MBobrik

If you stretch the definition of incremental enough, everything is just incremental progress. And in the other direction, large enough accumulation of small increments may amount to order of magnitude large change. I agree that the energy density won't change with chemical rockets, but I don't believe we are already close to the maximum physically possible engine TWR or tank fuel weight/dry weight ratio. And I don't believe at all that we are already close to the minimum physically possible manufacturing and operating costs.

Well, I flatly refuse. I will judge arguments according to their merit and nothing else. No faith in the clergy experts for me. Well, either that, or you just painted yourselves into some corner, like experts tend to when they start believing no new idea can come along...

This is tautological at best. only small improvements are possible because the technology is mature, but how do you know the technology is mature ? Because you don't think bigger improvements are possible.

Why is it straw argument ? This "if it were possible someone smarter than you would already have done it" reasoning prevents all attempts at improving anything. If it were valid, there would be no improvement in any area.

We could cut the "dead" mass. Or let the payload fraction stay the same but make manufacturing and operating much cheaper. There is no "basic physics" preventing us from doing that. I don't believe that the energy density is the only one parameter driving up the cost.

Yeah, If it were possible, people smarter than you would have already invent it in the past. So don't bother... Thinking that way, nothing would be improved ever. We would be still sitting in a cave and chipping stones.

I think we should avoid any jostling, moving, shifting, gimballing, any unintended and uncontrolled movement. The initial sucrose/moss spores mixture should be made stable enough to survive the gee forces of the launch even in perpendicular direction. Small size of the samples combined with the square/cube law should aid this. And because we will do a lot of testing of the mechanical stability of the sample holder anyway, we should go without capsules, inserting the moss directly to the compartments of the holder which will be molded as single piece of acrylic to simplify the design and to aid mechanical robustness. Understand. How much volume of air per sample is sufficient ? Mazon Del said, the samples will share common atmosphere, therefore the larger container has to do all the sealing anyway.

@Mazon Del I would like to reiterate my question. Can we completely do away with the sample containers and plant the moss directly into the compartments of the sample holding cylinder ? And I add another question. Are/can the samples be sealed inside their compartments or containers, or do they need to share (a presumably much larger) volume of common atmosphere ?

Give up folks. Negativist Nibb figured it all out. It's all impossible to begin with. Just give up on space, and go planting flowers in your garden.

@camera. There is a mathematical formula that connects camera params like chip size and resolution, lens focal distance and aperture with depth of field and distance of the viewed object from the camera lens, while the focal fistance and aperture themselves are constrained by required field of view, chip light sensitivity and wavelength of the light itself. And for rasp pi camera module the lens parameters are as fixed as chip properties because the lens is directly in the package with the chip. So technically, the minimum required distance between the sample and camera lens is a fixed function of the required depth of field. If we need 5 mm depth of field, the camera lens has to be at least 80 mm from the sample. If we need 15 mm depth of field, the camera lens has to be at least 150 mm from the sample. Adding microscope optics to the rasp pi cam , or even using a handheld microscope instead, would not help because microscopes have depths of field fractions of a milimeter at most. @using mirror My idea was a fixed mirror glued directly to the sat frame so that it won't lose alignment unless the sat itself is bent out of its shape. But in this case we are screwed anyway, aren't we ? It would of course require free space in-between, but that would be only marginally bigger than what will be needed w/o mirror, because to get at least the 5 mm DOF, the camera has to be at least 80 mm from the sample, which for all practical purposes means on the other side of the sat as the sample. @data rate constrains A few pages back, I computed a rough estimate - we can transfer cca 50 images per one communication window, which occurs ~ 2x per day per ground tracking station. So if we want to take picture each hour, and have some redundancy, we need one ground tracking station per 3 samples. Of course we can increase this by increasing the picture taking interval or/and decreasing image resolution. Or by adding moar ground tracking stations, which, given they are just ham radio with a good antenna, should not be all that difficult.

That's why I said we have to bounce the image through a mirror on the opposite side of the sat. So the path of the light will be from the sample, to the mirror on the other side, that will be like 7.5 cm, and then back to the camera which will be located inside the inner empty space of the ring, this way doubling the distance.

Why ignore ? it is one of many iterations we will go through. And yes. I made it in SketchUp, learning how to use it in the process. It took me almost 2 hours, mostly learning the GUI and controls, but the second time I believe I could do it in a few minutes.

Well, let's turn it around. Why do we need the capsules, when the moss can be directly in the cylinder sections themselves, and orientation of the moss from/to/perpendicular to gravity achieved simply by positioning and orienting the moss inside the compartments ? Because we won't have two cameras. The problem is depth of field of the camera. To have depth of field 1.5 cm long, the camera lens must be at least 15 cm from the sample. So the camera must be inside the ring, and the image bounced once through a mirror on the opposite side of the sat. Otherwise the camera has to sit on the other side itself, which will give us cca 8 cm camera distance and only 5 mm of depth of field, which means the sample would have to be only 5mm thick, otherwise only first 5mm of it would be in focus and the rest would be blurred.

