Doomsought
Well-known member
I can't think of any excuse for a gun launched missile where a two stage rocket would not avoid potentially lethal stress, except for the "We already have this tube, we want to have a missile as variant ammo".
I can't think of any excuse for a gun launched missile where a two stage rocket would not avoid potentially lethal stress, except for the "We already have this tube, we want to have a missile as variant ammo".
Spare me the mistaken sarcasm. Equating RAPs to rockets with space capable dV is like implying that any third world country with terrorists putting together shoddy Grads can also build a Falcon 9 too because both are rockets.Eh, I disagree. If you want to argue things that very nearly exist are impossible, you do you. I'm sure what we have in 2020 is the absolute limit of engineering. RAPs are super duper impossible engineering problems with no functional examples and no room for improvement if improvement was necessary. And not something that has been in development with functional prototypes and example since the 1980s.
Why would it suffer all that drag and gravity loss before reaching max speed rather than at the end of its range?Why do you think an AMRAAM has a delta v of 1,200-1500 m/s? It has a max speed around that, but that's something very different. Basic calculations suggest it would suffer something along the line of 4-6 m/s of drag at operating altitude and speed. Suggesting something like 250 m/s lost to drag, gravity losses may be another 250 m/s. So, were potentially already talking about 2 km/s delta v, in a missile that has to be optimized for the high drag environment of lower atmosphere against assumedly maneuverable targets.
Again, you forget the design mass tax plus engineering headaches added by cannon adaptation. For starters the rocket no longer can have super thin, barely sufficient to keep the rocket intact standing walls. Now it needs artillery shell walls. And similar issues apply to many other design elements. You save fuel for the first stage, at the price of making everything else lower performance and\or more expensive.One of the advantages of the gun is minimizing time spent in the densest part of the atmosphere, meaning you can focus more an high performance fuel, rather than a large low performance high thrust fuel, which balloons the overall rocket scale. Very high speeds low down would actually be counter productive, inducing more drag, making relatively low velocity guns better than high velocity ones on an efficiency measure.
My argument is that if your supposed cheap, spammable weapons requires a whole bunch of bleeding edge tech of the future to be even remotely feasible, it's probably no longer cheap and spammable, and if you have that tech available at all, there are better applications for it anyway.I just don't buy that this is particularly impossible, given all the other things we can do. Maybe missiles are cheaper or better for other reasons, in which case they would be more common. I am perfectly open to that argument. Your argument though seems to almost require a belief that what we do now, what we've been able to do since the 80s, is impossible. Not un-cost effective, impossible.
Okay, sorry, turns out I was wrong and these were partially solved problems in 1960s tech. I dramatically overassumed how novel the problems were.Spare me the mistaken sarcasm. Equating RAPs to rockets with space capable dV is like implying that any third world country with terrorists putting together shoddy Grads can also build a Falcon 9 too because both are rockets.
These shells have tiny sustainer motors that add mere tens to low hundred m/s over a relatively long time at the price of considerable payload reduction, with some of the boost being shared with the base bleed effect, not the kind of massive, high performance optimized motors you are talking about here. There is an insanely massive performance gap between that and space capable rockets.
Why would it suffer all that drag and gravity loss before reaching max speed rather than at the end of its range?
Also you forgot the speed of launching aircraft being part of the maximum speed.
Again, you forget the design mass tax plus engineering headaches added by cannon adaptation. For starters the rocket no longer can have super thin, barely sufficient to keep the rocket intact standing walls. Now it needs artillery shell walls. And similar issues apply to many other design elements. You save fuel for the first stage, at the price of making everything else lower performance and\or more expensive.
My argument is that if your supposed cheap, spammable weapons requires a whole bunch of bleeding edge tech of the future to be even remotely feasible, it's probably no longer cheap and spammable, and if you have that tech available at all, there are better applications for it anyway.
Marlet 3B
The Martlet 3B was similar to the Martlet 3A but using steel casings and attempting to solve some of the 3A model's other problems. The casings survived 5,100 feet per second (1,600 m/s), but the propellant failed at 3,400 feet per second (1,000 m/s). This was solved for later rockets by filling the propellant cavity with liquid, but only after developing the 3B model had ended.[32]
Martlet 3D
The Martlet 3D model was planned as a suborbital test rocket, using the first stage of the Martlet 4 solid rocket version. As the Martlet 4 was never built, no Martlet 3Ds were produced either.[32]
Martlet 3E
The Martlet 3E was a solid suborbital rocket designed to be fired from a smaller, 7-inch (180 mm) cannon used in the HARP project. Its basic concept revolved around packaging the rocket grain in a case with elastic properties to transmit the lateral strain to the gun tube. The 3E model utilized a new rocket grain construction technique that consisted of laminating sheet double-base propellant grain under hydraulic pressure.[14]
This is why earlier i said "go straight to battleship calibers". That's the only way to get required mass and size budgets to play around with militarily useful projectiles.Okay, sorry, turns out I was wrong and these were partially solved problems in 1960s tech. I dramatically overassumed how novel the problems were.
