GAME CHANGER - A little overlooked law of aerospace science.

[Dragonfire]

There has been a little discussion about the dynamics of the Oolite ships, and speed vs. weight, which got me to thinking about it in more depth. Then I remembered something that has been largely overlooked in Oolite - there is no gravity or friction in space (unless you're in the gravitational pull [gravity] or atmosphere [friction] of a planet. There is mechanical friction, too, by the by.) See Source

That, of course, changes a LOT of dynamics. It means that all the big ships aren't slow because of scientific limitations. They're slow because of financial and technological limitations on their engines.

In space travel, only intermittent thrust is needed to propel a ship at a constant speed (think about the planetary probes that NASA launched), because there is no friction to slow it down. Constant thrust will result in constant acceleration.

This isn't to say that a tiny bit of thrust can shove a Boa Class Cruiser at 0.8 speed. There is still a matter of mass. In space, a tiny rock hitting a massive meteor isn't going to move the meteor much at all. It will take more force to move more mass. But, that aside, there are no limitations to how fast a ship can be.

Due to size, obviously, it would take more force, time, and space to maneuver a big ship than a small one, as we already know. But when it comes to mere forward movement, the caps on thrust and top speed are not quite as we suspected.

Kinda opens up a whole new world for ships, doesn't it?

More on Space Propulsion

[Wyvern Mommy]

in space, speed isn't limited by thrust, it's limited by engine efficiency (in terms of exhaust speed) and fuel (in terms of mass ratio).

that's a fact oolite is overlooking (as is the original elite)

[Dragonfire]

The overlooked fact isn't too deeply ingrained in the game itself (the mistake can be ignored). The most important thing is that it creates new possibilities for ships.

[JensAyton]

there is no gravity or friction in space

Neither of these claims is remotely true. In real space flight, everything you do is restricted by orbital mechanics (i.e., gravity), and the upper limit on speed reachable by conventional means is determined by drag, even in interstellar space.

But Oolite doesn’t even try to be a space flight simulator.

[Dragonfire]

According to Nasa, they're true. I already brought up the conditions. Look at the links.

Anyway, I'm not saying Oolite is or should be a space sim. I'm just saying that there are less ship limitations than we thought.

[DaddyHoggy]

There's lots of gravity everywhere - all the time...

However, what you've chosen to miss/ignore is that the stuff coming out the back of the ship in Oolite isn't the propulsion of the ship, it's just the waste energy stream of the engines directed safely, if not necessarily harmlessly away from the ship.

Oolite cannot use "normal" i.e. Newtonian engines. Immense ships accelerating to decent fractions of the speed of light in a few seconds without squishing the ship and its occupants flat without using up any fuel (fuel after all is only used when hyper-spacing or overloading the engines by injecting raw quirium directly into the flux matrix), to hold that velocity without deviating from the chosen irrespective of the gravitational pull of any astronomical body in the vicinity and then to come to an absolute dead stop, again in a few seconds, and again, without using an fuel. Finally, an Oolite ship can hold this dead stop against the gravitational pull of even when in close proximity to the system's star, again, without the consumption of fuel or ejection of a reactionary material.

Oolite engines are therefore "magic" as our understanding of physics currently stands. Feel free to marvel, but there's no point in worrying about it (or suggesting its changed to something more Newtonian based).

[Dragonfire]

Well, I do know that the Oolite engines are rather special. I like 'em that way. Its a sci-fi. Again, the whole point of this topic was in light of someone talking about the limitations on top speed depending on the weight of a ship.

[drew]

there is no gravity or friction in space

Neither of these claims is remotely true. In real space flight, everything you do is restricted by orbital mechanics (i.e., gravity), and the upper limit on speed reachable by conventional means is determined by drag, even in interstellar space.

But Oolite doesn’t even try to be a space flight simulator.

Agreed on gravity, but not drag. Other than atmospherics, it's close to negligible a few AUs from a star. Available reaction mass is a far greater limiter on speed and the accompanying inertia of the resultant bulk - and currently 'c' remains the upper 'upper' limit.

As for Oolite. It's the Ooniverse, different physics applies. Light speed may or may not be something you could outrun in a Golf GTI, spaceships fly in the aether at a constant speed at full thrust. Planets don't orbit, spin in a couple of minutes and spaceships in your rearview mirror may appear close than they aren't.

Cheers,

Drew.

[DaddyHoggy]

According to Nasa, they're true. I already brought up the conditions. Look at the links.

Anyway, I'm not saying Oolite is or should be a space sim. I'm just saying that there are less ship limitations than we thought.

Well as a physicist and an ex-MOD rocket scientist, the first link is one of the worst answers I've ever seen to that question.

As for the Wikipedia link, well, not sure what you're point is - they're a collection of real propulsion systems and imaginary ones based on some very vague extremes on the edge of hypothetical physics.

And none of them cover the V&K 32.24 Ergmasters, with under-and-over firing tubes (the drive of the Anaconda for example) - which means that within the magic physics of the Ooniverse, supported by the game engine nothing on the Wikipedia page fits anywhere in the Ooniverse save perhaps the fiction section where two old-time spacers are laughing in a Seedy Space Bar about a new system trying to join Galcop but they're still using Ion Engines as a method of propulsion...

[Dragonfire]

Yeah, granted, neither link is perfect, but it kinda summed it up more or less. I just wanted to avoid some lamebrained blog as a source.

