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How do you think we can get to Proxima b?

How do you think we can get to Proxima b?

How do you think we can get to Proxima b?

(OP)
Soo.. the other day I read that the Alpha Centauri system might have several exoplanets apart from Proxima b.. so I looked for info about the Starshot project and found out that the team launched in July a 3.5 x 3.5cm satellite weighing 4 grams.. this encourages me to believe that the project can actually be achievable.. what do you guys think? do you think that a faster interstellar travel system will be developed even sooner?

I decided to make a video on this exciting topic and I would like to share it with you guys: https://youtu.be/jF2juqeDa-E

I honestly can't wait 44 years for receiving the first images of Proxima b, I would be 70 years old. There must be another way of getting there sooner.

RE: How do you think we can get to Proxima b?

it certainly a novel concept ... I'm not sure about the return signal ... not much power and an awful long distance !

another day in paradise, or is paradise one day closer ?

RE: How do you think we can get to Proxima b?

Larry Niven posited a light-sail boosting system in one of his stories; the aliens provided lots of tech in exchange for building a booster. If Earth refused, the aliens pointed to the supernova from whence they came. Earth got busy...

But, these aliens were extremely long-lived, and had a massive sail.

Note, however, one fundamental thing that most people seem to be missing is the divergence of the beam. A 5-m aperture at 1064nm produces an Airy diameter of 0.5 microradians. A 10-km diameter sail becomes smaller than the Airy diameter at a measly 2-millionth of a light year, which gets you to about 1/3rd of the way to Mars' orbit. And, that means that at 1 ly, only 3.25E-12 of your transmitted energy will reach the sail, even with perfect pointing.

As for getting any signals back, I think the shot noise of any of the Centauri stars would swamp the radio signal from a probe. Now, if the probe could build itself a fusion reactor, once it gets there, THAT might be promising.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: How do you think we can get to Proxima b?

A rough back-of-the-envelope calculation:

Proxima b is 4.2 light years away (1533 light-days). OK, lets say we're going to have the current Voyager 1 type of capability at that distance. At the moment, Voyager 1 is slightly over 19.5 light hours away using a 3.7 meter diameter antenna with a 22.4 watt transmitter sending data at about 160 bits-per-second. We can still communicate with it using multiple antennas on earth. Granted, Voyager 1 is older technology, but the physics remain the same, and to receive Voyager we are using the latest receiver and antenna methods we have. Granted, a newer, fancier modulation method might improve the link by 6 dB (factor of 2) But instead, lets be generous, and just round that distance up to 1 light-day away. The power relationship one-way is 1/r^2 .

So, to get 160 bps of data from a probe with a 3.7 meter antenna at the distance of Proxima b you need to transmit with a power of of a little over 52 Mega-watts.

RE: How do you think we can get to Proxima b?

i figured it'd be something "stupid" compared to the size of the "chip" we're sending ...

another day in paradise, or is paradise one day closer ?

RE: How do you think we can get to Proxima b?

The Starshot technology scales up to larger spacecraft sizes, provided you have a sufficiently large power source and, ahem, budget. So yes, I agree it's possible. The 30 year travel time sounds optimistic, for the reasons stated above.
The return signal is difficult and the Breakthrough website doesn't offer any details how that could be accomplished.

Latest sci-fi treatment of interstellar travel: Kim Stanley Robinson, Aurora (Tau Ceti in that story IIRC). As with all KSR stories, the technology of the spacecraft is thoroughly explored. He gave them fusion reactors and 3d printers that could replicate organic material to keep the crew alive.

A much more accessible, though still very difficult, target would be to accelerate a probe (Deep-Space-1 style ion thruster) to intercept an extrasolar asteroid as it passes through the solar system, like this one:
https://www.space.com/38580-interstellar-object-sp...
About 1/1000 the speed would be required to intercept, and telemetry sent back before it passes the orbit of Saturn, say, 10 years from now. That would get some alien material to study from another solar system "without leaving home".

STF

RE: How do you think we can get to Proxima b?

