Author Topic: Design a mission to Proxima b  (Read 18323 times)

Offline Star One

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Design a mission to Proxima b
« on: 08/24/2016 05:17 PM »
Just how would you get to Proxima b using existing or possible technology in the next twenty to third years for an unmanned mission.
« Last Edit: 08/24/2016 05:18 PM by Star One »

Offline Hauerg

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Re: Design a mission to Proxima b
« Reply #1 on: 08/24/2016 05:31 PM »
Just how would you get to Proxima b using existing or possible technology in the next twenty to third years for an unmanned mission.

I would start with a workgroup evaluating what kind of telescopes are possible in 50, 100, 200 years, whatever the mission timelines might be for interstellar probes.

Then younwould have to find a mix of instrument and propoulsion capabilities that can beat those future scopes.
Might be hard.

Offline Star One

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Design a mission to Proxima b
« Reply #2 on: 08/24/2016 05:35 PM »
It's not a straight line target as well, isn't Proxima Centauri at a fair old inclination to the Solar System?
« Last Edit: 08/24/2016 05:35 PM by Star One »

Offline whitelancer64

Re: Design a mission to Proxima b
« Reply #3 on: 08/24/2016 05:48 PM »
Two basic near-term options:

Nuclear pulse propulsion, like Project Orion / Daedalus / Longshot / Icarus, etc.

or Solar sail, possibly microwave or laser powered, like Starwisp / Dragonfly / Breakthrough Starshot, etc.

There are a few others, but they either require hefty amounts of new technology development or massive in-space construction efforts, or they have unsolved engineering challenges.

I agree with Hauerg that your better bet is to work on building a big telescope.
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Offline Archibald

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Re: Design a mission to Proxima b
« Reply #4 on: 08/24/2016 05:51 PM »
Project Orion is workable with sixty years old technology.
It could reach 10% of the speed of light thus reaching Proxima centauri in 50 years.
but of course politically it is unpalatable.

Offline geza

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Re: Design a mission to Proxima b
« Reply #5 on: 08/24/2016 05:55 PM »
It's not a straight line target as well, isn't Proxima Centauri at a fair old inclination to the Solar System?
If you want to reach Proxima Centauri within a few centuries, then you need a velocity, which is huge relative to the orbital velocity of Earth (30 km/s). Then, inclination relative to the ecliptic plane is irrelevant. Every trajectory is straight line at such velocities.

Offline JasonAW3

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Re: Design a mission to Proxima b
« Reply #6 on: 08/24/2016 05:59 PM »
For the short term, something on the order of the Webb Telescope on steroids.

For longer term, microprobes laser accelerated, or, if some goofy wonk makes a break through, the Canne drive.  And a further stretch, the "warp" drive.

   Truth be told, unless some one figures out a way to tap "Vacuum Energy" we really can't generate enough energy for the kind of propulsion and deceleration that would be required for anything much larger than microprobes to get there in a reasonable amount of time.
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Online RonM

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Re: Design a mission to Proxima b
« Reply #7 on: 08/24/2016 06:05 PM »
I think a FOCAL telescope at 550 AU is the way to go.

https://en.wikipedia.org/wiki/FOCAL_(spacecraft)

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #8 on: 08/24/2016 06:09 PM »
Mass beam propulsion.

Unlike laser tech, it's scalable to crewed missions as well (without Singularity-level resources).
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Online Joffan

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Re: Design a mission to Proxima b
« Reply #9 on: 08/24/2016 09:16 PM »
So, we want to get there in say 20 years, and presumably drop into orbit around Prox Cen.? Then have enough instruments and transmitting power to gather and relay useful information about the system, particularly about the star, and about A&B Cenatuari, and of course about the planet Proxima b, or whatever it's called by then.

Accelerating and then decelerating about about 0.6m/s/s (ie. about 6%g) seems to be sufficient to cover the distance, ignoring gravity wells. The continuous mass-independent acceleration solution conveniently hits a top speed of about 0.4c which is still "relatively" unaffected by the Lorentz factor.

A higher acceleration at the start and finish (with a long coast) would allow a lower top speed, perhaps desirable to reduce the impact hazards en route (although these are likely worse at the start and end anyway?) 0.25g for a year at start and end would give a top cruising speed of 0.26c.

Not including any considerations of propellant requirements, which is a bit like calculating how fast an elephant can walk across the Atlantic, but gives some initial framework.
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Offline shooter6947

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Re: Design a mission to Proxima b
« Reply #10 on: 08/24/2016 09:38 PM »
Just how would you get to Proxima b using existing or possible technology in the next twenty to third years for an unmanned mission.

I hate to make such a strident and depressing pronouncement, but it's just not possible using any current or foreseeable technology to get to Proxima Cen and do anything scientifically useful in the next 20-30 yrs.  Remember that it took a small spacecraft on our (then) largest launch vehicle 10 years to get to Pluto at 40-some-odd AU.  I can't even figure out a way to usefully get to a Planet 9 at 500AU much less Proxima in that kind of timeframe.

So in our lifetimes the only way to learn more is via better remote telescopic observation, barring a fundamental technological breakthrough.

Offline Star One

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Re: Design a mission to Proxima b
« Reply #11 on: 08/24/2016 09:57 PM »
Just how would you get to Proxima b using existing or possible technology in the next twenty to third years for an unmanned mission.

I hate to make such a strident and depressing pronouncement, but it's just not possible using any current or foreseeable technology to get to Proxima Cen and do anything scientifically useful in the next 20-30 yrs.  Remember that it took a small spacecraft on our (then) largest launch vehicle 10 years to get to Pluto at 40-some-odd AU.  I can't even figure out a way to usefully get to a Planet 9 at 500AU much less Proxima in that kind of timeframe.

So in our lifetimes the only way to learn more is via better remote telescopic observation, barring a fundamental technological breakthrough.

I was thinking of ideas like Project Starshot.

Offline rdheld

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Re: Design a mission to Proxima b
« Reply #12 on: 08/24/2016 10:53 PM »
plenty of time as the planet has not been confirmed.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #13 on: 08/25/2016 02:29 AM »
... in the next 20-30 yrs.... I can't even figure out a way to usefully get to a Planet 9 at 500AU much less Proxima in that kind of timeframe.
...
Deep Oberth burn right by the Sun, leave at ~100-120km/s (perhaps with help from RTG electric propulsion). Enter orbit via aggressive aerocapture (i.e. like a nuclear warhead's level of reentry difficulty, or the Galileo probe at 50km/s). That's the iffy-est part of the plan. Just doing a flyby should be quite doable.

Could get there in 20-30 years.


Still nowhere near interstellar-relevant speeds, but hey, if we don't have the imagination and physics knowledge to get to Planet 910, we definitely aren't going to Proxima b.

But if we all live to 120, then there IS a chance if you have like a trillion dollars.

But a really good telescope at the gravitational focus should give excellent remote sensing of Proxima b!
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Offline CameronD

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Re: Design a mission to Proxima b
« Reply #14 on: 08/25/2016 06:28 AM »
But a really good telescope at the gravitational focus should give excellent remote sensing of Proxima b!

If so, why not send a telescope (fitted with a really good data link) at regular speeds?  Hubble might do the trick.
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Offline john smith 19

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Re: Design a mission to Proxima b
« Reply #15 on: 08/25/2016 08:43 AM »
Just how would you get to Proxima b using existing or possible technology in the next twenty to third years for an unmanned mission.
Depends how you split the time up.

Range is about 4LY so assuming your probe is ready to go now you need to get it up to an average speed of about 0.134c. The data will come back at the speed of light (or faster if you have quantum entanglement comm link  :) ) in about 4 years

If you allocated 10 years to do development work  it's more like 0.2c or 60 million m/s.

A system that can maintain 10g of acceleration for about 7 days can do this.  The lightest package will be a flyby mission with no slowing down. Slowing down adds mass and lengthens the mission or raises the starting velocity. Voyager has demonstrated it's possible to design systems that can continue to function after 3 decades en route.

[EDIT the challenge of course is to build a system that can maintain 10g acceleration (Nuclear warheads are designed for 40g and are deployed in fairly large numbers so well within the open SoA). For lowest risk, earliest possible deployment propulsion I'd suggest essentially an SPS. Microwave generation is highly efficient  and PV cells can be made very light thin films or very high efficiency concentrator designs at 43%+. The goal would be concentrated power pointing away from Earth focused on a reflector with sub wavelength holes in it to lighten the design. We know a 200Kw space solar array is in the SoP ]
« Last Edit: 08/25/2016 12:22 PM by john smith 19 »
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Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #16 on: 08/25/2016 12:08 PM »
But a really good telescope at the gravitational focus should give excellent remote sensing of Proxima b!

If so, why not send a telescope (fitted with a really good data link) at regular speeds?  Hubble might do the trick.
At regular speeds, it'd take about 200 years to get to the focal point. That's why not.
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Offline ThereIWas3

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Re: Design a mission to Proxima b
« Reply #17 on: 08/25/2016 12:21 PM »
I think it would be much faster to build a very-long-baseline synthetic aperture telescope on the Moon.
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Offline Star One

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Design a mission to Proxima b
« Reply #18 on: 08/25/2016 12:21 PM »
Quote
chrislintott ‏@chrislintott
@ChrisInmanDrum @Maker_of_Things In my chat with the discoverers they were thinking of a dedicated mission to state at this star

From the context of the conversation they meant space telescope.

What would have to special about telescope just tasked at staring at Proxima Centauri and nothing else?
« Last Edit: 08/25/2016 12:22 PM by Star One »

Online scienceguy

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Re: Design a mission to Proxima b
« Reply #19 on: 08/25/2016 04:49 PM »
Wouldn't the James Webb Space Telescope be able to get a picture of this planet? The star is just a red dwarf.
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Offline whitelancer64

Re: Design a mission to Proxima b
« Reply #20 on: 08/25/2016 05:31 PM »
Wouldn't the James Webb Space Telescope be able to get a picture of this planet? The star is just a red dwarf.
Maybe. It depends on the apparent distance to the star. JWST does have coronagraphs that might enable a direct image to be taken of Proxima b, but if it can only distinguish Proxima b when it's at the furthest from the star from our perspective, it might be tricky to get the timing right.
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Online RonM

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Re: Design a mission to Proxima b
« Reply #21 on: 08/25/2016 05:42 PM »
Wouldn't the James Webb Space Telescope be able to get a picture of this planet? The star is just a red dwarf.
Maybe. It depends on the apparent distance to the star. JWST does have coronagraphs that might enable a direct image to be taken of Proxima b, but if it can only distinguish Proxima b when it's at the furthest from the star from our perspective, it might be tricky to get the timing right.

With an 11.2 day orbit, a well planned observation campaign should be able to catch Proxima b, assuming JWST can image it.

Offline TheSpaceRod

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Re: Design a mission to Proxima b
« Reply #22 on: 08/25/2016 05:47 PM »
Antimatter should do the trick for interstellar propulsion. You'd still need to invent some technologies, i.e. relatively affordable production and reliable storage of sufficient amounts of antimatter.

Offline whitelancer64

Re: Design a mission to Proxima b
« Reply #23 on: 08/25/2016 05:48 PM »
Wouldn't the James Webb Space Telescope be able to get a picture of this planet? The star is just a red dwarf.
Maybe. It depends on the apparent distance to the star. JWST does have coronagraphs that might enable a direct image to be taken of Proxima b, but if it can only distinguish Proxima b when it's at the furthest from the star from our perspective, it might be tricky to get the timing right.

With an 11.2 day orbit, a well planned observation campaign should be able to catch Proxima b, assuming JWST can image it.
We do have a couple of years to nail down the orbital inclination, distance, and time more precisely, and I'm certain that Proxima Centauri will be getting some intense scrutiny by many people!
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Offline sevenperforce

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Re: Design a mission to Proxima b
« Reply #24 on: 08/25/2016 07:11 PM »
Let's see here. Inclination will be an issue, which means we would definitely, absolutely have to execute a solar slingshot in order to get a free inclination change. The easiest way to do a solar slingshot, of course, is to do a Jovian slingshot. In order to actually get a gravity assist from Jupiter, you'd need to set it all up with a Martian slingshot.

So we have the beginnings of a mission profile. Let's limit ourselves to three LEO BFR launches and just two on-orbit robotic assembly events. Generously, let's say this gives us 900 tonnes in LEO.

From a mass basis, is it cheaper to use SEP or a solar sail to do the burn for the martian slingshot, or should chemical propulsion be used?

Once the slingshots begin, maximum propulsive capacity should be saved for the periapse of the solar slingshot for Oberth reasons. Chemical propulsion is nice here because it can permit very high thrust, which is ideal for an oberth maneuver, but would an ablative solar sail be a better use of mass? Or would it be better to have a combination of chemical propulsion at periapse followed by the deployment of a solar sail?

Remember that your whole system needs to be broken up into 300-tonne blocs in order to fit on three BFR launches.

Offline redliox

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Re: Design a mission to Proxima b
« Reply #25 on: 08/25/2016 07:49 PM »
Maybe. It depends on the apparent distance to the star. JWST does have coronagraphs that might enable a direct image to be taken of Proxima b, but if it can only distinguish Proxima b when it's at the furthest from the star from our perspective, it might be tricky to get the timing right.

With an 11.2 day orbit, a well planned observation campaign should be able to catch Proxima b, assuming JWST can image it.
We do have a couple of years to nail down the orbital inclination, distance, and time more precisely, and I'm certain that Proxima Centauri will be getting some intense scrutiny by many people!

Now that's it's confirmed to exist, I'm sure a floodgate will open to both it and Alpha Centauri.

I had read on (I believe it was Space.com) that Hubble was just below the threshold of detecting/imaging Proxima b, but the JWST should be able to; not certain on WFIRST but its coronagraph would greatly help.  The HD space telescope hopefully will be built with imaging Proxima's planets as a priority now.

Aside from pinning down the properties on the new planet, another objective should be to confirm is there's more to Proxima's system.  There's suspicions of a 2nd, outer planet, but no confirmation just yet.  If b can't be directly imaged even with new space telescopes, its would-be outer neighbors could be resolved.

As for a mission flying directly to Proxima...hard to say what should or could be done.  The starshot idea Steven Hawkins announced is probably the best we can do momentarily, and while I'm not a fan of solar sails I will say there's merit in employing them for star travel as opposed to heavy reactor-powered systems.  Depending on mass constraints, there could be 2 sails deployed; the 1st would using laser power from Earth but the 2nd would be deployed near Proxima to brake using the star's light; I suggest 2 because the 1st sail would probably be heavily damaged over time by the time the probe arrives.  Most likely the mission would be a flyby of Proxima but it could divert to visit Alpha Centauri next.

I'd say keep a Proxima probe in mind, but on the back burner, and primarily invest in a large space telescope charged with directly imaging anything around Proxima and AC.  Establishing the basic size, composition, and atmosphere ought to be possible in the near future; if you wish to be (reasonably) ambitious size the 'scope to be able to see continents on Proxima planets.
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Offline Star One

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Design a mission to Proxima b
« Reply #26 on: 08/25/2016 08:19 PM »
For those interested JWST appears to be discussing Proxima b on its Twitter feed at the moment.
« Last Edit: 08/25/2016 08:19 PM by Star One »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #27 on: 08/25/2016 08:49 PM »
Let's see here. Inclination will be an issue, which means we would definitely, absolutely have to execute a solar slingshot in order to get a free inclination change. The easiest way to do a solar slingshot, of course, is to do a Jovian slingshot. In order to actually get a gravity assist from Jupiter, you'd need to set it all up with a Martian slingshot.

So we have the beginnings of a mission profile. Let's limit ourselves to three LEO BFR launches and just two on-orbit robotic assembly events. Generously, let's say this gives us 900 tonnes in LEO.

From a mass basis, is it cheaper to use SEP or a solar sail to do the burn for the martian slingshot, or should chemical propulsion be used?

Once the slingshots begin, maximum propulsive capacity should be saved for the periapse of the solar slingshot for Oberth reasons. Chemical propulsion is nice here because it can permit very high thrust, which is ideal for an oberth maneuver, but would an ablative solar sail be a better use of mass? Or would it be better to have a combination of chemical propulsion at periapse followed by the deployment of a solar sail?

Remember that your whole system needs to be broken up into 300-tonne blocs in order to fit on three BFR launches.

...none of this is relevant for an interstellar mission lasting less than a century. Inclination not an issue AT ALL. Are you referring to a gravitational focus mission?
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Offline sevenperforce

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Re: Design a mission to Proxima b
« Reply #28 on: 08/25/2016 10:14 PM »
Let's see here. Inclination will be an issue, which means we would definitely, absolutely have to execute a solar slingshot in order to get a free inclination change. The easiest way to do a solar slingshot, of course, is to do a Jovian slingshot. In order to actually get a gravity assist from Jupiter, you'd need to set it all up with a Martian slingshot.

So we have the beginnings of a mission profile. Let's limit ourselves to three LEO BFR launches and just two on-orbit robotic assembly events. Generously, let's say this gives us 900 tonnes in LEO.


...none of this is relevant for an interstellar mission lasting less than a century. Inclination not an issue AT ALL. Are you referring to a gravitational focus mission?
I was more saying...given current and near future tech, what's the greatest dV you could get out of three BFR launches for an interstellar flyby mission?

If inclination is not an issue that still probably makes no difference since an oberth around the sun is going to be huge regardless.

Offline MAC74

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Re: Design a mission to Proxima b
« Reply #29 on: 08/25/2016 10:44 PM »
Wouldn't the James Webb Space Telescope be able to get a picture of this planet? The star is just a red dwarf.

Not even close.  Proxima b has a separation from it's star of about 20 milli-arcseconds.  The band limited Lyot coronagraphs in JWST's instruments have inner working angles varying from 400 mas to 800 mas.  So the coronagraphs would not be able to spatially resolve the planet or even come close to it.

In addition to that, there is the contrast problem.  A terrestrial planet in the habitable zone of a mid M dwarf has a contrast of about 1 X 10^-8 dimmer than its host star.  The coronagraphs on JWST are designed for about 1 X 10^-5 contract, since they are simple coronagrpahs without any wavefront control or diffraction suppression.

WFIRST would get closer but the inner working angle of the coronagraph would still be too large for this planet.

The best bet to study it in detail in the next few years would be if the planet transits its host star, which would allow JWST to use Transmission or Emission Spectroscopy on it.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #30 on: 08/25/2016 10:56 PM »
Let's see here. Inclination will be an issue, which means we would definitely, absolutely have to execute a solar slingshot in order to get a free inclination change. The easiest way to do a solar slingshot, of course, is to do a Jovian slingshot. In order to actually get a gravity assist from Jupiter, you'd need to set it all up with a Martian slingshot.

So we have the beginnings of a mission profile. Let's limit ourselves to three LEO BFR launches and just two on-orbit robotic assembly events. Generously, let's say this gives us 900 tonnes in LEO.


...none of this is relevant for an interstellar mission lasting less than a century. Inclination not an issue AT ALL. Are you referring to a gravitational focus mission?
I was more saying...given current and near future tech, what's the greatest dV you could get out of three BFR launches for an interstellar flyby mission?

If inclination is not an issue that still probably makes no difference since an oberth around the sun is going to be huge regardless.
Right. But "huge" relative to our current speeds. But even the Oberth boost is basically useless compared to the delta-v needed for less-than-a-century interstellar travel. You're limited by the escape velocity of the Sun. It'd be better if we had a black hole or at least a white dwarf or neutron star...
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Online KelvinZero

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Re: Design a mission to Proxima b
« Reply #31 on: 08/25/2016 11:13 PM »
In another thread someone suggested using a lightsail to hide the star. That was an interesting idea. Could that help even if it were not even a thousandth of the distance there? That is still a long way. Im not sure how you would keep the lightsail between your telescope and star for any prolonged period of time. Perhaps both need to have escaped the solarsystem.

Offline Star One

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Re: Design a mission to Proxima b
« Reply #32 on: 08/25/2016 11:39 PM »
Wouldn't the James Webb Space Telescope be able to get a picture of this planet? The star is just a red dwarf.

Not even close.  Proxima b has a separation from it's star of about 20 milli-arcseconds.  The band limited Lyot coronagraphs in JWST's instruments have inner working angles varying from 400 mas to 800 mas.  So the coronagraphs would not be able to spatially resolve the planet or even come close to it.

In addition to that, there is the contrast problem.  A terrestrial planet in the habitable zone of a mid M dwarf has a contrast of about 1 X 10^-8 dimmer than its host star.  The coronagraphs on JWST are designed for about 1 X 10^-5 contract, since they are simple coronagrpahs without any wavefront control or diffraction suppression.

WFIRST would get closer but the inner working angle of the coronagraph would still be too large for this planet.

The best bet to study it in detail in the next few years would be if the planet transits its host star, which would allow JWST to use Transmission or Emission Spectroscopy on it.
Well what's been posted on Twitter tonight by the official JWST account would seem to disagree with you on completely precluding anything at this point in time.

https://mobile.twitter.com/NASAWebb/status/768923069805125632
« Last Edit: 08/25/2016 11:42 PM by Star One »

Offline AS_501

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Re: Design a mission to Proxima b
« Reply #33 on: 08/25/2016 11:54 PM »
BFR launches probe that is just large enough to transmit some data and images from Prox b.  Stack 4, 5, or more high-energy upper stages on top of the BFR.  I wonder how fast the probe would be moving when the final stage drops away?  This would be Atlas V 551/New Horizons on steroids+.  Alas, I suspect even this scheme would not be enough to reach an appreciable fraction of light speed.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #34 on: 08/26/2016 01:36 AM »
BFR launches probe that is just large enough to transmit some data and images from Prox b.  Stack 4, 5, or more high-energy upper stages on top of the BFR.  I wonder how fast the probe would be moving when the final stage drops away?  This would be Atlas V 551/New Horizons on steroids+.  Alas, I suspect even this scheme would not be enough to reach an appreciable fraction of light speed.
No. Chemical propulsion is utterly incapable of interstellar travel within any kind of reasonable timeframe. And it doesn't even matter how big your rocket is. Could be the mass of the Sun, but still wouldn't have enough fuel to reach even 5% of lightspeed.
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Online Zed_Noir

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Re: Design a mission to Proxima b
« Reply #35 on: 08/26/2016 02:16 AM »
BFR launches probe that is just large enough to transmit some data and images from Prox b.  Stack 4, 5, or more high-energy upper stages on top of the BFR.  I wonder how fast the probe would be moving when the final stage drops away?  This would be Atlas V 551/New Horizons on steroids+.  Alas, I suspect even this scheme would not be enough to reach an appreciable fraction of light speed.

Better yet. Parked a stripped down empty BFR core with one Raptor Vac engine at Lagrange point 2. Added combo NEP & SEP cruise module and Proxima probe. Top off and lit the BFR core for the initial boost. Switch to ion thrusters powered by solar arrays & RTGs after separating from depleted BFR core. Jettisoning the solar arrays after going beyond Jupiter orbital distance. Then continuous boost with ion thruster powered by RTGs until Xenon depletion. Finally the probe separated from cruise module and is on ballistic encounter with the Proxima system. Of course presuming the probe lasted long enough for the encounter observation and got a working radio transmitter for a brief data transmission. For a reasonable chance of mission success, a series of probe launches is needed.


Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #36 on: 08/26/2016 02:29 AM »
BFR launches probe that is just large enough to transmit some data and images from Prox b.  Stack 4, 5, or more high-energy upper stages on top of the BFR.  I wonder how fast the probe would be moving when the final stage drops away?  This would be Atlas V 551/New Horizons on steroids+.  Alas, I suspect even this scheme would not be enough to reach an appreciable fraction of light speed.

Better yet. Parked a stripped down empty BFR core with one Raptor Vac engine at Lagrange point 2. Added combo NEP & SEP cruise module and Proxima probe. Top off and lit the BFR core for the initial boost. Switch to ion thrusters powered by solar arrays & RTGs after separating from depleted BFR core. Jettisoning the solar arrays after going beyond Jupiter orbital distance. Then continuous boost with ion thruster powered by RTGs until Xenon depletion. Finally the probe separated from cruise module and is on ballistic encounter with the Proxima system. Of course presuming the probe lasted long enough for the encounter observation and got a working radio transmitter for a brief data transmission. For a reasonable chance of mission success, a series of probe launches is needed.
No, this is still not nearly good enough. It'll be hundreds (if not thousands) of years before your probe arrives.

The usual approaches to exploring our solar system simply do not work.

Do the math!
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Online Zed_Noir

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Re: Design a mission to Proxima b
« Reply #37 on: 08/26/2016 03:53 AM »

Better yet. Parked a stripped down empty BFR core with one Raptor Vac engine at Lagrange point 2. Added combo NEP & SEP cruise module and Proxima probe. Top off and lit the BFR core for the initial boost. Switch to ion thrusters powered by solar arrays & RTGs after separating from depleted BFR core. Jettisoning the solar arrays after going beyond Jupiter orbital distance. Then continuous boost with ion thruster powered by RTGs until Xenon depletion. Finally the probe separated from cruise module and is on ballistic encounter with the Proxima system. Of course presuming the probe lasted long enough for the encounter observation and got a working radio transmitter for a brief data transmission. For a reasonable chance of mission success, a series of probe launches is needed.
No, this is still not nearly good enough. It'll be hundreds (if not thousands) of years before your probe arrives.

The usual approaches to exploring our solar system simply do not work.

Do the math!

Of course it will take many decades of flight time. It is what is possible with near term technology.

:P Please offer an alternate scheme that you think will be faster that might be possible in the next few decades..


Offline Elmar Moelzer

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Re: Design a mission to Proxima b
« Reply #38 on: 08/26/2016 04:00 AM »
At yesterdays NIAC presentation Philip Lubin from the University of California, Santa Barbara presented their concept for Directed Energy propulsion to accelerate a wafer sized spacecraft to 0.2c.
That would make Proxima B a 25 year mission.
http://livestream.com/viewnow/NIAC2016/videos/133838016

Offline MATTBLAK

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Re: Design a mission to Proxima b
« Reply #39 on: 08/26/2016 07:56 AM »
(My Concept For):

Interstellar Precursor Probe (IPP): Year of approximately 2030-2040 - Deep Kuiper Belt exploration spacecraft to develop technologies for eventual use on a future late-21st or early 22nd century interstellar probe for a mission to Proxima Centauri and it’s observed planetary target(s). The IPP concept would be the most expensive and sophisticated deep space exploration probe concept ever attempted.

Launch vehicle(s):  1x SLS Block 2 or 2B, utilizing advanced upper stage and boosters, plus 1x Falcon 9 (advanced) or a Vulcan 6-Solid Rocket Motor launcher. OR: 1x Falcon 9 (advanced version, with a Raptor powered upper stage) plus 2x Falcon Heavies – rendezvous and dock 1x 25 ton spacecraft plus 2x 60 ton Earth Departure Stages to assemble the ‘Mission Stack’.

Spacecraft: Tough, heavily-shielded ‘lightweight’ probe that nonetheless masses approximately 25 metric tons including Xenon propellants, instruments, cameras, ejectable solar power arrays, a large unfolding high-gain antenna and a mixed set of Plutonium and AM 241 Radiosotopic Thermo-Electric generators. The Plutonium RTGs are predominantly for the spacecraft’s hybrid Ion propulsion system – most likely an advanced and evolved array of gridded Hall thrusters. The very long life Americium 241 RTGs are for the science instruments and cameras. The SLS launcher uses a 10 meter option payload fairing to maximise options for a large, deployable high gain antenna array that will deploy out to between 15-to-18 meters in diameter.
SLS Mission profile: IPP is launched into Earth parking orbit on Vulcan or Falcon 9 launcher. SLS Block 2 series launcher with Exploration Upper Stage only as payload (largest possible propellant load) sends the EUS into an orbit within reach of the IPP, which then rendezvous and docks with the EUS.
The Earth Departure burn is then followed by some sort of staged combination of Earth, Venus and Jupiter gravitational assist flybys to eventually send the IPP on a high-speed departure of the Solar System. Within the inner solar system, the solar arrays feed power to the electric drive system, complimenting the Plutonium RTG sets. Though somewhat before the arrival in Jupiter’s space, the arrays are ejected and the Plutonium RTGs take up the lone task of supplying power to the electric drive thrusters, constantly 'burning' their tons of Xenon gas. Although the power level for the electric drive is now reduced; the IPP would then be already moving at very high speed (how fast??)
The electric drive would keep operating until the xenon propellant is starting to dwindle, by which time a flyby or two of large Kuiper belt objects should have occurred.

As for an Interstellar probe? Nobody can see the future with much other than mere practicality at the moment. But we can truthfully say that an Interstellar explorer should dwarf the IPP in size and complexity, the way relatively crudely-equipped polar explorers of the past are outstripped today by icebreakers, GPS, support ships and various aircraft.

http://www.kiss.caltech.edu/study/science/KISS%20How%20Fast%20How%20Far_strange_final.pdf

https://icubesat.files.wordpress.com/2015/05/icubesat-2015_org-b-3-4_amrtg_ambrosi.pdf

http://www.lpi.usra.edu/meetings/nets2012/pdf/3043.pdf


« Last Edit: 08/26/2016 04:43 PM by MATTBLAK »
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Online KelvinZero

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Re: Design a mission to Proxima b
« Reply #40 on: 08/26/2016 09:04 AM »
:P Please offer an alternate scheme that you think will be faster that might be possible in the next few decades..
Launching in the next few decades.. or arriving in the next few decades? VERY different question!  ;)

btw im not sure if it requires a new thread, but Im interested in imaging techniques specifically relevant to this planet that were not an option previously. Just the fact you have a single target to focus on makes a difference.

Example: I don't know if the gravitational focus is relevant to this, (can it image something that small, or is it better for larger objects at vast distance?) but one huge issue with missions to the gravitational focus is that you could only look at one precise direction, so you would have to have a very specific and worthwhile target, and you would not like to discover that there was a better choice when your probe is already on its way.

Of course the comparatively near range makes a difference also. Some technology that is irrelevant for all the other billions of stars in the sky, thus not worth considering, might be relevant for this one star and now worth considering.
« Last Edit: 08/26/2016 10:12 AM by KelvinZero »

Offline 93143

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Re: Design a mission to Proxima b
« Reply #41 on: 08/26/2016 11:17 AM »
:P Please offer an alternate scheme that you think will be faster that might be possible in the next few decades..

Fusion pulse with magsail braking.  Don't need fancy laser/Z-pinch/antimatter stuff; just use Teller-Ulam pulse units.  If we really wanted to, we could do it.

Pretty expensive for a first probe, though.  Hopefully we get some good news from those miniature laser-propelled probes, or a massive interferometer or some such, and the will materializes for a robust follow-up...

A major propulsion technology breakthrough is still possible, of course, and it could happen at any time; predictions of when to expect warp drive based on handwavy extrapolations of current progress in physics are probably worthless one way or the other and should not be listened to.  Probably the best approach is to not expect warp drive, but to keep half an eye out for it rather than dismissing it entirely.  (Unless you're in a position to help make it happen, in which case you should stop reading this forum and get some work done...)  Normally I'd consider warp drive off topic, but you did say "might be possible", not "is likely to be possible"...

Mass beam propulsion.

Unlike laser tech, it's scalable to crewed missions as well (without Singularity-level resources).

I must say don't like the idea of shooting relativistic bullets at a manned starship over light-year ranges (you can't use actual particle beams; they have to be immune to beam spreading and smart enough to maneuver).  Get one malfunctioning unit a little out of place, such that the ship can't compensate in time, and your mission is over.
« Last Edit: 08/26/2016 11:19 AM by 93143 »

Offline MAC74

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Re: Design a mission to Proxima b
« Reply #42 on: 08/26/2016 01:27 PM »
Wouldn't the James Webb Space Telescope be able to get a picture of this planet? The star is just a red dwarf.

Not even close.  Proxima b has a separation from it's star of about 20 milli-arcseconds.  The band limited Lyot coronagraphs in JWST's instruments have inner working angles varying from 400 mas to 800 mas.  So the coronagraphs would not be able to spatially resolve the planet or even come close to it.

In addition to that, there is the contrast problem.  A terrestrial planet in the habitable zone of a mid M dwarf has a contrast of about 1 X 10^-8 dimmer than its host star.  The coronagraphs on JWST are designed for about 1 X 10^-5 contract, since they are simple coronagrpahs without any wavefront control or diffraction suppression.

WFIRST would get closer but the inner working angle of the coronagraph would still be too large for this planet.

The best bet to study it in detail in the next few years would be if the planet transits its host star, which would allow JWST to use Transmission or Emission Spectroscopy on it.
Well what's been posted on Twitter tonight by the official JWST account would seem to disagree with you on completely precluding anything at this point in time.

https://mobile.twitter.com/NASAWebb/status/768923069805125632

I read that.  When they say Promixa b is a good target for JWST they mean for transits, not imaging.  I was responding to the original post about imaging.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #43 on: 08/26/2016 01:41 PM »
...
Mass beam propulsion.

Unlike laser tech, it's scalable to crewed missions as well (without Singularity-level resources).

I must say don't like the idea of shooting relativistic bullets at a manned starship over light-year ranges (you can't use actual particle beams; they have to be immune to beam spreading and smart enough to maneuver).  Get one malfunctioning unit a little out of place, such that the ship can't compensate in time, and your mission is over.
Much, much smaller than bullets. More like grains of dust. Realize that a starship is going to be encountering dust particles of the same speed on its way to its destination, so this is a problem that will need to be solved either way.

Don't have to self-maneuver, by the way, although that is an option.

Also, your idea of pulse nuclear is just as crazy sounding! Sending thousands of h-bombs to explode right below your butt! :D

...but I support both ideas. I think interstellar travel probably works best by pursuing multiple approaches at once. Mass beam propulsion up to 4-6%c, then pulse nuclear another 4-6%c to 10%c, then coast until you decelerate with a magsail.

But maybe something like Zubrin's Nuclear Salt Water Rocket should be considered? It's more compact than Orion-style propulsion, so at very least could be used as the final stage before coast.

By splitting up the tech into stages, it makes it more viable. Perhaps cooling and ablation constraints limits the Isp of Orion-like or NSWR-like propulsion such that only 3-4% c is possible? And with beamed propulsion techniques, perhaps diffraction or aiming constraints also limit the speed? But if you use them together, you can get to 10%c.

EDIT: Also, the "bullets" don't actually /have/ to be relativistic (i.e. >10%c) when they reach the starship. The energy-optimal solution is to accelerate the bullets to twice the spaceship's velocity-at-intercept, so that the intercept velocity is the same as the current starship velocity, but that's not actually the only option. You can also accelerate the mass beam so that it impacts the starship at a fraction of the current speed, so the intercept velocity is as firmly sub-relativistic as you like, though the efficiency is lower (but that matters less because the power source need not be on the actual starship).
« Last Edit: 08/26/2016 02:19 PM by Robotbeat »
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Offline R7

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Re: Design a mission to Proxima b
« Reply #44 on: 08/26/2016 01:59 PM »
1. Raise a few trillion dollars.
2. ??
3. Proxima b!
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Offline sevenperforce

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Re: Design a mission to Proxima b
« Reply #45 on: 08/27/2016 12:24 AM »
Three BFR launches, ~900 tonnes. A high-isp burn into a multiple-slingshot trajectory and everything else into a Project Orion burn at the solar periapse. How much dV can we squeeze out of 900 tonnes of Teller-Ulam devices, and how tightly can we make the solar swingby for maximum boost?

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #46 on: 08/27/2016 12:29 AM »
Three BFR launches, ~900 tonnes. A high-isp burn into a multiple-slingshot trajectory and everything else into a Project Orion burn at the solar periapse. How much dV can we squeeze out of 900 tonnes of Teller-Ulam devices, and how tightly can we make the solar swingby for maximum boost?
At least you're on the right track with pulse nuclear, here. But the solar swingby isn't very helpful. Skimming the surface, the escape velocity is 500km/s, which is all the help it could possibly give you (in practicality, the boost is going to be much less, maybe 100km/s).
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Offline Elmar Moelzer

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Re: Design a mission to Proxima b
« Reply #47 on: 08/27/2016 12:35 AM »
I still think that the directed energy system presented at NIAC makes the most sense. 10 minutes to 0.2c for a wafer size probe, 25 years to Proxima b and all that with technology that is conceivable today.

Offline Bob Shaw

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Re: Design a mission to Proxima b
« Reply #48 on: 08/27/2016 01:07 AM »
Tiny, laser propelled probes on fast flybys (perhaps with optical parachutes at target to increase encounter time) are entirely reasonable. We need, however, to industrialise the inner Solar System to make this work, and we also need to sort out major political issues on Earth.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #49 on: 08/27/2016 02:15 AM »
I still think that the directed energy system presented at NIAC makes the most sense. 10 minutes to 0.2c for a wafer size probe, 25 years to Proxima b and all that with technology that is conceivable today.
There are lots of problems with it. First of all, flyby at 0.2c is such a short time that you'd actually be better off with a really good telescope at the gravitational focus. Also, the forces involved would tear the probe to shreds. And such intense laser light even if nearly perfectly reflected would vaporize the sail. Also, getting diffraction-limited optics over such a large area and through the atmosphere seems unlikely to say the least.

There are, in fact, several other concepts that also use technology conceivable today to achieve interstellar travel within decades.

Though perhaps it's useful, if those challenges are solved. At very least, it'd be nice to actually map the interstellar medium around us so that we could send large probes or crewed missions out and be able to reliably use a mag-sail to slow down.
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Offline Elmar Moelzer

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Re: Design a mission to Proxima b
« Reply #50 on: 08/27/2016 06:50 AM »
I still think that the directed energy system presented at NIAC makes the most sense. 10 minutes to 0.2c for a wafer size probe, 25 years to Proxima b and all that with technology that is conceivable today.
There are lots of problems with it. First of all, flyby at 0.2c is such a short time that you'd actually be better off with a really good telescope at the gravitational focus. Also, the forces involved would tear the probe to shreds. And such intense laser light even if nearly perfectly reflected would vaporize the sail. Also, getting diffraction-limited optics over such a large area and through the atmosphere seems unlikely to say the least.

There are, in fact, several other concepts that also use technology conceivable today to achieve interstellar travel within decades.

Though perhaps it's useful, if those challenges are solved. At very least, it'd be nice to actually map the interstellar medium around us so that we could send large probes or crewed missions out and be able to reliably use a mag-sail to slow down.
Did you watch the NIAC presentation? Agree on the forces and the speed issues during flyby.
« Last Edit: 08/27/2016 06:51 AM by Elmar Moelzer »

Offline indaco1

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Re: Design a mission to Proxima b
« Reply #51 on: 08/27/2016 08:55 AM »
..Just the fact you have a single target to focus on makes a difference.
..

The answer is economic: very expensive, but reusable, particle beam/laser/microwawe generator and cheap mass produced mostly passive probes.

As we know expensive and expendable is bad.  Expensive and reusable is slightly better.
 
Cheap probes allow multiple targets.

A less cheap probe whit passive magsail braking capabilities is for a next phase, further in the future.

Proxima B is interesting, but I think that the day we'll be able to arrive and stop there, we'll not need a planet anymore. Ie: Sirius will be much more interesting at that time because provides more raw material and solar energy.
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Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #52 on: 08/27/2016 11:35 AM »
FYI reported on this very forum Dr Rodal reports after a lengthy peer review process Eagleworks latest paper on the EM drive has been accepted for publication in the American Institute of Aeronautics and Astronautics: AIAA Journal of Propulsion and Power.
And?
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Offline floss

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Re: Design a mission to Proxima b
« Reply #53 on: 08/27/2016 02:56 PM »
Build a massive 30,000 km Soletta in orbit of Venus Sun L 4  and use the solar power to make a large amount of Antimatter and open up the solar system up to commerce and use the left over antimatter to power interstellar space probes .

Pretty near term Technology just brute force economics.

Offline llanitedave

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Re: Design a mission to Proxima b
« Reply #54 on: 08/27/2016 03:30 PM »
I'm with those who say we should improve our imaging and remote sensing capabilities before we start planning an encounter mission with no information about what we would be encountering.  Let's concentrate on developing technology for Optical interferometry that can be applied to an array of good-sized telescope mirrors at a gravitationally stable location.

Probably not the Moon.
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Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #55 on: 08/27/2016 08:12 PM »
Build a massive 30,000 km Soletta in orbit of Venus Sun L 4  and use the solar power to make a large amount of Antimatter and open up the solar system up to commerce and use the left over antimatter to power interstellar space probes .

Pretty near term Technology just brute force economics.
Not near term as antimatter production is insanely inefficient (such that you wouldn't have enough left to "brute force" anything) and there's no way to stably store vast amounts of antimatter in a mass-efficient way. The storage/containment problem is huge. You'd be better off with fission or fusion.
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Offline Bob Shaw

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Re: Design a mission to Proxima b
« Reply #56 on: 08/27/2016 08:22 PM »
Send an observatory directly away from Proxima Centaurus, and park it at the Sun's microlensing point (about half a light year from home). Use it to survey the whole Proxima system.

Pros: great science, testbed for starship technology

Cons: not much less difficult than building a starship

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #57 on: 08/27/2016 08:30 PM »
Send an observatory directly away from Proxima Centaurus, and park it at the Sun's microlensing point (about half a light year from home). Use it to survey the whole Proxima system.

Pros: great science, testbed for starship technology

Cons: not much less difficult than building a starship
MUCH less difficult than building a starship.

This would be the most straight-forward way to get it there:
http://xkcd.com/1244
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Re: Design a mission to Proxima b
« Reply #58 on: 08/27/2016 10:55 PM »
Send an observatory directly away from Proxima Centaurus, and park it at the Sun's microlensing point (about half a light year from home). Use it to survey the whole Proxima system.
You only need to get a bit over 600 AU (~0.01 light year) to get to the suns gravitational focus, but it may not actually work better spending the same effort on a more traditional observatory (further discussion of the viability of the FOCAL concept should probably go in that thread)

Offline rdheld

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Re: Design a mission to Proxima b
« Reply #59 on: 08/27/2016 11:19 PM »
I read a paper that stated the solar focus is not sueful for sharp images.
no reason you cannot build bigger local imaging devices as you develop the infrastructor for making massive quantities of deuterium and antimatter

Offline Oli

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Re: Design a mission to Proxima b
« Reply #60 on: 08/27/2016 11:55 PM »
Wouldn't the James Webb Space Telescope be able to get a picture of this planet? The star is just a red dwarf.

Not even close.  Proxima b has a separation from it's star of about 20 milli-arcseconds.  The band limited Lyot coronagraphs in JWST's instruments have inner working angles varying from 400 mas to 800 mas.  So the coronagraphs would not be able to spatially resolve the planet or even come close to it.

In addition to that, there is the contrast problem.  A terrestrial planet in the habitable zone of a mid M dwarf has a contrast of about 1 X 10^-8 dimmer than its host star.  The coronagraphs on JWST are designed for about 1 X 10^-5 contract, since they are simple coronagrpahs without any wavefront control or diffraction suppression.

WFIRST would get closer but the inner working angle of the coronagraph would still be too large for this planet.

The best bet to study it in detail in the next few years would be if the planet transits its host star, which would allow JWST to use Transmission or Emission Spectroscopy on it.

A guy on planetary.org said upcoming 30m+ telescopes should be able to directly image the planet.

Quote
The planet is at the right place to have a temperature that allows the presence of liquid water on its surface. The question of habitability is however very complex. We need to confirm that this is a terrestrial planet. The best way to do that would be to directly image the planet using the giant telescopes equipped with extreme adaptive optics that are currently being built (i.e., the E-ELT, TMT, GMT). The angular separation between the star and the planet is 39 milli-arcsec, so a telescope as large as 30 m could resolve the system with the right instrument, detecting the planet and possibly giving us insights into its composition.

http://www.planetary.org/blogs/guest-blogs/2016/0824-proxima-centauri-b-have-we.html

Online KelvinZero

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Re: Design a mission to Proxima b
« Reply #61 on: 08/28/2016 12:19 AM »
A guy on planetary.org said upcoming 30m+ telescopes should be able to directly image the planet.
...
http://www.planetary.org/blogs/guest-blogs/2016/0824-proxima-centauri-b-have-we.html
Hey everyone, I have started up a thread on imaging btw.

