortune compared to the classical rocket, for small loads.

That's what this proposal is about. 6km/s gas gun launch of a single stage rocket providing an additional 3km/s which gets you to a circularized lower Earth orbit.
Of course now I wish I understood how guns are built beyond the basics so I could contribute to this conversation.
chuck - Toilet paper has no real value? Try living with 5 other adults for 6 months in a can with no toilet paper. Man oh man. Toilet paper would be worth it's weight in gold!

Offline JohnFornaro

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Re: A Cannon for Shooting Supplies into Space
« Reply #58 on: 01/19/2010 02:40 AM »
I gotta jump in too.  I like MagLev rocket assist to just under Mach 1.  Turns out that wasn't as much of an assist as I thought, and the cost of the infrastructure needed was very high.  It would certainly work better on the Moon, in vacuum, but hey.  That's just for background on one of my interests.

About the g-forces on mobile phones.  I dropped one in the driveway last year, and it didn't survive the g-forces of the sudden stop.  Hard to imagine COTS electronics withstanding the hi g-forces of the initial acceleration.  One ofthe comments about the article suggested 1721 G's  The article suggests 5K G's.

About launching propellant.  At it's largest incarnation, the payload is 1000 pounds of fuel in some sort of canister, which must be picked up by some sort of orbital tug.  Each one of those cannisters must be unloaded into the fuel tank of the intended spacecraft.  It sounds like filling a car with quart bottles of gasoline, and seems like an awful lot of moving parts.  Plus the tug vehicle would need to be designed, tested, built, launched and considered in the total project costs.  That $200/lb figure does not include these amortized costs, does it?

And then the depot design that "isn't        credible".  It's a struggle to accept such a design suggestion.  Why was it suggested?

$12M for a "prototype with a 1kg payload capability to orbit":  That payload must include the necessary fuel and thrusters to vector into orbit, correct?  That's unbelievably small, in my eyes.  Anyhow, Hunter is asking for $500M.
Sometimes I just flat out don't get it.

Offline khallow

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Re: A Cannon for Shooting Supplies into Space
« Reply #59 on: 01/19/2010 03:37 AM »

About the g-forces on mobile phones.  I dropped one in the driveway last year, and it didn't survive the g-forces of the sudden stop.  Hard to imagine COTS electronics withstanding the hi g-forces of the initial acceleration.  One ofthe comments about the article suggested 1721 G's  The article suggests 5K G's.

There are ways to improve the durability of electronics. For example, encase the bread board in a block of epoxy. You'll have heating problems (though probably not any worse than normal vacuum).

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About launching propellant.  At it's largest incarnation, the payload is 1000 pounds of fuel in some sort of canister, which must be picked up by some sort of orbital tug.  Each one of those cannisters must be unloaded into the fuel tank of the intended spacecraft.  It sounds like filling a car with quart bottles of gasoline, and seems like an awful lot of moving parts.  Plus the tug vehicle would need to be designed, tested, built, launched and considered in the total project costs.  That $200/lb figure does not include these amortized costs, does it?

That's the biggest drawback to large numbers of small payloads. You need additional infrastructure to take advantage of it.

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$12M for a "prototype with a 1kg payload capability to orbit":  That payload must include the necessary fuel and thrusters to vector into orbit, correct?  That's unbelievably small, in my eyes.  Anyhow, Hunter is asking for $500M.

Presumably, the rocket places the 1 kg in the desired LEO so that the payload doesn't require additional maneuvering capability.
Karl Hallowell

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