What would a realistic spaceship chase look like?

[Adam Reynolds]

In a setting that actually obeys the laws of physics, what should a proper spaceship chase look like?

Is there a way to make this dramatically interesting or is it simply a case of the cold equations dictating who will win or lose without any interesting options for strategy?

[chimericoncogene]

Geared variable thrust/specific impulse rockets, reinforcements/ticking clocks, and delta-vee limitations are some variables which may make space chases interesting.

Do you go for high thrust and run down the enemy before they can reach safety? Do they go for high thrust and get away, or do they try to minimize total travel time at a higher delta-vee (but lower thrust)? How do your reinforcements react? Are there multiple groups of potential reinforcements? Can the enemy wait for reinforcements? Which one of your pursuers can you afford to fight?

I have never modeled these mathematically, and am but an amateur, but these seem like good starting points for dramatic flair.

[Lord Revan]

Realistically speaking we should also remember that people won't be fighting over empty space, so a chase happening at random spot in Deep Space is not as likely as one happening in a star system and thus you got stellar "terrain" to consider as well (asteroids may not be that big of a hazzard but you can still hide on one, near one or possibly even inside one).

Also while your energy signature is like a flare at night in Deep Space, near a planet or a star it might not be as obvious as those have quite a signifigant energy signature of their own.

[chimericoncogene]

Realistically speaking we should also remember that people won't be fighting over empty space, so a chase happening at random spot in Deep Space is not as likely as one happening in a star system and thus you got stellar "terrain" to consider as well (asteroids may not be that big of a hazzard but you can still hide on one, near one or possibly even inside one).

Also while your energy signature is like a flare at night in Deep Space, near a planet or a star it might not be as obvious as those have quite a signifigant energy signature of their own.

If you have high-thrust torchships that get you to 100km/s delta-vee in under a week, stellar terrain becomes less relevant, and the opponent becomes much moreso. If you need a week to get out of Earth Orbit, that's another matter entirely. It's probably setting dependent.

For a near-future spaceship chase, see the excellent novel Saturn Run, which has a nuclear lightbulb being more-or-less chased down by a nuclear-electric spacecraft.

[Batman]

1960s technology didn't need a week to get out of Earth orbit. And 100kps in under a week is a fraction of one g. Torchship my ass.

[chimericoncogene]

1960s technology didn't need a week to get out of Earth orbit. And 100kps in under a week is a fraction of one g. Torchship my ass.

Well, a solar-electric bird that takes anything less than two months to get out to the Moon is "insanely overpowered" by current and near-future standards. I recall the 80s SEP tugs had estimates of six months to get to the moon. Modern tugs... ditto-ish. My napkins say a 300kW, 3000s Isp SEP tug can get ~30 metric tonnes to the moon in ~6 months, and NASA goals are to get an SEP cargo to the moon in under... two years.

Of course, a hydrolox upper stage could do it in two days, but spaceship designs will differ. Which is highly relevant for a spacecraft chase.

http://www.astronautix.com/s/septug.html

https://rocket.com/sites/default/files/ ... 0paper.pdf

See the table on page 14, and the stuff on page 12. They're looking at a one-year trip out to LLO with a 30 tonne payload and a 30 tonne spacecraft.

And I haven't quite seen any realistic slightly mature propulsion system that can get you 100km/s in a week. Maybe Orion or some kind of nuclear fusion/pulsed fission rocket, but those are quite mid-future, not immediate-future. Ion drives would take over a year to get to that at least, by my guess. A few hundred km/s within a few weeks gets you to Mars in under two weeks, Neptune in under a year and Saturn in a quick four months - it's nothing to sneeze at. Space is big, and rockets are hard.

As usual, it depends on the setting and distance into the future.

A fun mix into this is beamed propulsion. If some spacecraft are beam-riders (e.g. MagBeam), military spacecraft might be able to intercept them provided they have the delta-vee. The dynamic interactions between different propulsion systems and different safe havens/groups can be used to set up a range of scenarios.