Offline Bob Shaw

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Re: Design a mission to Proxima b
« Reply #62 on: 08/28/2016 12:24 AM »
I read a paper that stated the solar focus is not sueful for sharp images.
no reason you cannot build bigger local imaging devices as you develop the infrastructor for making massive quantities of deuterium and antimatter

I'm sure I read somewhere that it was much further than that! The problem, of course, is not just going there but coming to rest.

Offline Bob Shaw

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Re: Design a mission to Proxima b
« Reply #63 on: 08/28/2016 12:30 AM »
I'm hearing different comments re Proxima transits: are we in the right plane, or not?

If not, is the first step to send a high-ish speed probe to a point in space where it can loiter and look at transits?

Still difficult, but easier and easier as you head towards Proxima - perhaps a precursor mision...

Offline wdobner

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Re: Design a mission to Proxima b
« Reply #64 on: 08/28/2016 01:00 AM »
How about Fission Fragment propulsion? 

http://www.osti.gov/scitech/servlets/purl/6868318/

This apparently old paper (attached below) about the early FFRE concept with fibers in fissionable material makes the case that a 10GW FFRE would deliver a 1 ton payload to Alpha Centauri in a century.  Now we just need to find a way to build a 10GW FFRE.  And find a way to radiate 10GW worth of energy from the spacecraft during its 40 years under thrust.

The paper does make the case that this version of an FFRE is well suited to radiating the heat away from the fibers directly.  Would that also apply to the dusty plasma FFRE that's been proposed more recently?

Offline Bob Shaw

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Re: Design a mission to Proxima b
« Reply #65 on: 08/28/2016 01:12 AM »
How about Fission Fragment propulsion? 

http://www.osti.gov/scitech/servlets/purl/6868318/

This apparently old paper (attached below) about the early FFRE concept with fibers in fissionable material makes the case that a 10GW FFRE would deliver a 1 ton payload to Alpha Centauri in a century.  Now we just need to find a way to build a 10GW FFRE.  And find a way to radiate 10GW worth of energy from the spacecraft during its 40 years under thrust.

The paper does make the case that this version of an FFRE is well suited to radiating the heat away from the fibers directly.  Would that also apply to the dusty plasma FFRE that's been proposed more recently?

Fine for a Daedalus fast flyby, but we might want a fast (in interstellar terms) journey time and an encounter which is as slow as possible.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #66 on: 08/28/2016 02:14 AM »
How about Fission Fragment propulsion? 

http://www.osti.gov/scitech/servlets/purl/6868318/

This apparently old paper (attached below) about the early FFRE concept with fibers in fissionable material makes the case that a 10GW FFRE would deliver a 1 ton payload to Alpha Centauri in a century.  Now we just need to find a way to build a 10GW FFRE.  And find a way to radiate 10GW worth of energy from the spacecraft during its 40 years under thrust.

The paper does make the case that this version of an FFRE is well suited to radiating the heat away from the fibers directly.  Would that also apply to the dusty plasma FFRE that's been proposed more recently?

Fine for a Daedalus fast flyby, but we might want a fast (in interstellar terms) journey time and an encounter which is as slow as possible.
Magsail to slow down. If this can be made to work (and I'm pretty sure it can, if any of these interstellar concepts can), then magsail will probably be used for every interstellar mission concept since it doesn't require any continuous power or propellant.
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Offline rdheld

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Re: Design a mission to Proxima b
« Reply #67 on: 08/28/2016 12:43 PM »
has there been any testing of a magsail?  certainly not in space.

Offline TakeOff

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Re: Design a mission to Proxima b
« Reply #68 on: 08/28/2016 01:35 PM »
A steady stream of launched lenses in a convoy where each lens refocuses the energy beam from the Solar System to the next mirror ahead. So that the probe can be continuously powered, and even enter stellar orbit by using a reflector ahead of it to decelerate. Earth providing the Proxima mission with all the energy it needs all the way. It would become a Silk Road through space, but unfortunately requires many years of daily launches of magical laser lenses at interstellar speeds.

The probe's payload materials would reconstruct (3D print) itself, using the latest engineering science on Earth, to different configurations. First just like a very thin javelin to avoid collisions while in transit. Then to a stellar wind sail to help entering orbit. Then to a surveying orbiter. Then to a lander. Then to a factory. And then to whatever we want it to do. (Such as an image of ourselves, since the only ones who could do it will have a Christian heritage).
I think a FOCAL telescope at 550 AU is the way to go.

https://en.wikipedia.org/wiki/FOCAL_(spacecraft)
Yeah, this has to be done before launching anything there anyway. The lensing begins only about 1% of the distance to Proxima. And it is doable in twenty-thirty years. Maybe FOCAL is the next $100 million initiative of Yuri Milner? It fits both with SETI and the Starshot. I'm glad he aims higher and bigger, but using the Sun as a gravitational lens would be my first priority if I had interstellar monies.
« Last Edit: 08/28/2016 01:48 PM by TakeOff »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #69 on: 08/28/2016 02:10 PM »
has there been any testing of a magsail?  certainly not in space.
It should be tested, I agree. But the idea relies on well-understood physics. A magnetic field resists the flow of charged particles (the interstellar plasma).
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Offline Paul451

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Re: Design a mission to Proxima b
« Reply #70 on: 08/29/2016 01:49 PM »
Re: Solar gravitational focus
The problem, of course, is not just going there but coming to rest.

The solar gravitational focus is not a focal point, but a focal line. There's no reason to stop. It starts working around 540-550AU, but becomes useful beyond 600AU. The butter-zone is around 1000AU.

« Last Edit: 08/29/2016 01:50 PM by Paul451 »

Offline rdheld

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Re: Design a mission to Proxima b
« Reply #71 on: 08/29/2016 10:55 PM »
People realize that any orbital telescope for the solar focus is orbiting the solar system barycenter and not the center of the Sun. How much fuel would be needed to keep it at a point at that focus?

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #72 on: 08/30/2016 12:16 AM »
People realize that any orbital telescope for the solar focus is orbiting the solar system barycenter and not the center of the Sun. How much fuel would be needed to keep it at a point at that focus?
Basically none compared to how much it took to get there. And because at that far out, the force from the Sun is small. At 550AU, the acceleration due to gravity is a microscopic 2*10^-8 m/s^2. A very small electric thruster is more than sufficient if you wanted to "hover" there (though it's not at all obvious you'd want to hover there versus coasting along the focal line).
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Online MattMason

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Re: Design a mission to Proxima b
« Reply #73 on: 08/30/2016 12:39 AM »
Some thoughts:

1) No nation or private group is ever going to commit to a "starship" or probe until more is known about its destination.
2) As someone said, a space probe won't work. Unless we can create true artificial intelligence for it to operate itself, it would be increasingly impossible to control, activate (you're not going to let it run its power and fuel out over years) or even receive the data it finds because the distance needed to send and receive signals aren't going faster than light (and let's leave the SF out of it until someone invents something truly FTL).

I agree with others. The great successes from exoplanet detection are in its comparatively infant stage. Bigger and better telescopes can and will get more info on Proxima-b and many other places before we commit to something.

And that also gives our autonomous technologies enough time to catch up. Don't need to launch a new AI-filled Voyager-type spacecraft and have it come back to kill us centuries later. ;)

Joke aside, having an exoplanet so comparably close is a comfort and scientific high-fiver for so many studies abd new technology, not to mention fodder for the tin-foil "the planet is doomed, let's evacuate" folks who worry that the whole solar system is hosed.
« Last Edit: 08/30/2016 12:40 AM by MattMason »
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Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #74 on: 08/30/2016 02:06 AM »
Some thoughts:

1) No nation or private group is ever going to commit to a "starship" or probe until more is known about its destination.
This statement is trivially true. There is serious scientific hay to be made by JWST and the 39m E-ELT, instruments already under construction, let alone ones that will be built in the future.
Quote
2) As someone said, a space probe won't work. Unless we can create true artificial intelligence for it to operate itself
Like what? think of a probe as just a sensor. It just needs to receive information and broadcast it.
Quote
it would be increasingly impossible to control,
You pre-program it with instructions, obviously.
Quote
activate (you're not going to let it run its power and fuel out over years)
And why not? Voyager 1 and 2 look like they'll probably last for half a century, which is longer than Breakthrough Starshot will need (for instance).
Quote
or even receive the data it finds because the distance needed to send and receive signals aren't going faster than light (and let's leave the SF out of it until someone invents something truly FTL).
Why does the probe need to receive commands? Just program it to send the right information. It doesn't need "AI" except in the trivial sense that is already used today on Mars.
« Last Edit: 08/30/2016 02:06 AM by Robotbeat »
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Offline Paul451

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Re: Design a mission to Proxima b
« Reply #75 on: 08/30/2016 04:15 AM »
Why does the probe need to receive commands? Just program it to send the right information. It doesn't need "AI" except in the trivial sense that is already used today on Mars.

Assuming a flyby, much can be pre-programmed. But over the length of the flight, we'll inevitably learn more about the dynamics of the target and other planets in the system, maybe Proxima's version of the asteroid and Kuiper Belt; maybe even a moon of the Prox b. Enough that we want to slightly tweak a) the flyby path, b) the observation priorities.

Not to mention changing the comms protocols to adapt to improved receivers. And maybe improving the programming of the probe itself, increasing its abilities, or working around bugs or hardware breakage that emerged during the long coast.

It's only a maximum of four and bit years away, by EM. Even a short 20-30 year flight time leaves enough time to want to tweak things. And the longer the coast, the more likely you want to make changes.

Assuming an orbiter mission... everything I just said, multiplied by every new discovery the probe makes.

No current or planned probe/lander/rover is capable of changing its own mission priorities based on new discoveries. For example, if the probe images Prox b and the image shows moons or rings (or both), no existing or planned system would be capable of autonomously understanding the discovery, let alone working out the orbital mechanics necessary to explore the new find(s).

Offline Paul451

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Re: Design a mission to Proxima b
« Reply #76 on: 08/30/2016 04:22 AM »
People realize that any orbital telescope for the solar focus is orbiting the solar system barycenter and not the center of the Sun. How much fuel would be needed to keep it at a point at that focus?

It's worse than that. The telescope is, in essence, the "secondary mirror" of the whole system, the primary lens is the sun's gravity which can't be steered. So if you want to track a moving target (such as an orbiting planet), then - to skew the view - you need to physically move the telescope laterally to the direction of travel. Similarly to moving the suspended receiver on a fixed dish like Arecibo in order to track targets.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #77 on: 08/30/2016 01:08 PM »
People realize that any orbital telescope for the solar focus is orbiting the solar system barycenter and not the center of the Sun. How much fuel would be needed to keep it at a point at that focus?

It's worse than that. The telescope is, in essence, the "secondary mirror" of the whole system, the primary lens is the sun's gravity which can't be steered. So if you want to track a moving target (such as an orbiting planet), then - to skew the view - you need to physically move the telescope laterally to the direction of travel. Similarly to moving the suspended receiver on a fixed dish like Arecibo in order to track targets.
Depends on the field of view of the telescope.
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Offline TakeOff

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Re: Design a mission to Proxima b
« Reply #78 on: 08/30/2016 04:08 PM »
People realize that any orbital telescope for the solar focus is orbiting the solar system barycenter and not the center of the Sun. How much fuel would be needed to keep it at a point at that focus?

It's worse than that. The telescope is, in essence, the "secondary mirror" of the whole system, the primary lens is the sun's gravity which can't be steered. So if you want to track a moving target (such as an orbiting planet), then - to skew the view - you need to physically move the telescope laterally to the direction of travel. Similarly to moving the suspended receiver on a fixed dish like Arecibo in order to track targets.
Depends on the field of view of the telescope.
Yes, Proxima b's orbital diameter is only about 7 million kilometers. At about 40,000 million kilometer distance.

I wonder if Solar corona activity could not be monitored by close Solar probes to provide data to allow for adaptive gravitational lensing?

A FOCAL mission would have to be big like one of today's space telescopes, but I think that the Kuiper Belt and beyond is quickly getting much more interest today. Thanks to New Horizons and new distant Solar planetary discoveries. Along with heavier and cheaper launchers and miniaturization, it is getting more and more feasible to send a telescope to 600 AU (1% of a light year).

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Re: Design a mission to Proxima b
« Reply #79 on: 08/30/2016 05:31 PM »
Some thoughts:

1) No nation or private group is ever going to commit to a "starship" or probe until more is known about its destination.
This statement is trivially true. There is serious scientific hay to be made by JWST and the 39m E-ELT, instruments already under construction, let alone ones that will be built in the future.
Quote
2) As someone said, a space probe won't work. Unless we can create true artificial intelligence for it to operate itself
Like what? think of a probe as just a sensor. It just needs to receive information and broadcast it.
Quote
it would be increasingly impossible to control,
You pre-program it with instructions, obviously.
Quote
activate (you're not going to let it run its power and fuel out over years)
And why not? Voyager 1 and 2 look like they'll probably last for half a century, which is longer than Breakthrough Starshot will need (for instance).
Quote
or even receive the data it finds because the distance needed to send and receive signals aren't going faster than light (and let's leave the SF out of it until someone invents something truly FTL).
Why does the probe need to receive commands? Just program it to send the right information. It doesn't need "AI" except in the trivial sense that is already used today on Mars.

There's never been a probe that works autonomously. Probes can't anticipate the unexpected or fix issues themselves. From the Dawn probe, JAXA's Akatsuki to MER Spirit, human intervention is eventually required. Now multiply that matter when an issue is reported days, if not months later, and a command is sent to correct an issue when the probe might be pointed the wrong way or dead by the time the command gets there.

Durability of probes isn't my problem. JPL continually makes probes that outlast their mission design by years to decades. Now am I complaining about the versatility of many probes to fix many of its problems on its own. The problem is simply communication to fix what the probes cannot.

Voyager 1 and 2 have completed their missions.

Oh, we should also consider what power source these things would use. RTGs have a good life, but even they might have limits if a mission takes decades, and the scarcity of plutonium is one reason why Juno is using solar panels.

You're still talking years to send or receive anything. That can be managed except for some mission-critical issues that have occurred on missions before. Good planning and innovation might reduce those issues.
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Offline JasonAW3

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Re: Design a mission to Proxima b
« Reply #80 on: 08/30/2016 05:47 PM »
The problem here, I think, is more along the lines of conventional thinking.

     First off, there is a higher likelihood of something catastrophic happening to a single probe, traveling at 20% the velocity of light than there is of impact on either the Voyager or pioneer probes, which are traveling far slower.

     Thus, using a group of smaller probes, about the gram size and mass and numbering in the hundreds or thousands, networked together to act as a distributed neural network, could allow for a fairly advanced and sophisticated AI system to control the group as a whole.  Losses during transit could be more readily absorbed by a group, than a single probe.

