Can we build an interstellar starship with current technology?

Quaoar · 2021-03-10 18:06:32

Terraformer wrote:

Re. the deceleration phase, what are the objections to using a magnetic sail to slow down? Not enough drag from the solar wind at the destination?
Also, I'm now wondering what the Isp limits of ablative sails are. Mind, targeting issues (you're talking about vaporising it into a very hot plasma and then directing that with a magnetic nozzle) probably make it a non starter.

The idea was from Robert Zubrin and Dana Andrews: they found that neutral hydrogen atoms become ionized, in presence of a magnetic field traveling at relativistic velocity, because electrons and nuclei are accelerated in opposite directions. Here is a more recent article that uses a combination of a magnetic sail and an electric sail for deceleration: the magnetic sail for hi-speeds and the electric sail for slow speeds.

https://arxiv.org/pdf/1603.03015.pdf

Tomorrow I'll read it (now in Italy is 1 AM)

Terraformer wrote:

Still, I don't think you should give up on Orion just get. Fusion bombs + magnetic nozzles could potentially get 0.08c exhaust velocity? Enough if you pile them on to reach 0.2c, if you can use a magsail to decelerate...

For fusion bombs do you mean pure fusion bombs or conventional two stage hydrogen bombs?

Quaoar · 2021-03-10 18:54:24

tahanson43206 wrote:

For Quaoar re SpaceNut's post #37
Do I understand correctly that you are proposing to install the laser system on the surface of Mercury?
If that is correct, it would address the issue raised by SpaceNut, of the installation falling into the Sun.

You need multiple installation on the planet for continually tracking the starship and sometimes, if the star is on the orbital plain of Mercury, it will be some short eclipses. Another possibility is the statite, which never miss the star.

tahanson43206 wrote:

In the next issue raised by SpaceNut ... How long would the acceleration be needed?
In your earlier post you provided velocity values, but if you provided times for acceleration and deceleration I missed it.
If I understand your post correctly, you have addressed SpaceNut's point about needing to go all the way out to Pluto by explaining that the effects of gravity on the beam are minimal (ie, vanishingly small) and the issue of dispersion raised by GW Johnson you address by giving the relatively uncluttered environment of space itself (in the vicinity of Mercury) as a reason to expect the cohesion of the laser beam to hold up for the distances involved in acceleration

The dispersion of the beam depends by the diameter of the sail (Ds) the diameter of the laser array (Da) and the wavelength (Lw) of the light (which increase with velocity due to relativistic doppler effect).

The max distance at which the beam con be focused on the sail is given by this formula Dmax=Ds*Da/(2*Lw). So to focus a at thousands of UA you needs some thousands kilometer wide array. And you also have to trade-off between long wavelength, which gives the best reflectivity, and short wavelength, which can be focused at longer distance with a smaller array (I found the best compromise near 12 micron). Gravitational red shift is negligible: what matters is the red-shift due to doppler effect.

During the simulation, I found two strategies for a manned interstellar sail-ship:

1) constant acceleration of 1 g with the laser station that increases its optical power output as the ship increases its speed, to compensate for the red-shift. This strategy consents to reach the target velocity in a shorter distance, giving a less wide laser array, but needs much more power and a wider photovoltaic array. Acceleration distance and acceleration times are easy to calculate using the simple formulas of relativistic kinematic

2) variable acceleration at constant power, with the ship that gradually decreases its acceleration due to the red-shift of the laser beam. This strategy needs less laser power and a less wide photovoltaic array, but the distance at which the ship reaches the target velocity is increased, so the laser array has to be wider. Acceleration distance and acceleration times are very hard to calculate, due to the fact that the acceleration decreases with the red-shift, while the reflectivity increases, because graphite is more reflective at longer wavelength: I'm not so good in math to do the integral, so I wrote a spaghetti-code for the integration by part, which works quite well.

tahanson43206 wrote:

The first probe needs to include the deceleration component you've described, because there won't be a laser at the receiving solar system.