Project HARP - Wikipedia
en.wikipedia.org
Yes, but not with the limitations of a 155mm caliber, those barely got to high atmosphere with tiny payload. At minimum we are talking a stationary facility, cruiser, or giant SPG with something along the lines of a crazy long 8 inch gun.So, propellant grain and casing survivable to beyond what I needed the systems to do was a partially resolved problem in a relatively shoe string project in the 1960s.
Here, you can find diagrams of solid and liquid fueled rockets. Here's one with links to diagrams of the more common rockets launched in the program.
Martlet 3A
So, the big question this poses: is it possible to produce a lower performance gun in the future than was achieved in the 1960s? Mated with modern day tech used regularly by the military? Is 1960s engineering mated with modern day electronics a conceivable thing for the future to achieve? Could the future maybe even . . . exceed the accomplishments of a Canadian research program built on WWII surplus? Is such a thing conceivable?
By sheer required size alone, i don't think weapons with this kind of size are that cheap or spammable. We're essentially talking of something along the lines of a heavy to superheavy railroad gun, except with high elevation mechanism, put either on a stationary mount, but for purposes of not getting ganked easily, preferably put on some kind of rail system that goes into a tunnel underground or under a mountain for concealment and some degree of bombardment resistance.Your treating comparatively trivial problems that involve the refinement of 1960s capable tech as massive problems. Same as with the liquid fuel argument where you were also treating problems mostly resolved with 1960s-70s tech as grave problems that would make such a project in the future impossible.
Because for some weird reason the people with starships waging interplanetary war are less tech savvy than the 1970s.
So, my cheap, spammable weapons likely are actually going to be comparatively cheap and spamable, because the underlying technology isn't even 1990s tech as I was assuming with the W-82 example, but 1960s tech, refined! Apparently you you can actually reach the needed performance with sheet metal, no titanium or other exotics required!
Payload: 20 kg (44 lb). Gross mass: 155 kg (341 lb). Height: 2.15 m (7.05 ft). Diameter: 0.18 m (0.59 ft). Apogee: 250 km (150 mi).
The Martlet 3E was a full-bore, rocket-assisted, Fiberglas airframe vehicle 88.5 inches (2.25 m) long and 7.15 inches (18 cm) in diameter. The vehicle used six flip-out fins for stability, a straight tapered nose cone, and the recently-developed hydrostatic containment technique to support the rocket grain during launch. The launch weight of the Martlet 3E vehicle was 135 pound (61 kg) without payload, of which 94 pound (43 kg) was rocket fuel.
The Martlet 3E was initially designed to be launched at a velocity of 1200 m/sec (4000 ft/sec) from the HARP 7 inch guns with a 12 second ignition delay and a seven second rocket motor burn time. The specific impulse of the rocket motor was 280 sec./vacuum. The theoretical performance of the 3E would have allowed a 20 kg payload to be lofted to an altitude of some 250 km - well in excess of the Martlet 2 vehicles performance envelope. Higher launch velocities would have allowed heavier payloads or higher altitudes to be realized.
The theoretical performance of the Martlet 3A was for an 18 kg payload to be carried to an altitude of some 500 km at gun-launch accelerations of 12-14,000 g's and gun launch velocities in the range of 2100 m/sec (similar to the Martlet 2 series maximum launch parameters).
In what world the military payloads meant to intercept enemy spacecraft are a less demanding mission? And no, the payloads absolutely are not designed to withstand being fired from artillery anyway if they are being launched by other means...@Marduk
I'm not sure it does show that: for example, they also had 7 inch guns which also were able to achieve good mass ratios.
One can have stronger rounds, or more advanced rocket fuel to get away with lower muzzle velocity, lower payload needed through more advanced electronics, ecetera. The fact that the 7 inch projectile of the 70s only really needs marginal improvements to deliver needed effects strikes me as very reasonable.
The really large guns seem necessary for what HARP was working towards, namely payload delivery, with the end goal of a 3 stage orbital satellite delivery system.
This is a comparatively much less demanding mission, of delivering military payloads (which have to be designed to withstand being fired from artillery anyways) to a suborbital location.
Massively lower acceleration also doesn't seem to be the case with most of the HARP design: the long guns were used to achieve higher muzzle velocities, not lower accelerations.
Costs absolutely can skyrocket in artillery shells if you go for extreme ballistic performance. See: the cancellation of AGS... over shell costs.
As comparison, the artillery shell electronic ratings are for 15,500gs.
