Space ship and Thruster size vs Speed. Is it completely wrong

[Ben Ryder]

I dont know science and I dont know space stuff and physics.

I've had a thought in the back of my mind for a while and its been bugging me well since ED came out.

Know here the little bit I think I know about space stuff.

There is a good as nothing to slow you down once you get going.

Things dont weigh much., pretty much next to nothing.

So why is small ships with crappy small thrusters go faster tan big ship s with huge thrusters?

Shouldnt something like a T9 with its HUGE thrusters leave a puny cobra with its tiny tiny weak low power thruster far far behind in the blink of an eye?

If not why not? I jus dont know and it bothers me.

 

[Jimmysal]

Inertia. big heavy ship like the t9 wants to stay put if it's sitting still, or keep going the way it is going if you want to stop or turn. Little ship like the cobra has much less mass, much less inertia, and can be moved about easier. Would you rather push a ford focus or a ford f150?

 

[Zambrick]

I dont know science and I dont know space stuff and physics.

I've had a thought in the back of my mind for a while and its been bugging me well since ED came out.

Know here the little bit I think I know about space stuff.

There is a good as nothing to slow you down once you get going.

Things dont weigh much., pretty much next to nothing.

So why is small ships with crappy small thrusters go faster tan big ship s with huge thrusters?

Shouldnt something like a T9 with its HUGE thrusters leave a puny cobra with its tiny tiny weak low power thruster far far behind in the blink of an eye?

If not why not? I jus dont know and it bothers me.

Easy answer.


Yes, its wrong but its a fictional universe so I give it a pass.

Play space engineers and build your own ships in it. They react vastly different than they do here. If you want as much speed forward as you do backwards then you have the same thruster size. Reverski is not a real thing because with the thrusters on the ship.

 

[Zieman]

Concerning acceleration (one aspect of 'moving fast'): Mass has inertia. Thrust has to overcome this inertia to make the mass move (F=ma). Bigger ships have more mass, and thruster power increase with bigger thrusters is smaller than the mass increase when getting a bigger ship.

Top velocity then (the other aspect of 'moving fast'): Different ships have differing top speeds for gameplay reasons.

 

[Tom Melegaris]

picture space as a waterfront. big super tankers take time to develop sufficient inertia to overcome mass...

and stopping or turning the same super tanker takes time and distance (space)

err goes off to finds a more apt explanation

 

[Ben Ryder]

Mass has inertia. Thrust has to overcome this inertia to make the mass move (F=ma). Bigger ships have more mass, and thruster power increase with bigger thrusters is smaller than the mass increase when getting a bigger ship.

Didnt understand that. I don tknow science.

Can you explain that as if you were talking to a child (a thick one).

Are you saying big ships need big thruster cos they ar big and a the same size thruster as a cobra on a T9 wouldnt move it forward as fast even if its in space where there's no resistance andit doesnt weigh anything? Erm.

 

[Jimmysal]

The ships still have mass even though there isn't gravity in space. Think of it this way, if you push a car, you're not doing the same thing as lifting 4000lbs, but you still feel resistance. With pushing a car, some of that resistance is friction and whatnot, but most of it is just the fact that the car has some mass, and mass doesn't want to move unless something moves it.

 

[Ben Ryder]

The ships still have mass even though there isn't gravity in space. Think of it this way, if you push a car, you're not doing the same thing as lifting 4000lbs, but you still feel resistance. With pushing a car, some of that resistance is friction and whatnot, but most of it is just the fact that the car has some mass, and mass doesn't want to move unless something moves it.

Thanks. I understood that +1 (I feel dead clever now)

So even with thsi in mind.

Shouldnt tehe t9 (and other huge ships) still hurtle past the small ships as they have huge thrusters? I mean like really huge, power hungry thrusters.

 

[777Driver]

Can you explain that as if you were talking to a child

[video=youtube;dh4AGsofaV0]https://www.youtube.com/watch?v=dh4AGsofaV0[/video]

 

[Smecca is BMFE]

In space, I could throw a baseball 70 miles per hour, and it would stay at that speed until it interacts with something. I could not throw a bowling ball that fast. I would need a much bigger and stronger arm (thrusters) to move a "heavier" object as fast as a "lighter" object.

