Binary star system travel

[T.Neo]

Imagine you are an alien on a planet orbiting STAR A.
You want to send a spaceship to the planet orbiting STAR B.
STAR B is orbiting around STAR A.
What Dv would be required to reach the target planet, and what Dv would be required for braking at the destination?

EDIT:
NOTE: drawing not to scale, planets need not be in the positions shown at departure or arrival.

EDIT EDIT:
Say the stars are 20-30 AU from each other, and the planets are 1 AU from their respective stars.

 

[astrosammy]

You could try out it in Orbiter.
The best way would be to use Star A as the main Star, with Planet A as a planet, and add an additional huge planet as Star B with a moon called Planet B. I'll try to do that now.

 

[T.Neo]

I'm tearing my hair out trying to get this to work. :compbash2:

 

[astrosammy]

Ok I tried it, IMFD showed a ejection DV of 11.26k an a injection DV of 7.459k.

 

[T.Neo]

An external gravitational force seems to pull me away from Planet A, and I just got a CTD.

 

[dougkeenan]

STAR B is orbiting around STAR A.

Is that situation actually found in nature? (Just the stars, not any planets!)

When I think of a binary system my uneducated guess would be they each orbit the other (that is, the barycenter is outside both).

I don't know how that would alter the math if at all. Otherwise aren't we just talking about traveling to Jupiter?

 

[T.Neo]

When I think of a binary system my uneducated guess would be they each orbit the other (that is, the barycenter is outside both).

That is probably more likely, don't know how it would be simulated in Orbiter though.
Flying around binary system would be interesting.

Otherwise aren't we just talking about traveling to Jupiter?

No, we are essentialy traveling to jupiter's moon.
I was wondering if the relative velocities of Planet A and Planet B would impose any restrictions on travel.

 

[Ghostrider]

Otherwise aren't we just talking about traveling to Jupiter?

Well, if you fancy photosphere-braking...

 

[T.Neo]

Well, if you fancy photosphere-braking...

:suicide:

I've actually pondered photosphere-braking for interstellar craft.
Your heatshield will have to be either a mile thick of made of unobtainium.
You'll probably need a mile thick heatshield made of unobtainium. :hmm:

 

[Artlav]

Your heatshield will have to be either a mile thick of made of unobtainium.
You'll probably need a mile thick heatshield made of unobtainium. :hmm:

Depends on the size of a star. A red giant may be the size of earth orbit, but it's as dense as outer space.

 

[T.Neo]

Depends on the size of a star. A red giant may be the size of earth orbit, but it's as dense as outer space.

Wouldn't surprised it it was. But still, isn't it at extremely high temperatures?

 

[flytandem]

This discussion reminds me of the Pluto Charon binary dwarfs. (is that what they would be called?) Anyway, I've played around a little bit trying to get free returns between the two and mostly I look like I should be pulled over and breathalized. TransX is hopelessly inaccurate. The only good thing is that the deltaV for the many corrections is very small because the drawfs and so small. IMFD seems to have a much better prediction of the motions but I haven't learned that nav tool yet.

 

[donatelo200]

:suicide:
You'll probably need a mile thick heatshield made of unobtainium. :hmm:

What is unobtainium?:huh: Cause i thought it was an extremely unstable atom. (man-made though)

 

[Bj]

What is unobtainium?:huh: Cause i thought it was an extremely unstable atom. (man-made though)

unobtainium

wikipedia.org/wiki/Unobtainium

 

[tori]

Assuming all 4 bodies are in coplanar orbits. Best case:

Planet A is furthest from star B at the time of ejection, planet B furthest from star A at the time of insertion. In this situation the spacecraft needs to escape from planet A's orbit, raise the apoapsis to intersect the planet B's position at the predicted time of insertion, coast, and do the insertion. If both planets orbit their respective stars in the same direction the apoapsis will need to 'reach' behind star B, if they orbit in opposite directions the apoapsis will only need to reach the planet in front of star B (difference of 2 orbital radii of planet B).*

If we fit two Suns into roles of the stars and two Earths as planets A and B, each orbiting their respective star at 1 AU with stars themselves being 25 AU apart and we both launch from and end up with circular R=7M orbits, we get:
3.13 km/s for planet A orbit ejection
11.57 km/s for transfer orbit insertion
11.57 km/s for star B orbit circularization
3.13 km/s for planet B orbit insertion
total: 29.4 km/s

If planet B orbits in the opposite direction the situation changes dramatically:
3.13 km/s for planet A orbit ejection
9.93 km/s for transfer orbit insertion
roughly 50 km/s for star B orbit circularization (at this point star B accelerated you to around 40 km/s towards it)
3.13 km/s for planet B orbit insertion
total: over 65 km/s*

The delta-v is so immense because instead of using the star to do the heavy lifting (by capturing at periapsis) it's all done by the spacecraft. I think.

Movement of each star in its counterpart's rotating coordinate system was neglected (~10 km/s), and the integration was approximate to say the very least. But it should give a rough picture of the dv requirements for that flight.

Double sunset over Tatooine comes to mind

* I know this kind of a trajectory is idiotic, halfway through the calculation I realized that by doing a retrograde capture (flying an "8" transfer instead of an elliptic one) the dv requirements would be close, if not identical, to the previous ones.

 

[Quick_Nick]

That is probably more likely, don't know how it would be simulated in Orbiter though.
Flying around binary system would be interesting.

Does Orbiter allow a massless (or close to it) star? If so, could you use it to act as the barycenter of two planets which we'll pretend are stars? (you're going to need to figure out the orbit parameters beforehand)
Though I'm pretty certain that the moons (pretend planets) of these planets (pretend stars) just can't follow in Orbiter the path that they would really take. Hm... maybe Orbiter really isn't a good idea for this.

 

[Evil_Onyx]

Just a quick thought on this, but wouldn't a long transfer be better.

i.e. making several orbits of Star A and use sling shots with Planet A and Star B (and any other large bodies in the system) to decrease the required Dv at each maneuver.

 

[Linguofreak]

This discussion reminds me of the Pluto Charon binary dwarfs. (is that what they would be called?) Anyway, I've played around a little bit trying to get free returns between the two and mostly I look like I should be pulled over and breathalized. TransX is hopelessly inaccurate. The only good thing is that the deltaV for the many corrections is very small because the drawfs and so small. IMFD seems to have a much better prediction of the motions but I haven't learned that nav tool yet.

Actually, I think TransX is more accurate than Orbiter (without an ephemeris *.dll) with systems where the mass of a secondary is a large fraction of the mass of its primary. So it ends up being useless as a navigation tool because the sim isn't behaving correctly.