     This configuration also allows for a potential synthetic aperture sensor capability, allowing much more detailed information to be gathered during their transit through the Proxima Centauri system.

     Such a multiprobe approach would also add to the knowledge base of what hazards exist for human starflight at 20% C or higher velocities.
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Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #81 on: 08/30/2016 07:42 PM »
Some thoughts:

1) No nation or private group is ever going to commit to a "starship" or probe until more is known about its destination.
This statement is trivially true. There is serious scientific hay to be made by JWST and the 39m E-ELT, instruments already under construction, let alone ones that will be built in the future.
Quote
2) As someone said, a space probe won't work. Unless we can create true artificial intelligence for it to operate itself
Like what? think of a probe as just a sensor. It just needs to receive information and broadcast it.
Quote
it would be increasingly impossible to control,
You pre-program it with instructions, obviously.
Quote
activate (you're not going to let it run its power and fuel out over years)
And why not? Voyager 1 and 2 look like they'll probably last for half a century, which is longer than Breakthrough Starshot will need (for instance).
Quote
or even receive the data it finds because the distance needed to send and receive signals aren't going faster than light (and let's leave the SF out of it until someone invents something truly FTL).
Why does the probe need to receive commands? Just program it to send the right information. It doesn't need "AI" except in the trivial sense that is already used today on Mars.

There's never been a probe that works autonomously. Probes can't anticipate the unexpected or fix issues themselves. From the Dawn probe, JAXA's Akatsuki to MER Spirit, human intervention is eventually required. Now multiply that matter when an issue is reported days, if not months later, and a command is sent to correct an issue when the probe might be pointed the wrong way or dead by the time the command gets there.

Durability of probes isn't my problem. JPL continually makes probes that outlast their mission design by years to decades. Now am I complaining about the versatility of many probes to fix many of its problems on its own. The problem is simply communication to fix what the probes cannot.

Voyager 1 and 2 have completed their missions.

Oh, we should also consider what power source these things would use. RTGs have a good life, but even they might have limits if a mission takes decades, and the scarcity of plutonium is one reason why Juno is using solar panels.

You're still talking years to send or receive anything. That can be managed except for some mission-critical issues that have occurred on missions before. Good planning and innovation might reduce those issues.
These are the easiest problems to solve in the whole mission. All the probe needs to do is collect data and relay it to Earth.

By focusing on these "issues," you're vastly overestimating the difficulty of the propulsion problem. It's absurdly hard.
« Last Edit: 08/30/2016 07:43 PM by Robotbeat »
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Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #82 on: 08/30/2016 07:43 PM »
Falcon 9 is totally autonomous once launched. Sputnik 1 was autonomous.
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Re: Design a mission to Proxima b
« Reply #83 on: 08/30/2016 08:05 PM »
It seems to me that a probe to Proxima b is not a good idea.

Microprobe flybys (e.g. lightsail-propelled stuff) would have hard time collecting useful information: they can snap some pics at best, but how they would transmit the data back? Not trivial, you'd need a HUGE receiving antenna in Sol system.

Macroprobes we don't quite have propulsion for. Need to develop some fusion drive.

Developing a VERY powerful space telescope (interferometry?) can give you about the same information, sooner, with less R&D and mission risk (if something does not work out, you aren't at square one. You can debug it).
And also the 'scope can look and many, many other targets too, whereas probes capable of reaching Proxima will become even less tenable for targets farther away.

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Re: Design a mission to Proxima b
« Reply #84 on: 08/30/2016 08:28 PM »
It seems to me that a probe to Proxima b is not a good idea.

Microprobe flybys (e.g. lightsail-propelled stuff) would have hard time collecting useful information: they can snap some pics at best, but how they would transmit the data back? Not trivial, you'd need a HUGE receiving antenna in Sol system.
Lasers and with a large telescope.

Quote
Macroprobes we don't quite have propulsion for. Need to develop some fusion drive.

Developing a VERY powerful space telescope (interferometry?) can give you about the same information, sooner, with less R&D and mission risk (if something does not work out, you aren't at square one. You can debug it).
And also the 'scope can look and many, many other targets too, whereas probes capable of reaching Proxima will become even less tenable for targets farther away.
Do both.
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Re: Design a mission to Proxima b
« Reply #85 on: 08/30/2016 08:45 PM »
These are the easiest problems to solve in the whole mission.
It may well be the easiest problem, but it is far beyond anything we've done.

Quote
All the probe needs to do is collect data and relay it to Earth.
Not if you want to collect useful data. It needs to autonomously identify and select targets, select appropriate observations, and execute the observations with incredible speed, precision and reliability.

Falcon 9 is totally autonomous once launched. Sputnik 1 was autonomous.
That is not a reasonable comparison. You need to look at the amount of human time and effort that goes into planning real spacecraft observations. This is nothing like an LV flying a preprogrammed trajectory with some closed loop guidance. Even those "autonomous" LVs get a huge amount of human analysis and planning before the launch.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #86 on: 08/31/2016 12:14 AM »
New Horizons, when it entered flyby phase, was entirely autonomous for the same reason as a probe to Proxima b would be. It was given all its instructions of where to look beforehand.

You're making a mountain of a molehill. The real challenge is getting there.
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Online hop

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Re: Design a mission to Proxima b
« Reply #87 on: 08/31/2016 02:08 AM »
New Horizons, when it entered flyby phase, was entirely autonomous for the same reason as a probe to Proxima b would be. It was given all its instructions of where to look beforehand.
No, it was preprogrammed, not autonomous. The amount of autonomy was very limited, basically consisting of rebooting and continuing the sequence at a reasonable point. The sequences were developed through many person-years (decades, centuries?) of effort, and with human input up to a short time before the encounter. That human input was based on analysis of earlier data obtained from the spacecraft.

In any realistic scenario, knowledge of the Proxima system and the location of the probe will not be sufficient to have to develop the sequences in advance. To get much useful data, the probe will need to do the equivalent of planning the sequences itself. That is hard. Not as hard as some of the other problems, but nowhere near as easy your comments suggest.

An analogous New Horizons mission would be if it had been completely under spacecraft control after launch. It would carry out all the TCMs, navigate it's way to Pluto with no DSN, discover the moons that weren't known before launch, refine the orbits of Pluto and Charon beyond what was known at launch, do the analysis to decide the safe trajectory, plan all the specific observations based on its chosen trajectory, and execute it all perfectly without going into safe mode and phoning home for help (unlike the real New Horizons)
As hard as that would be, it would be much easier than doing the equivalent in a different star system.
Quote
You're making a mountain of a molehill. The real challenge is getting there.
Disagree. You are completely failing to grasp the amount of analysis and effort that goes into real spacecraft operations, and how much would have to be done by the spacecraft given a multi-year time lag and limited knowledge of the targets.
« Last Edit: 08/31/2016 02:10 AM by hop »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #88 on: 08/31/2016 02:13 AM »
New Horizons, when it entered flyby phase, was entirely autonomous for the same reason as a probe to Proxima b would be. It was given all its instructions of where to look beforehand.
No, it was preprogrammed, not autonomous....
Sure, that works.
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Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #89 on: 08/31/2016 02:14 AM »
...
Quote
You're making a mountain of a molehill. The real challenge is getting there.
Disagree. You are completely failing to grasp the amount of analysis and effort that goes into real spacecraft operations, and how much would have to be done by the spacecraft given a multi-year time lag and limited knowledge of the targets.
disagree? You ignored the second sentence right there. nothing compared to the challenge of getting there.
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Online hop

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Re: Design a mission to Proxima b
« Reply #90 on: 08/31/2016 02:33 AM »
No, it was preprogrammed, not autonomous....
Sure, that works.
Except it doesn't work for an interstellar mission.  That's the whole point. You cannot apply anything like the approach used by New Horizons or any other real space mission to date.

And yes, the disagree was only intended to apply to the mountain vs molehill ;) I fully agree that propulsion is an even bigger mountain :D

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #91 on: 08/31/2016 03:38 AM »
No, it was preprogrammed, not autonomous....
Sure, that works.
Except it doesn't work for an interstellar mission.  That's the whole point. You cannot apply anything like the approach used by New Horizons or any other real space mission to date.

And yes, the disagree was only intended to apply to the mountain vs molehill ;) I fully agree that propulsion is an even bigger mountain :D
But the molehill thing IS applying to propulsion as well.

This thing you keep talking about is /trivial/ compared to propulsion. I mean absolutely trivial. It's just ridiculously hard to get there. MUCH harder than we're used to thinking about.
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Offline rdheld

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Re: Design a mission to Proxima b
« Reply #92 on: 08/31/2016 11:33 AM »
it sounds to me you need enough fuel to slow down and have the main craft orbit Proxima?

Offline Stormbringer

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Re: Design a mission to Proxima b
« Reply #93 on: 08/31/2016 01:22 PM »
The US is re-establishing plutonium production. A small batch pilot program is over and it was successful. Plans are already afoot to scale it up to the needed levels. We will have all we need to make as many RTGs as we need as big as we need them to be.
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Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #94 on: 08/31/2016 02:21 PM »
it sounds to me you need enough fuel to slow down and have the main craft orbit Proxima?
Not all concepts bother to slow down. And those that do often find ways to slow down without fuel.
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Offline whitelancer64

Re: Design a mission to Proxima b
« Reply #95 on: 08/31/2016 03:14 PM »
No, it was preprogrammed, not autonomous....
Sure, that works.
Except it doesn't work for an interstellar mission.  That's the whole point. You cannot apply anything like the approach used by New Horizons or any other real space mission to date.

And yes, the disagree was only intended to apply to the mountain vs molehill ;) I fully agree that propulsion is an even bigger mountain :D
But the molehill thing IS applying to propulsion as well.

This thing you keep talking about is /trivial/ compared to propulsion. I mean absolutely trivial. It's just ridiculously hard to get there. MUCH harder than we're used to thinking about.

Trivial??  No it isn't.

Propulsion will be a challenge, indeed as you say, more difficult than anything we've ever done, but it is comparatively straightforward.

The Proxima b probe will need to have a level of AI far beyond anything we've ever been able to make. It will have to be able to detect new astronomical features, decide what they are, change its mission profile, calculate new trajectories, and so on. All on its own. It won't be able to receive new instructions from Earth like New Horizons repeatedly did.
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Offline Paul451

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Re: Design a mission to Proxima b
« Reply #96 on: 08/31/2016 03:20 PM »
So if you want to track a moving target (such as an orbiting planet), then - to skew the view - you need to physically move the telescope laterally to the direction of travel.
Depends on the field of view of the telescope.

How?

It'll already need a wide FoV to observe the entire Einstein ring around our sun. To change what object is "projected" onto that Einstein ring (or to track a moving object), it will need to physically move (not tilt, but move) laterally.

Yes, Proxima b's orbital diameter is only about 7 million kilometers. At about 40,000 million kilometer distance.

40 billion km is 266AU. What "distance" are you measuring?

[edit: It only registered later than you meant 40 trillion km. 4.3ish lightyears.]
« Last Edit: 08/31/2016 04:27 PM by Paul451 »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #97 on: 08/31/2016 03:30 PM »
So if you want to track a moving target (such as an orbiting planet), then - to skew the view - you need to physically move the telescope laterally to the direction of travel.
Depends on the field of view of the telescope.

How?

It'll already need a wide FoV to observe the entire Einstein ring around our sun. To change what object is "projected" onto that Einstein ring (or to track a moving object), it will need to physically move (not tilt, but move) laterally.
...
Image the entire system as an object. The distance b orbits from Proxima is about 1000 Earth radii.

Kepler, for instance, has 42 CCDs each ~2000x1000 pixels. So if the whole orbit was in view, you should have many pixels of resolution of the exoplanet. And of course, we could have 1000 CCD arrays instead of just 42.
« Last Edit: 08/31/2016 03:45 PM by Robotbeat »
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Offline Paul451

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Re: Design a mission to Proxima b
« Reply #98 on: 08/31/2016 04:11 PM »
Image the entire system as an object. The distance b orbits from Proxima is about 1000 Earth radii.
Kepler, for instance, has 42 CCDs each ~2000x1000 pixels. So if the whole orbit was in view, you should have many pixels of resolution of the exoplanet. And of course, we could have 1000 CCD arrays instead of just 42.

That's not how Einstein rings work.

At 700AU (so the focal angle is far enough away from the sun for the Einstein ring to be visible beyond the sun's atmosphere) the FoV of an Einstein ring is around 1.5 arcseconds. AIUI, in practice, the useful FoV will be about a tenth of that: 0.15 arcseconds.

A 14 million km orbit in the target system will have an apparent width of around 13 arcseconds. Nearly two orders of magnitude too wide to image from a single location.

To slew from one side of Prox-b's orbit to the other requires a lateral shift by the observer of about 37,000 km.

[edit: At 550 AU, the FoV is 1.7 arcseconds, the useful FoV is 0.17". In case you thought I was cheating by going to 700AU.]
« Last Edit: 08/31/2016 04:26 PM by Paul451 »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #99 on: 08/31/2016 04:17 PM »
Image the entire system as an object. The distance b orbits from Proxima is about 1000 Earth radii.
Kepler, for instance, has 42 CCDs each ~2000x1000 pixels. So if the whole orbit was in view, you should have many pixels of resolution of the exoplanet. And of course, we could have 1000 CCD arrays instead of just 42.

That's not how Einstein rings work.

At 700AU (so the focal angle is far enough away from the sun for the Einstein ring to be visible beyond the sun's atmosphere) the FoV of an Einstein ring is around 1.5 arcseconds. AIUI, in practice, the useful FoV will be about a tenth of that: 0.15 arcseconds.

A 14 million km orbit in the target system will have an apparent width of around 13 arcseconds. Nearly two orders of magnitude too wide to image from a single location.
No it won't. The orbit will be .05AU away from the star, and it's 4 light years away. That's 0.04 arcseconds. Do the math. That's well inside even the "useful" FoV.

https://www.google.com/search?q=.05AU%2F(4+lightyears)+radians+in+arcseconds
« Last Edit: 08/31/2016 04:19 PM by Robotbeat »
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Offline Paul451

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Re: Design a mission to Proxima b
« Reply #100 on: 08/31/2016 04:42 PM »
No it won't. The orbit will be .05AU away from the star, and it's 4 light years away. That's 0.04 arcseconds. Do the math.

Again, that's not how Einstein rings work. The image is as if the system was at the distance of the lens (in this case, the 700AU between the observer and the sun.)

You can't do the maths until you understand the physics.

A gravitational lens marks one end of an infinitely long cylinder the width of the lens, anything that touches that cylinder is projected onto the Einstein ring as if it were at the distance between the observer and the lens. This means that the width of the cylinder in the target system is 1.5 arcseconds, with a useful portion about 10% of that (I believe due to distortion near the edge of the cylinder.) That's the same whether the target system is 4 lightyears away or 4 million.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #101 on: 08/31/2016 04:48 PM »
No it won't. The orbit will be .05AU away from the star, and it's 4 light years away. That's 0.04 arcseconds. Do the math.

