henryrasia

Erm, just asking, is mossat.org down? Is everyone still on board?

Assorted Sciences Company? Multifarious Laboratories, Sundry Science, Eclectic Science Emporium? Make sure to give credit if you chose one from here! Best of luck!

That moment when Iran has a better space program than your country... Grim perspective for an aspiring aerospace engineer such as myself. From Brazil, BTW.

Oops, pardon my ignorance... But thank you guys for the answers! The question was to describe phi in terms of epsilon, radius, and altitude of Sat2. PakledHostage made me see that the problem is a silly SSA triangle problem where I should apply the law of sines. The mystery angle ended up being completely negated! I'm trying to simplify my resulting equation, as it appears it does not change when radius or altitude change, which is odd to me So yes, the answer was simple, but all I need to do now is simplify it, but I think I can do that on my own. I'll come back if I have problems. Thanks again! It was very helpful!

Hey! This isn't a mere HOMEWORK, this is RESEARCH! Seriously, though, I'll try my hand at it and report back. BTW, I don't think he kind of orbit of Sat2 is important at all. I only need to know the angles at a particular moment, which happens to be when it's right on the edge of the safety margin.

Right now I just want an equation that looks something like this (À is supposed to be pi): Φ=ε OR Φ=2ε OR Φ=ε*(À/2)-À OR some equation like that (the true one, of course) that lets me figure out Φ given an ε. If it's hard to visualize, imagine that point V can slide around the surface of the circle, but only between U and the S-Sat2 line. That freedom of position is what's going to change the value of ε, and therefore that of Φ (and that's why I need a general formula). Sat2 can also get closer or farther from the circle, which will change the positions of the red and blue lines, and therefore will also change the value of angle ε. I'm considering distance S-Sat2 to be of a known value A, and the elevation angle to be of a known value ε. I also know the radius of the circle ® if that's of any use. That's what I need, a general formula for Φ in terms of ε. (but not exclusively of ε) ___________________________________________________________________________________ Now why am I even posing this question. My project is, basically, to figure out mathematically what is the least amount of GPS satellites around the Moon needed for full coverage at all times. The mathematical way doesn't seem to be working out, so instead I've began a simple algorithm that's going to randomly generate orbits and see if they match the requirements. For that I'll use spherical coordinates in conjunction with Keplerian elements to determine visibility of satellites on the surface. But since the visibility cone on the ground has a safety margin elevation angle above the horizon (which I have yet to decide exactly how wide it'll be), I need to know what latitudes and longitudes, deviating from zenith, will be able to see the satellite. Maybe I'm overcomplicating this, but it's the only method I've come up with that can feasibly give me results that I can write about in the paper. All other methods are basically guessing, which is not exactly scientific. I realize that this is brute-force computing, but if you have any better ideas please let me know! Sorry for the long wall of text, but I hope things are clearer now, Henry

This is a smaller part of a bigger project that I'm doing for the IB Extended Essay (if you know what that is), which is a very extensive research paper (well, as extensive as it can be for a highschooler ) due as a draft (for me) at the end of this school year. Bottom line is, I need an equation with phi at one side and known numbers/variables on the other. This will be used later when I decide specifically what elevation angle (altitude?) and other parameters to use in my simulation. I previously arrived at the obviously wrong conclusion that phi=2*epsilon, it was then that I figured out the mystery angle was messing up my beautifully simple application of Eratosthenes' experiment. And now I need to figure out what is the true equation. The real killer? I need to explain everything on the paper, so using geogebra directly is not an option... I've asked here after a lot of thinking myself. And the furthest I've got is having a gut feeling that the solution might rest with using auxiliary lines drawn to suit our needs. But I haven't figured out if that's even true yet. It might very well be hiding under my nose but I can't see it . But hey! You're the Figaro GPS guy! How are you doing? Maybe you could actually help me with the second part of my project, which revolves around GPS line of sight and such! But that's enough for now, I don't want to bore you. Henry

PakledHostage thanks for your quick answer! Regrettably, however, the question is to find phi in terms of epsilon (or any other known value, written above). I just mentioned the missing angle because that sucker is the one that's keeping me from Eratosthenes' simple answer. I'll edit the picture to reflect that. Sorry for the confusion! BTW, the answer needs to be general, that picture is just one of the possible angle combinations, for better visualization. Thanks again!