[LadyTevar]

I always thought it would be more like StarTrek "Balance of Terror".

[Gandalf]

I always thought it would be more like StarTrek "Balance of Terror".

In what way?

[Adam Reynolds]

I always thought it would be more like StarTrek "Balance of Terror".

In what way?

I'm assuming in the slow deliberative sense like The Hunt for Red October. Depending on the type of acceleration, this might almost work.

[Tribble]

Also, I imagine that the weapons being used could have a big impact. How useful could maneuvering be if the spaceships are capable of using laser weapons which can cross the distance at the speed of light? Especially if they are able to adjust their orientation while firing? Unless it’s blocked by something you’d have to be very maneuverable to dodge and/or be at a large enough distance to have enough time to do so.

Not a scientist, but I imagine that a battle involving laser weapons would be pretty boring to watch? The laser would be invisible in a vacuum, and it’s effective range would likely be large enough that ships would be well outside human visual range while fighting?

[Lord Revan]

Also, I imagine that the weapons being used could have a big impact. How useful could maneuvering be if the spaceships are capable of using laser weapons which can cross the distance at the speed of light? Especially if they are able to adjust their orientation while firing? Unless it’s blocked by something you’d have to be very maneuverable to dodge and/or be at a large enough distance to have enough time to do so.

Not a scientist, but I imagine that a battle involving laser weapons would be pretty boring to watch? The laser would be invisible in a vacuum, and it’s effective range would likely be large enough that ships would be well outside human visual range while fighting?

depends on your point of view, you can make fight between invisible foes using invisible weapons not be boring, if you make kind of a cat and mouse where both sides try to line up the perfect shot to take out the enemy while avoid allowing the enemy from getting said shot. It's different from a typical pew, pew lightshow but it doesn't have to be boring.

and while deep space is empty, it's also utterly worthless and where there's anything of worth there tends to be ways of hiding from the enemy or at very least obscuring their view of you so that targeting will be harder.

[Gandalf]

I always thought it would be more like StarTrek "Balance of Terror".

In what way?

I'm assuming in the slow deliberative sense like The Hunt for Red October. Depending on the type of acceleration, this might almost work.

Yeah, slow and deliberative makes sense, but one of the defining characteristics of the space combat in that episode was that apparently making noise in a spaceship is apparently a problem.

[Jub]

It's spread out, but depending on your setting's technology and level of colonization there are going to be rogue planets well outside of a solar system's influence but very much worth inhabiting. They could easily be set up as pirate bases, military listening/observation posts, getaways for the super-elite, or anything else you can imagine doing in an out of the way location that's difficult to find and to reach. That could make a nice twist for a chase through otherwise empty space.

Other factors could make chases and battles with invisible weapons interesting. Heat could be a primary factor, can the small and nimble ship with high burst speed but low thermal mass dodge the larger and slower ship and reach safety or will the larger ship catch it up over days/hours/weeks as it remains able to accelerate and fire weapons? Did that grazing hit that tore open the water tank you were using as radiation shielding doom your crew or are they able to fit enough people into the still shielded sections of the ship to make it without losing important crew members/cargo?

[Eternal_Freedom]

Yeah, slow and deliberative makes sense, but one of the defining characteristics of the space combat in that episode was that apparently making noise in a spaceship is apparently a problem.

I always figured that it wasn't trying to be quiet aboard ship on purpose, but everyone did so anyway as a psychological thing. If you're trying to be quiet, you're going to be deliberately paying attention to avoid pressing anything that woudl emit signals the enemy can detect - which is what I think Spock did, pressed the wrong panel and emitted the ST equivalent of an active sonar ping by mistake.

[LadyTevar]

I always thought it would be more like StarTrek "Balance of Terror".

In what way?

I'm assuming in the slow deliberative sense like The Hunt for Red October. Depending on the type of acceleration, this might almost work.

