Author Topic: Design a mission to Proxima b  (Read 68884 times)

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.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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?
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline 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). 

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