satnet

In this case voltage, current, and resistance vary significantly with time and you also have to worry about impedance since we're dealing with an AC circuit with reactive components (see https://en.wikipedia.org/wiki/Ohm%27s_law#Reactive_circuits_with_time-varying_signals). I'm pretty sure the voltage will jump as high as it is going to get when you disconnect that switch. While it is superconducting you won't lose energy to resistance (at least through the inductor), but that will change when you quench (lots of energy dissipated as heat). That's assuming your capacitor doesn't burn out the moment you disconnect your supply. You can get the conditions to power fusion using inductors and capacitors to boost voltage since Farnsworth-Hirsch fusors commonly use high voltage flyback transformers (with ordinary inductors) to drive them. Unfortunately high voltage fusors generally don't reach an energy positive point. They are useful as neutron sources and research, but not useful for doing net positive work. The electric and magnetic fields of the plasma would change very quickly with time. This is one of the major hurdles of fusion, once you get it started the plasma generates its own electromagnetic fields that counter the beautifully orchestrated EM fields you used to get them to fuse in the first place.

Essentially you're talking about a boost converter, using the inductor as both the energy storage and the switching element. Using magnetic quench instead of a transistor for the switch is interesting, but probably not terribly efficient. Generally a boost converter is switched at a very high rate to minimize losses, which wouldn't be practical with magnetic quench since the time to re-cool the superconductor would be very long.

This type of station probably wouldn't be for satellite refueling. It would be for launcher fueling. For example you launch into a rendezvous orbit with minimal fuel left, dock, refuel and then continue to GEO, Lunar, or Mars orbit. This exponentially decreases the size of your rocket (or exponentially increases your payload capacity). If you did want satellite refueling, NASA has researched refueling satellites before and they did operate on the assumption that they wouldn't be provisioned for refueling which was proven to work on an ISS mission (Robotic Refueling Mission), though it wasn't a real satellite just a representative example. Chances are you wouldn't have the satellite come to you, but instead send out a tug with just as much fuel as you need to resupply it (see Space Infrastructure Servicing). Methane will be used by Vulcan's first stage (ULA), New Glenn's first stage (Blue Origin), and of course Starship (SpaceX). However, you do have a point since only Starship's orbital stage is methane so only it could benefit directly from methane in orbit. Having said that generating hydrogen from methane is relatively easy (pretty much all commercial hydrogen is produced this way anyway). You would need to liquefy it, which is difficult, but if you have the lead time, power, and cooling systems entirely doable. ULA's ACES upper stage is planned to have refueling provisions which would be able to benefit from a hydrolox refueling station. A fuel depot can afford the extra mass for active cooling, because they don't need to worry about their dry mass/wet mass ratio to the extent a spacecraft maximizing delta-v needs to. The real problem a fuel depot needs to overcome is economic. They need to have enough clients to justify the large up front cost and ongoing overhead. This means either it needs to be cheap to launch and operate or you need a high volume. If we go to the moon and stay for a prolonged period (or even just have an active tourist industry) you probably have the volume to justify it, but until then there probably isn't enough GEO, Lunar, Mars orbit launch volume to make this economically viable (ignoring the case where it is heavily subsidized, which it probably could be).

Definitely a dubious prospect. The engineering challenges are a huge hurdle and even after you solve them, the things it could launch force them into a pretty small niche. It does have one advantage over a lot of other non-rocket space launch systems: you can conceivably change your launch azimuth. A gun or linear accelerator approach would almost certainly be a fixed installation, but this one could change the release point or even rotate the whole launch system into the proper orientation (since it must be movable). Still like most non-rocket space launch systems it probably makes a lot more sense on an airless moon where you don't have an atmosphere in the way and you can scale down the system to something you can practically build because the orbital velocities are lower. Scott Manley did a video on them about a year ago. No huge surprise that a lot of the potential problems mentioned earlier in the thread were brought up, but he added few more and threw in a little bit of interesting history relevant to the topic.

