Physics of Elite Dangerous

[peteuplink]

Your frame of reference when you are sufficiently high above the planet (like in the rings, for example) is itself in orbit. That's just because the game defines it so. In that case, you are in orbit. The other thing about flying around in normal space above a planet not being in orbit, I agree with. Something marvellous happens to negate all outside forces and at 0 m/s you are static in relation to the planet, not orbiting it. At least, that's how it seems. But using that to declare that all physics in Elite is bunkum is a bit strange. Of course it's all bunkum at some level, they have to take some shortcuts to allow it to be a game. The easiest one is allowing the ship to define its own frame of reference - then, all things like elliptical orbits and high speeds just cease to be important.

Basically (with my games developer hat on here) what is happening in Elite Dangerous is your position above a planet is determined by your X,Y and Z coordinates, not your trajectory and speed as it would with an orbit. So if you move east to west, you're moving on the X axis, if you move north to south,you're moving on the Y axis and height is determined by the Z axis. When you move the ship around a planet it's just the game determining your position above the surface based on these three variables. For the orbits to be accurate there would need to be a constant calculation for your trajectory in relation to the planets surface. As you'd know, if you were a physicist, an object in orbit is in free fall, but it stays in orbit because it's falling fast enough so that it's trajectory causes it to miss the ground. (video below)

[video=youtube;pTydlh8ifoA]https://www.youtube.com/watch?v=pTydlh8ifoA[/video]

Trajectories are not calculated in Elite Dangerous. Instead your position is worked out relative to the X,Y and Z coordinates of your ship above the planet. The planets sphere in this case is treated like a plane and you're just moving along that plane. If you fly north at 172m/s at a height of 8km, you stay moving north at a height of 172m/s and 8km because the game is moving you along the Y axis of the planet with a Z axis of 8km (or whatever the values are before it's converted into m and km for our human eyes/minds to udnerstand). You're not orbiting as a real orbit would work, you're simply flying along a plane at an angle of 0 degrees a speed of 172 and a height of 8. If you fly east at the same speed you're moving along the X axis of the plane (90 degrees) at a speed of 172 and a Z axis of 8. But what! I hear you cry. You're talking about planes, any bozo can see the planets in Elite are round. Well, yest they are, but it's only working on the same principle as taking the Earth, laying it flat like a flat map and working out your longtitude and lattitude from it, except this time we're also determining how high you are above that flat my by using a third value. If you take a map of the earth and old a pencil 2cm above the UK and move all the way across to America holind your pencil at the same height, you've not orbited, you've simply moved along the lattitude and longtitude of the map, it's X and Y coordinates, while holding the pencil at 2cm above the surface in the Z axis... And that's basically all that's going on in Elite Dangerous as where, except the planes are translated into spheres.

If you were actually orbiting a planet, the ship wouldn't be held at a height it would be in free fall and the game would be calculating a curved trajectory ahead of your ship and that trajectory would be determined by your height and speed. So moving at 172m/s at 8km around Enceladus should be enough to ensure that your free fall trajectory misses the planet and you'd stay in orbit, if you slowed down the curve of the trajectory would decrease and you'd lose height until you fell back to the ground. If you increased you speed then your height would raise. None of this is calculated in Elite Dangerous so therefore what's happening in game is not an orbit. You're simply moving along at a set height angle and speed as you would along a flat plane.

Sorry, but that's how it works. it's really not as complicated as any of you think it is.

Accept it or not, but I can't explain it any simpler than that.

- - - Updated - - -

Or we could agree this is a game that has mechanics in place that pretend to sell the illusion of physics compromised by gameplay conveniences.
All discussion about the topic is moot.

I'm quite happy to accept it's a game and there's some fudging going on. Others seem to think it's some sort of NASA grade physics simulator...

 

[CMDR Gizmo]

I simply don't get over our thrust speed limitation, it just makes no damn sense.

