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Post by Topaz on Mar 3, 2005 23:28:06 GMT
I wonder if the supagun had rifling!!! - the problem is wouldn't the cylinders start tumbling as soon as they left the "GUN", now i have noticed post stating that they maybe had retros/control jets for attitude control .... hmm ...it would take monumental control inputs to correct a cylinder that is tumbling around in space, look at the film Apollo 13 when the astronauts are trying to maintain the booster/lander in steady flight ...I don't know if that would be possible in say a 200ft cyclinder at planetary escape speed. For one, the RCS nozzles could easily be at the ends of the vehicle, like the Space Shuttle. With that setup, you'd have a leverage equivalent to half the vehicle length. The other factor is not to let the system get out of control in the first place. The F-16 is unstable - it'd tumble end for end if not for the computers constantly tweaking the control surfaces. It only takes tiny amounts of force to keep the thing straight as long as you don't let large movements develop in the first place. The cylinder is in a similar situation, but without aerodynamic control surfaces to create the control forces. The shape is (edit 3/4/05 - aerodynamically) unstable, so it would take an active control system to keep it going straight. That could be an RCS system as much as anything else. You could use rockets to brake to orbit first, as you say, which would increase landing accuracy. The penalty is the weight of fuel you'd have to launch to do that. Another option is aerocapture, where you dive into the atmosphere enough to slow yourself down to orbital speed, then exit again and fine-tune with rockets into a stable orbit. The fuel penalty is smaller, since you only need enough to slow down out of orbital speed - although there is an additional small penalty in increased heat-shield weight. You have to do an entry twice to complete your landing. The NASA really wants to use aerocapture on future unmanned missions, since it results in a smaller, less expensive rocket booster for the original launch. The Martians would gain the same advantage, in terms of a lower performance requirement for the gun.
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Post by TOMAHAWK on Mar 3, 2005 23:44:23 GMT
Ahh but it would have to be a pretty sopisticated piece of kit the martians had controlling the cylinder ..i mean
bang ..cylinder shot up out of gun.....presumably at great speed ..NOW our rockets have fins, plus the speed is gradual ...the acceleration out of the gun would be tremendous ....that means the RCS would have to be working practically stright away ...as again the cylinder doesn't appear to have any other Stablity devices.
Now how big would the RCS have to be to maintain/manouver a big fully loaded cylinder banging in at high speed, were manouvers will be amplified , compared to a shuttle which doesn't use any powered momentum in space (it don't use it's engines) so the RCS can be small and you wouldn't need to use much in the way of RCS jet to perform the required manouvers.
wouldn't the RCS jets be CONSTANTLY firing off on the cylinder for the whole of it's journey, as the would be counteracting each other the whole time to keep it in a stright line (bearing in mind the cylinder is travelling at interplanetary speeds )
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Post by Topaz on Mar 4, 2005 0:00:23 GMT
Ahh but it would have to be a pretty sopisticated piece of kit the martians had controlling the cylinder ..i mean bang ..cylinder shot up out of gun.....presumably at great speed ..NOW our rockets have fins, plus the speed is gradual ...the acceleration out of the gun would be tremendous ....that means the RCS would have to be working practically stright away ...as again the cylinder doesn't appear to have any other Stablity devices. Now how big would the RCS have to be to maintain/manouver a big fully loaded cylinder banging in at high speed, were manouvers will be amplified , compared to a shuttle which doesn't use any powered momentum in space (it don't use it's engines) so the RCS can be small and you wouldn't need to use much in the way of RCS jet to perform the required manouvers. wouldn't the RCS jets be CONSTANTLY firing off on the cylinder for the whole of it's journey, as the would be counteracting each other the whole time to keep it in a stright line (bearing in mind the cylinder is travelling at interplanetary speeds ) The shuttle stack is also unstable during launch, so it requires active stabilization too, although this is done by gimballing the large rocket motors. The F-16 does this trick every second it's flying, so the technology, while complex, is nothing we couldn't do as of the 1970's. The control system would be most active during any phase that's flying through an atmosphere. It's the airflow that makes the cylinder unstable. Yes, the system would be very active during launch and re-entry. In space, the cylinder is 'coasting' just like the shuttle, so the RCS would likely only fire occasionally in response to the Martians moving around inside. Tiny moments like that could easily be countered instead by relatively small gyroscopes, as Lensman suggests. The ISS is controlled in that fashion most of the time as well, although it also has an RCS system for backup and large maneuvers.