Hello all! I would like to ask this question on the KSP forums and it's about geometry. In case you don't know, Eratosthenes was the Greek man who calculated the circumference of the Earth by investigating angles of elevation at different latitudes. Summarized in this diagram: I'm trying to resolve an unsettlingly similar problem, but instead of the sun satellites. The question basically is: What is the mathematical relationship between angle of elevation (aka altitude in the horizontal coordinate system) and latitude from the point of zenith (theta in the diagram). But here's the catch: I can't assume rays are parallel as Eratosthenes did! This is because the Sun can be considered infinitely far away, when a small satellite has a definitive answer. This adds an annoying extra angle that I need to account for but I do not know how. This is a simplified diagram of my problem: Trust me, my WIP version is WAY messier. See that missing angle between the pink and blue lines? That's the one I can't figure out. BTW pink lines are parallel, the circle is the celestial body, and everything else I can answer questions for. The answer should be as general as possible, but the final solution should be phi in terms of epsilon. Known distances are: radius of circle, distance from S to Sat2, and angle epsilon. If you could help me I'd be very grateful, as my end of year research project depends on this and I'm stuck! Also, if you could please show and explain the work (or simply reasoning) that'd be perfect! Thanks in advance, Henry

Wow, another fault with the ammonia system? Who built that thing? And how long has it been up there? Maybe this second failure warrants a complete reworking of that system?

Can't atmosphere composition be determined through spectrometers analysing the refraction of light by the gas? If this would be simpler than sticking multiple atmospheric probes in each individual capsules, than maybe we'd have one of these alongside our cameras (or maybe the cameras can double as spectrometers?) for analysis when each hourly* flash flashes (for the timelapse) *early, groundless estimate. Do not consider final.

From what I recall the chosen moss was good because it grew in the dark, which is important because it's easier to seal the sat for constant pitch bblack than it is regulating lighting inside the sat (orbital day-night cycles aren't exactly natural). The imaging would be done with flashes once every so long (moss doesn't grow that quickly, so we'll do a timelapse).Furthermore all moss samples will be identical and used mainly for redundancy. Though if we could hibernate them individually then Creature's suggestion would be very valuable, observing different gravities discreetly as opposed to one following the other. Finally, I don't even know of the ISS has tiny centrifuges. They definitely did experiments with plants before, but those have always been in 0 g, not in the 0-1 g range we're shooting for. BTW we chose this experiment exactly because no one has done it before and it's not so simple to be done on earth as opposed to space. And yeah, this is mostly to get the know-how of space exploration, which isn't really accessible to the public (not even hobbyists) right now. Our ultimate mission is to land something on Phobos (we'll figure out what exactly it would do there later ) just because it's cool. " We choose to go to Phobos in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too."

Well, I've heard vBulletin is the best without going full professional. But what about a subreddit? That'd be easy, free, and has hierarchical comment structure, allowing for natural organization of priority discussions. Doesn't seem to support posting images, though. Regardless, that is awesome LordQ! We're lucky to have you aboard!

Thank you newt, that was a very eloquent post, and I agree to every word of it. However, starting new threads would be, if nothing else, quite annoying to forum users not involved in this project but who nonetheless browse the science labs. Endersmen seems to be quite skilled in website making (far better than anything I could put up) but regrettably finds himself without access to a computer. If he can find a way around that it'd definitely be our best option. Until then, however, we can think about setting up our own vBulletin forum. It's free and without commitment: when we find a better alternative we just close it and move on. The website would be perfect, for example, as it already has different sections for different things, AND a dedicated file repository. I'll leave it up to @Endersmen to discuss the details.

Am I the only one who thinks this thread is getting crammed and hard to find info? @Endersmen, how's the website doing? Have you found an available computer yet? If not I hope you figure something out soon. Again, the sat's orientation will determine a bunch of things. Where did the 100W figure came from? But regardless I believe starting a mockup experiment right now here on earth would be very useful, coupling with a camera test. I still feel one picture an hour came out of nowhere, from my very limited biology knowledge I recall moss gre quite fast. @Mbobrik, that data transfer calculations ignore power constraints, are you sure we can afford beaming down that many images every orbit? @deljr15, that idea is pretty accurate, though it brings back up some old discussions. Since the sample ring (that looks like a donut, or a tube, what do we call it?) Is going to be circular, the gravitational gradient will not be negligible like it is on Earth. I calculated the vertical difference of a 5mm high Petri dish a lot of pages ago, and it turned out to be a lot greater than the maximum variation across planet earth. I still believe this will mess with the experiment. But besides that the gradient across 13mm of horizontal space will be much more noticeable (not to say the direction would change, no idea by how much though). My solution was to make the Petri dish concave to fit the ring nicely, I don't know how hard that'd be to do in solidworks, though. Finally, it has a lid, which is like a normal Petri dish. Just so we're all in the same page, isn't each Petri dish going to be sealed airtight months before it even launches? Is that not the requirement for any cubesat launch? Waiting for everyone else's feedback on this.

