- #1

Erik1801

- 15

- 3

I am grasping at straws here. I am working on a Hard-Sci Fi novel, plot, arcs, characters etc. are all worked out and i decided to take the deep dive in terms of Realism. For instance, there are no Fusion reactors. All that is important in terms of Setup is that we have Humans, and they want to go to a nearby Star system. Its ~4 Ly away and we would like for this transfer to not take 1000s of years.

The issue I am facing is that there seems to be no way to do this. I.e. achieve a high enough Velocity, fast enough, for the journey to not take 1000s of years. At least without breaking thermodynamics in a big fashion.

For example, I was told a Particle accelerator based propulsion system (using for example a Wakefield accelerator) could be a good method because the exhaust velocity is so high and it is pretty compact. In principle that is true, but when you go and do math, taking into account that the system will experience heating (We assume the Ship gets its power via a energy beam, microwaves or something. It doesn't carry the power generation equipment. The power is beamed to it). Even at a magical total system efficiency of 80% (So you pump in 100 Watt, 20 Watt is heat and you get to do work with 80), the real world acceleration might as well be nothing.

See this. It is possible that I didn't do the math correctly, but like Jesus.

As you can see, assuming a 400 GeV accelerator, a Radiator area of given, an Efficiency of 80% and a Ship mass of 100.000 tons (That number is based on some assumptions about Crew size, needed cargo capacity and some Ratios. For example that for each kg of Cargo you need ~0.25kg of Structural support), it takes 77000 Years to get to 0.127c.

I did similar math with Fusion (As in a Fusion reactor powered by the external beam), Anti-Matter, god dam light sails and even this really dumb concept, i think NWRE, which proposed to use a Fusion Engine to somehow cool an even better Engine.

My results were that while all of these would

*eventually*get us to the target, all of them took like half a billion years (Hyperbolic). As a matter of fact, the particle accelerator performs the best. Which is like.... 77000 years D:

As it is so often the case, the issue is Heat. If we had a Radiator the size of Luxemburg we could get much better acceleration. Which ignores that a radiator the size of a nation presumably weighs more than 100k tons but also the practicality of carrying such a thing.

Ideally, i would like to have a solution which can get to 0.5c in ~24 Months. Which would mean a constant acceleration of 2.5m/s². But as far as I can tell, this is just straight up not possible as long as thermodynamics are of any concern. Of course this "works" if you bump the efficiency to something stupid like 0.99999999, but even then the accelerator would eat 80 times more energy than the World currently consumes. Which, I don't think is impossible in principle. I just seriously doubt you can concentrate that much energy into a 800 meter long accelerator.

And this is were I am stuck. People on Reddit keep talking about fast Interstellar transfer methods but all the ones I looked at just don't work as advertised. Even the all holy Anti-Matter based propulsion systems cant do this, because the ships would just be to heavy for any serious acceleration.

That being said, there is the option that i missed something very obvious somewhere along the way, hence why all the numbers look so terrible. I just have the detailed breakdown for the method for the Wakefield thingy, but guys... no propulsion method is bussin ngl.

So, to finish this off, my two core questions are;

1. Is there anything obviously wrong with my Math and or am I missing something which solves the thermal issues ?

2. Are there any methods of propulsion which could do the task ? I.e. 0.5c in 24 Months.

I hope this is informative enough to make answering it possible, if not like I am sorry xD Hopefully i can give good clarifications to comments should the need arise. Also excuse any typos or bad gramma, Ich bin deutsch und hab legasthenie.