Great News for Breakthrough Starshot

[ProtoJeb21]

Recently, Breakthrough Starshot tested 6 Sprites in orbit around Earth. For those who don't know, these tiny 4-gram probes (sometimes called Star Chips) are planned to go to the Alpha Centauri and Proxima systems, being accelerated by light bouncing off huge graphite "sails". They would travel at 20% light speed, reach their targets in 20 years, and send their data back on a 4-year trip to Earth. While there was quite a lot of planning for these things, none have been officially tested until now. Based on the article, it seems like this test was to see how the tiny interstellar probes work in the vacuum of space and how well they connect/transmit data to each other. It was reported that all Spites were "performing as designed".

http://www.news.com.au/technology/science/space/prototype-star-chips-called-sprites-are-being-tested-in-orbit-ahead-of-a-proposed-visit-to-alpha-centauri/news-story/211d7e4b2db9d124e619a6b1c38689ab

Finally, after years of waiting, humanity is making its first big step on the road to interstellar travel.

[TheEpicSquared]

Oh yeah!  

[insert_name]

Interesting, wonder if they will include cameras on some of them, i want a pic of proxima b

[Shpaget]

I hate to liquid on their parade (again), but what exactly have they done? They glued a few small radios on third party sats in LEO and demonstrated that they can transmit and receive signals. They could have done that on Earth.

They still have not demonstrated a single technology that would make their goal feasible.

This demonstration is not noteworthy. Where are the solar sails and long range coms they can't do without? They talked about using the sail as a radio antenna dish. For that they need some actuators (winches) that will form the parabolic shape of the sail (since it needs to point both forwards and backwards), how are they going to do that? These actuators are also vital for their suggested steering (for which they also need, the still lacking, navigation).

What kind of transmitter do they plan on putting on the probes that would be capable of transmitting over hundreds of thousands of kilometers (assuming they launch one probe every few seconds for 20 years without missing a beat) while using a crappily malformed solar sail dish. They would need some serious umpf in that tx, even with a factory made highly accurate parabolic dish.

Speaking about umpf, what about the power? Solar cells of a few cm² will not cut it. I doubt they would be sufficient even in the region of Earth orbit. Interstellar space is out of the picture entirely.

All in all, to me, their campaign seems less than honest and the hype not earned.

[cubinator]

3 hours ago, ProtoJeb21 said:

Finally, after years of waiting, humanity is making its first big step on the road to interstellar travel.

It's a 4 gram step, mind you. I wouldn't expect humans walking around on Proxima b in the next hundred years based on this.

[magnemoe]

2 hours ago, Shpaget said:

I hate to liquid on their parade (again), but what exactly have they done? They glued a few small radios on third party sats in LEO and demonstrated that they can transmit and receive signals. They could have done that on Earth.

They still have not demonstrated a single technology that would make their goal feasible.

This demonstration is not noteworthy. Where are the solar sails and long range coms they can't do without? They talked about using the sail as a radio antenna dish. For that they need some actuators (winches) that will form the parabolic shape of the sail (since it needs to point both forwards and backwards), how are they going to do that? These actuators are also vital for their suggested steering (for which they also need, the still lacking, navigation).

What kind of transmitter do they plan on putting on the probes that would be capable of transmitting over hundreds of thousands of kilometers (assuming they launch one probe every few seconds for 20 years without missing a beat) while using a crappily malformed solar sail dish. They would need some serious umpf in that tx, even with a factory made highly accurate parabolic dish.

Speaking about umpf, what about the power? Solar cells of a few cm² will not cut it. I doubt they would be sufficient even in the region of Earth orbit. Interstellar space is out of the picture entirely.

All in all, to me, their campaign seems less than honest and the hype not earned.

Note that this technology would be interesting on an smaller scale for in system use. Asteroid flyby would be easiest. Followed by Uranus / Neptune and it moons followed by outer dwarf planets.
Far simpler and an nice test bed. 
Would also this technology be even more suited to propel larger probes to planetary speeds? You would have better control over larger actively controlled mirrors the larger probe would spend much longer getting up to speed so laser has to run longer but it would get up to huge speed in some days/ weeks. 

[RoadRunnerAerospace]

interesting concept these are!

[_Augustus_]

5 hours ago, Shpaget said:

I hate to liquid on their parade (again), but what exactly have they done? They glued a few small radios on third party sats in LEO and demonstrated that they can transmit and receive signals. They could have done that on Earth.

