Morning Discussion: Ada Lovelace Day
I don't particularly have a female tech hero but I've always been a fan of Aleks Krotoski. UK Shackers might recognise her from Bits, a late-nineties video games TV show hosted by three women which was quite clearly aimed at teenage boys. Bits was slightly cringe-inducing but it was exciting for me as Aleks and some of the other presenters clearly knew their stuff--Emily Newton Dunn went on to produce the Burnout series for a while, by the way. There hadn't been a strong female gaming figure on British television since the wonderful Violet Berlin in Bad Influence! four years earlier and it was great to have some again, no matter how awkward the wrapping was.
Aleks later came to write, blog and podcast about games and technology for The Guardian--a most respectable position--and earned a PhD with her thesis Social Influence in Second Life: Social Network and Social Psychological Processes in the Diffusion of Belief and Behaviour on the Web, speaking at tons of conferences and advocating more women in tech and the media along the way.
Her most recent foray into television involved interviewing technology luminaries including Tim Berners-Lee for the BBC documentary series The Virtual Revolution. That's an impressive progression and fine inspiration to us all. Cheers, Aleks.
And hooray for Ada Lovelace, arguably the world's first computer programmer.
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What twist of the laws of physics do you think has been most beneficial in video games? The ability to absorb hundreds of bullets and still keep going in DOOM? Running up the wall in Strider? Firing a railgun from your shoulder in Quake 2?
Do you think a recurring theme, like being able to jump 47 feet in the air, takes the cake, or is there one specific instance, like Gordon Freeman toting around a particle accelerator and a gluon gun on his back?-
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Yeah, came out yesterday (474mb download, free if you have the Cerberus Network):
http://ve3d.ign.com/articles/news/53881/Mass-Effect-2-Hammerhead-DLC-Released-Something-New-Happening-Monday
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AFAIK there are no rail guns that have an up & down orientation for the rails. They are always parallel at the bottom of the configuration so that gravity can hold the projectile. And I'm pretty sure, but I am not a railgun scientist, that the projectile recoils against the force moving it forward, which in this case is a moving magnetic field, not the rails themselves.
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If you're curious, here is a paper (with experimental data!) about recoil in a railgun: http://iopscience.iop.org/0022-3727/20/3/023;jsessionid=CCA4D33C3067215DCF29B3EB6D7D5100.c3
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Obviously you read the abstract? In relativistic electromagnetism the recoil force of a railgun should act on the magnetic field and absorb field energy-momentum. The Ampere-Neumann electrodynamics, on the other hand, requires the recoil forces to reside in the railheads and push the rails back toward the gun breach. Experiment confirms the latter mechanism.
And relativistic electromagnetism is what most of us probably learned in school. http://en.wikipedia.org/wiki/Relativistic_electromagnetism
In theory a rail gun has no recoil, but in practice it's shown it does. It has absolutely nothing to do with the plane on a treadmill, which even in theory is obvious to anybody who took basic science, but I appreciate you trying to throw a jab in there some place.-
Actually, a railgun will have the same recoil as any other gun with equivalent muzzle velocity, both in theory and in practice, and this should be obvious to , in your words, anybody who took basic science. Basic conservation of momentum, which holds in all fields of physics, requires that launching a projectile one way imparts a recoil in the opposite direction. I haven't read the abstract or the paper mentioned above but I can guarantee you that no practicing physicist would ever claim that a railgun shouldn't have recoil.
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I definitely think it's interesting, but I wouldn't say "surprising" just because I don't know all that much about the two types of electromagnetic theory they're talking about and what the differences are. Or put it this way: I don't find it surprising that a theory has some small flaw that predicts the wrong outcome. I would find it surprising if a physicist who should know better was convinced that there would be no recoil because of it.
It shows why data and experimentation is king though. 99% of the stuff in relativistic electromagnetism theory might be spot-on but one missed piece of the puzzle or one faulty assumption could have led that theory to produce an incorrect prediction. It's a lot easier to fix a theory when you have indisputable evidence that you went wrong somewhere.
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Recoil on a normal gun is caused by the expansion of gas as the charge inside the bullet casing explodes - this blast is what propels the bullet out of the barrel. This pressure is also what forces the bolt back on semi-auto and automatic weapons, allowing them to chamber another round.
