The quest for covers and heat dissipation 4


Question mark book cover

Everyone who has followed the Elite:Dangerous journey will be familiar with the word ‘soon’. Its a word used to describe a variable length of time and that my friends is how far away the cover is for Elite:And Here The Wheel. Very soon in fact. Super soon, but alas, not quite yet. I’m getting quite excited actually, like a kid at christmas. When the people of the world see my novel, this cover will be what they see first. 80% of them will judge their buying decision PURELY on the cover. Is the cover cool? Does it evoke the right emations? Is it right for THEM? If the answer is yes they will keep looking at the novel. If not, then they’ll move onto the next.

That is how tight this book selling business is. So I’m waiting with cliche-ridden baited breath to see what the designers at Fantastic Books Publishing have come up with. Its a big deal. There are some restraints such as fitting in to the box set and some other things I’ve been privy to, but its still going to be a bit of surprise. I’m nervous and excited, but somehow I’m managing to get to sleep at night. Once I have it I’ll be posting it here. For now, we need to wait for ‘soon’ to come.

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Flag on a Stick

With the release of the first Garry Clan newsletter, subscribers were invited to help decide the course of the Garry Clan narrative. There were three options and all three have been voted on by subscribers but one is clearly out in front.

This is the last week that you can vote on which course the story will take. Its time for another newsletter, so I need an answer to enable me to keep writing the story. There’s no agenda at my end – I don’t have any bias, I just need your help to decide on Robert Garry’s future. So make your choice on the poll and do it before next Monday the 19th May. After that I’ll tally up the votes and start writing the next part of the story.

Have you signed up for the newsletter yet? If not, I suggest you do so. As well as getting the Garry Clan newsletter with lots of background information on the clan, you also go in the draw to win this snazzy Garry Clan USB drive. Loaded with lots of goodies created over the course of the last year, all to do with the ‘And Here The Wheel’ journey. All the podcasts, all the versions of the novel, cover art, various articles, etc, its a bit of a treasure trove and could be yours if you sign up.

Don’t mess about.
Don’t be ‘Mr Last to Sign Up’.
That’s not cool.

Click here now: Sign me up!

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Heat dissipation was mentioned in one of the recent Frontier Development newsletters. Containing heat or dissipating it is directly related to how visible you are to other players. If you want to be invisible you have to turn off your engines and contain any heat produced in the ship. On the flip side if you use frame shift or dump heat as quickly as possible you will light up the sensors of every ship around in the solar system.

The idea of how heat could realistically be removed from a space ship of a given size was a fun engineering problem so I did some calculations awhile back for one of my Indiegogo newsletters. Its been about a year since I did that so I thought it might be time to bring that one back to life for those who didn’t receive the newsletter. It was an interesting calculation to work out how much ‘heat dump’ area I needed, based on some assumed power levels. Read, debate, and reply with your own calculations. Maybe you think my assumptions are way off. Let me know.

    Being an engineer this intrigued me and so I waded into it, thinking this could be useful knowledge for the novel. Obviously the design I came up with is my own and bears no resemblance to what will actually happen in the game, but I like to know how things can and cannot work and how realistic it would be. So I wanted to know what kind of cooling would be required for the classic Cobra Mk III, a ship measuring about 40m wide, 20m long and 10m deep.

    There are four ways to transfer heat from one place to another. The first is conduction, heat transferring through one solid mass into another solid mass. The second is convection, where heat at the boundary of a solid mass is transferred to a fluid (air, gas, water) surrounding the solid. The third is radiation, which is what happens when a hot thing is exposed to a cold thing (and vice versa) such as a sun to a planet. The planet gets hotter (and the sun gets cooler, but in such an example this effect is negligible) without any connection between the two.
    The fourth way isn’t strictly speaking a way to transfer heat. Instead you transfer mass, and the mass takes its heat with it.

    When a ship is sitting in a vacuum you pretty much have to cross off convection as an option. A vacuum is no good for convection heat transfer (which is why a thermos works so well).

    Conduction will work fine within the boundary of the ship (getting the heat from the centre to the outside of the ship) but can only go as far as the edge of the hull.

    This leaves options 3 and 4 as the only really viable options. Option 3, radiation, is attractive because it is effectively free. You take something with a large surface area to volume ratio, make it very hot (a ‘heat dump’), poke it out into the vacuum of space and it will cool down. All you have to do is pump your heat transfer fluid through the heat dump (pump it out hot, pump it back cold).

    On the other hand, option 4, mass transfer, has a series of minors costs to it which could add up to a major cost.

    Firstly, whenever you eject mass you will alter the trajectory (vector) of the ship. Newton’s third law of motion states ‘For every action (ejection of mass) there is an equal and opposite reaction (ship moves away from ejected mass). For the record this is exactly how a rocket/thruster works. Although the reaction which alters the ships vector may be minor, this needs to be corrected which will cost fuel.

    Secondly, what mass would you be ejecting? Coolant? That stuff isn’t free and if you are going to eject it, what are you going to replace it with? More coolant? So that means you need to store more coolant on your ship than you can use at any one time. That coolant will therefore be basically going for a free ride on your ship for most of its life. The coolant will take up volume on the ship which means you can transport less cargo. This coolant will also have mass which means the ship is heavier which means you will need more fuel to transport it from A to B. This means you will need to carry more fuel, which has a mass as well, which means more fuel, and on it goes.

