Uh, how do you plan on slowing it down?BWV said:
But you have up to an 8+ year communication lagruss_watters said:
An automated system could do it. It was interesting that the Boeing Starliner used an automated system to dock with the ISS even though there were two excellent pilots onboard.Baluncore said:
A trip would be likely done in stages. First stage: Reach the Proxima system. Second stage: assume an orbit around Proxima. Third stage: locate Proxima B, and observe it long enough to get a good fix on its orbit. Forth stage: alter orbit to one intersecting with Proxima B. Fifth stage: orbital insertion around Proxima B upon arrival.BWV said:
I'm not sure what problem you think that presents? The ship/probe can navigate itself.BWV said:
Using online calculators, the stopping fuel is about 25% of the mass with 1G acceleration to 0.2C, and that ignores what you maybe could do with gravity assists . You could accelerate the probe with a light sail or some other stationary energy source so only need fuel to stopVanadium 50 said:
None, as long as you are confident in your coderuss_watters said:
Nowhere near that with any kind of current or near future rocket system. Current systems use 90+% of their mass in fuel to reach say 9 km/s or a little more if going to the moon (~13 km/s) or interplanetary. That is 0.0003c.BWV said:
Certainly not current, but accelerating a very tiny probe to 0.2c with a light sail is not an unreasonable 'near' future. That is Starshot's goal, for example. Admittedly it does not involve slowing the craft downglappkaeft said:
You can't do anything substantial with gravity assists. You would need to find something moving near your 0.2c, and there isn't anything.BWV said:
Not even close. At 0.2c, you need to convert 2% of your mass to energy. Minimum. That's 20 MeV per proton. Even fusion provides 6-7 MeV. Your vessel needs to weigh thousands of tons just to carry the fuel to slow itself down. What's another 5 pounds for a computer?BWV said:
Breakthrough Starshot, while not unphysical, is a very long chain of very optimistic extrapolations of current technological development, that many really hard problems can be solved and the construction of a 100 GW laser. I not very optimistic that they will amount to anything, especially launching by 2036.BWV said:
But Proxima B will be moving at 0.2c when the probe gets there...Vanadium 50 said:
Har har. He means co-moving with you - relative to the system. Otherwise it's gone in a flash.berkeman said:But Proxima B will be moving at 0.2c when the probe gets there...
Sure, but something like this is the only conceivable way to send something that distance. It also depends whether eventually economic reasons exist to build the orbital manufacturing infrastructure necessary to make something like this - on that I am skeptical - outside of Earth's orbit there is likely nothing in the solar system of any value to us.glappkaeft said:
To get to 0.2c you have to accelerate so you accelerate halfway and then decelerate the rest of the journey so you end up with close to zero velocity when you get there.Vanadium 50 said:
Roughly speaking if you accelerate at 1G for one year you will be close to 1c, so 0.1G of accel for 2 years gets you to 0.2c. If you could imagine a sling that would get your to 0.2 G in say one second or so, the trip time would be some 20 years, so 0.1G for 2 years means you are at 0.2c fairly early in your trip so you would have to coast for some 16 odd years to allow you to decel at that same rate, 0.1G for two years does the job of getting you to Alpha Centauri with more or less zero velocity.sonhousen said:
There's the rub.sonhousen said:
sonhousen said:
