Plausible interstellar spacecraft

[3blake7]

 

This is a plausible interstellar spacecraft I am working on. I have a spreadsheet for calculating the trip and another for calculating the space station that attaches to the top. What I need help with is creating another spreadsheet for calculating the particle accelerator based thrusters.

 

The space station has a 1 million person capacity, 61 floors, gravity ranging from 10 to 9 m/s^2, has a 3 kilometer radius and a height of 50 meters. Here is my space station calculator: https://docs.google.com/spreadsheets/d/1mFxDcOCeMIcSz0SkMcrBNviBcmjU_Ru80dd7iFF_Vn8/edit?usp=sharing

 

Here is my trip calculator: https://docs.google.com/spreadsheets/d/12VQXeNwbLyUAzzwgPj4Qman6c0pUwHcGeE51MLeg5fw/edit?usp=sharing

 

It's using a constant acceleration approach and the spacecraft in the image can do 4.2 lightyears in 20.8 years. I had to guess the mass of everything but I think it's close enough for my science fiction purposes.

 

For the particle accelerator thrusters, I have 8 sections, each with 11 rings and I am claiming that it can accelerate Argon up to 99.9999999% the speed of light.

 

If you look at the trip calculator it has the performance of the particle accelerator thrusters. I was wondering if what I have is plausible.

[swansont]

For the particle accelerator thrusters, I have 8 sections, each with 11 rings and I am claiming that it can accelerate Argon up to 99.9999999% the speed of light.

 

If you look at the trip calculator it has the performance of the particle accelerator thrusters. I was wondering if what I have is plausible.

 

99.9999999% the speed of light for Ar-40 is somewhere in the neighborhood of 800 TeV, if my calculations are right. No, that's not plausible.

[Enthalpy]

If the fusion of 1 atom = 4e-25kg ²³³U releases 200MeV = 3e-15J, the fuel itself can accelerate to 100km/s = 0.0004c only, and the complete reactor, spacecraft and load less than that. Nuclear fission and fusion are too weak to achieve a significant fraction of speedlight - the claim of 0.3c, needed to reach stars within a decent delay, is not plausible.

[EdEarl]

The Large Hadron Collider generates 13Tev with an accelerator 17 miles (27km) diameter; 800Tev is more than 60 times 13Tev and would presumably take a much larger more massive particle accelerator.

[3blake7]

The Large Hadron Collider generates 13Tev with an accelerator 17 miles (27km) diameter; 800Tev is more than 60 times 13Tev and would presumably take a much larger more massive particle accelerator.

 

I read that the particle accelerator can have a smaller diameter if more power is used in the electromagnets.

 

In the pictures the radius of the largest particle accelerator is 3 kilometers with a circumference of 18.85 kilometers. It's smaller than the LHC but I am saying I used more power and stronger electromagnets. On the spreadsheet I just guessed how much power I would need, I would rather calculate it with a new spreadsheet. How do you calculate it?

[swansont]

 

I read that the particle accelerator can have a smaller diameter if more power is used in the electromagnets.

 

Smaller radius means more radiation emitted (you are accelerating the charges), which is a continual loss of kinetic energy, which likely means you have a smaller maximum energy.

[MountainGuardian]

I have always thought that particle accelerators would be the way to go as well, though I always had the idea of building the ship inside of an asteroid. Use the asteroid as protection from impacts of space debris and mine it from the inside for fuel to use in the accelerator. Use several nuclear reactors to power the craft. Position the craft with the accelerator and use planetary and solar gravity to sling shot it to higher speeds within the solar system and then sling shot out to where you are headed. Use the remaining asteroid and ship within when you get to where you are going as a base of operations.

.

You mention the accelerating to near the speed of light and you want to calculate the power and time required to do so, keep in mind it will take that much time and energy to slow back down as well before you reach your destination. I cannot hardly imagine the power even a small piece of debris would have with a speed differential of near light speed, it would likely become a nuclear detonation, which means if it weighs a few hundred pounds it would produce an explosion big enough to do vast damage to any kind of craft or even to a relatively good sized asteroid.