Magnetic railguns function differently - essentially, a piece of metal is placed in the 'chamber' and a magnetic charge is run down the sides of the barrel, bringing the metal bullet along with it. There are no moving parts, and there's no explosion/pressure wave.
The problem right now with railguns is both miniaturizing the power supply required to produce the magnetic charge, and developing conductors along the barrel that can pass the magnetic field fast enough to prevent the bullet from being attached to the side of the barrel and fusing with it.-
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It still has recoil. The electromagnets are propelling the object forward and being pushed in the opposite direction. They push against their housing (the railgun linear accelerator) and that pushes back against you.
So yes, they recoil. The one the Navy has in testing right now is a floating barrel because it travels a few feet each time it fires.-
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I'm not sure if we disagree here or not. I was pointing out that conservation of energy is different than conservation of momentum. AFAIK you cannot have a loss off momentum in the system like you can with the loss of kinetic energy. Kinetic energy of the system can be changed because it was changed into various other types of energy. However momentum cannot be lost as other forms of energy.
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Kentor linked part of the show above, but when they talked about the barrel they made no mention of it being freefloating http://www.youtube.com/watch?v=4OqlTXwLG40
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It still doesn't matter. recoil is there, maybe it's negligible but it's there. Magnetic force pushes both directions, on the projectile and in reverse.
Watch the VIDEO http://www.youtube.com/watch?v=mROlo4Wz1mI
recoil in action -
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Any self-contained system that flings a chunk of metal in one direction is going to feel recoil in the opposite direction. No matter what all forces are going on in that system, the net force is inevitably going to be recoil in the opposite direction from the projectile fired. There's just no way around that unless you have a self-propelled projectile or a counteracting force, like in the case of a so-called recoilless rifle.
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Newton would like to have a word with you.
http://www.physicsclassroom.com/Class/newtlaws/u2l4a.cfm-
Seriously, this whole subthread is mind blowing. Projectiles that are not entirely self-propelled generate recoil. Yes, you're using magnetic fields to propel an object, but those magnets aiding the object's propulsion need to be braced somewhere, within something, lest they fly off in the opposite direction.
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I generally agree, although having your HP refilled after every battle in FF13 was a great idea. I never did like having to spend so much time healing up after battles all the time. And, in spite of this, it's still plenty challenging.
But yeah, health regen in shooters is fucking lame. I think Far Cry 2 has the best injury management so far. You aren't hardcore until you flick bullets out of your arm with a knife and cauterize the wound yourself.-
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I liked that you would heal a Hitpoint if it wasn't completely bled out, unless it was one of your last two.
Also, Vietcong had a good mechanic. You'd take a hit, then bleed a little more if not bandaged immediately. Then, your permanent health was decreased by a percentage of the wound (like you get caught by an AK leaving you with 30% health, after you heal, your Max Health will be like 90%). And your Squad Medic can heal you more efficiently (often with no degradation).
Men Of Honor also had a "bleed out" mechanic. I don't remember it exactly, but I think it was similar to Far Cry 2's, if you take a hit bringing you below a certain threshold, it will bleed you out unless/until you bandage it.
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It works in some games. The "oh shit" rush to cover as your screen darkens is a nice addition, but it needs some tweaking so that it's not just a safety net.
I'd like to see it evolve to slow health regen (minute(s), not seconds, or only out of combat, similar to what we've had in RPGs for ages), and then usable inventory items for fast regen or instant heal.
Ducking behind a wall and having to decide if you want to use one of your five remaining bandages or if you think you can survive the fight without it and walk it off after the area is clear.-
Stalker did this best imo. You could equip artifacts that would slowly regenerate health over time. You carry bandages that restore a little health and stop you from bleeding. You also carry first aid kits that restore a large amount of health. And the bandages and kits have their own keypresses. A good system, but it could have been better by having a short cooldown time between first aid kit uses, because you could just spam the first aid key if you were in a difficult fight.
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I'm not so sure. It allows devs to make enemy encounters more challenging without having to shower you with healing items every 5 feet.