In my simulation I considered a laser station at both ends, because that is the scenario of my next novel. But you're right.

tahanson43206 wrote:

Going back to SpaceNut's points ... pointing the laser at the receding starship/mirror while moving wth Mercury in it's orbit will require some clever engineering.
(th)

I've many doubt about the feasibility of decelerating a starship at the destination star with a sun based laser station.

tahanson43206 wrote:

Do you have some preliminary thoughts about how you would design that feature of the system?
(th)

I imagine a dish shaped starship, surrounded by a ring shaped carbon-carbon drum with the furling sail. The instruments and the cargo at the center, the habitats are two nacelles attached to the ring, and the life support radiator is integrated in the surface of the dish. Two trusses are attached on the dish, one in the bow and one in the aft, with a compact fission reactor and a set of furling graphite anti-meteoroid shields at both ends (the aft shields are also used to shadow the ship from the laser beam). At the center of the last shield there are the laser point defense for meteoroids. The ship is symmetric so she has not to flip for the deceleration, but just to unfurls the sail and aligns whit the laser station of the destination system. The drum contains three sails: the main sail and two spare sails.

Last edited by Quaoar (2021-03-10 19:10:04)

SpaceNut · 2021-03-10 19:45:13

Mercury would have any transmitter not able to point towards its target ship for more than half og the orbital time as the sun is blocking the laser from shining on the target sail....Also other planets that get into the path of the sail will as well block the beam from reaching its target as well.
https://en.wikipedia.org/wiki/List_of_v … ed_records

https://en.wikipedia.org/wiki/Space_tra … celeration

https://sciencetrends.com/the-accelerat … to-use-it/

acceleration = (vFinal−vInitial)/(tFinal−tInitial) or a=Δv/Δt

https://www.instructables.com/How-to-ac … heroetica/

https://www.quora.com/How-long-would-it … ern-rocket

Quaoar · 2021-03-11 04:22:53

SpaceNut wrote:

Mercury would have any transmitter not able to point towards its target ship for more than half og the orbital time as the sun is blocking the laser from shining on the target sail....Also other planets that get into the path of the sail will as well block the beam from reaching its target as well.
https://en.wikipedia.org/wiki/List_of_v … ed_records
Only if the star is on the same plane of the orbit of the planets. Proxima for example would be ever tracked by an array located in the south pole of Mercury. Anyway, for an orbital laser station, you need to correct the error of parallax, that is bigger at short distance, so some fraction of power is wasted in corrections. That's why I think the best solution is the statite-station, which can be perfectly aligned to the point where the star will be at the time of arrival (to send a starship we need to perfectly know the proper motion of the stars).

SpaceNut wrote:

https://en.wikipedia.org/wiki/Space_tra … celeration
https://sciencetrends.com/the-accelerat … to-use-it/
acceleration = (vFinal−vInitial)/(tFinal−tInitial) or a=Δv/Δt
https://www.instructables.com/How-to-ac … heroetica/
https://www.quora.com/How-long-would-it … ern-rocket

for acceleration to relativistc velocity these formulas work better:

a=v*c/(t*sqr(c^2-v^2))

and

t=v*c/(a*sqr(C^2-V^2))

As you can see, to reach c, you need either an infinite instantaneous acceleration, or an infinite time at constant acceleration

Last edited by Quaoar (2021-03-11 09:28:01)

Calliban · 2021-03-11 09:23:38

Did you ever watch the mini-series 'Ascension'?
https://en.m.wikipedia.org/wiki/Ascension_(miniseries)

It is technically possible, using a fission-fusion hybrid approach. A direct fission fragment rocket would have exhaust velocity up to about 4% of c. If you could design an engine that uses fast neutrons from fusion reaction to fast-fission 238U or 232Th in thin fibres and then direct the released fission fragments using a magnetic field, then there is enough fissionable material on Earth to build a crewed space craft able to reach a few percent of c. So you could reach the nearest stars in a couple of centuries, when factoring in acceleration times. An orion type vehicle would probably be used to launch the star ship from Earth surface to solar escape velocity. After Orion separation, the much more efficient, but lower thrust fission fragment drive would activate.

