Interstellar travel

[Pthigrivi]

Im completely psyched for this. Im so used to gently coasting around the solar system in graceful ellipses its going to be quite a thing to learn brachistochrone trajectories and efficient solar escapes. There's a lot we don't know yet, and things that I just don't know about the reality of interstellar travel. Here are a few questions I have. We'll probably have to wait till near release to find out most of these but I thought I'd throw them out there to for us to think about. 

1) How many star systems will be available? And just how far away will they be? At KSP's 1/10 scale that would still put Alpha Centauri at .43 ly, or 400 billion kilometers. Compared to Jool at 72 million km thats a loooong way. It also seems like any in-game nearby star should have at least a couple of planets to make it worth visiting, which isn't too outlandish. Proxima Centauri, Wolf 359, and Lalande 21185 each have two confirmed exoplanets, Tau Ceti and Luyten's Star have 4, and HD 219134 has 6. 

2) What kind of max acceleration do we think these crazy sci-fi engines will be capable of? I recall that a ship accelerating at 1g would reach nearly the speed of light in about a year and could reach Alpha Centauri within 6. That sounds kind of absurd though and I haven't seen any near-futurish proposals that approach those speeds. Project Daedalus was designed to reach 12% the speed of light over a little less than 3 years and perform a flyby of Bernards Star in about 50 years, and Longshot and some beamed energy proposals I've seen range from 40 to 150 years to orbit nearby stars. At 1/10th scale those kinds of speeds sound more reasonable. And it would be a little easier to excuse omitting relativistic time dilation.

3) What are some other implications for interstellar travel? Will other stars have meaningful relative motion that we'll need to account for? Bernards star is moving at about 90 km/s and Alpha Centauri is moving at about 24 km/s relative to the sun, but that might also be scaled down by a factor of 10? or omitted for simplicity? Something I don't even know is if the sun's bow shock is dangerous at all radiation-wise?  If there are binary stars how will that effect orbital navigation? And of course this doesn't begin to consider all the wacky new planets they might have planned.  Will there be a discovery mechanic that unlocks them  when you reach a certain technological level and tells you a little about what to expect so you can plan your grand colonization projects? Or will you want to send fly-by probes first?

Anyone else been thinking about this?



 

Edited July 6, 2021 by Pthigrivi

[Dientus]

6 hours ago, Pthigrivi said:

Will other stars have meaningful relative motion that we'll need to account for?

This. I have been wondering this a lot. Afterall, we do not aim craft straight at alpha Centauri anymore than we do the moon. All stars are traveling at various speeds around the galactic core which is, itself moving.

 

And the oort cloud, will it be there in some fashion? It's obviously out there on the edges of Kerbol (and pretty much all stars) due to how star systems form and is hinted at by the roaming comets and asteroids in the system.

 

Also, will cosmic radiation play a role? If so, how realistic will it be portrayed? What about interstellar medium? Will there be just dust? Or will it realistically attempt to have hydrogen and helium? Will any of it be harvestable?

 

Tons of questions I wonder about so you are not alone.

[The Aziz]

1. They always say "multiple". Which implies at least two. And I say, for good replayability, at least 4 are needed. We'll see.

2. Thing is, you also have to decelerate. About halfway through, so the flight time extends significantly.

[MKI]

My guess on how the game will integrate alternate star systems, and manage the task of having to travel between them will probably be in the same vein as current travel around the Kerbal solar system.

I wouldn't be surprised if alternate star systems just "orbit" around the Kerbal one or all orbit around a shared point, making the entire setup similar to Kerbin and its moons. This would keep the same principles in place, but at a much grander scale. 

23 hours ago, Pthigrivi said:

And it would be a little easier to excuse omitting relativistic time dilation.

I think the game will sidestep this problem all together, where a Kerbal in their own reference frame would be the same to all observers, in regards to gameplay mechanics. They don't go hungry/go-crazy or get lonely so a Kerbal flying to another star system at a percentage of light speed would act the same as one stationary on the ground. Maybe this is some Kerbal physics general relativity law?

 

 

[Dientus]

6 minutes ago, MKI said:

I think the game will sidestep this problem all together, where a Kerbal in their own reference frame would be the same to all observers, in regards to gameplay mechanics. They don't go hungry/go-crazy or get lonely so a Kerbal flying to another star system at a percentage of light speed would act the same as one stationary on the ground. Maybe this is some Kerbal physics general relativity law?

Thats my assumption since time dilation doesn't exist in the original.

 

It could make for an interesting mod if someone can figure out a way to implement it, but I have no clue how that could be done atm.

[TLTay]

14 hours ago, The Aziz said:

2. Thing is, you also have to decelerate. About halfway through, so the flight time extends significantly.

Interstellar aerobraking challenge accepted.

[Pthigrivi]

28 minutes ago, Dientus said:

Thats my assumption since time dilation doesn't exist in the original.