Again, that's not how Einstein rings work. The image is as if the system was at the distance of the lens (in this case, the 700AU between the observer and the sun.)...
I didn't understand you were referring to the image, not the object.
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Offline Paul451

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Re: Design a mission to Proxima b
« Reply #102 on: 08/31/2016 04:48 PM »
That's the same whether the target system is 4 lightyears away or 4 million.

However, tracking a target does scale with the distance to the target system. The ratio of skew distance is the distance-from-the-target-to-the-sun / distance-from-the-observer-to-the-sun. So for this example, it's 4.3somit lightyears / 700 AU. Or about 380. So to track a 14 million km wide orbit, you have to track 37,000 km.
« Last Edit: 08/31/2016 04:50 PM by Paul451 »

Offline SICA Design

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Re: Design a mission to Proxima b
« Reply #103 on: 08/31/2016 09:04 PM »
That's the same whether the target system is 4 lightyears away or 4 million.

However, tracking a target does scale with the distance to the target system. The ratio of skew distance is the distance-from-the-target-to-the-sun / distance-from-the-observer-to-the-sun. So for this example, it's 4.3somit lightyears / 700 AU. Or about 380. So to track a 14 million km wide orbit, you have to track 37,000 km.

The solution is (mathematically) simple  ::)

Along with the telescope, just launch half (0.44) the moon's mass along the Proxima - Sun line. Your telescope can then orbit round this with a radius of 37,000 km and a period of 11.2 days. Thus no propellant needed to maintain Proxima B in your FOV!

Wait one moment... You want 37,000km diameter, not radius. In that case it's even easier; you only need 4^21 kg - roughly 5.5% of the moon or 4.5 times the mass of Ceres.
« Last Edit: 08/31/2016 09:18 PM by SICA Design »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #104 on: 08/31/2016 09:14 PM »
Why are we discussing imaging in two threads, now?
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Offline frobnicat

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Re: Design a mission to Proxima b
« Reply #105 on: 09/01/2016 11:25 PM »
That's the same whether the target system is 4 lightyears away or 4 million.

However, tracking a target does scale with the distance to the target system. The ratio of skew distance is the distance-from-the-target-to-the-sun / distance-from-the-observer-to-the-sun. So for this example, it's 4.3somit lightyears / 700 AU. Or about 380. So to track a 14 million km wide orbit, you have to track 37,000 km.

So it doesn't sound such a tremendous deltaV (conservatively 1km/s ??) to track 37000 km span back and forth (or ellipse) on a 11.2 days period for a few orbits, say 3 or 4 ? Wouldn't it be sufficient to have clean spectroscopy for both dayside and nightside ?

Offline Paul451

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Re: Design a mission to Proxima b
« Reply #106 on: 09/02/2016 04:25 AM »
So it doesn't sound such a tremendous deltaV (conservatively 1km/s ??) to track 37000 km span back and forth (or ellipse) on a 11.2 days period for a few orbits, say 3 or 4 ?

The delta-v per ellipse is small, tens of m/s. But unlike conventional telescopy, there's no way to use a guide-star, tracking is dark-maths. And since we don't know the angle of the target ellipse, we don't know the precise trajectory for the telescope. Which means it will take many observations to pin down the target's numbers well enough to perform a full ellipse.

Fortunately, the acceleration is fairly small, well within the capability of an ion drive, so fuel isn't a huge constraint, especially given the drive and power-source required to get you out to 500+AU in the first place.

The solution is (mathematically) simple  ::)
Along with the telescope, just launch half (0.44) the moon's mass along the Proxima - Sun line. Your telescope can then orbit round this with a radius of 37,000 km and a period of 11.2 days. Thus no propellant needed to maintain Proxima B in your FOV!

Overly complex. Just launch a modest-sized blackhole, use that for gravitational lensing and orbital tracking. Solve both problems with a single system. No need to travel out beyond 550AU, letting you operate the system close to Earth; and the blackhole's short focal distance means you can slew the telescope between targets with ease, much more like a conventional steerable 'scope.

Offline fast

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Re: Design a mission to Proxima b
« Reply #107 on: 09/02/2016 07:45 AM »
why are you at all discussing FOCAL as it have no image ability and results are difficult to interpret???

100-300m classical telescope (in space or on moon) looks like less technically challenging, gives probably better results but seems too boring for you?     


edit: maybe wrong tread as there second one about imaging, i just what to stop focal here, lets talk about missions to proxima b
« Last Edit: 09/02/2016 07:49 AM by fast »

Offline rdheld

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Re: Design a mission to Proxima b
« Reply #108 on: 09/02/2016 11:26 AM »
certainly cheaper for space borne or lunar large telescope then sending one out to the solar focus.

Offline Patchouli

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Re: Design a mission to Proxima b
« Reply #109 on: 09/02/2016 05:20 PM »
Project Orion is workable with sixty years old technology.
It could reach 10% of the speed of light thus reaching Proxima centauri in 50 years.
but of course politically it is unpalatable.

Project Orion is probably the easiest technically with Starshot the second easiest.

Starshot would have high up front cost in the laser but the nanocraft themselves would be very cheap and you can send thousands of them.
The disadvantage you're not going to have a particular great camera on a nanocraft as there is no mass for a telescope  think pointing a cell phone at a something so you won't see much detail unless you get close.
This is a limitation of the laws of physics there is nothing you can do about it.
The upside their cheap so you can send a lot of them in the hope some will get close enough to a planet.

Project Orion can carry a big telescope heck you can send something the size of Hubble but each craft is going to be expensive plus the stupid political issues with it.
« Last Edit: 09/02/2016 05:21 PM by Patchouli »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #110 on: 09/02/2016 07:10 PM »
A thing that space nerds often don't realize:
Interplanetary Nuclear Orion is different than Interstellar Nuclear Orion.

Interplanetary Orion can be done with 1960s tech. Interstellar Orion (at least /fast/ interplanetary, i.e. ~10%c or higher) cannot. Interstellar requires keeping the ablative rate low enough. It may require magnetic shielding of some sort. Interplanetary Orion can tolerate some ablative losses just fine.

For interstellar Orion, you need like 1,000,000s Isp. That means you can afford only a teeny tiny amount of ablative losses. For Interplanetary, 2000-10,000s Isp is just fine, and the ablation can even help you (from an energy standpoint) because it converts more of the energy into thrust.
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Offline aep

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Re: Design a mission to Proxima b
« Reply #111 on: 09/03/2016 06:20 AM »
In another thread someone suggested using a lightsail to hide the star. That was an interesting idea. Could that help even if it were not even a thousandth of the distance there? That is still a long way. Im not sure how you would keep the lightsail between your telescope and star for any prolonged period of time. Perhaps both need to have escaped the solarsystem.
Current ground technology with the Gemini Planet Imager on the Keck telescope can only resolve larger planets that have to be farther than 20 au and are reasonably bright in the infrared.

There is a proposal for a Starshade which would fly a steerable petal shaped shade about 50,000 km in front of the JWST to occult the main star. Maybe the project will get a boost because of this discovery.

Offline colbourne

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Re: Design a mission to Proxima b
« Reply #112 on: 09/03/2016 06:39 AM »
Depending on the result of CERN's  ALPHA project in to the gravitational rules for anti-matter this project might be feasible:-

https://forum.nasaspaceflight.com/index.php?topic=13542.0

A probe made from anti-matter is assumed to be repulsed by normal matter. It will accelerate away from our solar system but when close to its target will be deaccelerated with no additional power needed.

Offline rdheld

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Re: Design a mission to Proxima b
« Reply #113 on: 09/04/2016 12:38 AM »
I do not believe antimatter repulses matter graviationally. you would need negative mass for that.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #114 on: 09/04/2016 01:04 AM »
I do not believe antimatter repulses matter graviationally. you would need negative mass for that.
Correct.
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Online b0objunior

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Re: Design a mission to Proxima b
« Reply #115 on: 09/04/2016 01:15 AM »
I do not believe antimatter repulses matter graviationally. you would need negative mass for that.

You might be speaking of this.

https://www.jp-petit.org/science/Y_a-t-il_un_geometre_dans_la_salle/MPLA-singularite.pdf

Offline Paul451

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Re: Design a mission to Proxima b
« Reply #116 on: 09/04/2016 05:36 PM »
I do not believe antimatter repulses matter graviationally. you would need negative mass for that.

There is a theory that anti-matter will act as negative matter. It's not seen as very likely, but it's possible.

However, that still doesn't work the way Colbourne believes. If you drop a lump of negative matter on Earth, it doesn't "fall up". It still falls down, but at a very very slightly different rate than conventional matter. It's the slightness of that change that has made it difficult to test experimentally. Making a drive out of it requires that the (negative) gravitational slope of the negative matter exceeds the size of the slope of the positive matter. This requires a dense negative mass, the usual example is a negative mass blackhole.

Offline Soralin

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Re: Design a mission to Proxima b
« Reply #117 on: 09/04/2016 10:30 PM »
That's the same whether the target system is 4 lightyears away or 4 million.

However, tracking a target does scale with the distance to the target system. The ratio of skew distance is the distance-from-the-target-to-the-sun / distance-from-the-observer-to-the-sun. So for this example, it's 4.3somit lightyears / 700 AU. Or about 380. So to track a 14 million km wide orbit, you have to track 37,000 km.

The solution is (mathematically) simple  ::)

Along with the telescope, just launch half (0.44) the moon's mass along the Proxima - Sun line. Your telescope can then orbit round this with a radius of 37,000 km and a period of 11.2 days. Thus no propellant needed to maintain Proxima B in your FOV!

Wait one moment... You want 37,000km diameter, not radius. In that case it's even easier; you only need 4^21 kg - roughly 5.5% of the moon or 4.5 times the mass of Ceres.
Or slightly less absurd, a counterweight and a spare budget orbital elevator tether between them.

Offline colbourne

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Re: Design a mission to Proxima b
« Reply #118 on: 09/05/2016 07:25 AM »
Currently the exact effect of gravitational force on anti-matter is unknown. You are probably correct that it will fall down, but if it does fall up there is lots of future potential for its use, especially in long range communications.

http://alpha.web.cern.ch/

"We observed the times and positions at which 434 trapped antihydrogen atoms escaped our magnetic trap, and searched for the influence of a gravitational force. Based on our data, we can exclude the possibility that the gravitiational mass of antihydrogen is more than 110 times its inertial mass, or that it falls upwards with a gravitational mass more than 65 times its inertial mass."

Offline Rei

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Re: Design a mission to Proxima b
« Reply #119 on: 09/05/2016 01:26 PM »
I don't know why people keep bringing up Orion, as if technology hasn't moved on since then.  Compared to other concepts Orion has massively higher minimum system masses, much lower performance, far more difficult engineering, far higher radiation challenges, and on and on down the line.  I mean, if you're going to promote nuclear pulse propulsion, at least upgrade your concept to Medusa...

IMHO, I like fission fragment propulsion.  75% of the energy of each fission reaction is directed straight out the back into a magnetic nozzle as relativistic fission fragments.  The required dust suspension has been demonstrated in the lab with non-fissile fuel, and reactor modeling has been conducted.  ISP is upwards of 1m sec and it scales down to very reasonable craft sizes.  There's no ablation or anything of that nature, as it's a magnetic nozzle.  The same engine can provide both high ISP/low thrust and low ISP/high thrust (by ion standards), akin to VASIMIR and the like, via gas injection (limited only by the containment of the magnetic nozzle). 

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #120 on: 09/06/2016 01:10 AM »
I don't know why people keep bringing up Orion, as if technology hasn't moved on since then.  Compared to other concepts Orion has massively higher minimum system masses, much lower performance, far more difficult engineering, far higher radiation challenges, and on and on down the line.  I mean, if you're going to promote nuclear pulse propulsion, at least upgrade your concept to Medusa...

IMHO, I like fission fragment propulsion.  75% of the energy of each fission reaction is directed straight out the back into a magnetic nozzle as relativistic fission fragments.  The required dust suspension has been demonstrated in the lab with non-fissile fuel, and reactor modeling has been conducted.  ISP is upwards of 1m sec and it scales down to very reasonable craft sizes.  There's no ablation or anything of that nature, as it's a magnetic nozzle.  The same engine can provide both high ISP/low thrust and low ISP/high thrust (by ion standards), akin to VASIMIR and the like, via gas injection (limited only by the containment of the magnetic nozzle).
I like fission fragment, but what's the achievable specific power of the concept?
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Online KelvinZero

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Re: Design a mission to Proxima b
« Reply #121 on: 09/06/2016 04:05 AM »
I like fission fragment, but what's the achievable specific power of the concept?
Up front, my intuition must be wrong or this would be more popular... :)

... but I would have assumed it could be pretty high. I mean, if you compare it to SEP or even NTR the potential for this to dump energy without ever really having to deal with it as heat seems superb and I would have thought that was the major limitation on how many fission reactions per second per kg of engine you can have.

(with such huge ISP, high power does not mean high thrust of course)

I wonder if you could design a version of this that did not need highly radioactive elements on launch, like that recent Boeing patent using U-238. Obviously it is scary to think of a cloud of fissionable nanoparticles.. what if it sneezes? :)

IMO these things don't really belong in a Proxima b thread. We can't really design a mission around it but we can definitely advocate there should be ongoing tech development on ideas like this, perhaps record setting missions and pushing further out all the time.
« Last Edit: 09/06/2016 05:53 AM by KelvinZero »

Offline Rei

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Re: Design a mission to Proxima b
« Reply #122 on: 09/06/2016 07:59 AM »
I don't know why people keep bringing up Orion, as if technology hasn't moved on since then.  Compared to other concepts Orion has massively higher minimum system masses, much lower performance, far more difficult engineering, far higher radiation challenges, and on and on down the line.  I mean, if you're going to promote nuclear pulse propulsion, at least upgrade your concept to Medusa...

IMHO, I like fission fragment propulsion.  75% of the energy of each fission reaction is directed straight out the back into a magnetic nozzle as relativistic fission fragments.  The required dust suspension has been demonstrated in the lab with non-fissile fuel, and reactor modeling has been conducted.  ISP is upwards of 1m sec and it scales down to very reasonable craft sizes.  There's no ablation or anything of that nature, as it's a magnetic nozzle.  The same engine can provide both high ISP/low thrust and low ISP/high thrust (by ion standards), akin to VASIMIR and the like, via gas injection (limited only by the containment of the magnetic nozzle).
I like fission fragment, but what's the achievable specific power of the concept?