Whether it would be financially affordable is another question. Given that our knowledge of the closest exoplanetary neighbourhood is poor, you have to ask why it would make sense to undertake such a mission instead of colonisation of our own inner solar system. Especially given how much it is likely to cost. Colonisation of near Earth space, the asteroids and Mars, would offer direct benefits to people on Earth, in terms of orbital infrastructure and access to new resources. In building a starship, we would be sending a very small group of people on a multi generation journey into an uncertain environment. I think that would be a hard sell for any government to its people.

Last edited by Calliban (2021-03-11 09:30:09)

tahanson43206 · 2021-03-11 09:57:10

For Quaoar re Where is Proxima Centauri with respect to the Solar Plane ...

It would be helpful to have that information in the flow of this topic ... Your calculation puts acceleration duration at 111 days, which is more than one orbit of the Sun by Mercury. I expect that Proxima Centuri is ** NOT ** in the Solar Plane, so aiming should not be blocked by the Sun. There may well be other objects that are (or will be at the time) moving so they would intercept the beam.

Here is a Google snippet:

People also ask
Where is Proxima Centauri in the night sky?
Proxima Centauri can only be seen south of latitude 27°N. With an apparent magnitude of 11.05, it is is much too faint to be seen with the naked eye. It is in fact so faint that it would appear as a fifth magnitude star when observed from Alpha Centauri A or B.Jul 6, 2014
Proxima Centauri | Constellation Guide

I'm not sure what it means, with respect to the question of it's location as we view it.

Here is a site that seems (as I understand it) to show that the Centauri system is well below the Solar Equatorial plane.

https://earthsky.org/space/where-is-proxima-centauri

My interpretation is that there would be no obstruction of the beam from Mercury to propel a probe. I agree with Calliban that it would likely be easier to secure funding for a probe instead of trying for a full sized ship with crew.

Even a probe would be quite large (massive) it if includes the ability to slow down as it approaches the destination.

(th)

Quaoar · 2021-03-11 14:19:09

Calliban wrote:

Did you ever watch the mini-series 'Ascension'?
https://en.m.wikipedia.org/wiki/Ascension_(miniseries)
It is technically possible, using a fission-fusion hybrid approach. A direct fission fragment rocket would have exhaust velocity up to about 4% of c. If you could design an engine that uses fast neutrons from fusion reaction to fast-fission 238U or 232Th in thin fibres and then direct the released fission fragments using a magnetic field, then there is enough fissionable material on Earth to build a crewed space craft able to reach a few percent of c. So you could reach the nearest stars in a couple of centuries, when factoring in acceleration times. An orion type vehicle would probably be used to launch the star ship from Earth surface to solar escape velocity. After Orion separation, the much more efficient, but lower thrust fission fragment drive would activate.
Whether it would be financially affordable is another question. Given that our knowledge of the closest exoplanetary neighbourhood is poor, you have to ask why it would make sense to undertake such a mission instead of colonisation of our own inner solar system. Especially given how much it is likely to cost. Colonisation of near Earth space, the asteroids and Mars, would offer direct benefits to people on Earth, in terms of orbital infrastructure and access to new resources. In building a starship, we would be sending a very small group of people on a multi generation journey into an uncertain environment. I think that would be a hard sell for any government to its people.

It makes sense to leave the Sun's gravity well with an Orion-drive, the change to a FF-rocket, sparing years of spiralling outward. But why not to accelerate to 0.04 C with a laser sail, then decelerate with a FF-rocket at the destination star?

P.S.
As a second thought, I like your idea: Orion is perfect to transport huge payloads, so why not to use your combo to send the deceleration laser-station to the destination star?