But now we're getting into the difference between weight and mass.....Crap.

 

[Jukelo]

If you go purely by the size of the exhausts, Keep in mind that surface area always grows a lot slower than volume (and so -arguably- mass).

 

[Jimmysal]

Thanks. I understood that +1 (I feel dead clever now)

So even with thsi in mind.

Shouldnt tehe t9 (and other huge ships) still hurtle past the small ships as they have huge thrusters? I mean like really huge, power hungry thrusters.

Well there's top speed, and how fast you get to top speed (acceleration). The acceleration has to do with how hard your thrusters can push, and how heavy what you're pushing is. Since the t-9 is a big pig of a ship, it needs big thrusters. Since the cobra is tiny it gets tiny thrusters. But the t9 is so heavy (or massive) that even with those great big thrusters the weight of the ship takes way more to get going than even the baby cobra. Same way a tiny economy car can outrun a big rig even though the big rig has 10x the power. It's F=ma, like someone else said, where F is how hard the thrusters can push, m is the mass of the ship, and a is how fast it accelerates. You can rearrange that to a=F/m to figure out how fast something will speed up or slow down based on how much it weighs and how hard its being pushed. Since the t-9 weighs waaaaaaaaaaaaay more than the cobra, but only has way more thrusters; the cobra can still out accelerate it. Put it this way, 5 people can push an economy car up to speed faster than 10 people can push a tractor trailer up to speed. Sure the tractor trailer has double the people pushing it, but it weights 100 times as much.

Where ED's flight model doesn't work is with top speed. In practice, if you turned the thrusters on and just left them in a straight line, you would accelerate up to who knows what top speed, until you ran out of fuel. Then you'd just stay at that speed forever. So with "real physics" the cobra still beats the t9 in a drag race, but the max speed is way faster than anything we see in game.

 

[Mercury Shift]

@777Driver, I know you didn't make that yourself, but damn, well played. repped

To Ben: Now that you understand the mass portion, here is another way to see it all fit together:

Imagine that you are that astronaut in Driver's vid. There you are floating in a fixed point in space. You look to your left and there is a little mouse in a mouse-appropriate space suit. You both have an air horn, yours, the larger, is labeled "Human sneeze" and his, the smaller, is labeled "Mouse sneeze". If you both activated the one for your species either of you would be propelled at the exact speed of a paper airplane. If you, the human used the "Mouse sneeze" air horn, you would be propelled at the speed of soil erosion, but if the mouse snags your air horn and uses it, he would be entering the Trappist-1 system in a matter of minutes.

So:
The speed of the mouse (ship) is generated by applying the air horn (thrust of engines) against the mouse's mass (ship mass). A bigger mouse needs a bigger air horn, and the smaller the mass, the resulting speed is higher.

 

[Tom Melegaris]

Like this...

[video=youtube;qym9RACs76I]https://www.youtube.com/watch?v=qym9RACs76I[/video]

 

[Muetdhiver]

Didnt understand that. I don tknow science.

Can you explain that as if you were talking to a child (a thick one).

Are you saying big ships need big thruster cos they ar big and a the same size thruster as a cobra on a T9 wouldnt move it forward as fast even if its in space where there's no resistance andit doesnt weigh anything? Erm.

I think your troubles boil down to a rather common mixup between mass and weight.

Put in (kid's ?) language : mass is "amount of stuff" and weight is a force pulling you "down". They are tied together by the Newton's law :
Force (Weight) = Mass * Acceleration. Now, the trick is that Force is measured in Newtons [kg*m/s^2], but for weight it's usually measured
in kilogram-force instead of kilograms, with one kilogram-force being one kilogram * g, the earth gravity acceleration. In this unit system,
a one kilogram object on earth has a weight of one kilogram-force, which is a usefull short-hand.

Since in space, at rest, far from any object, there is no gravity acceleration, a = 0, so Weight = Mass * 0 = 0
In other words, in space a one kilogram object will weight zero kilogram-force.

Now, why it is that big ships need big thrusters ?