Yes, this. Cat and mouse, where you have to anticipate the other's movements, because a meter off on your movements could put your shots a thousand meters off target 'downrange'.

[LadyTevar]

depends on your point of view, you can make fight between invisible foes using invisible weapons not be boring, if you make kind of a cat and mouse where both sides try to line up the perfect shot to take out the enemy while avoid allowing the enemy from getting said shot. It's different from a typical pew, pew lightshow but it doesn't have to be boring.

and while deep space is empty, it's also utterly worthless and where there's anything of worth there tends to be ways of hiding from the enemy or at very least obscuring their view of you so that targeting will be harder.

See "Wrath of Khan" in the Nebula, where Khan is playing chess, and Kirk was playing 3D Chess and going over and under to line up the target. Or, again, Balance of Power, where a comet's tail is use to reveal a pursuer. Or... Red October. How many 'Crazy Ivans' would you have to do to find the one chasing you? Or would you risk the maneuver, if it'd cost you a lead?

Hell, we've a wealth of High Seas stories that can give ideas for what could happen in a Space Chase.

[Lord Revan]

depends on your point of view, you can make fight between invisible foes using invisible weapons not be boring, if you make kind of a cat and mouse where both sides try to line up the perfect shot to take out the enemy while avoid allowing the enemy from getting said shot. It's different from a typical pew, pew lightshow but it doesn't have to be boring.

and while deep space is empty, it's also utterly worthless and where there's anything of worth there tends to be ways of hiding from the enemy or at very least obscuring their view of you so that targeting will be harder.

See "Wrath of Khan" in the Nebula, where Khan is playing chess, and Kirk was playing 3D Chess and going over and under to line up the target. Or, again, Balance of Power, where a comet's tail is use to reveal a pursuer. Or... Red October. How many 'Crazy Ivans' would you have to do to find the one chasing you? Or would you risk the maneuver, if it'd cost you a lead?

Hell, we've a wealth of High Seas stories that can give ideas for what could happen in a Space Chase.

Yeah there's plenty of stories to draw from as long as you let go of the notion that this chase must happen at random spot in Deep Space as far from anything that could block or obscure sensors as humanly possible so that both sides will have clear visibility at all times and neither side would ever try to prevent the other side from seeing them.

[Captain Seafort]

Yeah there's plenty of stories to draw from as long as you let go of the notion that this chase must happen at random spot in Deep Space as far from anything that could block or obscure sensors as humanly possible so that both sides will have clear visibility at all times and neither side would ever try to prevent the other side from seeing them.

Why? There are plenty of examples of naval battles occurring in mid-ocean, out of sight of land. Why should interstellar battles be any different?

[Lord Revan]

Yeah there's plenty of stories to draw from as long as you let go of the notion that this chase must happen at random spot in Deep Space as far from anything that could block or obscure sensors as humanly possible so that both sides will have clear visibility at all times and neither side would ever try to prevent the other side from seeing them.

Why? There are plenty of examples of naval battles occurring in mid-ocean, out of sight of land. Why should interstellar battles be any different?

sure battles happen at high seas and I'm not saying battles would absolutely never happen in deep space however, space is huge and unless you're actively trying to intercept the enemy at deep space it's even less likely that ships would stumble into each other at deep space then it would for them to stumble to each other at high seas.

What I'm arguing against is that space battles absolutely must happen at deep space with 100% visibility and 0% cover on both sides. So I'm saying that battles could happen near stellar objects that could obstruct or confuse sensors, the same way some naval battles did happen near islands or coastlines.

After all you wouldn't defend a random piece of deep space no more then you'd defend a random piece of ocean with no land anywhere near, actually even less since a piece of ocean might have resources you'd want to harvest while deep space is by the very definition empty for all intents and purposes (if there's anything meaningful there it's not deep space).