[Janus]

I read that the particle accelerator can have a smaller diameter if more power is used in the electromagnets.

 

In the pictures the radius of the largest particle accelerator is 3 kilometers with a circumference of 18.85 kilometers. It's smaller than the LHC but I am saying I used more power and stronger electromagnets. On the spreadsheet I just guessed how much power I would need, I would rather calculate it with a new spreadsheet. How do you calculate it?

It's not just a matter of power, its a matter of total energy needed and where it comes from. To accelerate your Argon up to 99.9999999% of c requires 3.4e14 joules of energy per kg. Hydrogen fusion only produces 3.4e14 joules per kg of hydrogen. This means that you would need ~5.9 million kg of hydrogen per kg of Argon accelerated.

Now in order to travel 4.2 light years in 20.8 years (assuming a turn around and deceleration at the halfway point) would require 1.38 kg of Argon per kg of ship. But you need more Hydrogen than Argon to provide the needed energy.

In other words, you need more propellant mass than ship mass for your ship to perform as expected, but you would need more Hydrogen mass than Argon mass to provide the needed energy. These two requirements contradict each other.

[3blake7]

I read that the 200 kW VASIMR has an exhaust velocity of 300,000 m/s. Couldn't you just stack the effect and make a 5 kilometer long VASIMR with 200 megawatts and achieve 99.9999999% the speed of light exhaust velocities? Am I missing something?

[EdEarl]

If the power is generated by hydrogen fusion, ions of helium or another light element will need to be exhausted, and they might be used for thrust, too.

[3blake7]

Thanks for your help. I played around with the calculations and realized you are right, it requires an unreasonable amount of power, even for a civilization with trillions living in space on space stations.

[Janus]

If the power is generated by hydrogen fusion, ions of helium or another light element will need to be exhausted, and they might be used for thrust, too.

The 3.4e14 joules per kg includes the energy imparted to the fusion products. That energy can be turned to thrust either by using the fusion products as exhaust or tapping their energy to run the accelerator, but you can't use the same energy for both. Any of that energy used to run the accelerator will reduce the thrust coming directly from the exhaust and any energy used to produce thrust via the by-products will not be available for the accelerator and that is not even counting the energy lost as waste heat.

[swansont]

I read that the 200 kW VASIMR has an exhaust velocity of 300,000 m/s. Couldn't you just stack the effect and make a 5 kilometer long VASIMR with 200 megawatts and achieve 99.9999999% the speed of light exhaust velocities? Am I missing something?

 

Yes. The effects are not linear. Making it twice as long will not necessarily give you twice the propulsion. Even if you were in the classical regime, twice the speed, and thus twice the momentum, requires four times the energy. Accelerating charged particles causes them to radiate, which is an energy loss mechanism, so you need even more energy.

[michel123456]

 

The space station has a 1 million person capacity, 61 floors, gravity ranging from 10 to 9 m/s^2, has a 3 kilometer radius and a height of 50 meters. Here is my space station calculator: https://docs.google.com/spreadsheets/d/1mFxDcOCeMIcSz0SkMcrBNviBcmjU_Ru80dd7iFF_Vn8/edit?usp=sharing

 

3 kilometer radius and a height of 50 meters - That does not look to be represented correctly in your 3D model. It means a diameter of 6000 meters against 50 m height or a diametre 120 times larger than the height.

[michel123456]

It was not in my intention to kill this thread...

[3blake7]

Well the particle accelerate idea was a bust. I switched to Beamed Core Anti-Matter Rockets but they need a TON of anti-matter. To produce enough I had to say there was an Dyson sphere like ring around the Sun collecting several Exawatts of power. Even then I only produce enough anti-matter to send a 10 million person interstellar craft once every 100 years. AND that's assuming a 20% efficiency on anti-matter production, currently technology can only do 0.01% (theoretical maximum is 50%, so I read).