That code makes more sense, but you're still only calculating heat transfer for one neighbor. You have a constant heat source at x=0, which you have effectively modeled by starting at x=1 in your loop (once you have an x-1 neighbor calculation the x=1 cells will draw from the x=0 cells, but the x=0 cells will never change their value making them a constant source). You are effectively giving y=0 a constant temperature by starting at y=1, but y=0 is still participating in heat flow so it is not an insulator. I would assume you would calculate from y=0 to y=99 and use boundary checks to just not calculate heat flow in the out of bounds direction to simulate an insulator rather than have a row of constant temperature cells. When printing a double you should use %f or %e. For this I would use %e (scientific notation format) probably with a precision specifier (i.e. %.3e, which will give you a number with 3 numbers after the decimal like 1.234e+1). You might find %f more readable in early stages, though since it generally won't use an exponent. The %d specifier is for integers.

The Achilles heel of most of these air breathing engines (ram/scram jets) has been that their operating range it too narrow to go from 0 to orbital or even a significant fraction (by everyday flight standards they cover a huge range, but space flight requires 0 to 7.7 km/s which is a great deal larger). Within their operating range they have a higher overall propulsive efficiency, but to cover the whole range you need multiple engine types which means more mass for engines and less for payload often to the point of being sub-orbital. There are proposed dual-mode scram jets that can work at lower speeds, though I don't think they've been designed or demonstrated and I think they just get into the ram jet territory not down to subsonic ranges where turbofans dominate. Nuclear rockets tend to have a low thrust to weight ratio which usually means they are limited in the design to space or late stage sub-orbital where you need delta-V more than thrust. Of course this is also a problem for scram jets so you now have to low thrust to weight ratio engines which is a real problem. You might be able to use the nuclear reactor as the heat source for a dual-mode scram jet, which would at least help keep the weight down assuming the heat transfer mechanism isn't as heavy as the fuel injection system (and it could very well be as heavy or heavier negating the benefit). Of course as long as we're talking fission and not fusion, as @ARS pointed out you have the environmental and shielding issues to deal with. Isaac Arthur just did an episode on space planes and talks about ram, scram jets and a few other things. He has other episodes on nuclear rockets, though it has been long enough I don't recall if any would be relevant.

Unless your instructor gave you an existing library it is up to you to create the model. I don't know quite enough thermodynamics to know all the properties you'll need to track (temperature and density are probably a given, but I doubt that is all), but in general you'll need something to store the properties of each cell, in this case probably a C struct. If you are using a simple grid a 2d array of these structs would probably make sense where each index into the array represents your spatial step unit in either the x or y dimension. This is a simple model, but it sounds like your professor gave you a problem where a simple model is sufficient. Then as @Cunjo Carl indicated for every temporal step you update the cells in your array representing your new model using you old model array, display it, swap it into your old model array, then start again.

You also have a huge change in center of mass while trying to maintain the same center of thrust. Traditional rockets only shift it vertically so the thrust vector still passes through the center of mass. You could fire the engines on both craft, but that means the X-33 has less fuel post separation. All of the problems are probably solvable, but you need to answer the question: in the face of these challenges how is this better than BFR or something like it?

Actually Arduino uses C/C++, but has a pre-processor that auto-generates some of the things you normally need to do by hand (i.e. generating header files). It will gladly accept ordinary C/C++ in addition to the simplified version that only works with this pre-processor. There are a couple of projects that use Arduino's in quadcopters, which means that there is code out there for interfacing with sensors and making real-time adjustments to maintain stable flight. Unfortunately I checked my old links and they seem to be defunct. Having said that that I'm sure there are a few projects covered on Hackaday that would help you out. One thing I'll point out is before you do this is check all relevant laws (nation, state/province, city). Depending on where you live, building a fully guided rocket may put you on the wrong end of some serious arms control or flight regulations. Arduino is a pretty good choice. It was designed for people who want to do things with electronics, but aren't necessarily wanting to become software or electrical engineers, so it tries to make things as simple as possible. If you really want to use python (or any other language that isn't tied to a specific platform) you might want to look into a Rasberry Pi or a BeagleBone. They are both small boards designed to interface with hardware and run linux (which means full support for python, c, c++, or just about any other language) though they tend to lean towards one language or another. I haven't used a Rasberry PI, but I believe it has good python support. I have an old beaglebone I haven't touched in a few years. Oddly they use javascript for their preferred language, but if I recall correctly you can interface with most things via the linux filesystem, so any language should work, though performance may suffer.