Last edited by Quaoar (2021-03-11 14:50:00)

Quaoar · 2021-03-11 14:24:06

tahanson43206 wrote:

For Quaoar re Where is Proxima Centauri with respect to the Solar Plane ...
It would be helpful to have that information in the flow of this topic ... Your calculation puts acceleration duration at 111 days, which is more than one orbit of the Sun by Mercury. I expect that Proxima Centuri is ** NOT ** in the Solar Plane, so aiming should not be blocked by the Sun. There may well be other objects that are (or will be at the time) moving so they would intercept the beam.
Here is a Google snippet:
People also ask
Where is Proxima Centauri in the night sky?
Proxima Centauri can only be seen south of latitude 27°N. With an apparent magnitude of 11.05, it is is much too faint to be seen with the naked eye. It is in fact so faint that it would appear as a fifth magnitude star when observed from Alpha Centauri A or B.Jul 6, 2014
Proxima Centauri | Constellation Guide
I'm not sure what it means, with respect to the question of it's location as we view it.
Here is a site that seems (as I understand it) to show that the Centauri system is well below the Solar Equatorial plane.
https://earthsky.org/space/where-is-proxima-centauri

From Proxima to Toliman and Rigil Kentaurus are only 0.2 LY: think about what would have been easy for us to go interstellar if we were from Proxima: my sail-ship would have made the trip in 297.7 days of local reference time and 249.4 of ship-time, traveling at 0.25 C, with an initial acceleration of 9.8 m/s2 at constant power.

tahanson43206 wrote:

My interpretation is that there would be no obstruction of the beam from Mercury to propel a probe. I agree with Calliban that it would likely be easier to secure funding for a probe instead of trying for a full sized ship with crew.
Even a probe would be quite large (massive) it if includes the ability to slow down as it approaches the destination.
(th)

Sure. Even having laser-stations at both ends, before sending a manned sail-ship, we have to test our systems with unmanned probes, to prefect the laser-tracking system and the navigation system. Then we have to improve a lot our life support system technology to maintain alive the crew for all the 16.33 years of ship-time needed to reach Proxima at 0.25 C.

Last edited by Quaoar (2021-03-12 04:04:52)

tahanson43206 · 2021-03-11 15:37:35

For Quaoar ... May I (hopefully) entice you to open a new (less ambitious) line of inquiry?

To paraphrase an ancient saying ... it is good to walk before you run.

You could open a parallel topic: Can we build an interplanetary laser sailing craft with current technlogy?

I see no reason at all why the concept you've described for an interstellar journey could not be put to work here in the Solar System, with a laser station at the Moon at the Earth end, and one on Phobos at the Mars end.

Phobos needs impulse to keep it from descending further toward the Mars Roche limit, so pushing interplanetary vessels would (potentially) be helpful.

If you do decide to open a parallel line of inquiry, I hope you will consider a variety of scenarios offering a variety of velocities for consideration, and a variety of slow-down scenarios at Mars.

I do not approve of or support the use of the atmosphere of Mars to slow down vessels carrying humans, so hope you will consider avoiding that technique.

On the other hand, as the Ballistic Delivery topic shows, slowing non-living payloads in the atmosphere is practical and proven and potentially economical.

If your method can be adapted for the Ballistic Delivery case, I'd be quite interested to see your estimates.

(th)

SpaceNut · 2021-03-11 20:44:36

Thanks for point out where the star is relative to our solar plane...an image is worth a thousand words.

Seems that even if we did start it now we would be nearly a century before a manned flight to be taken....

This seems to also be a good way to test out beamed microwave power as well not just the energy to push the ship lasers but to power it as well since the energy would arrive at nearly the same time for both types...

Calliban · 2021-03-12 04:05:31

Beamed energy propulsion would require multiple terrawatts of power and an array of lasers capable generating beams with terrawatts of power. They will need to focus on a target perhaps a few tens of metres in diameter, at a distance of tens to hundreds of billions of kilometres. I am happy to be proven wrong, but this sounds like a project that would require huge amounts of infrastructure constructed in space. How feasible is it at a time when no human being has even ventured beyond low earth orbit in fifty years?

I agree that under some future scenario in which humanity has industrial scale space manufacturing, it may make sense to launch small interstellar probes using lasers mounted on solar power satellites. But we are nowhere near having those sorts of space manufacturing capabilities. It certainly would make sense establishing those sorts of capabilities, as they would have clear benefits in terms of supplying energy and valuable resources to people living on Earth. But interstellar probes will be a long-term side benefit of a space manufacturing programme. We need the horse before we can think about building elaborate buggies.

