Mini spacecraft for Alpha Centauri?

[rustigsmed]

NEW YORK — Stephen Hawking wants humanity to reach the stars.

The famed cosmologist, along with a group of scientists and billionaire investor Yuri Milner, unveiled an ambitious new $100 million project today (April 12) called Breakthrough Starshot (http://www.space.com/32548-20-percent-light-speed-to-alpha-centauri-nanocraft-concept-unveiled-video.html), which aims to build the prototype for a tiny, light-propelled robotic spacecraft that could visit the nearby star Alpha Centauri after a journey of just 20 years.
- See more at: http://www.space.com/32546-interstellar-spaceflight-stephen-hawking-project-starshot.html#sthash.VpoFcmE1.dpuf


http://www.space.com/32546-interstellar-spaceflight-stephen-hawking-project-starshot.html

I can't get Dr. Evil out of my head for some reason sharks with fr---en laser beams.

[bojan]

Hmmm
To get there is one thing.. but to call back home is another... and much harder me thinks

[rustigsmed]

yep, over 4 years to receive the data and at 20% the speed of light that is one hell of a fly bye! :eyepop:

[billdan]

I agree with Bojan, trying to receive a signal from 4 light years away will be virtually impossible, even if it had a 1 Megawatt transmitter on board.

NASA has enough trouble communicating with existing spacecraft on the edge of our solar system and they're only 1 light day away. Plus these spacecraft have a decent size parabolic dish pointing back at earth.

I think this is a publicity stunt ( a fool and his money) and needs a further re-think.

Bill

[glend]

Oh come on, all these problems are solvable, and none of these people need publicity for anything they do. The video shows the deployed sail, which could be made to function as an antenna and used to slow the craft on approach to the star system - Solar winds you know. If it can be used for the lasers to push against it can be used to decelerate. Where is your vision? I expect more than negativity from members here. At least they are trying.
This also creates a great opportunity for Australia, perfectly placed for the ground based laser pusher array.

[Atmos]

Don't have a chance to look over it yet but just as a little random fact, couple of years ago I calculated that to safely (if people are on board) accelerate and decelerate to near the speed of light takes about a year a piece; ie. a year to speed up and a year to decelerate.

[xelasnave]

I am seeking a couple of mill to develope a quantum entanglement communication system and am happy to work on this project.

I wonder if my "follow the money" principle of explanation to all things could yield a result.

Is it a tax minimization scheme? Or a front to hide something we will never know about.

Do they need more investors and government assistence?

Alex

[bojan]

Or telepathy...

[xelasnave]

I can do that just send me some money.

[raymo]

In 1978 Iain Nicolson published a great book called "The Road To The Stars",
in which he explored all the then current and foreseeable methods of
propulsion in space. Some we were knocking on the door of, and some were further down the track, and a few were probably a century or more away.
My point is that his posited methods are coming to fruition one by one,
and I'm sure that more will follow. It is my greatest disappointment, that I won't be here to witness all the breakthroughs that are
occurring in so many disciplines, not just space exploration; I would have loved to see men land on Mars.
When my grandmother was born, the town street lights were gas, no cars, aeroplanes, telephones, radio, or TV, and men landed on the
moon three years before she died, amazing. With technology hurtling along, who knows what can be achieved in another such single
life span. Don't pooh pooh these peoples' dreams; without pioneers we would still be in the dark ages. Some of the space ventures we have already carried out would have been deemed fanciful only a few short decades ago. End of sermon.
raymo

[Max Vondel]

There was a recent arXiv article about laser propulsion
Sending small payloads (4-10 grams) upto 20% light speed.
There is no return
Very exciting we can send 1000's of probes
Many will fail...but some will reach their targets
We will have reached the stars in something like 50 years!
Wow...what a vision!
:D

[bojan]

Hmmmm

I fully understand all the aspects of positive thinking expressed in this thread..
However, we have to be realistic in terms of restrictions the physics laws impose.
If you need GW transmitter to relay the message from star to star with decent data transfer rate, I can't see it being packed in the volume of couple of grams...
Of course, all functionality required for control module of such device is already packed in much smaller volume... there is no dispute here.

The problem is required SNR (Signal to Noise Ratio) for the reliable (and fast) communication link.
The probe travelling at 20% light speed will pass through Solar system in 24 hours max. It has to send the accumulated information back (otherwise, what is the point of such exercise?).

The real-time data rate used with communication with Voyager probes is 160b/sec, the current distance of V1 is 134.16AU
Alpha Centauri system is 300000AU away, further away by factor of 2236.
If the Voyager were there, the signal from it would have been 5,000,000 times weaker.
That means, to have the same data rate (lousy 160bps, 20B/s)), the transmitter power must be that many times more powerful.. which is around 100MW (23*5e6).
And those numbers will remain the same in the future, they are independent on technology development.

[lazjen]

I think this is a great idea - even if it's not fully successful, I expect there will be many spinoffs that will become part of our lives into the future.

Btw, if they can really mass produce these things, I wonder if each craft could act as a relay for comms? Instead of needing to have enough power to send data over 4+ lightyears, maybe it could be a fraction instead, relying on network communications?

Also, I would have thought that the laser array they're planning would be better situated in space. You eliminate any atmospheric issues then.

[billdan]

Chris that's what I would propose, send out a 1000 of these probes and one by one they stop and are say 1 light week apart. Then each one becomes a relay station to store and forward each transmission back to earth.

You would still need to solve the problem of accurate pointing of the Antennas in each direction.

Cheers

EDIT: Thinking about it a bit more, having a probe stop in space could be an issue as each probe will drift towards the nearest heavier object ( back to the Sun).

[FlashDrive]

:rofl:

Flash....

[raymo]

This could ultimately, I imagine, lead to humans [or whatever we have become by then] going along for the one way ride, and forgoing
communication with Earth, [no hardship, should Earth have become an
inhospitable place to be by then].
raymo

[bojan]

They do not need to stop. They can't stop, actually.
Still... a BIG challenge.

[blink138]

i knew you were going to say that!
pat

[lazjen]

Of course, you should have many of these in different positions for redundancy and maybe different facings as well. Plus, to keep in approx place, the "wind" on the sails might be enough? And finally, even if there is drift, each unit could report their changed position to be relayed throughout the grid, so maybe the drift over the lifetime can be compensated for and effectively "ignored"?

[julianh72]

Take a look a the actual Breakthrough Starshot website http://breakthroughinitiatives.org/Challenges/3 to get an understanding of the team's assessment of the challenges, including:

. Building a 100 giga-watt laser array (and designing a sail which can cop a blast from a 100 giga-watt laser array!)
. Gram-scale chip(s) for the laser comms, processors, cameras, nuclear power source, etc
. Pointing the (gram-scale) cameras for a planetary fly-by at 0.2 c
. Using the sail as a "Fresnel lens" for comms back to Earth
. Building a kilometre-scale receiving array to pick up the very weak signal from the spacecraft

[lazjen]

Ha, no surprise that some of the questions and solutions we've been discussing are already up on the site. Great stuff. :)

[Max Vondel]

Yes it's a monumental undertaking...but perhaps the only way to get there in our lifetime. And there are lots of technical problems to overcome, but we've visited all the planets in our solar system, something that would have sounded just as crazy 100 years ago.

[grimsay]

Exciting stuff! I really hope this venture or others it leads to succeed in my lifetime.

Would the effects of time dilation on a craft traveling 20% the speed of light over 4 light years be noticeable?

[Atmos]

At 20% of light speed it equates to a 4.2% difference in time dilation/length contraction.