I'm totally fine with science fiction, FSD and jumps (actually these even have some theoretical foundation), weapons, shields, all fine to me as long as they are consistent or at least well explained..

But that our thrust does not accelerate us further then an artificial speed limit really makes me cringe somehow.. this is well known 19th century physics and earlier: As long as thrusters are thrusting they should accelerate us linearly&indefinitely until relativistic effects set in at 0.1c or so.. but there is neither an in-game explanation nor the player-created explanations do not convince me at all:
- Combat wouldn't be fun and just degarde to jousting: Does not have to be this way, it would be little different but with tools in game to align with each others speed it doesn't have to end this way, and even jousting can be fun..
- It is a crash prevention (mostly to save stations): Seriously? I can fire at stations without leaving a dent, I can fly into station at 300m/s without a dent, but suddenly at 301m/s this would be different? And why is it different for every ship independent of mass? And why can I tune it? And if it is some kind of artifical limitation, why wouldn't any serious person, or priate, immediatly throw this thing out of the window, like tuning your car? We can go off radars with silent running, but not remove the damn fuse for this artifical limiter?

Again, everything else is fine for me, even that there is no real orbital flight modeled in E ("orbital" as in the gravity constantly turns your movement vector around to get an orbit, not "flying" around a planet where we are actually flying in a plane and get the orbiting feeling by clever x/y/z-polar coordinate transformations), but that our thrust in normal cruise works like in some Aether really worries me, still I love the game

 

[Jex =TE=]

Of course it's a real orbit! it's live, happening now, in orbit around our planet. The delta-v needed to achieve low Earth orbit starts around 9.4 km/s. Atmospheric and gravity drag associated with launch typically adds 1.3–1.8 km/s to the launch vehicle delta-v required to reach normal LEO orbital velocity of around 7.8 km/s (28,080 km/h).

Anyway let's have a look at this video of an "orbit" in Elite Dangerous.

https://www.youtube.com/watch?v=XE7WPstMzsM

If we look at the video at 0:20 you'll see that he zeros his pitch angle and cuts his thrusters at a height of 8.9km above the moon at a speed of 172m/s, And then we enter a time lapse of the orbit. All well and good.

However, at the 3:03 mark of the video, you can clearly see that that the main thrusters of the ship start firing with a nose down attitude. Firing you engines like this while in orbit would alter your speed and therefore the trajectory of your orbit. The engines fire for 33 seconds until the video fades. While the engines are firing the video reaches the 3:24 point where he says "Three hours later. Ship returns to original position at the same speed." but if this was a true orbit, the fact that the engines are firing and that he was nose down would mean that he would not be at the same speed and would likely have dropped to a much lower orbit, if not out of orbit entirely by that point. Enceladus is only small and a 33 second burn would have big consequences on an orbit.

What I say is happening here is not that the maker of the video is actually orbiting the moon using orbital physics, but rather that he is simply flying around the planet using the same game systems that would keep you from crashing if you were flying at 172m/s at 1km above the surface.

The true test to see if it's real orbital mechanics would be to change your velocity and seeing if that raises or lowers your orbit in accordance to Newtons laws of physics. If your orbit trajectory doesn;t change and you simply speed up, you're not in an orbit. You're just flying around by artificial means that are programmed into the game.

Sorry, but that's the truth.

Wouldn't you need to know the mass of your ship and the mass of the planet to be able to work out a stable orbit?

 

[peteuplink]

Wouldn't you need to know the mass of your ship and the mass of the planet to be able to work out a stable orbit?

http://www.physicsclassroom.com/class/circles/Lesson-4/Mathematics-of-Satellite-Motion As you can see the maths are quite interesting, and I seriously doubt anything this complex is going on under the surface of Elite Dangerous. Everything is being kept to a much simpler model using only the X,Y,Z and Speed variables.

 

[Max Stingray]

Or we could agree this is a game that has mechanics in place that pretend to sell the illusion of physics compromised by gameplay conveniences.
All discussion about the topic is moot.