They still have not demonstrated a single technology that would make their goal feasible.

This demonstration is not noteworthy. Where are the solar sails and long range coms they can't do without? They talked about using the sail as a radio antenna dish. For that they need some actuators (winches) that will form the parabolic shape of the sail (since it needs to point both forwards and backwards), how are they going to do that? These actuators are also vital for their suggested steering (for which they also need, the still lacking, navigation).

What kind of transmitter do they plan on putting on the probes that would be capable of transmitting over hundreds of thousands of kilometers (assuming they launch one probe every few seconds for 20 years without missing a beat) while using a crappily malformed solar sail dish. They would need some serious umpf in that tx, even with a factory made highly accurate parabolic dish.

Speaking about umpf, what about the power? Solar cells of a few cm² will not cut it. I doubt they would be sufficient even in the region of Earth orbit. Interstellar space is out of the picture entirely.

All in all, to me, their campaign seems less than honest and the hype not earned.

^^^^^ This.

Edited July 28, 2017 by _Augustus_

[Exploro]

7 hours ago, Shpaget said:

I hate to liquid on their parade (again), but what exactly have they done? They glued a few small radios on third party sats in LEO and demonstrated that they can transmit and receive signals. They could have done that on Earth.

They still have not demonstrated a single technology that would make their goal feasible.

This demonstration is not noteworthy. Where are the solar sails and long range coms they can't do without? They talked about using the sail as a radio antenna dish. For that they need some actuators (winches) that will form the parabolic shape of the sail (since it needs to point both forwards and backwards), how are they going to do that? These actuators are also vital for their suggested steering (for which they also need, the still lacking, navigation).

What kind of transmitter do they plan on putting on the probes that would be capable of transmitting over hundreds of thousands of kilometers (assuming they launch one probe every few seconds for 20 years without missing a beat) while using a crappily malformed solar sail dish. They would need some serious umpf in that tx, even with a factory made highly accurate parabolic dish.

Speaking about umpf, what about the power? Solar cells of a few cm² will not cut it. I doubt they would be sufficient even in the region of Earth orbit. Interstellar space is out of the picture entirely.

All in all, to me, their campaign seems less than honest and the hype not earned.

It is possible to use the surface of the sail for flat-geometry antenna as proposed here. Thus it is conceivable to negate the need to physically alter the sail shape to be parabolic. Further as I understand AESA radars demonstrate the ability to steer a radar beam electronically. Thus is it possible to develope a technology that could allow a deep space vehicle's radio antenna to point it's beam at Earth without having to mechanically point the antenna or maneuver the craft to to point the antenna Earthward?

Secondly I will point out that solar sail spacecraft IKAROS did not use winches to maintain shape nor use that for manuevering. Tip masses kept the sail unfurled as it spun and liquid crystals altered reflectivity to allow for steering. Granted IKAROS was not propelled by a laser; yet the principles that allow IKAROS to operate are the same that govern the operation of lightsail craft propelled by laser. Perhaps then a flight vehicle dispatched to Proxima or Alpha Centauri might look more like IKAROS as the mass of winches or other mechanical equipment as you describe are likely out of the question.

Power is obviously another challenge. But I think once more you are limiting yourself by restricting the power generation system to just the small chip craft. Much as the sail could be used as an antenna is it possible to place photovoltaic elements onto the sunward (or rather starward in the case of a craft on approach to it's destination star) for power generation? And remember the proposed sail is 16 sq. meters in area.

Edited July 28, 2017 by Exploro

[Shpaget]

1 hour ago, Exploro said:

It is possible to use the surface of the sail for flat-geometry antenna as proposed here. Thus it is conceivable to negate the need to physically alter the sail shape to be parabolic.

Interesting approach. But it does not solve the problem entirely. There is still the issue of having no antenna for receiving from the probes further out. What I mean is if the sail is "downwind" then the problem is perhaps solved for transmitting, but you still need an antenna for receiving. If the sail is lined with reflective material for transmitting, than the receiving signal can't go through the sail to reach the probe. You'd need to somehow place a receiver in front of the probe, and that would require rigid structure quite a bit in front of the probe, and the 4 gram budget is busted.

 

1 hour ago, Exploro said:

Further as I understand AESA radars demonstrate the ability to steer a radar beam electronically. Thus is it possible to develope a technology that could allow a deep space vehicle's radio antenna to point it's beam at Earth without having to mechanically point the antenna or maneuver the craft to to point the antenna Earthward?