For the Callisto baseline they're looking at 1GW.  Now, of course, with nuclear reactors you get a better "buy" on dry mass and efficiency the larger you go.  For an interstellar mission, it all depends on how large of a vehicle you want to send.  Either way, rather than having just ~2-3% of the vehicle mass be fuel as in a Callisto version, one would expect an interstellar probe to be 50+% fuel.  Doubling the weight of the craft = halved acceleration.  But of course on interstellar missions, the acceleration time is vastly longer than for a trip to Callisto!  ;)

And yes, unfortunately, no matter what concept you go with, the more ISP you want, the lower your thrust will be *or* the more power you need. There's an inherent tradeoff.  But, high power fission reactors are nothing new.  The cooling systems for operating them in space have not been built on such a large scale, nor has such a high power magnetic nozzle (although steering high power beams with quadrupole magnets is nothing new), and the fuel configuration is unique.  But it's the same basic operation principles as any other moderated fission reactor.

I look forward to seeing how the design evolves in the future.  Right now it's just a cloud of fuel, but I can envision, say, parallel planar layers, each one the maximum thickness density that the fragment cross section  is low enough for large fraction to escape into the interlayer space, which would be spaced broadly enough that the gyroradius would not extend into the next layer.  Then, each layer provides additional possibilities for capture without relying so much on moderation/reflection from the reactor walls (and thus moderator mass and heating, and thus cooling mass).

But, basics first!  ;)
« Last Edit: 09/06/2016 04:42 PM by Rei »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #123 on: 09/06/2016 12:08 PM »
Specific power means power per unit mass. That, along with Isp, can give you acceleration and an estimate at burnout velocity (order of magnitude). So unfortunately, just saying it's 1GW doesn't help much without the whole mass of the system.
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Offline Rei

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Re: Design a mission to Proxima b
« Reply #124 on: 09/06/2016 04:30 PM »
My apologies; I read power, not specific power.  The Callisto baseline is a 1GWt reactor in a 303t (including 60T payload) craft. Not all of the rest is engine, of course - the engine/nozzle/shield is ~113t, structure ~55t, thermal control ~64t, fuel ~4T, and the rest is things like RCS, the power subsystem, etc.  They also downrate the engine to half of its maximum ISP (aka, to 527k).

For an interstellar mission obviously the ratio of fuel to engine+cooling would be significantly increased (which would also somewhat, although not nearly as much, inflate the structure to engine+cooling ratio).  Aka, significantly increasing the fuel mass without increasing the size of the engine.

Contrarily, the larger you make the engine, the easier it is to approach the maximum theoretical ISP and the smaller the portion of the mass that's made up of the (relatively heavy) moderator/reflector (deuterium and/or beryllium both work well).  And there's significant room for improvement from optimizing the current design for a fixed power output as well, as discussed earlier.  Plus, the second heaviest component after the moderator is the magnetic mirror, and the recent improvements HTS magnets correspond directly to significant weight reductions in that as well, both in reduced magnet mass (or increased field strength) and cryocooler mass. 

If you want to play around with the numbers, also keep in mind that you can roughly linearly trade off ISP for thrust with propellant injection.  So if you need more thrust to minimize trip time, feel free to decrease the ISP correspondingly. 
« Last Edit: 09/06/2016 04:58 PM by Rei »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #125 on: 09/06/2016 04:58 PM »
So about 4000W/kg. Accelerating for 30 years, that's about 1e9 seconds. Characteristic velocity of sqrt(2*1e9s*4e3W/kg) or about 3e6m/s assuming high efficiency. 10%c, order of magnitude. Which compares well with the exhaust velocity. Of course fuel isn't massless, but there ya go.

I think I made a calculation error, as that seems too good.
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Offline Rei

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Re: Design a mission to Proxima b
« Reply #126 on: 09/06/2016 05:09 PM »
You might want to look over some of the documents to see if you missed anything:

http://www.rbsp.info/rbs/PDF/ans-nets2013.pdf
https://www.nasa.gov/pdf/718391main_Werka_2011_PhI_FFRE.pdf

I notice you didn't ask about efficiency - I think that's what you missed.  ISP only applies to the exhaust jet.  For example, while the reactor is 1GWt, they state that 699MW is dumped to space as IR, 24.2 MW is neutrons (30% captured), 95.6MW is gammas (5% captured), "Other" is 70.2MW, and the jet itself is 111MW.  If you were crediting the jet itself with being 1GW, that could be the reason the numbers came out as good as they did.  Then again, they repeatedly make

In case it helps, they also cite an exit velocity of 5170km/s (of course, that matches with the ISP of 527000 sec), a mass flow rate of 0.008gm/s, thrust of 43N, and uranium consumption of "approximately one ounce every hour" (0.25 tonnes per year)

Again, if you need more thrust (aka, if you're getting long acceleration times but only a small amount of fuel consumption), feel free to increase it, but downrate the ISP correspondingly.  And feel free to uprate the engine stats (ISP, specific power, efficiency, etc) if you scale up the engine size (but downrate it if you scale it down).  And likewise feel free to uprate it if you want to account for continuing advancements, both design-specific (discussed previously) or general (such as HTS magnets).

I'm curious as to what numbers you come up with.  :)
« Last Edit: 09/06/2016 05:17 PM by Rei »

Offline Rei

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Re: Design a mission to Proxima b
« Reply #127 on: 09/06/2016 05:22 PM »
Hmm, just found a spreadsheet that lists the above as the "Base FFRE design", compares to the "generation 1" design which offers "reduced heat load so less spacecraft radiator mass", and then the  the "generation 2" design which involves a "dual paraboloid moderator" that also offers "reduced heat load so less Spacecraft radiator mass", as well as  "2x" thrust of "86 N" and the same ISP, but "complex shape moderator, difficult to support & cool, weighs more".  Looking for more details...

(They have an image of the dual paraboloid, and IMHO it's pretty clever... rather than trying to have all of the fragments leave through a relatively narrow hole in the center, it's structured like a newtonian telescope, with a central moderator/reflector in front of the fuel and a larger parabolic one behind it, so all of the area around the central moderator/reflector is unobstructed on the way out)

The zero-"afterburner" (aka mass injection) base design had a 5850  day time to Callisto (16 years).  The Gen 2 is cited at 8 years, with assumption of no mass change, which they describe (rightly, from the look of it) as "conservative".

http://www.nasa.gov/pdf/637129main_Werka_Presentation.pdf
« Last Edit: 09/06/2016 05:30 PM by Rei »

Offline Admiral_Ritt

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Re: Design a mission to Proxima b
« Reply #128 on: 09/06/2016 08:30 PM »
Something along the lines of What JASON AW3 mentioned is required, because any probe sent a low "C" speeds
would be overtaken by faster more capable probes.
Quote
The problem here, I think, is more along the lines of conventional thinking.

     First off, there is a higher likelihood of something catastrophic happening to a single probe, traveling at 20% the velocity of light than there is of impact on either the Voyager or pioneer probes, which are traveling far slower.

     Thus, using a group of smaller probes, about the gram size and mass and numbering in the hundreds or thousands, networked together to act as a distributed neural network, could allow for a fairly advanced and sophisticated AI system to control the group as a whole.  Losses during transit could be more readily absorbed by a group, than a single probe.

     This configuration also allows for a potential synthetic aperture sensor capability, allowing much more detailed information to be gathered during their transit through the Proxima Centauri system.

     Such a multiprobe approach would also add to the knowledge base of what hazards exist for human starflight at 20% C or higher velocities.

Along those lines:  Invest in technology to make solar powered mass drivers, specifically to launch a few dozen grams of a granularized probe weighing 10 KG total to high C.   something close to 50%C  is a good target speed
Also invest in modular self assembling machinery that can maneuver in space and dock w/ themselves. send a lot redundant parts.   send them in stream, correcting for positional change of the Mass driver.   No braking on arrival though that just makes things messier an more complicated, besides  just send more copies to improve the data collection. at the high speed you will be passing avoid crossing Prox a,  ecliptic,  a nice pass just above the orbital plane is the ticket)

My guess is that this type architecture will beat ANY probe to Proxima that is launched via sail or nuke pulse propulsion.
« Last Edit: 09/06/2016 08:30 PM by Admiral_Ritt »

Offline Paul451

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Re: Design a mission to Proxima b
« Reply #129 on: 09/08/2016 02:28 PM »

Offline Rei

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Re: Design a mission to Proxima b
« Reply #130 on: 09/08/2016 04:26 PM »
Send a constant stream of mini-probes, IMHO.

That way, the probes in the rear can act as relays for data transmitted from the probes in the front, so the lines of probes can have smaller radios and sensors.

Everyone proposes this, but forgets that the size of the transmitters and receivers required.  Your probes in a Starshot-style scenario are transmitting with just a few watts of power.  How big of a receiver do you think to make out a couple watts of power  over a distance of 4,24/X light years where X is the number of probes?  Starshot calls for the entire supermassive laser array that sent it there to be the receiver.

Remember that for example New Horizons is 0.0005 light years from Earth right now and uses a 2,1 meter dish (a little bigger than Starshot's proposed sail) and something like 120W of power to talk to the massive dishes of the DSN. 
« Last Edit: 09/08/2016 04:33 PM by Rei »

Offline Rei

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Re: Design a mission to Proxima b
« Reply #131 on: 09/08/2016 08:10 PM »
But if you make it bigger, you also make it easier to communicate directly with Earth on its own.  In no situation does it become easiest to use relays.

Online Zed_Noir

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Re: Design a mission to Proxima b
« Reply #132 on: 09/08/2016 09:00 PM »
Just curious. What is the ratio of power generated by solar panels between Earth LEO distance and the likely orbital distance from Proxima during encounter? Never mind if the solar panels will last long enough for the encounter.

Offline 93143

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Re: Design a mission to Proxima b
« Reply #133 on: 09/08/2016 10:31 PM »
Stellar flux is supposed to be 0.65 at the planet.

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #134 on: 09/09/2016 02:02 AM »
Just curious. What is the ratio of power generated by solar panels between Earth LEO distance and the likely orbital distance from Proxima during encounter? Never mind if the solar panels will last long enough for the encounter.
The encounter will be so short, you might as well use chemical batteries for that portion of the mission. (Not saying  that'd be the right answer, but timewise, it works and for such a short duration, would trade well vs solar or nuclear... of course, the transmission back to Earth will take a lot longer.)
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Online hop

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Re: Design a mission to Proxima b
« Reply #135 on: 09/09/2016 02:48 AM »
Stellar flux is supposed to be 0.65 at the planet.
However, far more of the energy is at the IR end of the spectrum, so standard solar panels would probably see a lot less than 0.65 earth output. See attached Fig 1 from Meadows et al.: The Habitability of Proxima Centauri b II

I have trouble seeing much application for solar though. A flyby will only have a tiny window of usable power, and will still need power to transmit data back. An orbiter OTOH will by definition have access to mind-boggling amounts of power somehow.

Offline Paul451

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Re: Design a mission to Proxima b
« Reply #136 on: 09/09/2016 03:02 AM »

If you're sending a series of mini-probes, to relay data from the leading probes, how are the probes not-yet-in-the-system powered?

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #137 on: 09/09/2016 03:08 AM »
Stellar flux is supposed to be 0.65 at the planet.
However, far more of the energy is at the IR end of the spectrum, so standard solar panels would probably see a lot less than 0.65 earth output....
Of course you can make solar panels that work just fine with the wavelength of red/infrared light coming from Proxima Centauri.
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Offline Rei

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Re: Design a mission to Proxima b
« Reply #138 on: 09/09/2016 03:21 AM »
Stellar flux is supposed to be 0.65 at the planet.
However, far more of the energy is at the IR end of the spectrum, so standard solar panels would probably see a lot less than 0.65 earth output....
Of course you can make solar panels that work just fine with the wavelength of red/infrared light coming from Proxima Centauri.

I've actually read research on designing solar panels that work on the surface of Venus  (yes, the power output is incredibly small per square meter due to the heavy cloud cover, dense atmosphere, and high temperatures... but finite and greater than zero!  ;)  ).  It's pretty impressive how much careful selection of technologies can take you.

Re, nuclear, re: Starshot: I actually recommended over on their "feedback" boards that they look into nuclear decay-pumped lasers for the communication.  It's two birds with one stone - an RTG and a communications system (always-on, of course, but with an LCD at the end to modulate it).  Three birds, really, because the solar sail helps act as your radiator.
« Last Edit: 09/09/2016 03:27 AM by Rei »

Online Zed_Noir

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Re: Design a mission to Proxima b
« Reply #139 on: 09/09/2016 04:18 AM »
Stellar flux is supposed to be 0.65 at the planet.
However, far more of the energy is at the IR end of the spectrum, so standard solar panels would probably see a lot less than 0.65 earth output. See attached Fig 1 from Meadows et al.: The Habitability of Proxima Centauri b II

I have trouble seeing much application for solar though. A flyby will only have a tiny window of usable power, and will still need power to transmit data back. An orbiter OTOH will by definition have access to mind-boggling amounts of power somehow.
The flyby vehicle will be charging up batteries all the way in from entering the Proxima system to the encounter. If flight path post encounter is for a cometary flyby of Proxima, then the solar arrays will be produce more power as the vehicle approaches Proxima.


Online hop

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Re: Design a mission to Proxima b
« Reply #140 on: 09/09/2016 04:47 AM »
The flyby vehicle will be charging up batteries all the way in from entering the Proxima system to the encounter. If flight path post encounter is for a cometary flyby of Proxima, then the solar arrays will be produce more power as the vehicle approaches Proxima.
Taking Breakthrough Starshots 0.2 c as representative:

0.2c = 1.4 AU/hour.  Proxima b orbits at ~0.05 AU. So the probe would have >= 0.6 solar flux for a whopping ~8.4 minutes, assuming it gets arbitrarily close to the star. Jupiter equivalent would be something like 0.25 AU. You would want to start taking science data much further out than that.

edit:
Not claiming that it couldn't conceivably be useful in some scenario, just pointing out that the useful window really is extremely short, especially with a dim start like Proxima.
« Last Edit: 09/09/2016 05:14 AM by hop »

Offline Rei

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Re: Design a mission to Proxima b
« Reply #141 on: 09/09/2016 11:02 AM »
More on nuclear-pumped lasers and advanced fuels, from what I wrote on Starshot:

The fuel source: 232U.

It's not normally used in RTGs because it gives off hazardous gamma, making handling difficult.  But the tiny quantities needed for Starshot mean a tiny gamma flux.

 By my calculations 238Pu yields 0,57W/g year 1 and declines from there, down to 0,26W/g after 100 years. 232U is at 0,70W/g year 1, peaks at 4,8W/g year 15, and is down to 2,1W/g after 100 years. It's *far* more energy and power dense. 238Pu basically stops after the first decay down to 234U, but 232U decays to 228Th to 224Ra to 220Rn to 216Po to 212Pb to 212Bi to 212Po to 208Pb. And by far most of that energy is alpha (same as 238Pu), aka quite captureable.

232U is quite produceable - both from 233U(n, 2n), which is the fissile fuel used in thorium reactors; and 230Th(n,gamma), which is produced from the decay of 233U. Indeed, 232U is a common contaminant in the thorium fuel cycle.