Last edited by Calliban (2021-03-12 04:09:44)

Quaoar · 2021-03-12 04:20:46

tahanson43206 wrote:

For Quaoar ... May I (hopefully) entice you to open a new (less ambitious) line of inquiry?
To paraphrase an ancient saying ... it is good to walk before you run.
You could open a parallel topic: Can we build an interplanetary laser sailing craft with current technlogy?
I see no reason at all why the concept you've described for an interstellar journey could not be put to work here in the Solar System, with a laser station at the Moon at the Earth end, and one on Phobos at the Mars end.
Phobos needs impulse to keep it from descending further toward the Mars Roche limit, so pushing interplanetary vessels would (potentially) be helpful.
If you do decide to open a parallel line of inquiry, I hope you will consider a variety of scenarios offering a variety of velocities for consideration, and a variety of slow-down scenarios at Mars.
I do not approve of or support the use of the atmosphere of Mars to slow down vessels carrying humans, so hope you will consider avoiding that technique.
On the other hand, as the Ballistic Delivery topic shows, slowing non-living payloads in the atmosphere is practical and proven and potentially economical.
If your method can be adapted for the Ballistic Delivery case, I'd be quite interested to see your estimates.
(th)

By the moment the easiest way to Mars is a NTR spaceship, or a LOX-LCH4 Raptor powered spaceship with ISRU. We can build a laser-station on the Moon to propel a planetary sail-ship, but in this case the first Mars manned mission would be postponed of almost a century and nobody of us will ever see a human bean on the red planet. But in a future, once the laser-stations for interstellar travel have been built, they surely be also used for interplanetary travel, sparing a lot of propellant: we can image a digital currency: the sail-ship sends it to the station company and receives in exchange the beam.
With an interplanetary sail-ship the navigation technique is different: the sail has to be angled at 45° in the direction of the orbital motion (or in opposite direction) to change the orbit, and the laser has not to be so powerful, because 0.01 m/s2 accelerations are enough for deep-space navigation. Another valuable option might be to use the laser station to power the electric propulsion of an interplanetary spaceship: in this case we may have a variable thrust electric-drive (Cheng-Diaz's Vasimr might be an example), able to accelerate from 0.01 to 1 m/s2, that can be used either for impulsive, maneuver to leave planetary orbits, or to slowly accelerate in deep space, to reach Mars in three months.

lanetary sail-ship powered by laser-stations

Last edited by Quaoar (2021-03-12 05:38:24)

Terraformer · 2021-03-12 05:31:40

I expect for interplanetary travel, microwave beamed power and electric propulsion will be preferred. Use a small amount of matter and save a ridiculous amount of energy (300MW per Newton! That's crazy).

For interstellar travel... MagOrion intercepts about half the plasma from the nuclear bomb, so maybe 40% of the energy? Sounds like with nuclear fusion bombs (might need to be very big tbh, given that we want almost all the energy to come from fusion) we're talking about an effective exhaust velocity of 0.04c, so piling them on should get us to perhaps 0.1c... I don't know if further refinements would be possible to get this up significantly.

At least we'd already have a magsail built in for deceleration though, so that should be our cruise velocity.

Quaoar · 2021-03-12 05:55:08

Calliban wrote:

Beamed energy propulsion would require multiple terrawatts of power and an array of lasers capable generating beams with terrawatts of power. They will need to focus on a target perhaps a few tens of metres in diameter, at a distance of tens to hundreds of billions of kilometres.

With a 10,000 ton manned sail-ship, traveling with an initial acceleration of 9.8 m/s2, you need a 284.8 ton sail of 14.5 km of diameter, and a laser-station of 15.79 PWo@12 micron of wavelength with an array diameter of 1040 km, to focus at 2580 UA (the distance at which the acceleration phase ends). 15.78 TW of optical power, with lasers 0.9 efficient, needs 16.7 PW of electric power, with a photovoltaic array of 1104 km of diameter at 0.25 UA from the Sun (panels efficiency is 0.8%, very close to the theoric limit of 0.85%).

