Horn Brain

You can use bases that are <1. They have the weird property that the value of the digit grows to the right, not to the left. You also have to allow improper values into the digits, though (like allowing (11) (0) in base ten for 110.) This makes the representation non-unique, so another rule could be that you can only use 1 or zero in each place. This will give us some weird properties. An alternative would be introducing new symbols for numbers less than the base (You could have a= 1/6, b= 2/6, c= 3/6, d= 4/6). For your example, base 5/6, we can just calculate the representation of the number in base 6/5 and reflect the digits over the ones place. 1= 1 in all bases, since the ones place is (base)^0. I don't think I care to write what it would be in proper notation. Probably an infinite repeating pattern. 5/6 would be 10 (improper) or something horrible with our new symbols. Easier to just write b+c. 1/5 is 0.a or something horrible with 1's and 0's. 11/6 would be 11. 25/36 would be 100. 55/36 = 25/36 + 5/6 = 110. It's a damned mess.

Do the big fuel tanks really have a LOWER mass ratio than the smaller ones? Oh brother. When are we going to get some fuel tanks that aren't made out of uranium?

Resources would make these useful... I'm just saying...

You will not save any dV by rendezvousing in Kerbin's SoI, or any SoI other than the Sun's. The asteroid is going to be on a hyperbolic flyby trajectory when it enters Kerbin's SoI, probably with a very high periapsis. That means that to rendezvous with it you'll have to do a big burn to get your apoapsis out near the asteroid's path, then accelerate from basically a dead stop at the top of your highly-elliptic orbit all the way up to the speed of the asteroid, which will be some fraction of Kerbin's orbital velocity around the Sun, so we're looking at around 1 or 2 km/s, maybe more if the asteroid has a very different orbit from Kerbin's. THEN you have to dock and slow the rock down to below escape velocity, which at the high periapsis you'll be at will be almost the entire velocity of the asteroid, so double whatever that big burn you just did to rendezvous, but this time you're hauling hundreds of tons of space rock. Best case with this strategy: About 2 km/s without the asteroid, and about 1 km/s with the asteroid. Muuuuuuch more efficient is (surprise!) the NASA strategy: Do the escape burn at a convenient time to get yourself a cheap rendezvous with the asteroid several Kerbin years in advance of the close encounter, perform a small dV adjustment to cause the asteroid to fly by Kerbin with as low a periapsis as you can get, then either use a burn at periapsis, a munar flyby, or a combination of the two to bleed off the extra speed and capture the asteroid. Once it's caught, then it becomes relatively straightforward to send fuel up to the rock if you now need to make a big correction of its orbit. Best case with this strategy: about 1 to 1.5 km/s without the asteroid, a few hundred m/s or less with the asteroid.

You really can't do astrophotography with that budget. Get some binoculars for now. I have a nice pair and they will let you see all kinds of wondrous things that you couldn't make out in the sky before. You can see Jupiter's moons, the crescent of Venus, nebulae, etc. Not to mention the multitudes of stars that are just a bit too dim to see with the naked eye. For good astrophotographs, you need a camera mount and a telescope that can track your target automatically to account for Earth's rotation, otherwise you can only get grainy, dim snapshots of most things. Basically, you can spend your money and get a great pair of binoculars and be pleased, or you can buy the cheapest possible tools for doing astrophotography and get crap for your money. Either that or wait and save up for enough to do it right.

Well he definitely wouldn't be able to get to orbit. That would require being able to gain about 2 km/s of speed from flapping (not to mention he would have to bring along a rocket motor to circularize at apoapsis). That requires the same kind of propulsive power as it would on Earth (gravity not important here). As for how long he could fly, the method they were analyzing in the article was with a wingsuit. These are gliders with very bad L/D ratios. They can't be flapped for extra velocity. I would imagine he could fly a few tens of meters, then run a few steps and jump again. What people are usually talking about when they say people could fly on Titan without engines is with a bird-like mechanical wing that they flap themselves with their arms. I imagine the calculation goes something like: "how much power does a bird need to keep up airspeed by flapping? Scale this to the weight, required speed, and density of flying in Titan's atmosphere to get the power required by a person at Titan. How much power can a person supply for a sustained length of time using their chest and arm muscles? Is it enough?" So to really fly on Titan we need to build flapping wings.

These things can indeed be done by 2018 (the beginning of the EML2 station, specifically). They just need to be funded and directed. That's what's exciting about Congress being interested in this. If they want to fund it, we can absolutely do the flyby. The SLS actually becomes rather economical if we fly it once or twice a year.