So, combine that with a nuclear pumped laser, which is pumped by the decay alpha:

https://www.researchgate.net/publication/252617333_A_Proposed_Continuous_Wave_5854-nm_4HeNeH2_Gas_Laser_Mixture_Pumped_by_alpha-emitter_Radioisotope

Unfortunately I can't find any data on the efficiency of alpha conversion to laser power.  If you have half a gram of radioisotope putting out over 2W of alpha at the time of the flyby getting a 50% laser efficiency then you've got Starshot's goal of a 1W laser for communication and maybe 100 mWe to run your probe - no battery needed.  Of course, that's contingent on those sorts of efficiency figures and at such small scales.
« Last Edit: 09/10/2016 11:29 AM by Rei »

Online Zed_Noir

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Re: Design a mission to Proxima b
« Reply #142 on: 09/09/2016 06:16 PM »
The flyby vehicle will be charging up batteries all the way in from entering the Proxima system to the encounter. If flight path post encounter is for a cometary flyby of Proxima, then the solar arrays will be produce more power as the vehicle approaches Proxima.
Taking Breakthrough Starshots 0.2 c as representative:

0.2c = 1.4 AU/hour.  Proxima b orbits at ~0.05 AU. So the probe would have >= 0.6 solar flux for a whopping ~8.4 minutes, assuming it gets arbitrarily close to the star. Jupiter equivalent would be something like 0.25 AU. You would want to start taking science data much further out than that.

edit:
Not claiming that it couldn't conceivably be useful in some scenario, just pointing out that the useful window really is extremely short, especially with a dim start like Proxima.
Presuming encounter velocity around 0.05c or less for my mission profile.

Encounter velocity at 0.2c plus does make non-internal power source not very practical.


Offline Paul451

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Re: Design a mission to Proxima b
« Reply #143 on: 09/09/2016 06:43 PM »
Presuming encounter velocity around 0.05c or less for my mission profile.

So greater than 84 year flight time? Call it a century. What's the power source for hundred year interstellar portion of the flight?

Offline qraal

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Re: Design a mission to Proxima b
« Reply #144 on: 09/09/2016 09:34 PM »
The Japanese have been testing them the last few years in vacuum chambers with a plasma source.

has there been any testing of a magsail?  certainly not in space.

Offline qraal

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Re: Design a mission to Proxima b
« Reply #145 on: 09/09/2016 11:51 PM »
The Power-to-Mass ratio is the chief performance metric for rockets. We all know that a torch is a simple photon rocket, but that its battery stored energy is insufficient to accelerate in a meaningful way. Same with any other reaction engine - its acceleration depends on the average energy tied up in every newton of thrust and the mass of the engine/generator/battery supplying the power.

Acceleration takes time - a bit over 30,000,000 seconds is needed to reach lightspeed at 1 gee. Of course relativity makes that relationship a bit more complicated, though not from the point-of-view of the rocket. If you have an integrating accelerometer which adds up every moment of acceleration at a certain level of acceleration, then it'll quite happily tell you that you've exceeded lightspeed in a bit under a year at 1 gee.

The basic equations are available here: The Relativistic Rocket ...though Wikipedia's discussion is pretty decent these days.

The integrating accelerometer measures (using the notation from the link), in c units, the rapidity (call it r). It's related to the speed measured by an observer at the local standard of rest (LSoR) by:

r = gT/c    and   v = c.TANH(r)

So 1 c (measured on-ship) is 0.761 c measured by LSoR observers. The helpful thing with rapidity is that the Tsiolkovskii Rocket Equation works if the speed is the rapidity. In otherwords:

r = u.LN(Mo/Mf)

where u is the exhaust velocity.

If we want to know the mass-ratio (Mo/Mf) for a rocket that accelerates, then brakes to a stop under thrust, the equation is quite simple:

(Mo/Mf) = ((v+1)/(v-1))^(c/u)

...where v is in c units. The increase of the effective specific impulse as the exhaust velocity gets close to c is factored into the equation already. With a pure photon exhaust, all pointed in the direction of thrust, the equation is just:

(Mo/Mf) = (v+1)/(v-1)

If v is 0.99 c, then (Mo/Mf) = 1.99/0.01 = 199

That's some mass-ratio! If you can slam on the space-brakes instead and not need rockets to stop, it's...

(Mo/Mf) = SQRT((v+1)/(v-1)) = 14.1 for v = 0.99c

To boost all the way to Proxima b at 1 gee will take 5.85 years Earth-time and about 3.535 years via ship's clocks. Top r is 1.824 c while v is 0.9493 c, and the pure photon-rocket mass-ratio is 38.425 (6.2 with space-brakes.)


Offline Paul451

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Re: Design a mission to Proxima b
« Reply #146 on: 09/13/2016 04:06 PM »
But if you make it bigger, you also make it easier to communicate directly with Earth on its own.  In no situation does it become easiest to use relays.
Then explain cell towers...

Cell towers are much larger than the transceivers in cell phone handsets. They illustrate Rei's point.

A better example for you is mesh networks. But they are there to facilitate cross-network traffic, not single-line-to-base.

In single-line communication (probe to Earth, Earth to probe), you can substitute probe antenna-size/power for Earth-side antenna size/sensitivity. If the probes are also relays, they have to be able to receive the weak signals from other probes without such a trade-off. The smaller the probes, the worse they are as relays, but the more you need relays for the small probes... It's a catch-22.

Offline Rei

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Re: Design a mission to Proxima b
« Reply #147 on: 09/13/2016 04:12 PM »
But if you make it bigger, you also make it easier to communicate directly with Earth on its own.  In no situation does it become easiest to use relays.

Then explain cell towers...

Coverage.

When you want to send data long distance, you don't bounce it from cell tower to cell tower.  Towers are wired into the phone network and distribute traffic through it.

And it's the exact same situation: weak transmitter (cell phone) / big massive antennas (towers), a one-hop air gap. 

Offline whitelancer64

Re: Design a mission to Proxima b
« Reply #148 on: 09/13/2016 04:18 PM »
Presuming encounter velocity around 0.05c or less for my mission profile.

So greater than 84 year flight time? Call it a century. What's the power source for hundred year interstellar portion of the flight?
How about an Americium-241 fueled RTG. Americium-241 has a half life of 432 years.
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Offline Rei

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Re: Design a mission to Proxima b
« Reply #149 on: 09/13/2016 04:40 PM »
Presuming encounter velocity around 0.05c or less for my mission profile.

So greater than 84 year flight time? Call it a century. What's the power source for hundred year interstellar portion of the flight?
How about an Americium-241 fueled RTG. Americium-241 has a half life of 432 years.

Why not 232U, as per this post?:

http://forum.nasaspaceflight.com/index.php?topic=40996.msg1581019#msg1581019

241-Am has a very low energy density - it decays once to 239 Np, and that's pretty much the end of the story.  232U will take you all the way down to 208Pb - 8 separate energetic decays.

It's not normally used in RTGs because of the gamma from some of its later decays makes it hazardous to handle in larger quantities.  But a Starshot-style probe requires so incredibly little of it.  And it's easy to produce (an unwanted waste product, really).
« Last Edit: 09/13/2016 04:49 PM by Rei »

Online Zed_Noir

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Re: Design a mission to Proxima b
« Reply #150 on: 09/14/2016 01:14 AM »
Presuming encounter velocity around 0.05c or less for my mission profile.

So greater than 84 year flight time? Call it a century. What's the power source for hundred year interstellar portion of the flight?
How about an Americium-241 fueled RTG. Americium-241 has a half life of 432 years.
The problem with using any type of RTG for more than a couple of decades is not the nuke part. It is the deterioration of the thermocouples generating electricity.

Online KelvinZero

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Re: Design a mission to Proxima b
« Reply #151 on: 09/14/2016 07:03 AM »
If you are not actually aiming to stop at the target, could you use the incoming radiation/charged particles from your probe's speed of travel for electricity and warmth etc? Effectively you would be tapping off a little bit of the kinetic energy put into the craft initially.

Offline rdheld

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Re: Design a mission to Proxima b
« Reply #152 on: 09/14/2016 11:35 AM »
what is the upper limit on using a radiothermal generator?

Online hop

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Re: Design a mission to Proxima b
« Reply #153 on: 09/14/2016 04:19 PM »
The problem with using any type of RTG for more than a couple of decades is not the nuke part. It is the deterioration of the thermocouples generating electricity.
I very much doubt this is a fundamental limitation. Current RTGs lifetimes are sufficient for their missions, so beyond a certain point no one is going to trade power density or spend a lot of money trying to squeeze more out of them. Even if you can't do it with thermocouples, there are other ways to generate electricity. Compared to the other challenges of an interstellar mission, building extremely long-lived thermocouples or a heat engine that lasts centuries doesn't seem like a huge problem.

Offline Star One

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Re: Design a mission to Proxima b
« Reply #154 on: 02/01/2017 08:04 PM »
This paper is relevant here.

Quote
Deceleration of high-velocity interstellar photon sails into bound orbits at α Centauri

René Heller (1), Michael Hippke (2) ((1) Max Planck Institute for Solar System Research, Göttingen (GER), (2) Neukirchen-Vluyn (GER))
(Submitted on 30 Jan 2017)
At a distance of about 4.22 lightyears, it would take about 100,000 years for humans to visit our closest stellar neighbor Proxima Centauri using modern chemical thrusters. New technologies are now being developed that involve high-power lasers firing at 1 gram solar sails in near-Earth orbits, accelerating them to 20% the speed of light (c) within minutes. Although such an interstellar probe could reach Proxima 20 years after launch, without propellant to slow it down it would traverse the system within hours. Here we demonstrate how the stellar photon pressures of the stellar triple α Cen A, B, and C (Proxima) can be used together with gravity assists to decelerate incoming solar sails from Earth. The maximum injection speed at α Cen A to park a sail with a mass-to-surface ratio (σ) similar to graphene (7.6e-4 gram/m−2) in orbit around Proxima is about 13,800 km/s (4.6% c), implying travel times from Earth to α Cen A and B of about 95 years and another 46 years (with a residual velocity of 1280 km/s) to Proxima. The size of such a low-σ sail required to carry a payload of 10 grams is about 105 m2 = (316 m)2. Such a sail could use solar photons instead of an expensive laser system to gain interstellar velocities at departure. Photogravitational assists allow visits of three stellar systems and an Earth-sized potentially habitable planet in one shot, promising extremely high scientific yields.

https://arxiv.org/abs/1701.08803

Offline Katana

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Re: Design a mission to Proxima b
« Reply #155 on: 02/02/2017 06:25 AM »
If you are not actually aiming to stop at the target, could you use the incoming radiation/charged particles from your probe's speed of travel for electricity and warmth etc? Effectively you would be tapping off a little bit of the kinetic energy put into the craft initially.
0.2C=6E7 m/s
(near to) solar wind max velocity=600km/s=6E5 m/s

100 times the solar wind mass intensity and 10000 times  the solar energy density

Offline Katana

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Re: Design a mission to Proxima b
« Reply #156 on: 02/02/2017 06:28 AM »
More on nuclear-pumped lasers and advanced fuels, from what I wrote on Starshot:

The fuel source: 232U.

It's not normally used in RTGs because it gives off hazardous gamma, making handling difficult.  But the tiny quantities needed for Starshot mean a tiny gamma flux.

 By my calculations 238Pu yields 0,57W/g year 1 and declines from there, down to 0,26W/g after 100 years. 232U is at 0,70W/g year 1, peaks at 4,8W/g year 15, and is down to 2,1W/g after 100 years. It's *far* more energy and power dense. 238Pu basically stops after the first decay down to 234U, but 232U decays to 228Th to 224Ra to 220Rn to 216Po to 212Pb to 212Bi to 212Po to 208Pb. And by far most of that energy is alpha (same as 238Pu), aka quite captureable.

232U is quite produceable - both from 233U(n, 2n), which is the fissile fuel used in thorium reactors; and 230Th(n,gamma), which is produced from the decay of 233U. Indeed, 232U is a common contaminant in the thorium fuel cycle.

So, combine that with a nuclear pumped laser, which is pumped by the decay alpha:

https://www.researchgate.net/publication/252617333_A_Proposed_Continuous_Wave_5854-nm_4HeNeH2_Gas_Laser_Mixture_Pumped_by_alpha-emitter_Radioisotope

Unfortunately I can't find any data on the efficiency of alpha conversion to laser power.  If you have half a gram of radioisotope putting out over 2W of alpha at the time of the flyby getting a 50% laser efficiency then you've got Starshot's goal of a 1W laser for communication and maybe 100 mWe to run your probe - no battery needed.  Of course, that's contingent on those sorts of efficiency figures and at such small scales.

How do you separate it from 233U? The mass difference is only 1/3 of the mass difference of 235U and 238U.

Offline rdheld

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Re: Design a mission to Proxima b
« Reply #157 on: 02/02/2017 11:17 AM »
anyone see this? Might be informative.

Offline Rei

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Re: Design a mission to Proxima b
« Reply #158 on: 02/02/2017 11:27 AM »
How do you separate it from 233U? The mass difference is only 1/3 of the mass difference of 235U and 238U.

When you only need miniscule quantities, any isotopes are separable, by a wide range of means.  AFAIK low quantity separation for medicine / industry is usually done with calutrons (repurposed mass spec.)  Not very efficient, but it works for anything.
« Last Edit: 02/02/2017 11:28 AM by Rei »

Online gospacex

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Re: Design a mission to Proxima b
« Reply #159 on: 02/02/2017 12:08 PM »
232U is quite produceable - both from 233U(n, 2n), which is the fissile fuel used in thorium reactors; and 230Th(n,gamma), which is produced from the decay of 233U.

Only if you define "quite produceable" as "it is not unobtanium, it can be made (at great cost)".

Production from U233 requires, well, first production _of_ U233 (from Th232), then production of U232, and then U232/U233 isotope separation. As any isotope separation, it is expensive, and intense gammas of U232 don't help at all.

Production from Th230 requires Th230. Natural thorium is 232. Th230 has a half-life of 75380 years (very radioactive) and present only in trace quantities in uranium ores (it is in the decay chain of U238).

Compared to this, Pu and Am are almost dirt cheap.

Quote
Indeed, 232U is a common contaminant in the thorium fuel cycle.

It is present in very small amount (hence "contaminant"). Th cycle cares about it because its gammas are PITA.
« Last Edit: 02/02/2017 12:11 PM by gospacex »

Offline Robotbeat

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Re: Design a mission to Proxima b
« Reply #160 on: 02/04/2017 02:01 AM »
Meh, this is interstellar travel we're talking about. Isotopic separation of each atom of the craft is easier than the rest of the task.
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Offline rdheld

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Re: Design a mission to Proxima b
« Reply #161 on: 02/09/2017 11:16 AM »
estimate for planetary properties

Offline Stormbringer

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