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Author Topic: Space Fizzix  (Read 7932 times)

DelicateTask

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Space Fizzix
« on: October 16, 2012, 03:50:58 PM »

Every now and then, some wise guy says "It's space, why is there a max speed." So I bumped every ship's max speed to 10,000 and tried it out.

So I go to start a battle. Turns out that the max in-game speed is somewhere around 600. I'd forgotten that all ships are deployed at max speed. All of the deployed ships went flying into the middle of the map at 600su (or mph, or kph, or au, or whatever units we use) and crashed into each other. After managing to regain control, I flew around for a bit. I actually didn't feel like I was going any faster! Space is rather empty and I had very few visual references for my speed. I didn't even notice I was going over 200 until I was trying to turn around and accidentally sped past my target. At one point I ran into the edge of the map going about 150. Well, when you are asked if you would like to retreat, hitting no sends you back into battle at full speed again at 600. Unless you are super maneuverable or hit a nebula or another ship, you are not going to have much luck slowing down. And then there were ships outrunning projectiles and missiles...

Moral of the story:
UNLIMITED SPEED IS A BAD IDEA!
Game constraints are often necessary, and sometimes realistic scenarios are more frustrating and immersion breaking than imposed rules.

Also, I pose to you a question. Are not unlimited (potential) speed and unlimited acceleration two different things? The idea behind a chemically powered rocket (I'm ignoring game lore right now) is that any action has an equal and opposite reaction. Would your propulsion speed not be limited by the exit velocity of the burning fuel?
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Gothars

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Re: Space Fizzix
« Reply #1 on: October 16, 2012, 04:53:28 PM »

Sounds like a fun test :)

Also, I pose to you a question. Are not unlimited (potential) speed and unlimited acceleration two different things? The idea behind a chemically powered rocket (I'm ignoring game lore right now) is that any action has an equal and opposite reaction. Would your propulsion speed not be limited by the exit velocity of the burning fuel?

Speed and acceleration are very different, but not for the reason you think. For propulsion (in Newtonian physics) all you need is force in the opposite direction you want to travel in, it is not relevant if it's speed is lower than your own. The formula is force= mass x acceleration. Rocket engines propel matter at high acceleration because that allows them to use little mass. But in theory you could just as well use a very high mass at low acceleration, if it weren't for the problem of transporting that mass. In short, if you throw a stone out of the rear window of your spaceship you will go faster.

Quote
Game constraints are often necessary, and sometimes realistic scenarios are more frustrating and immersion breaking than imposed rules.

That's true in general, but in this scenario the problem starts with the fact that only a few of many parameters are realistic. Realistic space battles would not take place on a few square kilometers, they would probably span millions of kilometers through a star system. That would more than compensate for the high speed involved.
« Last Edit: October 16, 2012, 04:59:35 PM by Gothars »
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The Soldier

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Re: Space Fizzix
« Reply #2 on: October 16, 2012, 07:13:55 PM »

Oh dear...not another one! ;D
Anyways, physics HAVE to be ignored in games to provide balance, stability, and an overall feeling to a game.  Just look at BF3, where if you shot a tank shell at someone's foot, they die and their body gets throw 100 meters in the air (funny, though it defies the laws of physics XD), yet this has to be in-game to provide that feeling when you're driving a big, hulking tank around or a small, fast jeep, jumping over ledges and such.

And the only problem to having a Starfarer-esque propulsion system is the fuel needed to power it (it looked like a rocket engine, yes, we all know that, but I don't know anything about that nor am I willing to learn it. ;P)
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Thaago

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Re: Space Fizzix
« Reply #3 on: October 16, 2012, 09:05:06 PM »

...

Also, I pose to you a question. Are not unlimited (potential) speed and unlimited acceleration two different things? The idea behind a chemically powered rocket (I'm ignoring game lore right now) is that any action has an equal and opposite reaction. Would your propulsion speed not be limited by the exit velocity of the burning fuel?

You expel the fuel relative to your current velocity. If the exit velocity is 5km/s and you are stationary, the gas moves back at 5km/s. If you are moving at 10km/s (past some space station) then the gas is actually moving forward at 5k/s (past some space station) after you fire it. The force on you is still the same.

Fun orbital mechanics fact of the day: in an orbit, you get more delta v for a rocket burn close to a planet than far away. One explanation: A rocket burn boosts velocity by some u, so adds energy equal to m/2*(u+v)^2 - m/2*(v)^2/2m = m*uv + m/2*u^2, where v is the velocity prior to burn. The higher the initial v, the higher the added energy. In an orbit, the closer to a planet you are the faster you are going -> the higher the initial v. More energy = more velocity after escaping the planet, higher delta v from that burn.
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Aleskander

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Re: Space Fizzix
« Reply #4 on: October 16, 2012, 09:54:20 PM »

Thaago got all rocket math in this H**. Damn son.

