Dive bombing the sun - or OOPS, misplaced a decimal!

[Hal]

Hello Folks,
As I was envisioning what happens when you use a star system that is in motion, the question of "What happens when the sun is in the way of where you want to go" arises.

Question: At what point will a 1 G craft run into problems due to the gravitational effects of the Sun where the ship's acceleration is not sufficient to pull away from the sun's gravitational pull - causing the 1G ship to divebomb the surface of the star/sun?

Just an idle and curious question to be sure, but it would be perhaps interesting if one can determine where the danger zone is of coming too close to a star not because of environmental issues per se, but because getting too close risks the ship being pulled in.

Anyone have a way of answering that?

 

[Icosahedron]

You can mathematically calculate the radius at which the gravitational pull of a body is equal to 1G thrust with high school maths, if that is what you mean, but in practical terms it wouldn't help much, because both the ship and the star would both be moving relative to each other and escape velocity equations would muddy the waters. Move to University maths...

However, the simple answer to your question is - don't bother.

If you use the idea of gravity precipitating you out of Jump at 100D, you're safe anyway, but even if not, space is so huge compared with the pinprick size of ships and even stars, that the chances of accidentally finding yourself in harm's way are practically zero. The idea of jumping into a system and finding yourself plummeting into a star or being hammered by a meteor storm is pure cinematic fantasy.

You couldn't afford to buy enough dice to enumerate the infinitesimal chance.

You could do it by GM fiat, of course, but then why not make it up all the way - "you just happen to be within the star's reach - whatever that might be, and you need to make an Engineering roll to overstress the drives long enough to pull clear..."

 

[Hal]

You can mathematically calculate the radius at which the gravitational pull of a body is equal to 1G thrust with high school maths, if that is what you mean, but in practical terms it wouldn't help much, because both the ship and the star would both be moving relative to each other and escape velocity equations would muddy the waters. Move to University maths...

However, the simple answer to your question is - don't bother.

If you use the idea of gravity precipitating you out of Jump at 100D, you're safe anyway, but even if not, space is so huge compared with the pinprick size of ships and even stars, that the chances of accidentally finding yourself in harm's way are practically zero. The idea of jumping into a system and finding yourself plummeting into a star or being hammered by a meteor storm is pure cinematic fantasy.

You couldn't afford to buy enough dice to enumerate the infinitesimal chance.

You could do it by GM fiat, of course, but then why not make it up all the way - "you just happen to be within the star's reach - whatever that might be, and you need to make an Engineering roll to overstress the drives long enough to pull clear..."

What I'm looking to do is deal with the topic of normal space navigation. If someone were to use normal space instead of jump space - how would they go about it? Lets suppose for the sake of argument, that the "boat" can't use jump space, and that the reason such a craft may be involved in such a navigational plot is because the "boat" is involved in patrols.

 

[rust]

Question: At what point will a 1 G craft run into problems due to the gravitational effects of the Sun where the ship's acceleration is not sufficient to pull away from the sun's gravitational pull - causing the 1G ship to divebomb the surface of the star/sun?

It would probably depend on the position, speed and vector of the ship as well as the mass of the sun in question - obviously not easy to calculate.

 

[Hal]

It would probably depend on the position, speed and vector of the ship as well as the mass of the sun in question - obviously not easy to calculate.

Probably the only thing I can do is determine what the gravity gradients are based on the rules from Book 2: Starships and see what that gives me. Per the internet's wikipedia (how trustworthy is that?!!!), the surface gravity of the Sun is about 28G's with about 109 x the radius of that of the Earth. It probably won't be too difficult to do the math (I hope!)

Edit: At a guess? I would assume that the ship in question needs to accelerate for at least as many turns at 1g as the ship may need for escape velocity for the sun in question. In other words, if entering a region where the gravity of the sun at the distance indicated is 1/2 that of its surface gravity, it would ned to have a built up velocity of around 14 g's or 14 turns at 1 G before entering that "band" of gravity gradient. Mind you this is but a guess. I'll have to try out some vector movement to see just how it would act.

 

[far-trader]

Probably the only thing I can do is determine what the gravity gradients are based on the rules from Book 2...

Yep, that's what I was going to suggest

Wiki looks in the ballpark close enough for Traveller anyway. Plugging the numbers into the formula I get a "surface" G of about 27, and a Traveller size code of about 108.5

Your guesstimate looks good enough for gaming imo. But I'm only guessing too

If you want to do other suns you can probably assume the same average density (about 0.25 Earth, that's the K in the Traveller formula for those wondering) and find the diameters by googling.

 

[Maladominus]

You could do it by GM fiat, of course, but then why not make it up all the way - "you just happen to be within the star's reach - whatever that might be, and you need to make an Engineering roll to overstress the drives long enough to pull clear..."

Just to make the game interesting.... I've done something like this whenever the Navigator (Astrogator) made a skill roll of a "2" (snake eyes, critical failure, fumble).

 

[Hal]

Just to make the game interesting.... I've done something like this whenever the Navigator (Astrogator) made a skill roll of a "2" (snake eyes, critical failure, fumble).

It works well enough from a drama driven game, but for a mathematically driven game (ie where you pick your course and you HAPPEN to shave it too close) then you've got a different ball park to play in. One is for role playing, the other is for war gaming. I'm looking for the wargaming answer

As an example of what can come into play, is when a interplanetary vessel is on a path between worlds and has to avoid the sun which may be between where it needs to go to and where it is now, in an effort to catch up with the planet as it goes its merry little way.

 

[Icosahedron]

Ok, I think I see what you're trying to do now. There are two ways of dealing with it: you can use some pretty awful calculus to figure a slingshot around the star, or you can use the Book 2 Vector system as a near-enough game approximation. I know which I'd rather do!

Just scale up the Book 2 vectors by using different units so that you can put the whole of your journey on a tabletop, creating a sort of 'strategic map', and use that to figure out your route. As long as you scale everything up in the right proportion the maths should still work and you'll get an overall picture that you can scale back down again to your 'tactical map' when you need to do combat, etc.

Just remember that Navigators are usually better at this sort of thing than players and have a powerful computer system to help them plot a course.
As a player, I'd be a little miffed if my GM had me crash into the sun just because i'd initially pointed my model half a degree too far clockwise...
But I'm sure you already have that covered.

 

[BlackBat242]

And remember, you can pass a lot closer to the sun and still escape if you use a "glancing" vector rather than a direct in/out vector. After all, as you get closer, the sun's gravitational pull accelerates you, so you just need to apply enough sideways vector to shift your course at (or just before) the desired point of closest approach.

Preferably while the hull temp is still in the safe range.