I definitely like the feeling of having to work through an entire area without accumulating too much damage, but regenerating health does allow for enemies to be more aware and deadly.
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Removing the need to hunt around for health kits (busy work) to top off your health is brilliant, but the fact it affects the pace of battle makes it suck to see this in EVERY GAME EVER NOW.
I'd rather see it be much slower, enough you wouldn't do it mid-fight, or see health auto-regen at the end of fights (which would be very videogamey, but what isn't). -
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The Colon of Holding has got to be pretty high up there. A character's ability to carry massive quantities of weapons, ammo, grenades, tools, armor, money, and random crap, irrespective of the physical bulk of the items and despite the character not wearing so much as a knapsack, is pretty integral to a lot of games.
As to the name, well, all that stuff has to go somewhere. -
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It was more a comment about flight sim style space shooters.
There's nothing really stopping missle locks in space. But everything would occur orbiting something else. It'd be pretty pointless to use a projective with propellant and a navigation system in space for long ranges. Anything with enough mass or energy to do damage to another ship would have to be so large it's delta V capabilities are going to be less than any target of value. Since you have to atmosphere to push against for course changes, all changes will be made with energy from Delta V. Given the amount of energy to alter orbits (all space battles would be orbiting _something_) it just isn't a very effecient way of trying to intercept another craft. Unless you are talking about really short ranges where two "capital ships" line up and broadside eachother with torpedos. But that'd be a pretty stupid strategy in space.-
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More generally you're changing relative velocities.
The flip side is that your target has just as much difficulty changing velocity as your missile does. Possibly more. That sort of implies that there's an envelope of ranges, dependent on your velocity, your target's velocity, your missile's maneuver characteristics, and your target's maneuver characteristics, where you can fire a missile and it will be capable of intercepting the target. Essentially the missile can apply enough acceleration to put itself in the target's path, and the target can't apply enough acceleration to avoid the missile.-
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You might think so, but you are forgetting that the missle would have to travel at much much higher velocities in order to intercept the craft. Higher velocities means more deltaV to make minor changes.
The target craft could make one minor inclination change and the missle would have to make the same change with an order of magnitude higher deltaV to alter its own orbit.
If the target craft continually "side stepped" via small degree changes, the missle would run out of deltaV long before a long range craft would.
As a matter of rule, missles do not have more range than what launches them. Range here isn't the issue, it's amount of DeltaV to make course changes.
When a missle is trying to intercept a moving target in space orbiting another body, you can't just make a burn and "go that way". The velocity the missle is already carrying is already making you go on a specific orbit.-
Yeah and that means your missile's velocity would be limited by various factors unlike what we traditionally think of with a missile, where you fire up a rocket on full burn and point it at the target, and it makes small course corrections to what's otherwise a straight line. I just made a post somewhere below about this same thing, so I won't just copy it here.
So like I said, I do think the missile would have an easier time course correcting than a large target. It just wouldn't work at any arbitrary velocity. Maybe you need a missile that has more delta V capability by two orders of magnitude, then its speed can be higher by one order of magnitude or whatever.
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Since science tells us we won't get near light speeds, this doesn't really apply.
Missiles (smaller self propelled rockets) will always be more maneuverable and have potential acceleration greater than a large ship with high mass. Unless you are already moving away at a speed that is faster than the missile can reach and over take, you should get caught, even with changes in course. Orbital factors don't really come into play for the missile itself, only the target and assailant.-
It absolutely applies. If you're shooting at something several light-seconds away, what you're actually seeing is where the target was and what they were doing several seconds ago. You can shoot at them based on that, but there's no guarantee that they haven't changed their velocity in the mean time. That will throw your shot off and make targeting much more difficult.
Orbital factors (more generally, relative velocities) apply because your missile is going to have the same initial velocity that your ship does.
In space, there is no distinction between maneuverability and potential acceleration. Missiles have high potential acceleration, but it's relatively short-lived. Their fuel stores are sharply limited. The more acceleration they use increasing velocity, the less they have available for maneuvering and the more acceleration required to maneuver. That's what makes targeting hard at long ranges.-
you are bringing science fiction into this argument about what will or wont work. We have no way to approach light speed, near light speed, or anything remotely fast enough that would be measured in light seconds and affect tracking and targeting. At least nothing that we would be targeting with weapons. If it was that far away, it's not going to be caught with a missile. You aren't shooting a long range vehicle at a target, you are shooting a missile. I'm probably talking distances under 100 miles.