    If ejecting coolant was to be your main method of expelling heat you would want to ensure that you carried enough coolant to get you from A to B. You don’t want to run out half way there and have a meltdown. But what if you are attacked by pirates? Regenerating shields, firing lasers, using the maneuvering thrusters, these will all make heat. How many dog fights should you calculate in to your coolant storage? What if you need to make an emergency hyperspace jump to stay alive? You will have to travel in system all over again. Will you allow for this extra distance in your coolant budget too? It would be a nightmare to decide exactly how much coolant to carry, knowing that your life depends on you getting it right.

    So my personal preference would be option 3, though it does have its downsides. For one, it isn’t ideal to have great big heat dumps hanging off your ship during combat. Combat is when your ship is at its most stressed, when heat removal requirements are at their greatest. The ability to eject coolant would provide instant relief, though arguable an internal heat sink could be used temporarily until you are safe and able to use your external heat dumps again. It is likely a ship would require a combination of methods with radiation the primary and ejection as an alternative.

    I did some rough calculations, what old engineers would call a ‘fag packet check’ for radiative cooling. The situation of a ship in space can be simplified to a finite object surrounded by an infinite black body. The calculation becomes pretty simple then and is dominated by the difference in heat between the hot and cold bodies to the fourth power. A small change in the hot temperature makes a big difference in the amount of heat transferred.

    I made an assumption of 50MW for the power plant for a Cobra Mk III. I assumed that about 10% of that energy would produce waste heat. That is pretty realistic, in fact maybe a bit high if we assume that by the year 3300 engines are even more efficient than those of today. I imagine a heat dump shaped like the sail from an old sail ship could be extended outside of the hull and maintained at a temperature of 1200 degrees Centigrade. Two sails at 2.4m x 2.4m would be sufficient. For a ship the size of the Cobra that would not be a problem.

    Realistically you would probably want to have a set of sails extend from all sides of the ship so that regardless of the ship’s orientation a heat dump would be on the side facing away from stars and planets.

    I also completed some quick calculations on coolant ejection. Modern day coolants are designed for low pressures and I can’t find any data for high pressure. So I turned to steam as my heat transfer medium. Steam has many quirks which can make it hard to handle, but it has an extremely high ability to absorb and retain heat, more so that any other regular fluids. For example, nuclear power plants use steam (heated from the reactor) to turn turbines to make electricity. Nuclear plants in the U.S.A are typically ‘Pressurised Water Reactors’ and run the steam in a secondary loop (isolated from the radioactive heat medium) at about 160bar, or 16 mega pascals of pressure. I decided to run my theoretical Cobra’s coolant system at 22 mega pascals or 220 bar. This is pretty much the limit (known as the ‘critical point’) of saturated steam. Above this point the steam becomes ‘super critical’ and its heat transfer usefulness begins to decrease.

    These rough calculations show that to maintain 5MW of heat dissipation (10% of the 50MW heat plant), the Cobra must eject around 230 grams of steam per second. In the game First Encounters it took nominally one week to fly from your hypespace exit point to a space station. I’ll leave you to do the maths on that one.

    One thing I haven’t touched on is the fact that the hull of the starship itself will act as a heat dump. Simply routing coolant around the inside of the hull will provide significant passive cooling. When your body gets hot your blood vessels expand and draw closer to the surface of your skin to help you cool down. Another trick of your body is evaporative cooling. This is when liquid water (sweat) evaporates into water vapour (a ‘phase’ change) and a lot of energy is absorbed in doing so. Some form of ablative heat removal system may be useful. Even lining the hull of the ship with a row of heat pipes (a sealed and contained pipe which takes advantage of this phase change to transfer high levels of heat) may be an option.

    So what are my conclusions after all this? Well I think that there isn’t one answer to the problem. There will need to be many different systems to keep the ship cool under all conditions. I’ve attached a few pages of my rough calculations below in case anyone is interested.

image014

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Another week gone by, another week closer to release. Anyone else jumping out of their skin with excitement? Just me?

Thank for stopping by, catch you next time.

Thanks,

John


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4 thoughts on “The quest for covers and heat dissipation

  • redravens

    Nice fag-packetry.

    The concept of how to vent sinks is a pretty crucial one if you’re running any sort of near-realistic setting. You can absolutely handwave it away, but it’s a really interesting concept to play about with in any case, If heat is a toxic substance on a spaceship, it throws interesting questions about what sort of procedures and structures are in place to prevent the occupants from roasting.

    • andherethewheel Post author

      Agreed, it should has as many safety interlocks/systems as say a nuclear reactor on a sub. I found it an enjoyable exercise, but I’m a geek so there you go. I think my main conclusion is that whatever you do it will actually take up space and weight in your ship and you have to allow for that.

  • Ron Goodman

    Hi John.. I am also signed up ED as well as all the audio books and have just seen Dan’s announcement for the preliminary covers. They are all looking really good but I think yours has to be my favorite.

    We are getting close now and I am really looking forward to seeing (and hearing) the results of your work. I can honestly say following the whole journey and been most interesting and I am really hoping that carries on well past delivery…

    • andherethewheel Post author

      Thanks Ron, Yeah I really like the cover as well. Pretty bold and bright and sets itself apart from the others a bit yet has some resonance with them and the Gollancz covers. Yup the more I look at it the more I like it. I can totally see that sitting on the bookcase 🙂

      I really appreciate your support, thank you. This site won’t be going away any time soon, so keep it bookmarked and keep coming back after launch. We’ll find new journeys to talk about 🙂

      Cheers,

      John