Another interesting tech, but frankly I don't know enough about it, so until I read up on the subject, I can't comment.

1 hour ago, Exploro said:

Secondly I will point out that solar sail spacecraft IKAROS did not use winches to maintain shape nor use that for manuevering. Tip masses kept the sail unfurled as it spun and liquid crystals altered reflectivity to allow for steering. Granted IKAROS was not propelled by a laser; yet the principles that allow IKAROS to operate are the same that govern the operation of lightsail craft propelled by laser. Perhaps then a flight vehicle dispatched to Proxima or Alpha Centauri might look more like IKAROS as the mass of winches or other mechanical equipment as you describe are likely out of the question.

IKAROS steering concept is ingenious, but works only with significant solar flux. It also gives us a ballpark for the sail mass - 10 grams per m² (not counting panels and spinning weights).  Another problem for Starshot to overcome.

1 hour ago, Exploro said:

Power is obviously another challenge. But I think once more you are limiting yourself by restricting the power generation system to just the small chip craft. Much as the sail could be used as an antenna is it possible to place photovoltaic elements onto the sunward (or rather starward in the case of a craft on approach to it's destination star) for power generation? And remember the proposed sail is 16 sq. meters in area.

You can have the solar cells as large as you want, but there is no sunshine (or starshine) in the deep space worth mentioning. A huge solar cell array producing nothing per square cm is still producing nothing, and you need a lot to transmit over vast distances with poor antennas.

[SuperFastJellyfish]

29 minutes ago, Shpaget said:

Another interesting tech, but frankly I don't know enough about it, so until I read up on the subject, I can't comment.

https://books.google.com/books?hl=en&lr=&id=vVtnDPhi43YC&oi=fnd&pg=PR7&dq=phased+array&ots=79sJwN0GtR&sig=RW8uQ9uz71AfKWyNso0ZkkkcUlc#v=onepage&q=phased array&f=false

Edited July 28, 2017 by SuperFastJellyfish

[Spaceception]

Why wasn't this in the news!? I mean, it's not the biggest step forward, but testing components in space is a really important step! When will they test with small solar sails?

[wumpus]

Reality check:
escape velocity of the solar system: 42km/s (from Earth Orbit)
.2c: 60,000 km/s

These "Sun Sprites" can take as long as they want to get to 42km/s, but then only have to suddenly accelerate to relativistic speed before leaving the solar system.  Solar power simply is *not* a way to gain relativistic speed (and triple-digit km/s seems really unlikely).  The rocket equation retains its tyranny, and requires extreme effort to get to relativistic speed.

Not to say that a solar sail is necessarily bad for speeds up to (and slightly beyond, presumably with a push from Jupiter) solar escape velocity.  They just can't go much beyond it.  The simple requirement is their efficiency falls terribly past Mars, and once they get some speed they start going well past Mars (and only get a tiny bits of acceleration thanks to Kepler's laws governing rate of time in orbital positions, and can't get another orbit after they hit 42km/s).

[RoadRunnerAerospace]

well there has been ideas for a super powerful lazer which would (in theory) drive a solar sail

[Spaceception]

51 minutes ago, wumpus said:

Reality check:
escape velocity of the solar system: 42km/s (from Earth Orbit)
.2c: 60,000 km/s

These "Sun Sprites" can take as long as they want to get to 42km/s, but then only have to suddenly accelerate to relativistic speed before leaving the solar system.  Solar power simply is *not* a way to gain relativistic speed (and triple-digit km/s seems really unlikely).  The rocket equation retains its tyranny, and requires extreme effort to get to relativistic speed.

Not to say that a solar sail is necessarily bad for speeds up to (and slightly beyond, presumably with a push from Jupiter) solar escape velocity.  They just can't go much beyond it.  The simple requirement is their efficiency falls terribly past Mars, and once they get some speed they start going well past Mars (and only get a tiny bits of acceleration thanks to Kepler's laws governing rate of time in orbital positions, and can't get another orbit after they hit 42km/s).

4

They're going to be pushed to that velocity by lasers, really powerful lasers.

[Green Baron]

Any science on this ? On how to transmit a ping over 4ly (a flat "antenna" has terrible characteristics, works with a decent power source on short distance) ? Apropos power source (yeah radionucleids) ? Instruments ? Or how and where to mount the fans errr lasers to blow them away ? And power them with what ? How many new technologies would have to be invented or existing ones improved ? All of them ;-) ?