3 kilometer radius and a height of 50 meters - That does not look to be represented correctly in your 3D model. It means a diameter of 6000 meters against 50 m height or a diametre 120 times larger than the height.

Height refers to the shortest side in the picture, I just called it that because that's what that side is called on a cylinder.

[Enthalpy]

It's worse than that. You claim to achieve 0.3c - which is indeed the kind of speed necessary to reach the nearest stars within a few years - and this speed demands to annihilate ~1/4 of the initial vessel's mass, needing 1/8 the initial mass in antimatter. Of course, the emitted energy must be fully directed opposed to the desired force, so it needs gamma rays mirrors.

 

Then, you want to brake at destination, needing again 1/8 the mass, so the antimatter is 1/4 the vessel's start mass.

 

Though, I approve the choice of antimatter as the only energy dense enough per kg to reach 0.3c - it's just that Mankind has no means to store nor poduce significant amounts, which isn't bad news considering its danger.

[3blake7]

It's worse than that. You claim to achieve 0.3c - which is indeed the kind of speed necessary to reach the nearest stars within a few years - and this speed demands to annihilate ~1/4 of the initial vessel's mass, needing 1/8 the initial mass in antimatter. Of course, the emitted energy must be fully directed opposed to the desired force, so it needs gamma rays mirrors.

 

Then, you want to brake at destination, needing again 1/8 the mass, so the antimatter is 1/4 the vessel's start mass.

 

Though, I approve the choice of antimatter as the only energy dense enough per kg to reach 0.3c - it's just that Mankind has no means to store nor poduce significant amounts, which isn't bad news considering its danger.

I was using the information on this site: http://www.projectrho.com/public_html/rocket/enginelist.php#ambeam

 

Assuming those are correct, with a constant acceleration approach, my top velocity is 23,000 km/s which means interstellar dust might rip my ship to pieces before I get there.

[3blake7]

I did some research on interstellar dust, for the Daedalus project they used Beryllium erosion shield and autonomous space craft that would fly ahead of the spacecraft and release dust clouds to clear the path.

 

Also, I found this article on Beamed Core Anti-Matter Thrusters and they did new simulations showing the exhaust velocity could actually be double of what the site I previously posted claims.

 

http://arxiv.org/pdf/1205.2281.pdf

[3blake7]

I am having difficulty finding the efficiency of a Beamed Core Anti-Matter Rocket. I know that some energy from the input fuel mass is converted into neutral pions which decay into gamma rays. Only negatively and positively charged pions are used to generate thrust. What percentage of the hydrogen + antihydrogen's mass is negative and positive pions?

Updated my render:

Edited February 4, 2016 by 3blake7

[pavelcherepan]

I am having difficulty finding the efficiency of a Beamed Core Anti-Matter Rocket. I know that some energy from the input fuel mass is converted into neutral pions which decay into gamma rays. Only negatively and positively charged pions are used to generate thrust. What percentage of the hydrogen + antihydrogen's mass is negative and positive pions?

Updated my render:

 

Probably some more experienced people can correct me. For obvious reasons you won't have neutral hydrogen/antihydrogen atoms that you're going to be annihilating, because you can't safely store neutral antihydrogen. So it all comes down to proton-antiproton annihilation.

 

 

 

The strong nuclear force provides a strong attraction between quarks and antiquarks, so when a proton and antiproton approach to within a distance where this force is operative (less than 1 fm), the quarks tend to pair up with the antiquarks, forming three pions. The energy released in this reaction is substantial, as the rest mass of three pions is much less than the mass of a proton and an antiproton. Energy may also be released by the direct annihilation of a quark with an antiquark. The extra energy can go to the kinetic energy of the released pions, be radiated as gamma rays, or into down or strange quarks. The other flavors of quarks are too massive to be created in this reaction, unless the incident antiproton has kinetic energy far exceeding its rest mass, i.e. is moving close to the speed of light. The newly created quarks and antiquarks pair into mesons, producing additional pions and kaons. Reactions in which proton-antiproton annihilation produces as many as nine mesons have been observed, while production of thirteen mesons is theoretically possible. The generated mesons leave the site of the annihilation at moderate fractions of the speed of light, and decay with whatever lifetime is appropriate for their type of meson.^[5]