Calliban wrote:

I am happy to be proven wrong, but this sounds like a project that would require huge amounts of infrastructure constructed in space. How feasible is it at a time when no human being has even ventured beyond low earth orbit in fifty years?
I agree that under some future scenario in which humanity has industrial scale space manufacturing, it may make sense to launch small interstellar probes using lasers mounted on solar power satellites. But we are nowhere near having those sorts of space manufacturing capabilities. It certainly would make sense establishing those sorts of capabilities, as they would have clear benefits in terms of supplying energy and valuable resources to people living on Earth. But interstellar probes will be a long-term side benefit of a space manufacturing programme. We need the horse before we can think about building elaborate buggies.

You are perfectly right: in this post I would only show how we can go interstellar without any new physic or technological breakthrough, like metallic hydrogen, room temperature superconductivity, antimatter production and storage system, fusion reactors or rockets, energy shields and warp drive, but only with the technologies we just have.
Take for example the 1942 B-29 Superfortress: all the technologies to build it (aluminium and piston-engines) were already present 39 years before, at the time of the first flight of the Wright Brothers' Flyer One. It was only a question of investing money in R&D to perfect them and pass from a little and rudimentary flight machine to a huge long range bomber. On the contrary the jet engine was a technological breakthrough, which lead to supersonic flight, infeasible at the times of Orville and Wilbur.

Last edited by Quaoar (2021-03-13 13:41:11)

tahanson43206 · 2021-03-12 15:58:16

For Quaoar re topic ... I'd like to try to renew my inquiry about the possibility of using the technology you've imagined for an interstellar probe, for a much less exotic but perhaps quite useful application in the Earth-Mars transportation circuit.

It seems to me that a laser station can be installed and operated from the surface of the Moon (of Earth) while a comparable one can be installed for service from Phobos. The one on the Moon would be strong enough to propel a manned vessel (such as one of RobertDyck's Large Ships) toward Mars at a faster clip than is possible with simple chemical rocket propulsion. The one on Phobos would need to be strong enough to slow the vessel as it approaches Mars.

I would be ** most ** interested to see calculations your software might be able to provide, for such a system.

(th)

Quaoar · 2021-03-12 17:07:26

tahanson43206 wrote:

For Quaoar re topic ... I'd like to try to renew my inquiry about the possibility of using the technology you've imagined for an interstellar probe, for a much less exotic but perhaps quite useful application in the Earth-Mars transportation circuit.
It seems to me that a laser station can be installed and operated from the surface of the Moon (of Earth) while a comparable one can be installed for service from Phobos. The one on the Moon would be strong enough to propel a manned vessel (such as one of RobertDyck's Large Ships) toward Mars at a faster clip than is possible with simple chemical rocket propulsion. The one on Phobos would need to be strong enough to slow the vessel as it approaches Mars.
I would be ** most ** interested to see calculations your software might be able to provide, for such a system.
(th)

My software is optimized for interstellar travels, relativistic velocities, light years and direct radial acceleration, coast and deceleration from a star to another one. In a planetary system we have to compute fast orbital transfers so the math is different. I would have to write another code, but it's not a one-day-job.

tahanson43206 · 2021-03-12 17:55:57

For Quaoar re new inter-solar-system code ...

It is encouraging to see you are willing to consider this imposition on your time ... I hope it will seem worth while ...

The chances of securing funding for a project seem greater (at least to me) if you can offer a way to reach Mars more rapidly than the current chemical rocket paradigm will allow.

There are some in the population of Earth who are enthusiastic about developing the Moon, in contrast to those who want to skip the Moon and go directly to Mars. The idea you've introduced into this forum might appeal to ** both ** camps!

There is competition shaping up between China and the rest of the world, to see who can establish dominance over Mars.

Your vision of a faster way to deliver goods and supplies, and collections of people to Mars may appeal to a small set of well connected folks.

Or, at a minimum, your work can lead to Science Fiction works that are focused upon the near term Solar System exploration.

***
I just received encouragement from Analog Science Fact and Fiction to offer them Fact articles based upon several initiatives in progress within the forum .... If you have not considered them as a market opportunity, please take a look ... they have a history of over 70 years of concentrating on the subset of Science Fiction you appear to be actively pursuing.