Agreed +Rep

 

[Max Stingray]

I simply don't get over our thrust speed limitation, it just makes no damn sense.

I'm totally fine with science fiction, FSD and jumps (actually these even have some theoretical foundation), weapons, shields, all fine to me as long as they are consistent or at least well explained..

The very personal explanation I gave to myself to be able to live with it (I.e the speed limitation) is that the magic of the frame shift drive is never completely off. It has three modes of operations the jump, the super cruise and the normal space, so normal space is not really normal space with Newtonian physics. Some magic is need in normal space as as the ships can pull some significant gees and can crash into the ground at 400m/s without killing the pilot as well as hover over a high g planet without any significant loss of propellant mass. This magic tech is some sort of inertial dumper/anti gravity device whose effectiveness decreases with velocity (which velocity, from which reference .. .. well let's just ignore that) hence the max speed. It can be tweaked by engineers up to a point.


Out of pure curiosity (and not to prove or disprove anything) has anyone tried to see what happens if you take off from a planet surface, fly 5-10k high, switch all engines off and let it fall . Will the ship accelerate up to a max speed in a very non Newtonian way? I suspect it will. Would an SRV behave the same way? (you can put one on top of a ship)

 

[Jex =TE=]

http://www.physicsclassroom.com/class/circles/Lesson-4/Mathematics-of-Satellite-Motion As you can see the maths are quite interesting, and I seriously doubt anything this complex is going on under the surface of Elite Dangerous. Everything is being kept to a much simpler model using only the X,Y,Z and Speed variables.

What I mean is if the physics in ED were realistic then wouldn't you need to know the mass of your own ship plus the mass of the object you wished to set up orbit with to work out the velocity needed to hold a stable height?

Or is every object treated equally no matter what their mass so an eagle / anaconda are treated equally and can go as fast as they like or as slow and still maintin height and orbit.

I think the fact that just increasing your speed or decreasing your speed and maintining your height is enough to shoot down ED as accurate on the physics front.

 

[John Rhys]

Out of pure curiosity (and not to prove or disprove anything) has anyone tried to see what happens if you take off from a planet surface, fly 5-10k high, switch all engines off and let it fall . Will the ship accelerate up to a max speed in a very non Newtonian way? I suspect it will. Would an SRV behave the same way? (you can put one on top of a ship)

Depends on the Gravity of the Planet. If it's below 0,5g it will take a very long time. Highest i tried was 1.7g and my python plummeted from ~ 25 km to the ground like a big rock. At 2k i reactivated my thrusters, but it was to much for the puny retro thrusters. And at that speed without atmosphere, she isn't flyable. Ended with ~ 30% Hull. I think the max speed was around 2000 m/s

 

[Ddraig]

Ok.

You cant just drop your ship at +1000m/s and get out with 30% hull HP and then start a topic about realism.
That does not compute for me. It is a game that sells some illusion of physics and realism and that´s it. No more no less.
This whole thing is pointless. I am out.

 

[Max Stingray]

Depends on the Gravity of the Planet. If it's below 0,5g it will take a very long time. Highest i tried was 1.7g and my python plummeted from ~ 25 km to the ground like a big rock. At 2k i reactivated my thrusters, but it was to much for the puny retro thrusters. And at that speed without atmosphere, she isn't flyable. Ended with ~ 30% Hull. I think the max speed was around 2000 m/s

I expected the initial acceleration to to depend on the size of the planet, obviously,,but did you really exceed the maximum speed you can do with the engines on? Thats' cool. I'll try it out tonight with a sidey just for fun and see if the acceleration is equal to the declared one.

Would two ships with different mass fall with the same acceleration as expected in reality, with no atmosphere?

 

[John Rhys]

I expected the initial acceleration to to depend on the size of the planet, obviously,,but did you really exceed the maximum speed you can do with the engines on? Thats' cool. I'll try it out tonight with a sidey just for fun and see if the acceleration is equal to the declared one.