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Post by Lensman on Mar 5, 2005 4:03:59 GMT
In a pure metoritic impact the earth wouldn't have just "splashed" it would have -exploded- outward, probably digging a quarter mile crater... We all seem to be in agreement that the cylinder did not hit with full meteoric speed, somewhere in the neighborhood of 25,000 mph. We're just arguing over the degree, and method, of slowing down before it hit. If it *had* hit without slowing, and the mass is that indicated by a shell of solid metal about 2 feet thick and 90 feet across, then the impact would probably have been even greater than the Arizona meteor crater, which IIRC is a mile across. You are simply not going to convince me that the cylinder slowed to less than a few hundred MPH. It must have hit with at least that speed-- there's no other reasonable explanation for Wells' description of the earth "splashing." You can call it an "explosion" if you like, but an explosion isn't required to create a crater pattern. Try dropping steel balls into a pan full of flour; you'll see the same splash effect, the same crater pattern, just like an asteroid impact. Very different than just "digging in."
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Post by Lensman on Mar 5, 2005 4:16:01 GMT
To quote, the guys at Armidillo Aerospace, "Rocket Science isn't complex, it's just not -common-" <snip> Solid fuel rockets are even simplier, and I don't see any good reason to rule them out, either... Wow, Lanceradvanced: I'm really, really surprised you'd bring up the example of Armadillo Aerospace. Have you read their online "progress" logs? "Lack of progress" is more like it. Reading over those is a very good lesson of just how complicated rocket science is. Putting a small single rocket onto a test stand and test firing it is not too horribly complex, you're right. Some model rocket enthusiasts get up to that level of expertise; see also the autobiographical book Rocket Boys, which became the wonderful movie "October Sky." But add in controls, vectoring and steering, multi-rocket systems, fuel pumps, cutoff system, etc. etc... and it gets very complex, as Armadillo Aerospace has discovered to its sorrow. That's why the term "rocket science" is a synonym for something very difficult and complex. You don't see any reason to rule out solid rockets? There's an excellent one: You can't shut them off once they're lit. Not exactly what you want for a controlled landing!
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Post by Lensman on Mar 5, 2005 5:43:53 GMT
bang ..cylinder shot up out of gun.....presumably at great speed ..NOW our rockets have fins, What happened to the fins after the cylinder landed? No, there were no fins. ...the acceleration out of the gun would be tremendous ....that means the RCS would have to be working practically stright away ...as again the cylinder doesn't appear to have any other Stablity devices. None were seen on the part of the cylinder seen by earthmen. No holes near the end as would have been present for RCS. Ergo, no RCS. The stabilization system was most likely internal. As I said: Gyroscopes. wouldn't the RCS jets be CONSTANTLY firing off on the cylinder for the whole of it's journey, as the would be counteracting each other the whole time to keep it in a stright line (bearing in mind the cylinder is travelling at interplanetary speeds ) Why? The Mercury, Gemini and Apollo capsules were allowed to spin randomly during missions. The only time it's important to be oriented in a certain direction is during firing of the main rockets, orientation for proper reentry angle, and duriing astronomical observations. Certainly there's no need to keep the thing absolutely stable for the entire trip. Since we can't use fins, then we either need honkin' big internal gyroscopes, or-- a better solution-- the capsule is spin-stabilized. As long as the G-force from the spin is .4 G or less, there shouldn't be any problem. Even relatively small gyroscopes can be used to gradually bring the spin up to speed, or to stabilize it during flight when necessary. Oh, and from the cylinder (and the Martian crew)'s point of view, Tomahawk, they're not "travelling at interplanetary speeds," they're just drifting at rest in zero-G. It's not any more difficult for them to stabilize their motion than it would be if they were in orbit. For most of the journey, the only way they can tell they're moving towards earth and away from mars is by looking thru a telescope.