I think its been confirmed that they aren't doing it. I was just saying at less than 15% the speed of light it seems okay to handwave it away. 

18 hours ago, Dientus said:

And the oort cloud, will it be there in some fashion? It's obviously out there on the edges of Kerbol (and pretty much all stars) due to how star systems form and is hinted at by the roaming comets and asteroids in the system.

And supposedly there's a trans neptunian object analog besides eeloo maybe? 

18 hours ago, Dientus said:

This. I have been wondering this a lot. Afterall, we do not aim craft straight at alpha Centauri anymore than we do the moon. All stars are traveling at various speeds around the galactic core which is, itself moving.

This seems like it could be one of the more profound and interesting challenges in the game, and one of the things Im most excited to learn. There are also cool ideas like Bussard ramjets but I believe its been determined that they're not feasible.  I think Nate also confirmed solar sails wouldn't be available at launch but I'd love to see something like that and beamed energy propulsion maybe in an expansion down the road.

 

Edited July 7, 2021 by Pthigrivi

[Dientus]

1 hour ago, Pthigrivi said:

and beamed energy propulsion maybe in an expansion down the road.

I play a mod in KSP that uses beamed energy, very intriguing to say the least. Sometimes it's very cool and wonderful, sometimes very clunky and troublesome. 

 

1 hour ago, Pthigrivi said:

I think its been confirmed that they aren't doing it. I was just saying at less than 15% the speed of light it seems okay to handwave it away. 

I agree, especially for gameplay... but to play devils advocate, what if they use the helical engine that can hypothetically travel 99% the speed of light?

 

1 hour ago, Pthigrivi said:

And supposedly there's a trans neptunian object analog besides eeloo maybe? 

I keep wanting to use the gravitational and mass formulae to explain Eeloo s orbit but just never crunched the numbers. I bet @K^2

May have a better understanding of that.

 

Sorry edit mobile bug struck again

It would be useful to verify the theory and hypothesize the mass of the object.

[K^2]

6 hours ago, Dientus said:

I keep wanting to use the gravitational and mass formulae to explain Eeloo s orbit but just never crunched the numbers. I bet @K^2

May have a better understanding of that.

Nothing terribly useful, I'm afraid. If we were to imagine that Eeloo's orbit is caused entirely by some external source, then it has to come close to Eeeloo's apoapsis, which is actually not all that far out. If some mysterious planet X is lurking far away from Kerbol, surely, it'd be much further than that. However, the fact that Eeloo's periapsis is close to Jool's orbit makes it way more likely that Eeloo's orbit was altered by Jool's gravity. In the latter case, current orbit of Eeloo tells us nothing about what deflected it into inner system to begin with.

Now, Eeloo and Jool don't currently pass all that close to each other - closest approach is about 16 million km due to inclination, which is greater than distance between Kerbin and Kerbol. If Eeloo was deflected by Jool, the orbits had to have come a lot closer than that some time in the past. It's hard for me to say if perturbations from Jool's gravity alone could account for that much drift. But then, there is no other obvious source. Unless a rogue planet happened to pass through Kerbol system at some point in the past, I have no other explanation.

[Bej Kerman]

12 hours ago, MKI said:

I wouldn't be surprised if alternate star systems just "orbit" around the Kerbal one or all orbit around a shared point, making the entire setup similar to Kerbin and its moons. This would keep the same principles in place, but at a much grander scale. 

I'd imagine each star's position is defined by RA/Dec and distance, rather than SMA, inclination and eccentricity as with KSP 1.

[Dientus]

5 hours ago, K^2 said:

Unless a rogue planet happened to pass through Kerbol system at some point in the past, I have no other explanation.

Thank you, I always love your insight and accuracy. Your rogue planet idea throws questions to my mind, and actually is thread related. 

 

Could a rogue planet explain Dres' orbit? Are there rogue planets that can be encountered during interstellar travel? If so, will any of these planets have travel orbits/lines like the stars, independent around a central mass, or could they potentially be caught in a large orbit around two or more stars?

 

That could be interesting, ride a rogue planet to the next star system.

[K^2]

10 hours ago, Dientus said:

Could a rogue planet explain Dres' orbit? Are there rogue planets that can be encountered during interstellar travel? If so, will any of these planets have travel orbits/lines like the stars, independent around a central mass, or could they potentially be caught in a large orbit around two or more stars?

The only reason Dres looks weird is because it's alone, and I think that's purely a limitation of a game being a game. If we were to see Dres as just largest of the belt asteroids, its orbit looks like remnants of a failed planet formation which could be due to interaction with Jool.

A rogue planet can definitely be captured if it interacts with any planets within the system, but stable orbits involving more than two objects are exceptionally rare. The only exception I'm even aware of that occurs naturally is the Janus / Epimetheus situation, and that one's only possible due to both of them being light compared to Saturn that they are in orbit of. There are some theoretical multi-body structures that are gravitationally stable, but they are all too precise to occur naturally. (See N-Body Choreography). So a rogue planet is bound to remain a true rogue unless captured, potentially passing through star systems, but no more than once.

