# Kardashov 1.5 Starship Energy requirements.

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The recent discovery of what -might- be a partial dyson sphere has piqued my interest.

We know the object(s) orbits an F class star every 750 days and obscures 25% of the star's disk when it does transit.

How much light energy does the "structure" receve?

How long would it take to fuel an antimatter poweres starship, if the hypothertical aliens can produce antimatter at the theoretical limit of efficiency?

How does the energy generation compare to the energy requirements of a Abercrombe Warp Drive? (assuming the theory works out)

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Well, it depends on the efficiency of the solar panels, the distance, and the energy output of the star overall. Not sure about the rest, though.

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I think unless you need obscene amounts of antimatter, it would be easier to harvest it from the magnetic fields of the gas planets in your solar system. If you can harvest the energy of a star, it's probably more efficient to just pump it into beams that fling your ships around.

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I think unless you need obscene amounts of antimatter, it would be easier to harvest it from the magnetic fields of the gas planets in your solar system. If you can harvest the energy of a star, it's probably more efficient to just pump it into beams that fling your ships around.

I'm looking into comparative scales here. How many tons could that much light energy accelerate at 1g, with a perfect light sail?

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There are many different configurations, depending on what you want to do. I think the best theoretical design would give you around 110 mm/sÃ‚Â² at 1 AU from the sun, with just sunlight, and an 840m diameter sail. With a circular sail, that would receive about 2.4 gigawatt I think, based on the energy received per square meter at that distance, and the surface area. So if you were to somehow apply 240 gigawatts, you could get an acceleration of 1G. I think, I'm doing math off the top of my head here, and using my rather basic understanding of photon sail mechanics.

A complete dyson sphere of 1 AU radius around our sun would receive about 311300000000000000000 watts, or 311 exawatts if I'm not mistaken. That's a lot of energy to squeeze into a laser sail. It's a bit different at 750 million KM, but I wonder if a dyson sphere wouldn't circumvent the inverse square law to an extent?

Now, whether or not antimatter is more efficient is a question I can't answer. Using the numbers from Atomic Rockets, a 10 ton beamed core antimatter rocket produces 10 meganewtons of thrust, with an thrust power of 500 megawatts.

It's just an assumption, that pumping all that energy into a laser sail would be more efficient than producing antimatter.

Edited by SargeRho
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Abercrombe Warp Drive?

Unless some new variety of warp technology came out, I think you mean Alcubierre Drive

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There are many different configurations, depending on what you want to do. I think the best theoretical design would give you around 110 mm/sÃ‚Â² at 1 AU from the sun, with just sunlight, and an 840m diameter sail. With a circular sail, that would receive about 2.4 gigawatt I think, based on the energy received per square meter at that distance, and the surface area. So if you were to somehow apply 240 gigawatts, you could get an acceleration of 1G. I think, I'm doing math off the top of my head here, and using my rather basic understanding of photon sail mechanics.

A complete dyson sphere of 1 AU radius around our sun would receive about 311300000000000000000 watts, or 311 exawatts if I'm not mistaken. That's a lot of energy to squeeze into a laser sail. It's a bit different at 750 million KM, but I wonder if a dyson sphere wouldn't circumvent the inverse square law to an extent?

Now, whether or not antimatter is more efficient is a question I can't answer. Using the numbers from Atomic Rockets, a 10 ton beamed core antimatter rocket produces 10 meganewtons of thrust, with an thrust power of 500 megawatts.

It's just an assumption, that pumping all that energy into a laser sail would be more efficient than producing antimatter.

But these people (if they really exist) dont have a FULL dysn sphere.

They have a collection array that obscures 25% of an F class star's disk when transiting. How big is that in megameters?

How far is it orbiting? it's in a 750 day orbit of an F class star... is that habitable zone?

How much energy can an array that size collect?

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It's about 2.05 AU for a 750-day orbit if I calculated it right. That would be, actually, almost exactly at the corresponding point to Earth's orbital distance (inner edge of habitable zone). Maybe they built right on their planet and use it as an anchor .

Edited by Findthepin1
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An extremely large number, Magnitudes of times more than a large number. That's how much energy it receives if it is in fact a Dyson Ring/Sphere.