Dr. Robert L. Forward has described a light-sail with a detaching fresnel lens/mirror system to help re-focus the beam during outbound travel, and then detach and reflect the beam at the midpoint to decelerate the spacecraft for target system orbital entry. Do-able? Maybe...but power generation several orders of magnitude beyond our current capabilities is required...amongst other difficulties.

http://www.lunarsail.com/LightSail/rit-1.pdf

RE: How do you think we can get to Proxima b?

I have had the idea of getting a momentum transfer from a passing near Earth asteroid. Having something like an elastic tether or pneumatic cylinder and just get in front of the asteroid and compress the cylinder or stretch the tether and then (if it doesn't break) as it recoils you could get twice the velocity of the original asteroid. I know the forces would be immense, like shooting the bottom of a pogo stick with a howitzer, but that's an engineering challenge I think could be resolved. If you could make a spacecraft rugged enough to survive that with perhaps an ion thruster for control you could get somewhere quick.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

RE: How do you think we can get to Proxima b?

They already do that with gravity-assist. That's why some of the outer planet probes take so long to get there; they spend a big chunk of time getting gravity assists in the inner solar system

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: How do you think we can get to Proxima b?

I was thinking of a more direct momentum transfer, i.e. letting the probe get hit by the asteroid in a "controlled" elastic collision.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

RE: How do you think we can get to Proxima b?

I don't think that'll work very well ... incoming satellite would have some KE to impart to the asteroid, the asteroid will not notice since the satellite is negligible mass. I don't think you could recover the original KE from the impact.

It'd probably make more sense to use the asteroid, or whatever, for a gravity assist manoeuvre ... many orbits gradually building speed. The advantage of this is you don't need a tiny satellite ... a heavier satellite would need more orbits. But this would be limited to a small fraction of c. The intention of the light sail is to use laser energy to accelerate a tiny mass.

another day in paradise, or is paradise one day closer ?

RE: How do you think we can get to Proxima b?

I'm not trying to change the asteroid's path with the satellite, I'm trying to change the satellite's path with the asteroid. Average asteroid velocity is 25 km/s. Voyager 1 is 17 km/s. Even if we got a completely plastic collision with an asteroid we would end up faster than the Voyager probes. If we could get an elastic collision and end up with a higher velocity and still have a functioning spacecraft it would be a huge jump start. It's interplanetary billiards.

I'll be honest the idea of a spacecraft being able to survive this is almost laughable, but we could control the impact to some extent. Using thrusters to reduce the relative velocity between the spacecraft and asteroid. Choosing an asteroid with a lower initial velocity. Increasing the elastic stretch of the collision to reduce the acceleration of the spacecraft, though whatever part contacts the asteroid can't avoid the full speed of impact.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

RE: How do you think we can get to Proxima b?

I get that you not trying to change the asteroid. I guess if you targeted the satellite to hit the asteroid head on, the satellite might rebound with a higher velocity, depending on how well you collected the impact energy (Vs+Va) so that after impact the satellite is moving along with the asteroid (ie -Vs has become Va) and then if you liberate all of the impact energy the satellite speed would be 2Va+Vs (with minor changes in Va to preserve momentum (Ma >> Ms, so delta Va is small). It'd still only be a tiny fraction of c, and probably would require very large inertial forces.

Something that'd "help" would be if you left some of the satellite mass on the asteroid, so the rebound momentum was associated with a smaller mass than the impact, increasing the rebound velocity.

But, as you agree, the idea doesn't sound very practical.

another day in paradise, or is paradise one day closer ?

RE: How do you think we can get to Proxima b?

"Average asteroid velocity is 25 km/s. Voyager 1 is 17 km/s. Even if we got a completely plastic collision with an asteroid we would end up faster than the Voyager probes. "

Funny. Earth's orbital velocity is 30 km/sec, how come that's not enough?

Oh right, the probe loses speed as it climbs the gravity well. Comparing Voyager velocities at 90 AU distance to asteroid velocity at 2-3 AU is...well, not correct.