I think the flyby to Mars and Venus is a good opportunity to test interplanetary travel. We get a free-return, so we don't have to do much maneuvering, but we can still test the reliability of various components that would be needed to, say, do an orbital insertion. It would be like Apollo 10 : Apollo 11 :: Mars flyby free return : Mars orbital mission. BUT It makes no sense to do this mission as a one-off publicity stunt. It has to be a part of a concerted effort to develop the ability to send humans to other worlds, eventually permanently. If this accelerates the SLS program and we get a EML2 space station out of it, then I would be for it, because it would be a part of a clear direction to establish a presence outside of LEO, learn how to live for long periods without an immediate escape opportunity constantly available, and develop hardware for living in space and getting back and forth from the surface of another world. My notional plan given this opportunity: 2017: Test of Orion and SLS. There is a push to make this manned, but I don't think it's necessary given the accelerated schedule. 2018-2020: As many SLS flights as needed to establish and operate the EML2 station. Could be one or two if the wet workshop model is used (but I would like a module with windows -- That's important). Testing life support and other driving factors for the Mars flyby should be done early. Infrastructure for refueling and/or resource processing could also be a goal of testing. 2021: Mars and Venus flyby. Ultimate proof that we can send humans beyond the Earth's domain and bring them back safely. Pictures of Mars and Venus through the windows get everyone really excited. 2022 and beyond: Shift focus back to the Moon, developing landing technology and testing surface EVA tech: New suits, rovers, etc. We should establish a permanent base wherever is most convenient (I would argue for the poles because of illumination concerns as well as resource opportunities). This will also give us another data point on the effects of other-than-one-g gravity on humans in the long term. (If 1/6 g is enough or nearly enough, then 1/3 will be great!). If resource processing testing is done at EML2, another interesting possibility would be to do the Asteroid Redirect Mission and park the asteroid at EML2 with the station for continued access. We could use our pet asteroid to test NEA/Martian moon mission technology without leaving cislunar space. It's important the the 2022+ lunar operations are always clearly defined as a testbed for reaching further. We should put it in the name of the program. Designs should focus on using as much hardware that is compatible with a Mars mission as possible.

Nice try, Ayatollah.

Hindsight. Everything could have been prevented if we had just known that it would happen as it did. We don't know what's going to happen. We are often surprised by things happening in ways that we never anticipated. We try to avoid these things where possible. We are not perfect. All of the arguing in here is silly.

I think your vehicle is already way faster than mine. From what I can tell by watching the last few runs, it all comes down to three things: Takeoff at the last possible second to delay MET start. Turn immediately and cut as close to the buildings on the first loop as possible. Survive the bridge run! That's all! Land quickly. It took me 8 seconds after wheels down to stop because I didn't cut the throttle. I also hit the brakes too soon again when turning to land. I think there is a lot of time left on the course, but it will take some luck, mostly on landing and the bridge run. I just did a few more runs and I couldn't get through the bridge because I was trying to push it. The hardest part for me is building something that's not too twitchy to fly fast, but still responsive when going under the bridge.

It's cool to look at the old runs and see how much we've progressed. One easy metric is checking MET when you first pass the tracking station. I think we've cut that split by over half.

What about the big white radial engines?

Since we have utterly dispensed with going around the west end of the runway, I hope it's ok if I buzz the tower. 0:53, same vehicle. If I would have gotten off the throttle earlier I could have probably done in the 40's, but darn that spool-down time! This is fun. I hope you beat me again! (PS, if I need to do it again and go past the runway, that's fine. I think the tower might be more fun to turn around, though. That shot was so cool!)

Wow, bravo. I think I'm going to need another engine. Dat acceleration. Also, I'm going to have to get the joystick out.

^Hahahahahaahah I love the ion attempt. You should allow a separate category for him. It's too cool to be last. Also, I did it again with airbrakes instead of the parachutes (B9 mod) to much effect. (1:11) I was way too quick on the brakes at the end. I think maybe 1 minute is possible! Call it: the Gnat Mk. II

So in the description it says you have to fly around the west end of the runway, but the drawing (and some attempts) don't do that, they just indicate flying behind the buildings and crossing over the runway. Can we cut over the west end of the runway? If so, I'm going to try again.