Yeah, but we need moar samples. Mazon Del wrote about N x 3 samples each cca 1.5 cm x 1.5 cm x 1.5 cm, where the higher N the better. I was thinking about somehing more compact with less unused space between the samples. Something along the lines of , where the sample cylinder is more or less one piece of molded acrylic, and gears and servos and support go inside the cylinder.

It needs not be either-or. I am reasonably sure Solidworks can import at least some formats Sketchup can export, and vice versa. So anyone could make his component in Sketchup, and then we would integrate it together in Solidworks. Me too. Curious about your idea.

What's wrong with them ?

It's free like sketchup ?

Oh, welcome back! Well, I assumed the entire sat will be heated to 20 °C, and the surface reflectivity will be that of aluminium. If we heat and insulate only the samples and batteries, and keep the rest of the sat at say -10 °C heating requirements will drop to less than 2 W. And maximum cube projection area is, I believe sqrt(3) * one side, which would give us 3.5 watt with 3 non-foldable panels. But that would require the sat to rotate around its diagonal, which is awkward at best. And is a waste of panel efficiency. So I too think that the unfolding the panels will be unavoidable. In the calc sheet I thus counted 4 foldable panels and 1 fixed giving us 11 Watt total. And when I am already mentioning the google sheets, could you please add - the toquer calc sheet and https://docs.google.com/spreadsheets/d/13vQUH8vK43XcgI-o--lxWRhwMzHNJw0X-DgyFmitKKs/edit?usp=sharing - the part weigt/volume/cost sheet https://docs.google.com/spreadsheets/d/1rU0J4dMLqgI2b2MDWhZML-ffgUhhBwcTbRDssW3zcZc/edit?usp=sharing to the first post, so that they don't get lost ? And while adding links, - a comfortable and free 3D modeling tool http://www.sketchup.com/products/sketchup-make It's not a professional CAD, but still better than drawing in MS Paint .I think we should use it to visualize our ideas, and even for the final design. edit: fixed swapped links

As I said above. Most of the cost comes from the PLACEHOLDER parts, which we most probably will replace with regular, more than order of magnitude cheaper components. Even if we have to buy the solar panels, there is a chance we need not that many of them. I believe K^2 said he will calculate the total power needed for heating, but he seems to be occupied. My own back of the envelope calculations show we need only 3 watt max if we want to heat the entire cube, which translates into 6 watt of solar panels. I personally think that we can send the bird flying for cca $20 000 + launch cost.

That's the ambiguity. Do they mean maximum entropy production per second ? Then fire wins. Do they mean maximum total entropy ? Then fire loses to life because even when chemical end-products might be the same, fire released a lot of low entropy types of energy like light and infrared. But in this case, life would lose to slow uncatalyzed oxidation, which might take millennia, but produces the most total entropy.

Then any dry wood would catch fire, instead of being slowly decomposed, or submerged into a peat bog and converted to coal, because that way it would create entropy much faster. edit: And in general, the total entropy production of earth is determined only by the spectrum of outgoing electromagnetic radiation, which is in turn determined mostly by albedo across the spectrum, and absorption spectrum of earth's atmosphere. And while life surely influences both, I don't think that it does in a way that maximizes total entropy production.

One of the things that sound profound, but may be very trivial when looked at closely. Increasing entropy more means you are just extracting more energy from the environment, which , anything else being equal, grants you a survival advantage. Life thus evolves to collect energy pretty efficiently, and thus to efficiently increase total entropy. On the other hand, life, bacteria, fungi and saprophytes could live off a dead tree branch for months, but one forest fire will consume it in minutes, and thus increase entropy much faster than life ever could. . And it says nothing about the creation of life. Surely, at molecular level, the thermodynamically more favorable reaction usually outcompetes the less favorable. But there are kinetic considerations as well. It is more likely, that the first self-replicating reaction won over other chemical reactions not by releasing the most entropy, but by being able to proceed kinetically much faster, because, well, the catalyst reproduced itself.

The red "placeholder" values in the sheet are just the first what I found. I's just a starting point, a placeholder put there so that the field is not blank. The sheet is editable. Anyone can, and should, if he find something cheaper, or more suitable, just replace the part.

What do you mean with "experiment indexing mechanism" ? you mean, how the moss samples will be packed and how they will be moved into the camera view ? I imagine a hollow cylinder with 90 mm outer diameter, 73 mm inner diameter, 15 compartments, and 1mm thick acrylic walls. Servos and cogs that rotate it will be inside. The problem with thickness is, that if it has to be 15 mm thick, the camera depth of field has to be 15 mm too. and a quick calculation shows, that the viewing distance has to be 150 mm. so we would have to bounce the image once through a mirror to get the distance from the camera. If we don't want this, then we will get maximum cca 80 mm view distance, and thus only 5 mm depth of field, so the sample should not be thicker. and thus question @ Mazon Del. Can the samples be cca only 15mm x 15mm x 5mm ?

As a mater of fact, as we specify and design our own parts instead of the insanely expensive placeholders, it will get cheaper. For example the ground station is basically a glorified ham radio. If we gave 10 % of the cubesat shop price tag we would overpay it. The same goes for structure, antenna, power supply and batteries. We will most probably have to pay up for solar panels, and if we don't manage to find someone to design a custom transceiver for us, then the transceiver too.