Would two ships with different mass fall with the same acceleration as expected in reality, with no atmosphere?

As expected in reality, they would NOT fall with the same acceleration - gravity DOES play a role in this, although i have to admit, that the flight characteristics are...wonky, under heavy gravity. Still, this doesn't need to be a physical problem - it probably is just the crappy software from the Pilots Federation.

A Sidewinder will fall considerably slower. F=m*a, or rather a=F/m - Newtons second law is working very well.

 

[peteuplink]

What I mean is if the physics in ED were realistic then wouldn't you need to know the mass of your own ship plus the mass of the object you wished to set up orbit with to work out the velocity needed to hold a stable height?

Or is every object treated equally no matter what their mass so an eagle / anaconda are treated equally and can go as fast as they like or as slow and still maintin height and orbit.

I think the fact that just increasing your speed or decreasing your speed and maintining your height is enough to shoot down ED as accurate on the physics front.

You would need the mass of the object to know the speed you'd need to achieve to maintain orbit, and the mass of your ship to know what a thrust you would need to achieve that speed.

For a much more realistic representation of how orbits work look at Orbiter.

[video=youtube;p4aWMdNMuCE]https://www.youtube.com/watch?v=p4aWMdNMuCE[/video]

or Kerbal Space program.

 

[Max Stingray]

Ok.

You cant just drop your ship at +1000m/s and get out with 30% hull HP and then start a topic about realism.
That does not compute for me. It is a game that sells some illusion of physics and realism and that´s it. No more no less.
This whole thing is pointless. I am out.

I think we all (most?) agree that "It is a game that sells some illusion of physics and realism and that´s it.", and I am happy with it

Personally I am just curious to figure out how it actually works, what is actually realistic and what is not. Call it a "PRES" (pointless reverse engineering syndrome), as that's what it is.

 

[Vorxian]

All this clever tech, and in ED, you still cannot get a monitor screen to show commodity prices around the sector.

Heck, Ceefax did a better job in the early 1970s. Why it's so hard in 3300 when it's possible to run an interactive telepresence the other side of the galaxy in real time, no latency and 100% stable?

meh!

That's entirely down to gameplay reasons.

..and that is exactly my issue. At what point is it ok to smother realism to make game more gamey?

 

[Max Stingray]

As expected in reality, they would NOT fall with the same acceleration - gravity DOES play a role in this, although i have to admit, that the flight characteristics are...wonky, under heavy gravity. Still, this doesn't need to be a physical problem - it probably is just the crappy software from the Pilots Federation.

A Sidewinder will fall considerably slower. F=m*a, or rather a=F/m - Newtons second law is working very well.

You may want to reconsider that above statement. In absence of atmosphere objects fall with the same acceleration regardless of mass .... Galileo, Newton, etc etc ...

In your a = F/m the force is F = G (M*m)/r^2 leading to a = G M/r^2 which on earth is called g.

[video=youtube;5C5_dOEyAfk]https://www.youtube.com/watch?v=5C5_dOEyAfk[/video]


https://en.wikipedia.org/wiki/Gravitational_acceleration

 

[Jex =TE=]

You would need the mass of the object to know the speed you'd need to achieve to maintain orbit, and the mass of your ship to know what a thrust you would need to achieve that speed.

For a much more realistic representation of how orbits work look at Orbiter.

https://www.youtube.com/watch?v=p4aWMdNMuCE

or Kerbal Space program.

Ok so then we get to the point I was trying to puish you towards (lol) - What is the mass of your ship and the planet and what is the speed required to maintain an 8.9km orbit?

I'm pretty sure the first 2 videos posted telling you that you were wrong had done this prior to making the videos which is why they had orbits orrrr..... you were absolutely correct and the people telling you that you were wrong didn't in fact know what they were talking about.