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All just roughly guesstimating. Fermi Estimation.

Well it's blocking 25% of the disc, and that's about 25% of the full sphere, and I'll guess the star is 10% as luminous as the Sun (EDIT: That luminosity is incorrect). All told, about 0.001 solar luminosities. Considering the efficiencies in any conversion process, probably 0.0001 solar luminosities goes to antimatter, a leading fuel for an interplanetary spaceship.

So about 3 x 10^24 Watts. In a year, about 10^32 Joules of energy.

How much is that? Well here we go

https://en.wikipedia.org/wiki/Orders_of_magnitude_%28power%29

https://en.wikipedia.org/wiki/Orders_of_magnitude_%28energy%29

We're looking at a civilization that could feasibly push planets around in its star system, or blow them to smithereens like the Death Star, though both would be major undertakings. Of course we kind of know that already because to build such a megastructure in the first place demands you take planets to pieces. That said, that the energy a Dyson Sphere can produce is comparable to the energy it takes to build tells us something - it tells us that a small Dyson structure can support its own expansion over sensible timescales.

But what about spaceships? Well to get something up to most of the speed of light takes energy equal to its own mass energy. So this civilization could each year be sending off an interstellar ship of about 10^15 kg. That assumes a beamed power system to circumvent the rocket equation, it would be less if all the fuel had to be carried.

https://en.wikipedia.org/wiki/Orders_of_magnitude_%28mass%29

We're definitely talking building masses, shading into small asteroid masses here. They could probably send a Rama to another star if they wanted.

Edited by cantab
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The "Sphere", as Dr. Freeman Dyson imagined it originally, wasn't a solid shell surrounding the star completely. It was a spherical constellation of hundreds of thousands of habitats orbiting the star.

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Like a Dyson Swarm.

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Well it's blocking 25% of the disc, and that's about 25% of the full sphere, and I'll guess the star is 10% as luminous as the Sun. All told, about 0.001 solar luminosities.

The star is bigger than the Sun. It is 1.58 times wider and 1.43 times as massive as the Sun.

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Considering the star in question is ~1,400 light years away, I'm somewhat curious how much progress they will be seen to have made if we were to somehow lob an FTL craft at them.

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The "Sphere", as Dr. Freeman Dyson imagined it originally, wasn't a solid shell surrounding the star completely. It was a spherical constellation of hundreds of thousands of habitats orbiting the star.

you could step the orbits so that inclined orbits would not collide, you could eve tie them together if you coukd deal with the n-body problem(I.e cannabalize all the natural satellites in the system) Thus you could create bands of material but the width would be smallish.

The is no dyson structure that explains this system, it seems a natural anomoly.

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1/4 of a disc equates roughly to 1/8 the volume. Maybe it's sone strange natural phenomenon...? Even so, harvesting a star's power is literally awesome.

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The star is bigger than the Sun. It is 1.58 times wider and 1.43 times as massive as the Sun.
Whoops, I got my stellar classes mixed up, F is brighter than G not fainter. But what's a couple of orders of magnitude between friends.
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So, even if it's a collecter array that size, if they didnt need a significant portion of it to power their civilization, they could launch interstellar colonization missions with some regularity. Is that correct?

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It's about 2.05 AU for a 750-day orbit if I calculated it right. That would be, actually, almost exactly at the corresponding point to Earth's orbital distance (inner edge of habitable zone). Maybe they built right on their planet and use it as an anchor .

Makes a lot of sense, at least build it nearby the planet, and no this is not an 1/4 of an dyson sphere, its more like an solar collector going out to moons orbit or something, probably not one fixed structure either. Even so they collect 100 times more energy than required for an Kadashov 1 civilization.

Far more than needed for launching starships.

And they have to use all that energy in space, on planet and they will cook it. The other space industry will probably be heavier than the solar farm too.

- - - Updated - - -

So, even if it's a collecter array that size, if they didnt need a significant portion of it to power their civilization, they could launch interstellar colonization missions with some regularity. Is that correct?

yes, launching something like the starship in Avatar would use as much energy as earth receive. They receive 100 time more as an minimum.

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