I'm assuming you play KSP, since outside of that there are only real jobs that require that kind of math, and those people don't play video games.
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billi999

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Re: Space Fizzix
« Reply #5 on: October 17, 2012, 03:12:36 AM »

Delicious orbital mechanics

Wow, so burning at an apoapsis on a parabolic orbit to alter its shape to an elliptical orbit is actually quite inefficient? What more efficient alternatives could there be other than burning on a periapsis? Could you burn retrograde to your orbit somewhere between the periapsis and apoapsis and actually burn more efficiently than burning at the apoapsis? I'm guessing it could be possible but it'd require seveal burns at different points.
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phyrex

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Re: Space Fizzix
« Reply #6 on: October 17, 2012, 07:42:38 AM »

Every now and then, some wise guy says "It's space, why is there a max speed." So I bumped every ship's max speed to 10,000 and tried it out.

So I go to start a battle. Turns out that the max in-game speed is somewhere around 600. I'd forgotten that all ships are deployed at max speed. All of the deployed ships went flying into the middle of the map at 600su (or mph, or kph, or au, or whatever units we use) and crashed into each other. After managing to regain control, I flew around for a bit. I actually didn't feel like I was going any faster! Space is rather empty and I had very few visual references for my speed. I didn't even notice I was going over 200 until I was trying to turn around and accidentally sped past my target. At one point I ran into the edge of the map going about 150. Well, when you are asked if you would like to retreat, hitting no sends you back into battle at full speed again at 600. Unless you are super maneuverable or hit a nebula or another ship, you are not going to have much luck slowing down. And then there were ships outrunning projectiles and missiles...

Moral of the story:
UNLIMITED SPEED IS A BAD IDEA!
Game constraints are often necessary, and sometimes realistic scenarios are more frustrating and immersion breaking than imposed rules.

Also, I pose to you a question. Are not unlimited (potential) speed and unlimited acceleration two different things? The idea behind a chemically powered rocket (I'm ignoring game lore right now) is that any action has an equal and opposite reaction. Would your propulsion speed not be limited by the exit velocity of the burning fuel?

just picturing that made me chuckle  :D
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Hardlyjoking67

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Re: Space Fizzix
« Reply #7 on: October 17, 2012, 04:39:13 PM »

I think that trying to apply school to video games was a bad idea.
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DelicateTask

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Re: Space Fizzix
« Reply #8 on: October 18, 2012, 05:22:10 AM »

just picturing that made me chuckle  :D
Yeah, it was pretty hilarious bouncing all over the place uncontrollably. It's kind of like being a rubber ball in a small room. ;D
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frag971

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Re: Space Fizzix
« Reply #9 on: October 18, 2012, 07:32:24 AM »

Just because the current battle maps are so small, the weird fact that you start at 600 speed instead of 0 and there is no UI to support long-range interactions doesn't mean the idea itself is bad, just implementing it in the limitations of the game itself is... uh... limiting.
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GUNINANRUNIN

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Re: Space Fizzix
« Reply #10 on: October 18, 2012, 10:39:10 AM »

In short, if you throw a stone out of the rear window of your spaceship you will go faster.
SIG
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In short, if you throw a stone out of the rear window of your spaceship you will go faster.

Aleskander

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Re: Space Fizzix
« Reply #11 on: October 18, 2012, 12:50:43 PM »

In short, if you throw a stone out of the rear window of your spaceship you will go faster.
SIG
I think I'll design a spaceship off of that principle now.
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DelicateTask

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Re: Space Fizzix
« Reply #12 on: October 19, 2012, 09:39:33 AM »

I would absolutely love to see that. If you can make it work, you're amazing.
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GUNINANRUNIN

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Re: Space Fizzix
« Reply #13 on: October 19, 2012, 10:11:26 AM »

In short, if you throw a stone out of the rear window of your spaceship you will go faster.
SIG
I think I'll design a spaceship off of that principle now.
I can picture entire ranks of convicts chained in the back of the vessel, being forced to throw pebbles for all time. When the Captain calls for flank speed they'd throw two rocks at the same time.
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In short, if you throw a stone out of the rear window of your spaceship you will go faster.

Gothars

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Re: Space Fizzix
« Reply #14 on: October 19, 2012, 11:46:22 AM »

 :D What have I started?  Now, to end it:

Weight of a small ship: 5,000,000 kg
Weight of a Stone: 0.5 kg
Acceleration by human throwing: 50 m/s²  (roughly estimated)
Frequency 1 stone/second

Force of a stone: 0,5 * 50 = 25 N
Acceleration of the ship by one throw: 25N/5,000,000 kg = 5x10^-6 m/s² = 0.000005 m/s²

Distance between planets by example of earth-mars: 3x10^8 km

Time it would take to bridge that distance using the stone-drive: 6.9*10^7s = 2.2 years (assuming atmospheric deceleration)

Except for possible sore arms quite reasonable, eh?

Well....
Necessary amount of stones in the cargo hold: 6.9*10^7 = 70 million
Weight that has to be  swept under the carpet: 34,500,000 kg

Solution: place portal under carpet. All is perfect! ;D
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