(th)

Quaoar · 2021-03-13 04:23:57

tahanson43206 wrote:

For Quaoar re new inter-solar-system code ...
It is encouraging to see you are willing to consider this imposition on your time ... I hope it will seem worth while ...
The chances of securing funding for a project seem greater (at least to me) if you can offer a way to reach Mars more rapidly than the current chemical rocket paradigm will allow.
There are some in the population of Earth who are enthusiastic about developing the Moon, in contrast to those who want to skip the Moon and go directly to Mars. The idea you've introduced into this forum might appeal to ** both ** camps!
There is competition shaping up between China and the rest of the world, to see who can establish dominance over Mars.
Your vision of a faster way to deliver goods and supplies, and collections of people to Mars may appeal to a small set of well connected folks.
Or, at a minimum, your work can lead to Science Fiction works that are focused upon the near term Solar System exploration.
***
I just received encouragement from Analog Science Fact and Fiction to offer them Fact articles based upon several initiatives in progress within the forum .... If you have not considered them as a market opportunity, please take a look ... they have a history of over 70 years of concentrating on the subset of Science Fiction you appear to be actively pursuing.
(th)

I'm waiting for the call to be deployed in Sicily with the Italian Civil Protection Agency Vaccination Team. By the moment I have a lot of free time, but soon I'll be very busy.

Last edited by Quaoar (2021-03-13 12:44:46)

SpaceNut · 2021-03-13 10:37:06

Thank you Quaoar for the update of service to your country men as its showing what we will see in the future here as vaccines continue to roll out.

Its also a surprise to see that you doing coding as well as write SF novels....

The travel starts today for interstellar travel if we design the means to provide the power to the ship which would make it there.

A 20 year period of time for nuclear to survive does not seem all that hard if we do not activate it until we are mostly there as the energy for the ship can come from the system that pushes it towards the new suns to which it would orbit around.

Quaoar · 2021-03-13 13:03:06

SpaceNut wrote:

Thank you Quaoar for the update of service to your country men as its showing what we will see in the future here as vaccines continue to roll out.
Its also a surprise to see that you doing coding as well as write SF novels....
The travel starts today for interstellar travel if we design the means to provide the power to the ship which would make it there.
A 20 year period of time for nuclear to survive does not seem all that hard if we do not activate it until we are mostly there as the energy for the ship can come from the system that pushes it towards the new suns to which it would orbit around.

Yes, it's not very hard: I imagine four sails (one main sail and three backup sails), four nuclear reactor for coasting (I'm exploring the possibility to use four FF-direct conversion-bimodal reactors, which can also be used as FF-rockets for mid-course corrections) https://en.wikipedia.org/wiki/Fission_fragment_reactor (during the acceleration and deceleration phases we can extract electric energy from the laser beam integrating into the sail some kind of thermionic converter). Attitude control can be done integrating into the sail some kind of variable reflectivity panel, like Ikaros did.

The habitat needs a 20 T superconductive coil to deflect GCR and must be surrounded by 25 cm of water or polyethylene to stop incoming neutral hydrogen atoms (i'ts interesting to note that the sail is almost transparent to neutral hydrogen at relativistic velocities) and four or five furling debris shield in 0.5 micron thick graphite-fiber-reinforced-graphite, which can also be used as laser-shadow shield. The sails have to be furled like an origami into a carbon-carbon ring of 100 m of diameter, with two habitat nacelles attached near the rim for artificial gravity and a central nacelle with all the navigation stuff in the middle.

https://d3i71xaburhd42.cloudfront.net/a … ure6-1.png

https://owdt-17dd0.kxcdn.com/wp-content … 649825.jpg

https://earth.esa.int/documents/163813/ … ros_Auto22

https://earth.esa.int/documents/163813/ … ros_Auto21

https://earth.esa.int/documents/163813/ … ros_Auto1F

https://earth.esa.int/documents/163813/ … ros_Auto1E

https://owdt.com/origamis-revolutionary … lications/

After the acceleration phase, the sail can be furled again inside the ring like, an origami, using carbon nanotube artificial muscle integrated into the stiffening ribs, in the same way the insects fold their wings inside their elytra.

https://pdfs.semanticscholar.org/ead5/6 … ef8a99.pdf

The life support radiator has to be put inside the ring, between the nacelles. That's the 10,000 ton Star Clipper of my next novel.