For the purpose of a game like KSP2, I would be happy with a rogue planet just having a fixed position - same with stars. You can have considerable relative velocities between stars, but in a game, that introduces a lot of technical questions that just aren't worth addressing, IMO.

[Dientus]

14 minutes ago, K^2 said:

There are some theoretical multi-body structures that are gravitationally stable, but they are all too precise to occur naturally. (See N-Body Choreography). So a rogue planet is bound to remain a true rogue unless captured, potentially passing through star systems, but no more than once.

Reading through some papers linked to that got me thinking but those thoughts are beyond the scope of this thread. Thanks for the good start!

 

16 minutes ago, K^2 said:

For the purpose of a game like KSP2, I would be happy with a rogue planet just having a fixed position - same with stars. You can have considerable relative velocities between stars, but in a game, that introduces a lot of technical questions that just aren't worth addressing, IMO.

True. I can get behind this and use the KISS rule.

[magnemoe]

On 7/7/2021 at 10:32 PM, TLTay said:

Interstellar aerobraking challenge accepted.

Reminds me of an Man-Kzin story, Drop an small ship of an buzzard ramjet at relativistic velocity and aerobreak it in the sun. 
Its pretty large an the heat is not an issue compared to having to get rid of perhaps 100 ton relativistic mass. 
The Kzin would be believe this was done just to generate an solar flare. Downside is that you need an stasi field 

[magnemoe]

On 7/6/2021 at 10:35 PM, Pthigrivi said:

Im completely psyched for this. Im so used to gently coasting around the solar system in graceful ellipses its going to be quite a thing to learn brachistochrone trajectories and efficient solar escapes. There's a lot we don't know yet, and things that I just don't know about the reality of interstellar travel. Here are a few questions I have. We'll probably have to wait till near release to find out most of these but I thought I'd throw them out there to for us to think about. 

1) How many star systems will be available? And just how far away will they be? At KSP's 1/10 scale that would still put Alpha Centauri at .43 ly, or 400 billion kilometers. Compared to Jool at 72 million km thats a loooong way. It also seems like any in-game nearby star should have at least a couple of planets to make it worth visiting, which isn't too outlandish. Proxima Centauri, Wolf 359, and Lalande 21185 each have two confirmed exoplanets, Tau Ceti and Luyten's Star have 4, and HD 219134 has 6. 

2) What kind of max acceleration do we think these crazy sci-fi engines will be capable of? I recall that a ship accelerating at 1g would reach nearly the speed of light in about a year and could reach Alpha Centauri within 6. That sounds kind of absurd though and I haven't seen any near-futurish proposals that approach those speeds. Project Daedalus was designed to reach 12% the speed of light over a little less than 3 years and perform a flyby of Bernards Star in about 50 years, and Longshot and some beamed energy proposals I've seen range from 40 to 150 years to orbit nearby stars. At 1/10th scale those kinds of speeds sound more reasonable. And it would be a little easier to excuse omitting relativistic time dilation.

3) What are some other implications for interstellar travel? Will other stars have meaningful relative motion that we'll need to account for? Bernards star is moving at about 90 km/s and Alpha Centauri is moving at about 24 km/s relative to the sun, but that might also be scaled down by a factor of 10? or omitted for simplicity? Something I don't even know is if the sun's bow shock is dangerous at all radiation-wise?  If there are binary stars how will that effect orbital navigation? And of course this doesn't begin to consider all the wacky new planets they might have planned.  Will there be a discovery mechanic that unlocks them  when you reach a certain technological level and tells you a little about what to expect so you can plan your grand colonization projects? Or will you want to send fly-by probes first?

Anyone else been thinking about this?

My guess is 10% scale or perhaps less, say 1000x distance to Jool or in the 50-100 billion range. 
We seen the huge fusion craft 

(Musk this is an starship, you are building an fully reusable heavy lift rocket who can be refueled in space) 

We have orion pulse nuclear but that is very marginal for interstellar, decent chance the above will overtake it. 

Will we get antimatter, some of the power plants we seen hint about this as they are gigantic, scaled more for powering countries than an small colony. 

They also hinted about an Epstein  style engine as kind of the end game reward. 

We can do burns while not having the ship in focus. This allows for week or month long burns. 

Star movement, as you will be moving at many thousands of km/s my guess is that the stars are stationary. This make its easier with very long games, dlc and mods with new stars and binary stars who will rotate around their center of gravity. 
-----
My guess is that going interstellar will be longer than deep space missions in KSP1. Yes I'm already thinking of the above ship in an 1+6 asparagus config. 
On the other hand even orion pulse nuclear will make travel inside the kerbol system an joke, an month to Jool will be standard.