You could probably design a system that was safe. For fusion the exhaust isn't really a problem being mostly helium, though some reactions do produce radioactive atoms like tritium. You probably don't want a fusion torch drive because of the electromagnetic radiation (particularly UV and X-rays), but one where the reaction is contained should be something that can be safe (assuming you can afford the weight of a reasonable amount of shielding). All of this assumes of course that net-positive fusion can be miniaturized once we work out how to achieve it. Tokamak's that might achieve net-positive fusion are building sized (ITER), so that design is probably out. There are reactor designs that are smaller like the Lockheed Martin Compact Fusion Reactor, though I'm a little dubious being such a far departure from existing efforts. You do have the problem of neutron activation of the reactor material itself, though most proponents consider that manageable with the right materials. Assuming you aren't using tritium or another naturally radioactive fuel you don't have the problem of raining radioactive fallout in the case of a RUD event. The challenges for a fusion based in atmosphere rocket are going to be public perception and getting the size/weight down to the point where it is practical. Even nuclear fission can avoid a radioactive exhaust with the right design. The problem there is you if the rocket explodes you now have an uncontrolled nuclear material falling from the sky. You also can't really turn it off (just slow it down) which means you need to be cooling it all the time. This is another advantage of fusion since it can be shut down when not in use.

They might use a mission designation instead of the ship name (i.e. CRS-42 instead of Heart of Gold) during a mayday. On the other hand I skimmed some of the Apollo 10 transcripts and they seemed to handle ships named Snoopy and Charlie Brown without too much drama, and they did use them as handles during radio transmissions (along with 10, Apollo 10, and Snoop). This did lead to a rule change at NASA, but apparently Apollo 16 called their command module Casper anyway. It isn't anything new, though SpaceX's situation does give them the freedom to use as much whimsy as they like (or at least more than most).

As part of the tests they ran on snoopy the docking port was ejected, so it wouldn't be an option.

An SSTO would have an altitude compensating nozzle of some kind. You are basically trying to match pressures between the exhaust and the ambient atmosphere, which is changing as you ascend. As the outside pressure drops the ideal nozzle size grows until it is infinite in a pure vacuum (in the real world we must settle for something less than infinite, fortunately the point of diminishing returns fits within a interstage). A mechanically adjusting "jet" style nozzle which allowed it to expand while in a vacuum would be an option, though generally for the reasons @Dundral mk2 mentioned the approach is usually a different geometry rocket that doesn't require significant mechanical adjustment. If you could afford the weight, had materials that could withstand the stress, and your SSTO spent a non-trivial time in atmosphere it might make some sense to have a mechanically adjustable nozzle (though probably not). It would probably be much longer and expand much wider than anything you would see on a jet, but would visually resemble it. Basically with a little hand-waving you could have a nozzle like that, but the chances of that ever being what we see in the real world are slim. Scott Manley's video on nozzles is relevant (and as usual excellent):

They could land it on a barge in the Atlantic and ship it back. You still need to move it by sea, but you can avoid the canal, though at an average of US$54,000 for an entire ship passing through the canal they might just add that to the launch cost and still be ahead of their competition by a fair margin (assuming it delivers an appreciable reduction in launch costs). They could also land it on the west coast of Africa and then ship it back (which might be cheaper than going through Panama, but obviously not faster). You could also land on west Africa, refuel, then do a sub-orbital hop back to Florida, which would be very expensive, but extremely fast and a good demonstration of rapid reuse. Since Starship will be returning with at least some dV they can boost back towards land after going out to sea. If they start re-entry over land, but at a point where even a post-breakup ballistic trajectory would take the debris out to sea they might convince NASA and the FAA to allow it, which would minimize the boost back dV. If they aggressively use aerodynamic drag and whatever fuel they can afford to slow down they might be able to maintain a trajectory that ensured the Starship would land in the ocean without going too far away from the landing zone then fly back towards the landing zone and trajectory similar to a Falcon 9. My best guess is that they'll go with the US west coast landing and trip through the canal until either launch cadence or competition forces them to look into one of the other options.

I did a little digging and it looks like the founders are from Generation Orbit which worked on the X-60A, an air launched rocket for hypersonic research. Giving them the benefit of the doubt they may simply underestimate how hard it will be to take that experience and turn it into something that really can be used for passengers (my cynicism says, they probably have some idea). To be fair Boeing thought they could do the same thing (see the video), though they did at least think they could fly domestic flights when they started and they were only going for about mach 3.