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Just hypothetically, wouldn't larger fuel stores be conceivable with, say, an onboard Mr. Fusion or (even more hypothetically) anti-matter / matter reactor? I'd imagine you could have a huge energy supply from a small amount of mass, certainly orders of magnitude more power per gram than any chemical accelerant.
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Hitting a target with a missile would be no more difficult than launching a fighter and commanding it to ram the target. You'd essentially need a cruise missile kind of concept with on-board guidance that constantly adjusts course as it gets closer and its measurements are known to be more up to date.
It would be more about active guidance and less about predicting where the target will be and then burning through all the fuel to get there as quickly as possible.-
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Of course not, and I didn't say that. On board computers would have to calculate the necessary thrust to course correct to an intercept. There would be some amount of uncertainty in that intercept based on the capabilities of the target. I imagine your missile's speed would be limited by the product of that uncertainty and the limitations of your missile's ability to course correct, as well as other factors like the relative motions of the attacker and target, and what kind of approach angle that would produce, etc.
Does that sound better? -
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Accelaration is not the problem. It's changing course.
To intercept a target "ahead" of you you need to go faster than it is currently going. These courses aren't straight lines, they are orbital lines. The faster the velocity, the more energy required to change course. You aren't intercepting relative from the attacker to the target. This is where you are making your mistake. You are launching a missle, altering the missle's orbit to intercept the target. So now they are on an intercept course if the target becomes aware of the projectile, it can alter it's course slightly, with a small amount of delta V. Now the amount of delta V required to alter the projectiles course to fit the new orbit is much much greater because the projectile is traveling at a higher speed.
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If you really want to get into this and have any propensity for math, go google hoffman transfers or one tangent burns for equations. Then make the velocity for the "missle" 100x greater than the intercept target. Then alter the target's orbit by a miniscule amount. Redo the burn equatrion and you are in for a suprise.
We can debate this all damn day, but the equations for orbitial intercepts have been around for decades and it's pretty pointless to debate with english.-
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Hohmann transfer describes moving from one orbit to another. An attacking projectile is not attempting to change orbit, and while you would not be making a straight line attack from destination to target because of gravitation forces, you are also not attempting to maintain speed vs radius to maintain altitude. Once you get to the destination your speed no longer matters... where in an orbit change your speed matters a LOT, too fast and you shoot right out of your orbit.
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This is why you aren't getting it.
You ARE changing orbit. You do not do anything in space without changing orbits. A change in course, is a change in orbit. If you want to send one projectile to intercept another, you are performing a transfer.
Also, you don't "shoot out of orbit", you leave one sphere of influence for another. If you left Earth, you'd be in the Sun's orbit. If you left the sun's orbit you'd be in the milky way's sphere of influence.
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In leiu of responding to anymore posts I'm going to ask that you go post this to an orbital mechanics forum (they exist, here's one: http://orbiter-forum.com/) post this question and then post the link to the shack.
I bet 100 bucks you don't.
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That just means that there's a limiting factor on the projectile velocities you'd try to achieve versus the maneuverability you'd like to have.
Like I said above, think of it as a cruise missile or even a small piloted kamikaze craft. It probably wouldn't work well to accelerate as fast as possible as early as possible, so there'd be a penalty in the target's warning time. But the smaller craft that can afford to burn all its fuel in a short time (which among other things would make course corrections a LOT easier) could certainly catch up and make a hit. You'd probably just constantly accelerate at a low rate so that you get faster as you get closer and your maximum necessary course correction shrinks. (since a large target craft's maneuverability will be limited in comparison, your uncertainty in the target's course & location would only shrink as you got closer)
Maybe the problem is thinking of simple atmospheric missiles rather than the more complex destructive vehicles they'd likely be.
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It comes down to diminishing returns. Any craft large enough to carry something large enough to attack another craft worth attacking is going to have more deltaV potential than what is coming towards it. Given suffiecient warning (easy to do in space), you just alter your orbit slightly and the projectile has to use exponentially more energy to alter it's course because it's traveling so much faster relative to the target.