 

From https://en.wikipedia.org/wiki/Annihilation

 

There are also some pretty graphs and Feynman diagrams in this paper: http://arxiv.org/pdf/1004.2152.pdf

 

Basically, it's not as simple as electron-positron annihilation and you can end up with a whole load of different products that you will all need to direct to actually get some acceleration going.

[Enthalpy]

23Mm/s=c/13: this needs less antimatter, but the next star takes 2/3 century then.

 

Dust: why worry? There is occasionally some on low-Earth orbit but not farther in our Solar system. Do you expect any in the interstellar medium? Then, whether beryllium or brick doesn't change anything - except that I'd avoid a brittle metal like beryllium as an armour. And I'd prefer redundancy (as combat aeroplanes have) and automatic leak tightening (works at tyres, possible source of inspiration).

 

Pions and so on: why neglect photons? Gammas are "difficult" to reflect but they give substantial thrust. Even if the ones emitted forward are absorbed instead of reflected, they still give half of their ideal thrust.

 

(Little) some serious science has been done (at Cern and elsewhere) about antimatter propulsion and is available on arXiv.

[3blake7]

So, updated my render which is attached and here is an update on my progress for a plausible interstellar spacecraft.

 

After, being told that the particle accelerator thrusters would require too much energy and being told about the relativistic kinematics equations, I did the calculation and came to the same conclusion. I just read that the Large Hadron Collider could accelerate particles to 99.9999999% the speed of light and made the erroneous assumption that it wouldn't require that much additional energy to accelerate a propellant to that high of an exhaust velocity.

 

My search for a thruster design with the highest possible exhaust velocity lead me to this site:

http://www.projectrho.com/public_html/rocket/enginelist.php#ambeam

 

Which has a Beamed Core Anti-Mater Rocket with an exhaust velocity of 100,000,000 m/s, the highest on the site. However, with more research I found a research paper that did new simulations with the better Geant4 software and came to the conclusion the exhaust velocity would actually be higher:

http://arxiv.org/pdf/1205.2281.pdf

 

So the exhaust velocity for the Beamed Core Anti-Matter Rockets is 206,856,796 m/s and actually requires a magnetic field much less than originally predicted, only 12 Tesla, which is doable with current technology.

 

For a large interstellar colony ship to make the trip to the nearest star in a reasonable amount of time, I need A LOT of anti-matter. So, I did some research and there is only one structure that can produce enough energy to mass produce enough anti-matter in a reasonable amount of time and that is a Dyson Swarm.

 

I created a spreadsheet for Anti-Matter Production, which builds a Dyson Swarm around the Sun, to collect solar power, to mass produce anti-matter for interstellar colonization:

 

https://docs.google.com/spreadsheets/d/1v2HqosYMZbY_RM7DjeIxC-m0qEo0lsC08b7RhSKzds8/edit?usp=sharing

 

The satellites in the Dyson Swarm only block 5% of the Sun and can produce 1200 megagrams of anti-matter a day. I included solar cell efficiency at 68% which is higher than what is currently possible but is considered possible with more advance multi-junction solar cells. I also included the energy to anti-matter conversion efficiency at 0.01%, which is higher than what we currently have but I read a NASA paper that said it's possible with a purpose built anti-matter production facility using known technology.

 

I also updated my Interstellar Trip Calculator to not do Constant Acceleration because that wastes anti-matter. It now accelerates up to speed, cruises for decades, flips around and then accelerates in the opposite direction to slow down. I also updated my calculator to have more realistic masses, such as the mass for the radiator, mass of the atmosphere, mass of food and water, nutrients for hydroponics, etc. It's still not NASA quality but it's closer than what I had before.