Gravity assists can give all (or a large part of) the orbital velocity of the larger body to the smaller, in a perfectly elastic fashion. Almost as importantly, you change the vector of the velocity (angle) for the probe without expending any (or at least a tiny amount of) fuel to do so, if you do it right.

Which makes me wonder, could global warming be caused by the shift in earth's orbital radius due to gravity assist maneuvers by orbital probes? Hmm.

RE: How do you think we can get to Proxima b?

oh great ! now we've brought global warming into the discussion ... bigsmile

another day in paradise, or is paradise one day closer ?

RE: How do you think we can get to Proxima b?

And chemtrails are caused by asteroids...atom

RE: How do you think we can get to Proxima b?

I wasn't even thinking about the change in orbital velocity based on distance from the sun. I'm really not well versed in that. About the asteroid chemtrails, I believe during the close approach of Halley's comet near the beginning of the 20th century there was a booming business in devices and pills to protect you from the "comet gasses".

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

RE: How do you think we can get to Proxima b?

While we're having fun speculating... my 2-cents worth...

What about an across-the-sun sling-shot towards alpha Centauri B trajectory?

during a timed launch widow...

Launch toward the moon with a free-return trajectory. During the return to earth, accelerate with a long thrust burn for an Earth-gravity assist into an almost direct shot [steep diving trajectory] at the sun for sun-grazing gravity assisted acceleration and turn-towards alpha Centauri system trajectory [path]? very high departure velocity can be anticipated. NOTE: this would mimic the path of an interstellar asteroid just discovered racing past the sun with a non-return trajectory at exceptionally high speeds and shallow trajectory turn.

This path would require...

substantial shielding/insulation/radiation protection from the sun.... beneficial for interstellar coasting and protection from the 3-stars of Alpha Centauri at the other end. NOTE: cleverly integrated, this shield might also work as a directional high-gain antenna and as a solar-energy collector/storage-cell.

A booster for the initial high acceleration from the moon toward the earth is needed.

A propulsion system for in-solar-system acceleration and course corrections is needed.

A substantial service module [bus] that includes an ion propulsion system for interstellar course corrections, stabilization and [ultimately]deceleration at destination. Jettison-able fuel tanks and/or very light fuel bladders would be necessary.

Not to mention all spacecraft design elements... structures, systems, avionics/computing-AI/instrumentations/antennas/communications/optics, TNG/electrical power, thermal control elements and insulation [including micrometeorite protection], etc... for long-duration 'interstellar flight' to Alpha C system.

OH yeah... and while the spacecraft is coasting... develop an expansive network of radio astronomy/comm spacecraft... distributed solar-system wide aimed directly towards alpha C and/or the spacecraft's trajectory... continuously listening-for the 'lonely bird' running from home.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: How do you think we can get to Proxima b?

Might want to break up the probe into several units. They all depart together from the same launch, but later they separate. They will then reach the target star at different velocities. One can be released before any deceleration is done, and it will go whipping past the target star to take a quick first-pass look at the planetary system. Another could be released part-way through the deceleration phase, but still proceed ahead and be given a slingshot around the target star. It can be sent off on a trajectory at right-angles to the earth-star line of sight. This one could act as a radio relay station off axis from the target star, allowing Earth to get a better signal from the probe. Would 100 bits per day be enough? Close to the star it would have solar power to amplify the signal.
The process of releasing these units can also involve a momentum transfer to aid the deceleration of the main ship.

STF

RE: How do you think we can get to Proxima b?

Actually slinging the probe around the sun for a gravity assist doesn't gain you any net speed. The speed gained diving towards the sun is lost again as the probe climbs back out of the suns gravity. The velocity-gravity assist available from slinging near a planet comes from the orbital angular velocity of the planet around the sun.

Somewhere I read that the best way for the probe to communicate would not be radio, but laser. I seem to recall from the article that about 200,000 watts would be required from a very well focused beam at several light years distance. NASA will soon demonstrate laser communication from Mars that will allow 1 to 10 Mbps data rate - 10 to 100 times what is available with radio. https://www.nasa.gov/mission_pages/tdm/lcrd/index....

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