That is... Really cool! Deljr15, if that's a sketch I can't even think how good's your serious business! About 3D/CAD software, I've heard of Autodesk inventor, which has a trial version, is there such a thing for solidworks? Like an education version? Another thing, sketchup doesn't seem to be geared towards mechanical engineering, though I'm not really experienced with it so I might be wrong. That's an awesome design, deljr, though I disagree the wheel should be on the side. If it were dead center it'd have less problems stabilizing. We'd just need to figure out how to balance it with the other components. The spheres look unnecessarily large and wasteful of space ( no offense). In my mind it'd be one single tube section with the inner walls divided into sections for the moss to grow. Finally, wasn't that going to be sealed? If so we wouldn't need an opening as it'd be assembled in advance, locked into place. Finally, about the shape of the magnetorquers, Mbobrik posted a while back some images of how they would fit inside the cube, and it's kinda like three circles inscribed at different orientations. I don't see how they could serve as heaters, though... I'm really excited for how this is coming along! And welcome all newcomers! As always any help helps - - - Updated - - - That is... Really cool! Deljr15, if that's a sketch I can't even think how good's your serious business! About 3D/CAD software, I've heard of Autodesk inventor, which has a trial version, is there such a thing for solidworks? Like an education version? Another thing, sketchup doesn't seem to be geared towards mechanical engineering, though I'm not really experienced with it so I might be wrong. That's an awesome design, deljr, though I disagree the wheel should be on the side. If it were dead center it'd have less problems stabilizing. We'd just need to figure out how to balance it with the other components. The spheres look unnecessarily large and wasteful of space ( no offense). In my mind it'd be one single tube section with the inner walls divided into sections for the moss to grow. Finally, wasn't that going to be sealed? If so we wouldn't need an opening as it'd be assembled in advance, locked into place. Finally, about the shape of the magnetorquers, Mbobrik posted a while back some images of how they would fit inside the cube, and it's kinda like three circles inscribed at different orientations. I don't see how they could serve as heaters, though... I'm really excited for how this is coming along! And welcome all newcomers! As always any help helps

Just thought I'd share. How hard can rocket science be anyway? I just love the engineers in this. So Kerbal.

Hey friend, no sweat. I think the same too. Though we're debating the general systems components for now, I definitely agree that we'll need to take into account more lowly, wordly issues such as physical size. Unless we're willing to step up development speed, that is... And about the centrifuge idea, it's just as good (and bad) as independent antennae/solar panels. But that is a problem that needs to be addressed, as we'll have significantly less signal strength and power if we use passive systems, unless we get really creative, in exchange for mechanical simplicity and safety. So there's a trade-off there between creativity and capabilities.

Hey, in light of all of the problems relating to the sat being spinning (solar panels and directional antennae not being able to point to a particular place), how about we ditch that? An alternative would be to have a normal, still satellite with a centrifuge inside. This way we can control both spin rate and direction better. The only problem I see (besides figuring out a centrifuge) is the fact that we'd have to have double navigation for the sat while having a massive centrifuge inside (essentially an uncontrolled gyro). What do you think?

K^2 and Mazon Del, what do you guys think about the discussion on stopping-restarting vs independent axis? MBobrik thinks the latter would be too mechanically complicated, but I think the former would be too electricity-expensive and risky (if that fails the whole mission is a goner). But more than that I would think the spin rate should be constant for the experiment, as decreasing and increasing would interfere severely with the results. The independent axis could be maintained by two small and weak magnet holder contraptions* that could serve as their own mini pseudo magnetotorquers (for the rod, not the whole thing, see the asterisk). The only problem with this is that the Sat should be spinning very stable at all times, which is a non-problem since it should be regardless (to keep the experiment ok). *The sat itself does not need to be pressurized, only the moss samples. If there's two holes along the spin axis through which passes a rod (to which solar panels, transmitters and what have you are attached ) the connecttion would be like this: two disks on the rod, one in each side of the sat wall. Magnets in these disks and in the sat wall would keep them in place. This construction would be mirrored on the other hole for balance. Then needed, extra electromagnets would be activated to decrease/ increase rotation OF THE ROD. This of course would affect the sat, but since the sat is more massive its own magnetotorquers would easily make up the difference. And since this would be a passive system (only being used to correct small imperfections), both the power usage and risk of failure would be low. Also, the contraptions can be very small and light as we aren't expecting big forces (remember the stability requirement?). Is this description clear or do we really need 3D animation? Because I'd really love if we did, text is hard...