Assuming artillery exists, Archer systems being fairly standard equipment with forces seems quite reasonable, and based on all this having anti -orbit rounds available also seems quite doable: in military aerospace terms its fairly minor add ons to already existing systems: you already have the targeting computer, data links, artillery hardened electronics, control surfaces (to gimbal the thrust or veins, depending on what's optimal).
It doesn't actually have reason to all that much more expensive than existing guided shells, which are in the $80,000 to $40,000 range, especially when its an old, developed technology: an Excalibur round right now is still cutting edge in development limited run production. After a 100 years of development and refinement and million+ production run, costs can be pretty low relatively.
Missiles also have their place as more capable weapon systems, but something fairly small and low individual capacity seems like it could be quite useful too, while mostly using the future equivalent of off the shelf components.
From the sound of it, future's penny pinchers in the defense department trying to do orbital defense cheaply at any cost.Am I the only one mystified that one side in this fight explicitly has interstellar spaceships and we're presuming the ground forces have no better than 60s-modern tech?
Am I the only one mystified that one side in this fight explicitly has interstellar spaceships and we're presuming the ground forces have no better than 60s-modern tech?
In what world the military payloads meant to intercept enemy spacecraft are a less demanding mission? And no, the payloads absolutely are not designed to withstand being fired from artillery anyway if they are being launched by other means...
Also look at the acceleration figures mentioned in HARP. Intentional or not, there is a reason why the currently used guided shells have parts tested to 30,000g.
Who cares about mass ratios if your payload budget is 20kg and about 50-200 km short of typical spysat and space station orbits even if directly above the gun?
Downscaling so far with a gun based system is a terrible idea considering how it ends up with a system with minimal if any utility, pretty much no versatility, and no room for upscaling, unlike slapping boosters on rockets or scaling down payload in larger options.
Having either a meanngful reserve of potential altitude for non-vertical shots or second stage, maneuvering projectiles with separate dV reserve is necessary for these guns to have some kind of practical engagement area coverage.
Costs absolutely can skyrocket in artillery shells if you go for extreme ballistic performance. See: the cancellation of AGS... over shell costs.
The grand irony of this is that by that same line of thinking, it was supposed to be a relatively cheap and compact alternative to reduce the need for large and expensive Tomahawk missiles... Ending up with a cost similar to one.Long-range projectiles for Navy’s newest ship too expensive to shoot
At $800,000 per round, the Long Range Land Attack Projectile has been priced out of business.arstechnica.com
Shell costs are not magically mandated to be small, they are being kept small at the cost of compromising away more ambitious performance goals.
Secondly, why would any interstellar civilization maintain long production runs and expertise in them for what is essentially minimal performance defensive weapon of desperation?
If anyone would want this, it would be with their asses on fire, to be done within weeks or months.
1.WH40,when IG have units using Napoleon age tactic which still work,and best are like USA from Vietnam war.Am I the only one mystified that one side in this fight explicitly has interstellar spaceships and we're presuming the ground forces have no better than 60s-modern tech?
It does make me wonder what the technology on the invading interstellar spaceship is like. Steam? Oars?Well, one of us presumes ground forces will be able to, at the very least, duplicate the achievements of the 1960s, and may even, just maybe, surpass those achievements.
The other seems to believe gun and missile tech peaked in the 1950s, and is offended that the far future might, maybe, be able to do a bit better.
That seems to be the current argument, whether the future might be more advanced than the 1960s.
Well,in WH40 big guns on battleships are loaded by slaves.....It does make me wonder what the technology on the invading interstellar spaceship is like. Steam? Oars?
It does make me wonder what the technology on the invading interstellar spaceship is like. Steam? Oars?
There is a reason why tanks are armed with cannons, not hypertech ballistae firing tungsten bolts at 1500 m/s. There are limits to what certain technologies can do no matter what.Honestly, guns of some sort seem quite reasonable. Its hard to do better in a small package than chem guns. I could see something very much like the OTO-Melara could arm the patrol boats of the year 3,000.
Its quite hard to get better energy density than chemical fuels. As far as I'm aware, this generally requires either nuclear (which generally has handling or minimum scale issues) or some types of superconductors, which tend to be temperature finicky.
For a small boat/vehicle/spacecraft, chem guns/missiles are likely a viable contender for widespread use under quite a wide range of plausible tech.
Tech proliferation however can be quite funny with that stuff, including in military matters. For example, IRL most third world countries have supersonic fighter jets, even though very few are even close to being able to make those. It gets even more ridiculous with stuff like cellphones.Especially with the tech pyramid and power rules (80/20). If your space empire has a 1,000 inhabited worlds and 100 billion citizens, 1 planet (likely the capital) will have 25 billion, next closest 15 billion, 10 will have over a billion, 40 worlds with 300 million ish, 150 with 100 million pops, and 800 with sub 10 mil, many even sub mil, populations.
