3 ms·

Pedantically, wouldn't Δv-accessible mean it would take a long time to get here, and we'd see it coming for a very long time? Possibly easy to address... maybe

Pedantically, wouldn't Δv-accessible mean it would take a long time to get here, and we'd see it coming for a very long time? Possibly easy to address... maybe, it was small and dim, and in line with a bright star, so we'd interpreted it wrongly.

TeMPOraL 8y ago
It would. I'd assume humanity knew about it for decades before it became "reachable" - preparing a colony ship (and creating a necessary infrastructure) would take many, many years. There's also a story to be found in the two planets being in radio range for a hundred years past leaving travel range.
- hyperpallium 8y ago
  I was thinking more of a scale of tens of thousands of years, even millions.
  - hyperpallium 8y ago
    Let's say the rogue system is 4-40-400 light years away (nearest star is 4 ly). What's a reasonable ∆v? We get some free ∆v from Earth's orbital velocity of 107,000 km/h, or 29.7 km/s. Our fastest spaceship (which is around sun, https://wikipedia.org/wiki/List_of_vehicle_speed_records#Spacecraft https://wikipedia.org/wiki/List_of_vehicle_speed_records#Spa...) is 252,792 km/h, or 70.22 km/s - which isn't including the ∆v to cancel that, ∆v to return to Earth, cancel again. This 70.22 km/s is about 2 ten thousandths of the speed of light (70.22/299,792). It would take about 20,000 years for alpha centuri (4 ly) to arrive at that speed, and 200,000 years to travel 40 ly, 2,000,000 years for 400 ly. Of course, maybe we can go faster in future. but propellant is a problem, you have to come back, and a manned mission is orders of magnitude heavier. Space is big. funexercise: propose a means of propulsion that could do this. EDIT a new one is going 692,000 km/h, over twice as fast. At that rate of improvement, maybe we'll get closer to it sooner than I thought. https://www.space.com/41447-parker-solar-probe-fastest-spacecraft-ever.html https://www.space.com/41447-parker-solar-probe-fastest-space...

TeMPOraL 8y ago

It would. I'd assume humanity knew about it for decades before it became "reachable" - preparing a colony ship (and creating a necessary infrastructure) would take many, many years. There's also a story to be found in the two planets being in radio range for a hundred years past leaving travel range.

hyperpallium 8y ago
I was thinking more of a scale of tens of thousands of years, even millions.
- hyperpallium 8y ago
  Let's say the rogue system is 4-40-400 light years away (nearest star is 4 ly). What's a reasonable ∆v? We get some free ∆v from Earth's orbital velocity of 107,000 km/h, or 29.7 km/s. Our fastest spaceship (which is around sun, https://wikipedia.org/wiki/List_of_vehicle_speed_records#Spacecraft https://wikipedia.org/wiki/List_of_vehicle_speed_records#Spa...) is 252,792 km/h, or 70.22 km/s - which isn't including the ∆v to cancel that, ∆v to return to Earth, cancel again. This 70.22 km/s is about 2 ten thousandths of the speed of light (70.22/299,792). It would take about 20,000 years for alpha centuri (4 ly) to arrive at that speed, and 200,000 years to travel 40 ly, 2,000,000 years for 400 ly. Of course, maybe we can go faster in future. but propellant is a problem, you have to come back, and a manned mission is orders of magnitude heavier. Space is big. funexercise: propose a means of propulsion that could do this. EDIT a new one is going 692,000 km/h, over twice as fast. At that rate of improvement, maybe we'll get closer to it sooner than I thought. https://www.space.com/41447-parker-solar-probe-fastest-spacecraft-ever.html https://www.space.com/41447-parker-solar-probe-fastest-space...