 

"Breakthrougzh Starshot is a plan to send man-made probes across the gulf of space to our nearest neighbour, Proxima Centauri."

"The 3.5cm by 3.5cm packages, weighing no more than 4 grams, will carry sensors, solar panels, processors and transmitters."

Yeah, exactly. And the next news will be that they work on a method to shrink humans to fit in the ship errr chip ?

 

Every other day someone comes up with a new idea, but few really become reality one day. This one most probably not, i dare say.

 

[wumpus]

2 minutes ago, Spaceception said:

They're going to be pushed to that velocity by lasers, really powerful lasers.

Earth or space mounted?  They need (ignoring relativistic mass increase) 7.2*10¹² J of kinetic energy going into that thing.  If they only have a month to bombard the sprites (before it slips out of range at .2c), they will need 3MW of power delivered by laser.  That doesn't mean "3MW lasers" firing continously for a month, that means "3MW of laser converted into kinetic energy", which means gods only know what type of power delivered from the lasers.

Not that this isn't outside the realm of possibility (although I suspect that anything going .2c will be gone before a month's time).  The completely impossible bit is keeping the radio transmitter (and any implied sensors) alive after superheating the thing into a plasma.  It also leads into question how an organisation floating such a proposal will obtain multiple (hundreds of?) megawatt lasers spaced around the globe for continuous firing.

[RoadRunnerAerospace]

probably in space powered by solar panels, they would also be firing pulses too (if what i`m hearing is correct)

[Spaceception]

2 minutes ago, wumpus said:

Earth or space mounted?  They need (ignoring relativistic mass increase) 7.2*10¹² J of kinetic energy going into that thing.  If they only have a month to bombard the sprites (before it slips out of range at .2c), they will need 3MW of power delivered by laser.  That doesn't mean "3MW lasers" firing continously for a month, that means "3MW of laser converted into kinetic energy", which means gods only know what type of power delivered from the lasers.

Not that this isn't outside the realm of possibility (although I suspect that anything going .2c will be gone before a month's time).  The completely impossible bit is keeping the radio transmitter (and any implied sensors) alive after superheating the thing into a plasma.  It also leads into question how an organisation floating such a proposal will obtain multiple (hundreds of?) megawatt lasers spaced around the globe for continuous firing.

I would be (As far as I know so far) a 1^2 km array of Earth mounted lasers, totaling about 1 GW of energy, the nanosats, and over the course of a few minutes, they would be boosted to 20% c.

We know how to build really big powerplants, and it could use Nuclear or solar (Or a combination of several energy sources) to power the lasers.

The biggest issues with that is:

What kind of energy losses would need to be accounted for a laser firing on an object at least 100 km away?

And, how will they be able to focus such a large and powerful laser onto a tiny spacecraft without pushing it off course, or destroying it?

[wumpus]

11 minutes ago, Spaceception said:

What kind of energy losses would need to be accounted for a laser firing on an object at least 100 km away?

And, how will they be able to focus such a large and powerful laser onto a tiny spacecraft without pushing it off course, or destroying it?

Energy losses (beyond the atmosphere, and make sure you use expensive adaptive optics) should be minimal, although even the thinnest mylar sail will weigh a few grams (to cover expansion of a beam across 100km).  But 100km is completely irrelevant: that's LEO, and once you start hitting the thing it is leaving LEO fast (i.e. once it gets up to Earth escape velocity).  At that point you will need a bigger sail (to remain remotely efficient).

"Without destroying it", well that's the joke.  Radiating MW/g is a technology so far beyond magic to go well into heavy duty miracles.  You are sending a recondensed plasma to the stars.

https://what-if.xkcd.com/13/   I might be vastly underestimating the difficulty in keeping the beam tight.  Although I remember the Apollo program leaving a small reflector on the Moon that was hit by Earth lasers.  Note that the Moon has a rather low albedo and you don't need a very tight beam for such an experiment, but it certainly needs a diameter closer to the m range than the 10-100km range shown in the what-if.

[magnemoe]

57 minutes ago, Spaceception said:

They're going to be pushed to that velocity by lasers, really powerful lasers.