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Post by Lensman on Mar 5, 2005 6:02:21 GMT
The fireball from the propellants certainly created an explosion, but not a detonation which would've created a strong blast wave. The problem I'm having with your statement is that the dictionary definition of "detonation" is synonymous with "explosion." I guess what you mean is the explosion had a very low energy yield because the hydrogen was still in liquid state; it was very cold and therefore much of the heat and expansion of the explosion was taken up with heating the hydrogen. That doesn't mean "It wasn't a detonation." It means "The detonation had a relatively low energy density." I've done a little initial research already and any kind of 'conventional' gun isn't going to cut it, much for the reasons you state above. What, we agree on something?? 'Scuse me, I need to run out and buy a lottery ticket! Any system that's going to meet the requirements has to keep adding gas to the gun to keep the pressure relatively constant, and so keep the G-loads lower and also fairly constant. I've started working up a hybrid of staged combustion and light-gas guns. More to come as I have a little time to put the information together. Hmmm, I have no idea what you mean, but you've certainly proven you know more about rocket systems, propulsion, and the math involved than I do. I look forward to more details.
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Post by Topaz on Mar 5, 2005 6:15:01 GMT
The problem I'm having with your statement is that the dictionary definition of "detonation" is synonymous with "explosion." I guess what you mean is the explosion had a very low energy yield because the hydrogen was still in liquid state; it was very cold and therefore much of the heat and expansion of the explosion was taken up with heating the hydrogen. That doesn't mean "It wasn't a detonation." It means "The detonation had a relatively low energy density." Perhaps my use of the word 'explosion' is the problem. My gasoline-into-a-torch analogy is probably the best one. The combustion was accelerated by the load of LOX mixed with the hydrogen fuel, but it's still essentially plain combustion. The report I read was pretty clear that the shuttle broke up from aerodynamic forces, not the fireball from the released propellant, and that's the essential part of the point I was making. I'll diagram out the 'gun' concept once I get a chance to get the first part of the analysis done. I'm a little under the weather at the moment and not feeling particularly like doing the math.
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Post by Lensman on Mar 5, 2005 6:24:00 GMT
I wonder if the supagun had rifling!!! - Since Topaz won't let me use gyroscopes of reasonable size for stabilization, then I presume it did, for spin-stabilization. Dunno how rapid a spin is necessary for reasonable stabilization, tho. If the centrifugal force* from the spin is more than .4 G, then the Martians have a problem; altho one might argue that any force up to 1 G would be acceptable, for obvious reasons. *If anyone reading this is one of those ivory-tower physicists who try to insist "there's no such thing as centrifugal force," then I don't want to talk to you. ;D
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Post by Lensman on Mar 5, 2005 6:32:22 GMT
I'm a little under the weather at the moment and not feeling particularly like doing the math. Sorry to hear that, Topaz. I *am* enjoying our discussion/ debate, even if I get a bit cantankerous at times. Be well!
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Post by Lensman on Mar 5, 2005 6:39:48 GMT
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Post by TOMAHAWK on Mar 5, 2005 13:34:44 GMT
Lensman ; When I said OUR rockets have fins , I meant that WE have fins to stabilize the rockects ...I dodn't think the cylinders had fins which lead me to the problem of it tumbling shortly after leaving the gun, also
If the cylinder is spinning due to rifling ...then are the martians spinning inside also ...some very sick martians!!!! or is the cylinder double walled , ie the martians are in a stable area and the outer walls of the cylinder rotate,
that leads me to this point ....look at a spinning propeller , a plane tends to head (or is easier to turn to the direction of travel of the prop) you counteract this with a rudder...Now if the cylinder is spinning clockwise, won't the gyro's have a hard time trying to counteract this spin, i can imagine it will be fishtailing around ...., but there must be power source or jets to control its say left / right movement as the thing doesn't have a rudder.
A V1 flying bomb used gyro for control ...ok in stable flight but ...