Endersmen, I forgot to reply to your post! I personally think this thread is getting too small to house our multiple discussions, especially with new people joining in without context. That website you were building would fit us like a glove, especially that mini-forum section! Are you still working on that? And MBobrik, ok fair enough. I still think stopping transmitting and spinning back up is exceedingly wasteful of time, electricity, and maneuvering. We should really prioritize having all systems passive as much as possible. That's why I suggested having all nonspinning components along the rotation axis in a structure that remains stationary in relation to the sun (solar panels) and a point on the ground (ground station). It sounds complicated, but I think solving that problem is MUCH better than solving the stop-restart one. If anything else the latter would mess with the gravity experienced by the moss, potentially ruining the usefulness of the whole experiment. Mazon Del could correct me on this, of course.

It's Mazon Del who has access to the moss samples. So I forward the question to him. Can you do it? Like an IR camera filming a small sample of the moss (doesn't need to be fancy at this point) for a few days with the most FPS (one frame picture per hour?) So we can then see if that's overkill and, if it is, speed it up through post-editing to see what's the sweetspot of least FPS with good video for analysis. MBobrik, you seem to have overlooked over my main concerns:

Yeah, my post was apparently swallowed by others in the previous pages... I would think it'd be a good idea for everyone to read all posts they missed, not just the latest page. Definitely for a project like this.

MBobrik, wow. Just wow o_0 . I guess I should take a crash course on aerospace engineering these vacations, I'm sure I'll find one somewhere... (any aerospace engineers out there who can advise me? ) Now, onto the maths: That's unorthodox indeed. What does that even mean? I'm a visual kind of guy, so the lack of 3D models is making this thinking quite a challenge of imagination That sounds awfully complicated to me, and is it really necessary? Our plan is to have the thing spin continuously for the duration of the moss's life. This means there will be an axis of rotation that, thanks to space weightlessness and vacuum, can be ANY axis! So we can get creative with exactly what axis will it be spinning around in order to get our solar panels, antennae, and cameras placed in equally creative positions to work their best. Again, 3D visualization would be very helpful here. Really? I think that's really overkill. According to this artificial gravity calculator we'd only have to increase 20 RPM every "step", assuming we start with 0.1 g and work our way up, as was the experiment iirc. Again there's the discussion if we should add any deployable solar panels / directional transmitters along the rotation axis and have them "counter-rotate" to stay still in relation to the sun or ground station. Weren't the magnetotorquers supposed to double as our heater for thermal control? If so shouldn't they be inside? Now that I think of it, how will we fit them inside a 1L cube? Also, are we going to have them for all 3 axes? or just the main one? Because if it deploys tumbling then we wouldn't be able to correct it, which could prove disastrous. Now to answer bounding star, Sensors: That's a question for Mazon del and his professor Luis, who knowabout the experiment. I personally would guess CO2/O2/sucrose concentrations and maybe pressure just to be safe. Launch at night: The battery should already be made to survive orbital nights, so as long as we can get it up there charged, and maybe leave the sat on sleep mode just the first orbit, we should be safe. Separation: Don't quote me on this, but from what I remember personally it can either be sent to the ISS and launched from there or it can ride along a fairing or outside of the ship as a counterweight of sorts that the gets ejected into space. This last option they don't let the sat be on until after the main rocket has ejected it and is far away. PS: Sorry I can't answer the other posts that came before this one, it's really late where I live *yawns* I'll get to them tomorrow

If KSP had a "part creation" building where you could create your own parts (like stretchy tanks, or was it procedural parts?) the yes, clipping would be wrong. But since we don't have that, and unfortunately SQUAD does not appear to consider this a main gameplay feature as they should >, then it's perfectly fine to get our designs to work like we want them to. Part-clip away, young man! Seriously, part creation...