The light will also be reflected forward and back between the two mirrors many times, each reflect on target will add an multiplier to the trust. 
This would be easier with an heavier probe with more control accelration and top speed would also be lower same with laser effect requirements for an relevant system for sending small probes in the solar system. 
Start here 

 

[monophonic]

11 hours ago, Shpaget said:

There is still the issue of having no antenna for receiving from the probes further out. What I mean is if the sail is "downwind" then the problem is perhaps solved for transmitting, but you still need an antenna for receiving. If the sail is lined with reflective material for transmitting, than the receiving signal can't go through the sail to reach the probe. You'd need to somehow place a receiver in front of the probe, and that would require rigid structure quite a bit in front of the probe, and the 4 gram budget is busted.

I think this is one of the actually solvable problems in the scheme. "Just" fashion the sail into a center fed planar slot antenna and place the probe in the center. Sure you'll waste half your power transmitting in the wrong way and pick up some extra noise when receiving, but at least this layout leaves communication possible with both the preceding and succeeding probe.

Now back to those unsolvable problems... how exactly does one condense a solar sail nanoprobe out of a puff of hot plasma?

[Shpaget]

On 7/28/2017 at 8:04 AM, SuperFastJellyfish said:

https://books.google.com/books?hl=en&lr=&id=vVtnDPhi43YC&oi=fnd&pg=PR7&dq=phased+array&ots=79sJwN0GtR&sig=RW8uQ9uz71AfKWyNso0ZkkkcUlc#v=onepage&q=phased array&f=false

Nice piece of reading!

I haven't had a chance to go through it thoroughly, but one thing jumped at me - on page 10 the graph shows that even with large number of elements, an array antenna can't produce a beam narrower than about 0,45 radians (~25°), which is pretty useless for long range coms.

 

14 hours ago, Green Baron said:

Any science on this ? On how to transmit a ping over 4ly (a flat "antenna" has terrible characteristics, works with a decent power source on short distance)

Their proposal is to use multiple probes that would form sort of a train of moving relays.

14 hours ago, wumpus said:

Earth or space mounted?  They need (ignoring relativistic mass increase) 7.2*10¹² J of kinetic energy going into that thing.  If they only have a month to bombard the sprites (before it slips out of range at .2c), they will need 3MW of power delivered by laser.  That doesn't mean "3MW lasers" firing continously for a month, that means "3MW of laser converted into kinetic energy", which means gods only know what type of power delivered from the lasers.

The thing is, if they take a month to accelerate one probe, than the probes are 6 light days away from each other. For comparison, Voyager probes are around 17 light hours away and require a 23 W transmitter with a 3,7 meter parabolic dish. Furthermore, on the receiving end, we use 34 meter parabolic dishes. The bandwidth they can achieve is something ridiculously low.

So, they would need to significantly increase the acceleration to cut down on the distance between the probes (or use multiple laser installations for simultaneous launching of several probes).

14 hours ago, wumpus said:

Not that this isn't outside the realm of possibility (although I suspect that anything going .2c will be gone before a month's time).  The completely impossible bit is keeping the radio transmitter (and any implied sensors) alive after superheating the thing into a plasma.  It also leads into question how an organisation floating such a proposal will obtain multiple (hundreds of?) megawatt lasers spaced around the globe for continuous firing.

Yeah, that's one thing I haven't addressed - the politics. I figured basic laws physics will be enough, but if they somehow manage to brake those, there's no way of cutting through the red tape.

13 hours ago, monophonic said:

I think this is one of the actually solvable problems in the scheme. "Just" fashion the sail into a center fed planar slot antenna and place the probe in the center. Sure you'll waste half your power transmitting in the wrong way and pick up some extra noise when receiving, but at least this layout leaves communication possible with both the preceding and succeeding probe.

That would compromise the structural integrity. You need to pull some serious gees in order to accelerate fast enough so as to not get out of range of the next probe.

[YNM]

Scott Manley said that the separation for the sprites weren't perfect. Would it mean that the results aren't as they are ?

[wumpus]

I'm not kidding about "recondensed plasma".  A 4g spacecraft at .2c needs 7.2*10¹² J of energy to get that fast (not including relativistic changes in mass).  Even spreading the energy fired at it over a month (by which I think it should be outside Pluto, a distance which you simply *can't* focus lasers.  Look at the Hubble pictures for obvious proof) gives you power requirements in the MW/g range.  And here's the thing: adding more heatsinks or radiators add the mass but don't change the MW/g needed from the lasers.  The radiators will have to somehow radiate all the inefficiency converting MW of laser power into speed.

This might be a great method for building a spacecraft that can outrun Voyager, but will never get near relativistic speed.

Edited July 29, 2017 by wumpus
strikethrough bug strikes again.