It's interesting to point out that at relativistic velocity a EVA will be fatal for a human, due to the impact of neutral hydrogen atoms, so all the extravehicular repairs have to be performed by drones.

Last edited by Quaoar (2021-03-13 13:56:27)

SpaceNut · 2021-03-13 14:00:00

Nice origami very small package...
So the nuclear size still needs to be determined to match the size of the laser which is needed to push the ship to the near by sun....

Quaoar · 2021-03-13 14:16:18

SpaceNut wrote:

Nice origami very small package...
So the nuclear size still needs to be determined to match the size of the laser which is needed to push the ship to the near by sun....

My laser-stations are solar powered. Nuclear reactors are on the ship to produce energy during interstellar coasting (the ship has also some laser but only as a point-defense from space debris). Reactors size depends on the size of crew: almost 2.5 kWe/person plus the avionics and the instruments. If reactors are also used as FF-rocket for mid course corrections they need more power.

Last edited by Quaoar (2021-03-13 14:20:10)

Terraformer · 2021-03-13 14:36:54

Only 2.5kWe per person? Seems kind of low for something that has to feed its passengers for 20 years... that's at least 4 tonnes of food per passenger you're going to need to store, if they can stomach the sort of food that stores that long.

Quaoar · 2021-03-13 15:13:24

Terraformer wrote:

Only 2.5kWe per person? Seems kind of low for something that has to feed its passengers for 20 years... that's at least 4 tonnes of food per passenger you're going to need to store, if they can stomach the sort of food that stores that long.

That's from a NASA study for a 18 months mission with a 6 crew transhab. I guess you are right and a 17 yrs interstellar mission needs much more kW/person: probably because it may be more convenient to have a near closed-cycle life support system, able produce food on board via hydroponics (in this case the reserve food supplies can be stowed near the habitat walls, to add passive shielding material).

Last edited by Quaoar (2021-03-13 15:13:42)

tahanson43206 · 2021-03-15 10:10:05

In a post earlier in this topic, Quaoar showed a link to a paper that reported on study of a particular concept for nuclear fission spacecraft propulsion (the "dusty" method).

The paper contained a table which contained an entry that I did not understand. Quaoar confirmed that (in his judgement) the display of data from the table was correct and not a misprint

In his reply, Quaoar confirmed that the authors were imagining a projectile to be accelerated by their system that would have an atomic weight of 10 to the 8th power. Today I continued searching for a molecule of that mass.

I'd like to comment here upon the continuing and obvious advance of the AI that Google is constantly improving to help with search.

I entered the typical crude search request and it produced no useful results (lots of results but not what I wanted).

However, I rewrote the request in normal English: Please find a molecule with an atomic weight of 10^8

This time the top citation is an offering by a PhD chemist for calculation of the atomic weight (mass) of molecules.

I'm going to paste the link and a snippet, and am asking Chemistry majors (eg, PhD in the membership) to please follow the guidelines and post examples of molecules that would have the mass defined by the authors of the paper Quaoar cited for optimum performance of the "dusty" propulsion system.

https://www.thoughtco.com/how-to-find-m … ass-608487

By Anne Marie Helmenstine, Ph.D.
Updated November 06, 2019
The molecular mass or molecular weight is the total mass of a compound. It is equal to the sum of the individual atomic masses of each atom in the molecule. It's easy to find the molecular mass of a compound with these steps:

Determine the molecular formula of the molecule.
Use the periodic table to determine the atomic mass of each element in the molecule.
Multiply each element's atomic mass by the number of atoms of that element in the molecule. This number is represented by the subscript next to the element symbol in the molecular formula.
Add these values together for each different atom in the molecule.
The total will be the molecular mass of the compound.

(th)

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