- - - Updated - - -

I think we all (most?) agree that "It is a game that sells some illusion of physics and realism and that´s it.", and I am happy with it

Personally I am just curious to figure out how it actually works, what is actually realistic and what is not. Call it a "PRES" (pointless reverse engineering syndrome), as that's what it is.

This - who cares that much about the physics anymore as ED is just a game now.

 

[Ddraig]

I think we all (most?) agree that "It is a game that sells some illusion of physics and realism and that´s it.", and I am happy with it

Personally I am just curious to figure out how it actually works, what is actually realistic and what is not. Call it a "PRES" (pointless reverse engineering syndrome), as that's what it is.

My "I am out" seems hypocrite now. But oh well.
No complains from my side to your need to know and understand. It is within your right, and whatever float your boat is alright.
And I am also quite content with the game selling me the inconsistent illusion of physics and realism as it is, could be better though and I hope that as time goes by it will be improved to trick me even better. I want to be tricked! That is why I purchase a game, to entertain me and delude myself in fiction.

What triggers me a bit is people trying to convince others with an almost religious fervor that the game is close or similar to a NASA project and then doing something cartoonish as plummeting your ship at over 3500 km/h and come out "alive" and still trying to hold on the discussion of realism. It makes me short circuit. I admit that is within their right as well to do just that, but I am within my right to short circuit to absurdity.

That´s it.

 

[John Rhys]

You may want to reconsider that above statement. In absence of atmosphere objects fall with the same acceleration regardless of mass .... Galileo, Newton, etc etc ...

In your a = F/m the force is F = G (M*m)/r^2 leading to a = G M/r^2 which on earth is called g.

https://www.youtube.com/watch?v=5C5_dOEyAfk


https://en.wikipedia.org/wiki/Gravitational_acceleration

Right...sorry - i totally forgot about that. Regardless of the acceleration, i still believe, that the force on impact will be greater for the object with more mass.

http://hyperphysics.phy-astr.gsu.edu/hbase/flobi.html

To lazy, to calculate it myself. Using the tool above, the speed should be the same, but with the Python weighing in at 895t and the Sidey with 55t...well.

My "I am out" seems hypocrite now. But oh well.
No complains from my side to your need to know and understand. It is within your right, and whatever float your boat is alright.
And I am also quite content with the game selling me the inconsistent illusion of physics and realism as it is, could be better though and I hope that as time goes by it will be improved to trick me even better. I want to be tricked! That is why I purchase a game, to entertain me and delude myself in fiction.

What triggers me a bit is people trying to convince others with an almost religious fervor that the game is close or similar to a NASA project and then doing something cartoonish as plummeting your ship at over 3500 km/h and come out "alive" and still trying to hold on the discussion of realism. It makes me short circuit. I admit that is within their right as well to do just that, but I am within my right to short circuit to absurdity.

That´s it.

Who want's to convince anyone, that the game is close or similar to a NASA project...? Never have i claimed, that Elite has absolute physics in place, or upholds all laws of physics or whatever.

I also never said, that i impacted with 2000 m/s. But this is exactly the reason, why there has to be lore (at least, for me). "Always" plummeting down to your death and watching the rebuy screen, or having limits imposed by laws, that are made up by the ship manufactures. As i said, the simple reason why the maximum speed is limited is gameplay/lore.

But - have fun short circuiting

 

[Max Stingray]

My "I am out" seems hypocrite now. But oh well.
No complains from my side to your need to know and understand. It is within your right, and whatever float your boat is alright.
And I am also quite content with the game selling me the inconsistent illusion of physics and realism as it is, could be better though and I hope that as time goes by it will be improved to trick me even better. I want to be tricked! That is why I purchase a game, to entertain me and delude myself in fiction.