Anyway, the point is still the same. There is no reason why the larger ships should be slower.

[Okti]

Lbh pna punatr gur znk_fcrrq bs nal fuvc gb gur inyhr lbh jnag

Note: Was tagged as "off-topic" but other than a rot13 I don't know it was auto flagged or whether somebody didn't see the point of the post

[JensAyton]

According to Nasa, they're true. I already brought up the conditions. Look at the links.

Neither of those links attributes the claims you made to NASA.

The first says “ if you are in orbit or otherwise feel no acceleration (no gravity)”, which is misleading but acceptable in a resource intended for small children. An astronaut in orbit is affected by gravity, but it doesn’t cause an appreciable acceleration relative to to the vehicle. It does cause an appreciable acceleration relative to the Earth, otherwise the hypothetical astronaut wouldn’t be in orbit.

The Wikipedia article uses “in the absence of gravity” in a sloppy way in a footnote, but doesn’t claim that there is no gravity in space.

Even halfway through an interstellar voyage, a ship will be in orbit of the galaxy’s centre of mass. Within a solar system, again, [wp]orbital mechanics[/wp] dominates all navigation, which is why interplanetary probes take curved approaches often passing several different planets before getting to their destination.

As for friction: I recall reading a NASA paper which estimated the peak speed achievable by a beam-propelled solar sail in interstellar flight would be between 0.2c and 0.3c because of the drag of the interstellar medium. I can’t find it now. This short paper frome the University of Leicester suggests a peak of 0.015c after ten to a hundred thousand years of acceleration, assuming ambient interstellar hydrogen density but radiation pressure similar to sunlight at Earth. Almost any other means of propulsion offers more power (at the cost of carrying reaction mass), but this illustrates that the interstellar medium is present and not negligible.

[greenseng]

I never complain about the physics in Oolite.
The reason is that it is not impossible.

We are always referring to our rather limited knowledge of time and space.
But Oolite refers to a system that has a much more advanced experience of the universe.

If a ship would have its own gravity-field, and not being affected from any outside field - then things changes.
It would be like the ship is in a bubble - and has its own gravity. The bubble moves but that would not in any way affect the ship.
For the pilot it would be like sitting and watching a movie. S(he) would not have any experience of, for example, acceleration.
Neither would the ship.

If the ship could also handle the more relativistic effects that occures drastically in these velocities.
Then I cannot see any problems.

This is of course very simply explained - because of my rather limited knowledge of physics.
But still - the point is that a so sophisticated system has access to a totally different technology.
A technology that we cannot even dream about.
Because there are thoughts that we have never yet been thinking.

We laugh about that people at a certain point in time, saw the world as flat.
But nothing changes, really.
Try to think about what people will laugh about when it comes to us. People 1000 years into the future.
Big Bang?
Maybe just an example of many peoples problem to grasp the word - eternity.

[Killer Wolf]

"after ten to a hundred thousand years of acceleration,"

lol, that's quite a window.

[drew]

As for friction: I recall reading a NASA paper which estimated the peak speed achievable by a beam-propelled solar sail in interstellar flight would be between 0.2c and 0.3c because of the drag of the interstellar medium. I can’t find it now. This short paper frome the University of Leicester suggests a peak of 0.015c after ten to a hundred thousand years of acceleration, assuming ambient interstellar hydrogen density but radiation pressure similar to sunlight at Earth. Almost any other means of propulsion offers more power (at the cost of carrying reaction mass), but this illustrates that the interstellar medium is present and not negligible.

Ok, I'll let you have-non negligible in the context of a solar-sail ship given it has very low propulsion.

Given the particulate density in interstellar space is about 3 atoms per cubic metre, at 0.3c you would encounter 299792458*0.3 per second per square metre of surface area.

Say a reasonable solar sail is 1000 square metres that would give you around mean your ship would encounter about 90 billion atoms a second at 0.3c. Which is going to cause friction, (though not very much), but perhaps enough to equal the propulsive force of the solar wind or laser that is propelling the solar ship. I have no idea how strong that is.

Put it another way, at 0.3c the solar ship would be encountering about 1.5 x 10^-13 grams of hydrogen every second. (That's based on 1 mole of hydrogen weighs 1.008 g, 1 mole = 6.02 x 10^23 particles, thus mass of 1 atom = 1.008 g / 6.02 x 10^23 = 1.67 x 10^-24 g)

However, I can't see solar-sails being viable outside of a solar system anyway, so I'd submit they were an irrelevance for interstellar travel.

The friction from 90 Billion atoms would still be negligible to a conventional rocket or ion motor however and could be safely discounted, assuming such a ship has sufficient reaction mass to reach that speed (chemical rocket=impossible). The cross section of a 'conventional' ship would also be much smaller.

1 bar air pressure is about 10^25 molecules per cubic metre by comparison. Friction is a big issue.

Of course, what we really need is a technology that can give a sustained 1g acceleration without stupid amounts of reaction mass. That would get us to Alpha Centauri in a little over a year...

As for Elite/Oolite. In my Ooniverse friction is extremely high because of the 'aether' (Ooether?). Lightmach != Lightspeed. Ships therefore need to thrust against this to maintain a constant speed and can aerodynamically manuoeuvre using this friction (similar to Star Wars really). Top speed is therefore limited by ship design, mass and propulsive force. Exhaust outputs are some kind of reaction mass. (Except Thargoids who have a 'spacedrive') Your mileage will vary.

Cheers,

Drew.