So it looks like SAFE is the lightest nuclear power plant (it was designed for space, after all) at ~500 kg / 100 kWe. That means it's about 2 tons for 400 kWe just like the solar farm. It would be more compact, though. This energy problem is hard!

I guess I should say I call my vehicle the Gnat.

Done. 1:37. Forgive my horrible lag. I'm not used to recording yet so I think I may have done a pretty bad job.

One other thing: if we count the MET as the official time, then you can cheat by waiting to take off until the end of the runway since the MET doesn't start until you're wheels up. It could account for several seconds difference, especially if we are comparing a VTOL and an HTOL vehicle.

Can anyone link me to the easiest to set up and use video recorder (that isn't my smartphone)? I got it in 1:42 without cutting corners and I can do better. Stock aero.

To get power requirement (roughly) multiply the thrust (in Newtons) by the Isp by 9.81 m/s/s. That puts you in the ballpark. Then you divide by the efficiency (about 60% for VASIMR, I think) and that gives you the proper power. The thrust and Isp numbers are often fudged, though, since VASIMR means VARIABLE SPECIFIC IMPULSE Magnetoplasma Rocket. So you have a peak Isp (with low thrust) and a peak thrust (with low Isp). Usually they will quote both at the peak values to make the thing sound better. The efficiency is also a function of the mode that the engine is operating in, so there is a lot of variation. Usually, the power requirement is the best place to start. Take the power requirement, multiply by the efficiency and divide by 9.81 m/s/s, then divide by peak thrust to get Isp at peak thrust, or divide by peak Isp to get thrust at peak Isp. These will give you your two modes of operation (assuming equal efficiency). There is another problem with VASIMR, though that they haven't completely nailed down: the plasma may not detach from the magnetic field of the rocket, causing it to loop around and hit the spacecraft. It's not really dangerous, I don't think, but it does cost you thrust. That means that the efficiency that is quoted is likely an overestimate. This effect is not easy to pin down, though. So in the OP, we have an example of a 6000 s Isp, 4 N thrust engine. If we do the math with 60% efficiency, we see that the power requirement for that would be 400 kW. That's twice as much as the VASIMR they are planning to fly on the space station in 2015. Solar panel power production mass is quoted (by the VASIMR people) as between 2 and 7 kg/kW. That means we're looking at ~2 tons of (high tech, never before flown) solar arrays, plus heat rejection systems (radiators), plus the VASIMR itself, plus tankage. If we fly that vehicle with no payload, we are looking at a burnout acceleration (acceleration on the last drop of fuel) of about 3.6 m/s per HOUR (give or take a factor of two). or about 0.001 g. That means if we had a vehicle accelerating at that rate from LEO starting today, it would take it until between July and October to escape the Earth's gravity and build up speed for an interplanetary transfer (delta-v requirement for these low thrust, spiral escapes is much higher, like 10-20 km/s, than for impulsive burns in LEO). We really need some better power options.

I was trying to figure out earlier if we could define new Kerbal units of mass and length that would fix the problems we see (time I held constant because unless we do everything in fast or slow motion a second is obviously the same in the kerbal universe as in ours). I don't think I was able to find enough equations that related back to real life to fix the units, though.

It's kind of a hard problem. Right now, SAS works by trying to point the active "command from here" part at a set attitude (determined by when you turn on SAS, or when it leaves damping mode). If you ship is rigid, that's fine, because everything is rotating the same way. When your ship is wobbly, like a big stack of docked modules, it doesn't account for the extra inertia and momentum of the other parts properly, so the other parts act like big, floppy arms that drag your command vessel's attitude around in ways that the SAS doesn't anticipate. The SAS then starts correcting in the opposite direction, but sometimes this causes the floppy arms to gain energy because of resonance. The best solution (it seems to me) would be to have SAS work individually from each part that applies torque to try to keep it pointing in the right direction. This would make any torque modules on the floppy arms work to damp out the rotation in the arms, and by tuning the SAS controller properly, you can ensure that the structural rigidity of the vessel will dominate in the end to keep everything pointed straight. This is not going to happen anytime soon, but in that case you would probably just want to distribute torque modules in proportion to the size and mass (rotational inertia) of the various parts of your spacecraft. In the current situation, I think that we can do some rigid body dynamics to determine the best strategy to place torque modules. I'm working on it a little bit, but it is pretty complicated, and what's worse is we're not really guaranteed that we can help the wobbles by placing the torque modules properly. The wobbles may be an inherent consequence of the simplistic control scheme in use.