What triggers me a bit is people trying to convince others with an almost religious fervor that the game is close or similar to a NASA project and then doing something cartoonish as plummeting your ship at over 3500 km/h and come out "alive" and still trying to hold on the discussion of realism. It makes me short circuit. I admit that is within their right as well to do just that, but I am within my right to short circuit to absurdity.

That´s it.

I understand. Same here +rep but I run out.
----
To be fair the person that was talking about plummeting at warp speed, in this case, and coming out alive was just reporting what he has observed in game.
I would much prefer if you died after such a hit but fact is that currently you don't

 

[Eros]

only read the first page - bad practice i know.

But on the hyperspace jump and the supercruise modes, there is no reason why a device that operates as an Alcubierre Drive in supercuise could not act as a hyperspace device.

Why must we consider Star trek when talking about these devices? Star Trek's concept of subspace is not at all justified by scientific theory or concept. It is simply another form of Deus Ex Machina that TNG was famous for... the show was massively inconsistent and the only ones trying to find any consistency are the fans who so want it to be real they miss the point...

SO back on track.

The Alcubierre Drive as stated, creates a flat 'normal' space-time bubble around the ship, it then creates a positive displacement behind the ship, as though the there is a virtual heavy mass there, and creates a equal but negative displacement in front, causing space time to push your ship along. Why would it be possible for this device to be reconfigured to bridge the stars?
Simple
1) It has 'some' way of generating positive mass, warping spacetime
2) It has 'some' way of generating negative mass, warping spacetime

The negative energy densities are the handwavium parts because we have no workable concepts of producing such things, and no evidence to their existance... anyway that aside lets look at the hyperspace jump

When people talk about folding spacetime and passing through, what the closer concept is, that you are creating a space in which you are at exactly the same potential as the place you want to be, and creating an Einstein-Rosen bridge from your start point, to the desired location. To do this you first are required to generate an artificial mass signature that allows you to fold or pinch spacetime. In order to open the bridge, you must do so using negative mass or negative energy density.

BOTH of those functions would be available to a Alcubierre Drive like device. IF it could exist, no need for subspace or anything like that.

So what is the maximum range of such a device? and what features would determine is behaviour?
Max range - determined by prior knowledge of your local gravitational environment, and ALL objects nearer to you than your intended target. The local conditions should play a big role too... it should be easier to fold between two heavy stars... than to say a heavy and a light one. From a few papers iv read on the subject (abstract mathematics that everyone quotes as proving the whole 'wormhole' concept as real, despite the paper clearly stating it requires negative mass) The width or physical volume limit you can pass through the bridge is related to the amount of negative mass used to pry it open. THUS if you are wanting to open a huge bridge, it will require naturally huge (negative) energy density. So maximum range... would be very short in order to have any kind of control over your exit point. The amount of degenerate solutions would be horrible.

Features - You would predominantly want to arrive extremely close to, if not, inside heavy objects... LOL
-Failed jumps would likely cause physical damage... sheering forces / compression / expansion as the whole thing collapses and returns you to regular potential.

- Jumping in the middle of nowhere (like far from a heavy object) would be more difficult than closer.

- Sudden drop from Alcubierre Drive would likely not result in splattering your face into the canopy depending upon the drop mode... ultimately, a drop would be a weakening of the spacetime bump and dip... if these are equalised in a controlled manner the pilot would likely not feel a thing... the only places that would be effected are at the extremities of the bubble should it stop being a bubble of normal space around the ships physical volume. If the device failed say, and the bubble shortened such that the negative mass volume of spacetime was able to exist say in the same space as the ship... yeah... very bad things would happen.

Thats about it really as far as i can conceptualize. I have a PhD in Physics, and these kinds of fringe concepts are always quite interesting if we are to do the 'what if it works like x' the issue with a lot of sci-fi writing is that many are not scientists at all, and these days the worse part is that many sci-fi concepts are being built upon old universes where the science fiction is taken as science fact in order to build more fiction. Understanding where the current box is, is very important when trying to figure out the stuff outside the box.