So, you might have your super advanced Clark tech, but only 5% of your planets have the scale and tech level to play the cutting edge game, and really its only the top 1% of planets are actual contenders providing 80% of the cutting edge tech, like FTL or advanced weapon systems.
These 76mm guns that barely reach orbit will be utterly useless against space commandos with a stealth bus, because actually detecting the bus in a timely manner allowing effective fire against it with such slow weapons will be something way beyond the capability of a C3I and sensor network of a planet desperate enough to rely on such crappy weapons.Meanwhile, 200 worlds should be quite capable of trivially producing a 76 mm cannon, and another 600 could produce it either in its entirely, or at least some parts of it, like basic shells and support structures, and only needing to import the guidance packages and precise lightweight motors, or such.
And the final 200 worlds too marginal to even produce 76 mm parts still likely need some level of protection, at least to the level where 30 rebels/commandos can't conquer the planet with a space bus. Super death beams may be more valuable than the entire colony, or at least cripplingly expensive to maintain on local economy/shipping needs.
Those would be *far* more useful against the commandos once they get to the ground, or at least below 20 kilometers.76 mm tanks/boats gives the local government enough firepower they can't be easily taken over by IRA/Al Qaeda type organizations, while adding a bit more friction to enemy actions.
Sounds like Ground Forces still have a role in interstellar warfare then.These 76mm guns that barely reach orbit will be utterly useless against space commandos with a stealth bus, because actually detecting the bus in a timely manner allowing effective fire against it with such slow weapons will be something way beyond the capability of a C3I and sensor network of a planet desperate enough to rely on such crappy weapons.
Those would be *far* more useful against the commandos once they get to the ground, or at least below 20 kilometers.
There is a reason why tanks are armed with cannons, not hypertech ballistae firing tungsten bolts at 1500 m/s. There are limits to what certain technologies can do no matter what.
With chemical guns, the limit is gas expansion rate. You either go to some truly exotic chemicals or gun technologies with their own issues, or switch to something completely different.
And... energy density is not everything. A railgun using the chemical energy stored in fuel powering some super-capacitors may be worse in energy density as a total system, but can fire slugs at mach 10 or more. Chemical guns won't do that, period, no matter what.
Tech proliferation however can be quite funny with that stuff, including in military matters. For example, IRL most third world countries have supersonic fighter jets, even though very few are even close to being able to make those. It gets even more ridiculous with stuff like cellphones.
These 76mm guns that barely reach orbit will be utterly useless against space commandos with a stealth bus, because actually detecting the bus in a timely manner allowing effective fire against it with such slow weapons will be something way beyond the capability of a C3I and sensor network of a planet desperate enough to rely on such crappy weapons.
Those would be *far* more useful against the commandos once they get to the ground, or at least below 20 kilometers.
No, energy density counts only as much as volume is a constraint.For a lot of roles though, such as a vehicle mobile weapon system, energy density counts for quite a bit. A 3,000 m/s muzzle velocity would also likely be quite worse for this job anyways. Its already a compromise vs missiles, a railgun takes all the problems of a gun system and makes them worse.
They are already there, not potentially imported if needed. As fourth hand hand-me-downs if nothing else.Sure, there are planes in Africa. There are very few planes built in Africa. The ability to import stuff doesn't really counteract my point any. When we are on one planet and nothing is more than a 24 hour plane ride away, importing stuffs a non issue (and even in that situation, maintaining a mechanized force there is difficult). If it takes some time to import things, that becomes a more pressing issue.
Yup. On the other hand, if you are going to bother making things locally, at least make them decent and with some export potential. Who wants weapons of desperation while they still have a choice as to what to import?Especially if space is particularly big travel time wise: it might take a week to get to the nearest system with a comparative hub of a 100 million, 6 months to the actual big planets. Relaying on things only made in the big two systems is increasingly questionable.
Welp, if they can make such large scale things, they should be able to make it either somewhat up to date, or make something, anything to sell and exchange for such.Of course, that bring in issues of how sustainable low tech colonies are. Somewhere with short sleave planets you can make do with pretty low tech. An asteroid its still an open question what tech level you can survive with that. Theoretically you get get by fairly low tech once you have a sealed habitat built and some source of light and heat to keep a biosphere going, but it seems somewhat pushing things.
It's an extremely shitty anti missile and anti orbit system. It's only tolerable as a point defense system in a multi role setup for ships right now.Open question though.
Sure, a 76 mm is a point defense weapon after all. The extended range is there mostly to, well, extend its threat range. Its primarily an anti-missile anti air weapon, with some anti orbit squeezed in so its not totally helpless.
Mostly self defense. You need the 2-3 stages in the 130 to 250 mm guns to get serious firepower, and even there its still primarily a harassment weapon. Though on smaller planets you can get quite a bit of range: 800 m/s puts you 40% to orbital velocity on the moon. An 88 Flak can apparently shoot roughly 180 km in such conditions.