A the thing wasn't spinning and it had wings for stability B the slightest knock put the gyro out and the thing crashed (Brit pilos used to tip its wings)
If you took the wings off a V1 and its engine then you more or less have a miniture cylinder ...now launch that from a gun/rail ...and BANG ...gyros or not ...its just gonna tumble end over end ...Given that all the weight would be at it's nose ..it's gonna pitch down stright after launch..
Now we dont know how the martians distributed the weight, but I presume with the nose of the cylinder being used to hit and dig the crater then i suspect all the weight was to the middle / rear ... now wouldn't that make the nose pitch UP ..
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Post by lanceradvanced on Mar 5, 2005 15:34:46 GMT
...then are the martians spinning inside also ...some very sick martians!!!! Or some very happy martians to have centrifugal gravity during the trip from earth to mars....
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Post by lanceradvanced on Mar 5, 2005 15:45:31 GMT
Wow, Lanceradvanced: I'm really, really surprised you'd bring up the example of Armadillo Aerospace. Have you read their online "progress" logs? "Lack of progress" is more like it. Reading over those is a very good lesson of just how complicated rocket science is. I've also seen their videos of their test flights, and rigs, and heard how one of their major problems with being able to go ahead with later flights was obtaining peroxide, All in all, I was rather impressed with their "lack of progress" And perhaps misleading, when you compare it to the complexity of other "sciences", or more precicely, the devices they produce.
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Post by jeffwaynefan on Mar 5, 2005 15:46:25 GMT
Now that would make a great ride at Alton Towers.
'Roll up, roll, up, step right this way. Ladies and gentlemen, boys and girls, time to be amazed, time to be captivated, time to look in ore at the worlds first War Of The Worlds Martian Cylinder Controlled Landing'
Comes complete with free martian soft toy, photo of you on ride and a souvenir sick bag.
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Post by lanceradvanced on Mar 5, 2005 16:10:34 GMT
You are simply not going to convince me that the cylinder slowed to less than a few hundred MPH. It must have hit with at least that speed-- there's no other reasonable explanation for Wells' description of the earth "splashing." I don't have a problem with them coming in at a few hundred miles an hour, that only takes free fall from a mile or so up, but the "uncontroled" descent with aerobraking, even if combined with shock absorbant couches, and some other shock absorbing system, simply isn't adequte to slow them to that degree. Coming in at the speeds that kind of descent impiles, even if it was surviable would have resulted in a far larger crater than wells describes... You're missreading me... an explosion is what you get if the cylinders had come in uncontrolled, even with aerobraking you get a heck of lot bigger hole, and the the surrounding country side is so leveled that the narrator and curate get turned into paste... The earth is gonna move regardless of how they come in, you've got a enormous volume to excavate, very quickly it's gonna look the same almost regardless of the method used to move it.
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Post by TOMAHAWK on Mar 5, 2005 16:13:19 GMT
lol, what with free entry to the lazer ...sorry Heat ray quest ....hmm the winner is the that doesn't come out melted ...no under 5's allowed
Get your souvenier piccy of yourself being drained of blood by the HM only £5 (to be presented after you have recovered in hospital ..or in certain circumstances at your bedside!!!!!!!!) ..see terms and conditions No refunds on death
or what about paint ball, but with heat rays ..now that would Rock!!!!!!!!!!!!!!!