This might be a good application for holographic storage assuming it could be developed beyond proof of concept. For this application we don't need read-write capability, so a dense write-one-read-many approach would work. Theoretically you can get 1 bit per cube of the laser's wavelength, which means ~30 TB/cm3 with a fluorine excimer laser (157 nm). If we use a blu-ray laser (320 nm) it would have a theoretical maximum of ~3.5 TB/cm3. You're looking at somewhere between 0.035 m3 and 0.3 m3 for an exabyte assuming we can get close to the theoretical limit (I would assume something close to 0.1 m3 accounting for error-correction, redundancy, etc.). Obviously this wouldn't beat single atom storage for density, but it could probably handle the occasional cosmic ray. You probably would also want an archive of knowledge and teaching materials, particularly for skills that would be hard to maintain on a generation ship (assuming that is what we're talking about). For example geology would be a little hard to maintain on a ship.

You are confusing the number of states with the number of bits. A color depth of 16,777,216 means that the pixel can be in one of 224 states (which happens to be the first power of 2 which can represent more colors than the human eye can distinguish in most cases). This is only 24-bits of information because it can't be in an arbitrary combination of those 16 million+ states simultaneously, it can be in only one of them. Put another way you translated 224 information into 16,777,2161 information, but mistakenly took this to mean you had 216,777,216 information. This confusion is inflating your numbers by quite a lot. Also because you are going from digital to analog and back to digital you need to add in some error correction to account for the fact that both the displaying and reading of these pixels will be imperfect. Using more than one state or level to represent more than 1 binary bit of data per unit is not uncommon in computer hardware, though it tends to be used selectively where the increased density per unit outweighs the higher chance of one state being so close to another state that it is read as the wrong one. One example is multi-level cell solid state drives which use different charge levels to represent more data per cell (2, 3, and 4 bit per cell variants exist). You'll also see it used in data transmission, particularly wireless communications. Quantum computing really is its own thing and can't be modeled with classical computers. They are probability based and work with gates that shift the probabilities in various ways, but ultimately don't guarantee a specific outcome. For specific problems they have a high chance at arriving at the correct answer, but you need to either re-run the calculation several times or confirm it with a classical computer to know if it is the right answer. They excel in cases where the search space is vast and simply cannot be brute forced in a practical period of time.

The ports available for actually docking of spacecraft are: 4 Russian SSVP Docking Ports 1 International Docking Adapter - IDA/NDS/IDSS (Another one is scheduled to launch in July, and IDA-1 was lost with CRS-7) 1 Pressurized Mating Adapter - PMA (Actually there are 3, but 2 have things permanently docked to them) 2 Common Berthing Mechanism - CBM The US modules are joined by using CBMs. The US and Russian sections are joined by a PMA. The Russian modules are joined by a variant of the SSVP. The IDA adapter is used by commercial crew (Crew Dragon and Starliner) The SSVP is used by Soyuz and Progress. The PMA was used by the Shuttle and they are being converted to IDA (except PMA-1 which links the US and Russian sections). The CBM is used by Dragon-1, Cygnus, H-II Transfer Vehicle

Based on DuPont's technical report it actually handles both extreme heat and cold very well. According to their site it does see some applications in space, though it isn't a long list. It is susceptible to degradation under UV light and according to the Texas space grant consortium link provided in the original post it tends to sublimate in the vacuum of space. It also tends to absorb humidity and without sealant would let it evaporate into space. It is worth pointing out that Bigelow's inflatable habitats are based on Vectran, which is very similar to Kevlar (it is actually twice as strong). There probably are more than a few applications where it would be a good fit, but it doesn't seem to have found its niche in space just yet.

Elon basically said this a year ago in a reddit AMA here. Granted that was the previous BFR design, but I doubt they've changed this. He did mention a cryocooler was an option down the road. I recalled there was a section on space storable propellants in Ignition, the most relevant part is this: "After all, the hard vacuum of space is a pretty good insulator, and when you have, in effect, a Dewar flask the size of the universe available, you can store a low-boiling liquid a long time. An arbitrary upper limit (—150°) was set for the boiling point of a space-storable, but the custom is to stretch this limit to include the propellant you want to sell. OF2, boiling at —144.8° is considered a space storable, but if you want to call its ideal partner, methane, CH4, boiling at—161.5° one too, nobody is going to complain too loudly." Temperatures are in Celsius and this is from a time where OF2 is something people considered flying (wouldn't bet on it today). This does make things interesting though because LOX has a boiling point of -182.9 degrees, so we need to stretch the definition of space storable a little further.