 

https://docs.google.com/spreadsheets/d/12VQXeNwbLyUAzzwgPj4Qman6c0pUwHcGeE51MLeg5fw/edit?usp=sharing

 

So, my conclusion I guess is that interstellar colonization is possible with a Dyson Swarm covering 5% of the Sun, converting solar energy into anti-matter and using the anti-matter in Beamed Core Anti-Matter Rockets to propel spacecraft to other stars. Based on my rough calculations, you can send a 1 million person space stations to Alpha Centauri in 75 years, with only 30 years of anti-matter production.

Oh, I also wanted to add that I stole the ideas from Project Daedalus to handle interstellar dust. There are "dust bugs", autonomous spacecraft that fly 200 km ahead of the main spacecraft, releasing particle clouds to "clear the path". There is also erosion shield made from Beryllium.

https://en.wikipedia.org/wiki/Project_Daedalus

I could use some engineering advice. The previous picture, I was thinking it would be too much stress on the support beams, so I broke up the thrusters/fuselage into 8 smaller ones and moved them to the inside of the ring. Based on my currant calculations, the thrusters would collectively do 5.4 m/s^2.

 

I was thinking I could do 16, 8 on the inside of the ring and 8 on the outside. I am not sure if I even need the support beams, or if the ring would be structurally sound without them. This is entering the realms of materials physics and engineering so I don't know.

[Moontanman]

Do you have your heart set on anti matter? This may point to an alternative.

 

https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket

 

https://en.wikipedia.org/wiki/Fission-fragment_rocket

[3blake7]

Do you have your heart set on anti matter? This may point to an alternative.

 

https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket

 

https://en.wikipedia.org/wiki/Fission-fragment_rocket

 

I've looked into both of these concepts. The biggest issue is the low exhaust velocities, which means I will need a lot more propellant flow per second to achieve the same thrust. That means bigger storage tanks for the propellant, which means more weight, which means more propellant. At interstellar distances, it can really add up. Another issue is that fissionable materials are finite, it's not renewable so once I use up everything in the Solar system, I'll have to switch to anti-matter anyways, which can be produced from particle collisions powered by solar energy. Anti-matter in effect, is renewable. The last thing is, I am not sure how much fissionable material there is in the Solar system, or how assessable it is. The Beamed Core Anti-Matter Rockers is by far the top performer, once you have a ridiculously large antimatter factory. Even at the predicted capability of a 0.01% conversion efficiency, and a solar cell efficiency of 68%, it would only take a Dyson Swarm that covers 5% of the Sun to produce 1200 megagrams of antimatter a day. There is plenty of raw materials in the Asteroid belt to build it. That would allow me to send 1 million people every 30 years or so, to another star, with the trip taking about 75 years.

 

As far as building it goes, I have an Autonomous Self-Replicating Industry, which includes Surveyors, Excavators, Haulers, Loaders, Feeders, Crushers, Separators, Smelters, Mold Casters, Part Casters, Grinders and Assemblers. It's like the entire industrial process broken down into automated spacecraft for zero G or large rovers for moons. The idea would be that they would self-replicate to a size much larger than Earth's economy, and be able to build a Dyson Swarm in a couple hundred years. This technology is nearly in our reach now so I don't think it's a big stretch to say we could have it in 50 years or so. I personally think a corporation that already produces most of those steps in mobile form, could adapt it for the moon/asteroid belt right now if they had the incentive. The harder part would be producing components like computer processors, which may be solved in the near future by NanoFactories. I saw a video by Nanorex of a NanoFactory concept that could produce a computer from nothing but Acetylene. We could mine hydrocarbons on Titan to supply a molecular manufacturer with the raw materials to build the next generation of computers for the ASRI. I originally came up with the ASRI for the terraforming plan I was working on, you can see it on my blog in the signature.