The answer boils down to : to make amount of stuff move faster, one has to apply a force to get an acceleration.
Since F = m*a, or a = F/m, the greater the mass (not the weight), the greater the force needed to get a given acceleration.

In simple words : if ship B is 10x more massive than ship A, to get the same acceleration, it will need 10x more powerfull thrusters.

 

[JesusRocks1988]

Didnt understand that. I don tknow science.

Can you explain that as if you were talking to a child (a thick one).

Are you saying big ships need big thruster cos they ar big and a the same size thruster as a cobra on a T9 wouldnt move it forward as fast even if its in space where there's no resistance andit doesnt weigh anything? Erm.

I'll try and use your own words to explain, rather than fill you up with jargon, but firstly:

Weight and mass are different. An object always has mass wherever it is. It's weight is determined by the force pulling on it, like gravity. In simple terms objects only have weight in gravity - like on a planet's surface. But it still has mass in space - and mass is the key thing. Resistance and weight are almost 0 in space, but those two things have a minimal effect on how much power you need to put behind something to move it compared to mass, which is the overriding factor when resistance and weight are low.

Something with a high mass needs more power to make it move.

A Cobra has less mass than a Type 9. The Cobra has whatever size thrusters it has to make it move quickly. A Type 9's mass is huge, but the thruster power doesn't scale with its mass. The ship/thrust relationship of a Cobra is much greater than the ship/thrust relationship of a Type 9. The Cobra has thrusters that can accelerate it to 200m/s within a couple of seconds, but a Type 9's thrusters, though bigger, still aren't big enough to do that to such a massive object.

 

[Whitehair]

One other thing that you seem to not have a clear picture of Ben:

Acceleration vs Speed.

You keep asking why large ships with large thrusters don't go faster than smaller ships with smaller thrusters.

As already explained, to move a large mass requires more energy. So if a large ship and a small ship start their thruster at the same time, the smaller ship will accelerate more quickly, due to having to move less mass and therefore not needing as much energy to move that mass.

Because it accelerates more quickly it gets to its top speed sooner than a large ship. Next time you are at a trafficlight in your car with a motorbike next to you, you will see how this works

So - smaller ships will tend to be moving faster because they get to top speed quicker than the larger ships.

Also, as already mentioned earlier in the thread, different ships are limited to different top speeds by the game. It's not 'real life' accurate, but is done to make the game more fun.

 

[Thetele]

I would add to above the mass of the space ship or thruster size alone doesn't tell how fast acceleration ship has. The combination of both is what matter. Thrust/mass ratio is what matter, A ship with more thrust per ton will accelerate faster. (no idea if this is true in elite)

However in elite the speed of every ship is capped. In reality there is no such thing as max speed as long as you fire engines to same direction the ship would accelerate and move faster and faster until close to speed of light (current theories suggest that mass can't achieve the speed of light), in elite that doesn't happen and every ship has max speed, that isn't determined by any physics, but values and calculations decided by frontier.

Elite is a video game and a lot of stuff in elite doesn't make any sense. Like ship's masses don't make any sense at all, same with module masses. Some stats get only affected by the stock hull mass of the ship, nothing else and other stats are effected by the total mass of the ship (hull mass+mass of all modules+cargo mass+fuel mass). If you want to learn how stuff work in elite physics won't give good answers as only some parts are realistic and most stuff follow game mechanics and rules set by the developers and not by physics.

 

[rennarda]

Interesting factoid - in zero gee you'd be able to move any object my muscle power alone. You could 'pick up' (actually, there is no 'up') a 10ton cargo container. You'd have to apply muscle power to it for a long time to get it moving, but it would move.

BUT - that 10ton container still has 10tons of mass. If you got in it's way you're still going to get crushed to death by it, because you have to overcome it's inertia to stop it. You'd need an equally long amount to time that you took to get it moving to stop it moving.

This is why real world docking manoeuvres are done VERY SLOWLY...

 

[Morbad]

It's a balance thing.

If you go purely by the size of the exhausts, Keep in mind that surface area always grows a lot slower than volume (and so -arguably- mass).

Generally, ships in elite get exponentially less dense as they get larger.