The faster the velocities, the more energy requried to change the course.
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You aren't getting it. The space craft just need to alter it's inclination by a small degree with a small burn. The amount of energy the intercept craft now has to expel to alter it's inclination by one degree is squared proportional to it's current velocity. Since it's velocity is an intercept speed, it's velocity is much greater relative to the target.
Unless the missle has the capability to do a constant burn it will almost always use up it's capability for deltaV before a target ahead of it will.-
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K. Please show me the math for the following:
Ship A and B have identical circular orbits, planes and inclinations, at a apogee of 152,000,000 kmaround the sun and are currently traveling at 30 km per second. Both ship A and B weigh 10,000 kilograms
Ship A's node is a striaght line radial intercept of 100 km from ship B's node.
Ship A releases a missle that somehow instantly changes velocity from 30 km per second to 300 km per second targeted with a standard hoffman transfer for B. The missle weighs 100 kilograms.
10 seconds after the missle is fired, ship B alters it's orbital inclination by 1 degree, changes the perogee of orbit to 152,000,100 km.
Please calculate the following:
The original time to intercept for the projectile to intercept ship B
The delta V required by ship B to make the above changes
The distance traveled after node A by the projectile after 10 seconds
The delta V required for the 100 kilogram projectile to match the new orbit 10 seconds after it leaves node A
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I disagree with this completely. Imagine you are sitting in a spaceship in space, and out the front mirror you see a missile streaming towards you. Assuming you have thrusters in all directions, your best bet of avoiding it is to thrust straight up or down, and that will cause it to have to turn the most.
You thrust 1 meter up, the missle alters its intercept angle by like 2 degrees effortlessly, and you're still toast.
You'd have to shift your 5000 megaton spaceship straight up, very very very fast, whereas a tiny missile barely needs any fuel at all to course-correct to follow you. -
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I always admired how in Wing Commander games your velocity was given in kilometers per second. 500 km/s is more than 1,000,000 mph, but for some reason you can visually spot enemy fighters -- which aren't supposed to be any bigger than modern fighter jets -- long before they reach you. That's damn good eyesight.
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Son, back in my day there was no preview script. You typed those shacktags out by hand and you took your chances. Sure many villagers lives were needlessly lost in shacktag disasters, but this was the wild west age of shack, and it was either you or them, so you shacktag'd your way to the top all over their face. Man up and uninstall that preview script! You'll be better off for it.
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Well this is the first shacktag that has caused physical injury. I'm still not over my infection, saw this post, started laughing, started coughing, blacked out, fell sideways out of my chair and faceplanted. Came to on the floor.
I'd like to post the whole MAD ME MAD meme and get a lol but I can't remember it fuck.
Back to the hospital.
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Vietcong did a neat thing where guns with 30 round mags only had 28 rounds loaded in them. This was a common practice (even today) as fully loaded a magazine wears out the spring and would cause rounds not to be fed properly. I think nearly all the rifles and SMG's did this in Vietcong.
Otherwise going by spec of fully loaded doesn't bother me. But VC's approach was a really nice touch.
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I still think it's blatant disregard for inertia. The Quake guy is carrying an axe, seven guns, 99 rockets, hundreds of nails and shotgun shells, and wearing a full suit of armor -- he must weigh like 10 tons. But he runs at about 60 mph. Accelerating from rest would take the force of a rocket booster, and his momentum would make him crash through walls before stopping. Maybe noclip is more respectful of the laws of physics than we thought...
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Being able to come to an almost complete mid-air stop in an aircraft to line up a machinegun pounding on a vehicle or to spray bullets into a building for like 10 seconds straight, then being able to throttle your way back into high speed flight having lost zero altitude, was pretty awesome even though it was tremendously game-ey.
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I'm gonna go with Just Cause 2's ability to let you free fall for a few kilometers, then at the last second grapple yourself to the ground, making you collide with earth EVEN HARDER but that keeps you from getting hurt. Also, Saint's Row let's you teleport into the driver's seat of any car simply by standing on the car and pressing Y.
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