[Eternal_Freedom]

Yeah there's plenty of stories to draw from as long as you let go of the notion that this chase must happen at random spot in Deep Space as far from anything that could block or obscure sensors as humanly possible so that both sides will have clear visibility at all times and neither side would ever try to prevent the other side from seeing them.

Why? There are plenty of examples of naval battles occurring in mid-ocean, out of sight of land. Why should interstellar battles be any different?

Like what? The only one I can think of that occurred actually mid-ocean (and not with one force coming from/going to somewhere else and being intercepted, like Midway) was the Denmark Strait, and that was Bismarck being hunted by half the Royal Navy to stop her from raiding the convoys. Out of sight of land, yes, but there was still some form of "terrain" - convoys heading to port, one force intercepting another before it reaches it's target etc. I can't think of any that occur with two forces meeting up in the middle of the ocean and just opening up on each other.

I think that's an important point for this "realistic spaceship chase" idea - why is one spacecraft chasing another? Is it intercepting a commerce raider before/after an attack on a convoy? Is it pursuing/intercepting a strike on a planet/space station? Is it customs officers running down a smuggler?

[Lord Revan]

I think that's an important point for this "realistic spaceship chase" idea - why is one spacecraft chasing another? Is it intercepting a commerce raider before/after an attack on a convoy? Is it pursuing/intercepting a strike on a planet/space station? Is it customs officers running down a smuggler?

Yeah that's a very good point, battles happen rarely if ever "just because", same for chases and there's generally a reason for them happening it (it might not be good reason but it's typically more then "they were there and I had guns"). So the question "why is this happening" tells us what the terrain will be.

[Jub]

Like what? The only one I can think of that occurred actually mid-ocean (and not with one force coming from/going to somewhere else and being intercepted, like Midway) was the Denmark Strait, and that was Bismarck being hunted by half the Royal Navy to stop her from raiding the convoys. Out of sight of land, yes, but there was still some form of "terrain" - convoys heading to port, one force intercepting another before it reaches it's target etc. I can't think of any that occur with two forces meeting up in the middle of the ocean and just opening up on each other.

I think that's an important point for this "realistic spaceship chase" idea - why is one spacecraft chasing another? Is it intercepting a commerce raider before/after an attack on a convoy? Is it pursuing/intercepting a strike on a planet/space station? Is it customs officers running down a smuggler?

Do escorts fighting off submarines in the Atlantic count because there was a whole part of both World Wars just about battles taking place as far away from other fleets and defences as possible.

[Captain Seafort]

Do escorts fighting off submarines in the Atlantic count because there was a whole part of both World Wars just about battles taking place as far away from other fleets and defences as possible.

There was also the Glorious First of June - a French Revolutionary War fleet action fought over a convoy.

[Eternal_Freedom]

Again though, those still have "terrain" of a sort - think of it as "anything that constrains the battle area" rather than geographic features. So - the convoy escort actions, or the Glorious First of June (which, in fairness, had slipped my mind) still had something that made them fight there. There was some factor that dictated when and where the battle would be, rather than just "ship A runs into ship B in the open ocean and opens fire."

The closest thing I can think of that fits that description would be commerce raiders encountering merchant ships but there is still a reason why the ships are there.

[Captain Seafort]

Again though, those still have "terrain" of a sort - think of it as "anything that constrains the battle area" rather than geographic features. So - the convoy escort actions, or the Glorious First of June (which, in fairness, had slipped my mind) still had something that made them fight there. There was some factor that dictated when and where the battle would be, rather than just "ship A runs into ship B in the open ocean and opens fire."

The closest thing I can think of that fits that description would be commerce raiders encountering merchant ships but there is still a reason why the ships are there.

I agree that it would be extraordinarily rare (and I use that term only because the word "never" has a habit of kicking it's users in the teeth) for any battle to be fought completely independently from strategic geography. My comments were more aimed at the objections being raised to battles fought independent of physical geography.