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Post by TOMAHAWK on Mar 5, 2005 16:17:27 GMT
What if the cylinder has a sort of screw tacked onto the front and if the cylinder is spinning then that would allow it to dig itself into the ground...would that not lessen the intial force of the landing if it is already digging through when it hit ..the only prob in stopping
That seem to be a point ...just how did the martians stop, what was to stop them ploughing 50/100 ft down into the Earth, they would be pretty chuffed at that
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Post by Lensman on Mar 6, 2005 5:39:18 GMT
Lensman ; When I said OUR rockets have fins , I meant that WE have fins to stabilize the rockects Sorry; my bad! ...I dodn't think the cylinders had fins which lead me to the problem of it tumbling shortly after leaving the gun, also If the cylinder is spinning due to rifling ...then are the martians spinning inside also ...some very sick martians!!!! Only if the Martians are located on the axis of the cylinder. If they're closer to the outside wall, they won't experience a spinning motion, but rather "artificial gravity" from centrifugal force. Obviously we don't want the cylinder-- and the Martians-- to spin too rapidly; not as fast as a rifle bullet spins. or is the cylinder double walled , ie the martians are in a stable area and the outer walls of the cylinder rotate, Tempting, but I think that would violate the "Martians don't use the wheel" rule. In fact, I think that's a weak place in my advocacy of gyros... weights evenly spaced around a circle and spinning on an axis is getting awfully close to a wheel. Maybe there's a way of generating gyroscopically stabilizing force without using what we think of a gyroscope, but I can't think of it. if the cylinder is spinning clockwise, won't the gyro's have a hard time trying to counteract this spin, i can imagine it will be fishtailing around ...., but there must be power source or jets to control its say left / right movement as the thing doesn't have a rudder. Nope. You've got a series of gyroscopes mounted in a series of different locations and orientations to control yaw, pitch and roll. The series of gyroscopes replace rudder, wing flaps and ailerons. You could set up a series of governors on the gyros to automatically compensate if the cylinder's spin becomes crooked. Gyroscopes would not have any harder time compensating for spin in any one direction than any other. Gyroscopes can be spun in either direction; you spin them in the direction opposing the cylinder's spin to stop the cylinder from spinning in that direction. A V1 flying bomb used gyro for control ...ok in stable flight but ... A the thing wasn't spinning and it had wings for stability The primary purpose of the wings was to let the buzz bomb fly thru the air, not for stabilization. I didn't remember they were gyroscopically stabilized, but if so then perhaps we can refute Topaz' assertion that using gyros for stabilization would take up an unreasonably large amount of the cylinders' internal space. B the slightest knock put the gyro out and the thing crashed (Brit pilos used to tip its wings) So what's your point? That a sufficiently large outside force could send it spinning out of control? Granted. The same is true of any control system. If you took the wings off a V1 and its engine then you more or less have a miniture cylinder ...now launch that from a gun/rail ...and BANG ...gyros or not ...its just gonna tumble end over end ...Given that all the weight would be at it's nose ..it's gonna pitch down stright after launch.. No, the cylinder emerges from the end of the space gun with more than Mars' escape velocity. It's going so fast that it zips thru the thin Martian atmosphere in just a few seconds. Presuming the space gun has rifling to impart even a relatively slow spin to the cylinder, there's not even any need for gyros on launch. What you need the gyros for is to stop the spin (after it's left the atmosphere*), stabilize it when you want to make telescopic observations, orient the capsule for landing, and start the spin again for landing sequence spin-stabilization . *...or not, if you want the Martians to have artificial gravity all the way. Come to think of it, it might be a good idea to expose them to gradually increasing artificial gravity all the way... Now we dont know how the martians distributed the weight, but I presume with the nose of the cylinder being used to hit and dig the crater then i suspect all the weight was to the middle / rear ... now wouldn't that make the nose pitch UP .. The whole point of spin-stabilizing, or gyroscopic stabilization (which is just a different way to spin-stabilize something) is to prevent just that sort of thing from happening.
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Post by Lensman on Mar 6, 2005 5:51:02 GMT
one of their major problems with being able to go ahead with later flights was obtaining peroxide They had all sorts of problems with the peroxide, especially getting the the silver catalyst screen to work properly. Eventually they abandoned their attempt to use peroxide because it was no longer available in industrial quantities. They've gone "back to the drawing board" and are now experimenting with more conventional, separate fuel and oxydizer. At least, that's what I read the last time I made any serious attempt to read their logs, a month or 2 ago. All in all, I was rather impressed with their "lack of progress" I guess that depends on how you look at it. If you look at it as a few guys (and one gal!) puttering around in their garage, I spoze it's impressive. As compared to the Scaled Composite SpaceShipOne project-- professional aerospace designers & engineers with a history of building custom-designed aircraft, which started long after Armadillo Aerospace did, and zipped ahead of them in just a few months-- it's not.
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