I would recommend Saturn Run. I consider The Martian superior, but it also treads the line between being hard sci-fi and writing a good story reasonably well. It does have a few elements that are a bit more fantastic than The Martian but at least most of the human tech is a reasonable extrapolation of things we either have or have designs for. Basically they discover an alien device at Saturn and there is a race to get to it. The main sources of drama are issues from the quickly cobbled together mission and some political intrigue. I would also recommend Aurora by Kim Stanley Robinson. It is about a colony ship sent from Earth generations ago, its last years before reaching the new world, the starting of the colony, and what happens after. This is the same author who wrote the Mars trilogy, but I prefer this since it is self contained and spends a little more time exploring the technology. If you haven't read any of his works before I will forewarn you that he spends a fair amount of time on the politics/social dynamics that arise in these situations. It is a little more pessimistic in the end than I would have liked, but it was an enjoyable read and the science seems reasonable. From the classical side, Arthur C. Clarke's Rendezvous with Rama has aged reasonably well. It is about a large alien spacecraft detected moving towards the solar system and the crew that investigates it. The spacecraft is a cylinder with spin gravity and deals with some of the implications of that environment and the technology needed for such a long voyage. There are two sequels, but they are collaborations with another author and have a very different feel.

In addition to the effects in flight there are the effects on transport. The reason a Falcon 9 is 3.7 meters wide is because that is the widest they could make it and transport it by road. Having said that, Blue Origin is going with wider rockets (7 meters). I don't know how they plan to transport it from the assembly plant to the launch site, though transport by sea seems probable. SpaceX is building the BFR (9 meters) at a port so that it can be transported by sea. Basically the trend seems to agree with you, but it creates some complications in terms of locating assembly facilities and transporting the assembled rocket.

I would also like to add Practical Engineering's video. It doesn't go quite as deep into the subject as Veritasium, but he actually builds one himself. This is why I always preferred the Kibble balance approach. Basically it can be replicated by anyone with reasonable effort (though for extreme precision/accuracy you still need the resources of a nation-state or at least a large corporation).

Balance is definitely at the top of the list, power is another one, and anything with living creatures in it has a certain unpredictability to it. Though it is worth noting that the ISS isn't a closed loop and doesn't pretend to be. There are more than a few steps where it generates something unusable and they just vent it. Obviously this means some resupply, but it save multiple tons of water and oxygen that would otherwise be required. Basically at this point we can extend out our expendables by quite a bit, but we're a long way from a closed loop. If we're talking about a small research group that will ultimately return extending out expendables is probably good enough for a Mars mission. For a Mars colony you would want something a lot closer to closed. We just aren't there yet, though there is research in that direction. The Mars 2020 rover for example has a CO2 to O2 generator it is testing. I think it would take quite a bit of effort to reach a system that is closed enough and reliable enough to support a colony on Mars (a Moon colony could have some more margin since resupply from Earth is still feasible). Room - The Space Journal had an article recently about using algae that was pretty good (sorry, no free link as far as I know). In the short term it is probably a good avenue since (at least according to the article): 1. Algae are more efficient photosynthesizers than multi-cellular plants. 2. They can generate biomass very quickly. 3. They don't have a lot of dependencies in their life cycle. 4. They are single celled and don't really care about microgravity. The downside is that while we can eat it, to really get nutrition out of it you humans need help from supplemental enzymes. Also they don't exactly meet most people culinary expectations. Still if they were providing oxygen and supplementing pre-packaged food, algae might be a good interim step towards a closed loop.

The short answer is that it isn't exactly 100 km, but for reasonable values in that equation it is so close to 100 km most people accept that (there is still some debate). It does vary a bit based on atmospheric conditions also. This is one of those values that isn't completely arbitrary, but there are inherent assumptions and variability in any value you pick so we went with a nice round number which is very close to what you would get with reasonable assumptions and variations. Pulling from wikipedia: L is the lift force ρ is the air density v is the aircraft's speed relative to the air S is the aircraft's wing area, CL is the lift coefficient.[7]