Jump to content

blakemw

Members
  • Posts

    191
  • Joined

  • Last visited

Reputation

110 Excellent

Recent Profile Visitors

1,951 profile views
  1. The quoted value for 90Sr beta emissions (which is higher energy than some other emitters) I found was 4 mm of aluminium which is much thicker than a spacesuit or the walls of something like the apollo lander. Of course the RTG thermocouples should also attenuate the radiation some. But basically no, a spacesuit or the walls of a light capsule won't block high energy beta radiation.
  2. I had to actually, but actually in Kerbalism it appears to be based on90Sr because it has a halflife of 28.8 y, hence it emits beta radiation, which certainly has the penetrating power to get through the spacesuit of a Kerbal who disrespects the square cube law and decides to hug the RTG.
  3. I was wondering how best to shield ships and bases from CMEs (especially bases, since they are harder to orientate to the sun), so did some testing. The first thing, is that it appears a raycast is done from the center of the habitat to the sun, and anything intersected counts as shielding: this means that a single surface mounted small battery can shield the habitat if it happens to be on that line between the sun and the center of the habitat. The next thing: is that it seems putting anything in between the sun and the habitat module reduces radiation by a lot: a flag reduced radiation by about 74%, a solar panel reduced radiation by about 91%, a structural panel reduced radiation by 95%, a Cargo Bay reduced radiation by 99.4%. Shielding layers stack well. Putting TWO flags between the habitat and the sun, reduced radiation by 86%, two solar panels reduced radiation by 99%. I tested "standoff", whether moving the shielding object further from the ship improves shielding. It does, but by very very little. For example in a particular solar storm, a flag on the surface of the habitat reduced radiation to 0.444 rad/h, the same flag at the maximum extension of a 1P4 telescoping cylinder, reduced radiation to 0.441 rad/h. So there is an effect, but it's absolutely negligible. The surface attached part can be inside the habitat, that is fine. However if the raycast starts INSIDE a part, that part does not contribute to shielding: embedding a habitat inside a larger part such as a fuel tank does not help. However if the larger part has internal walls such as a structural tube or a service bay then it does work, the principle is probably that the raycast has to hit a wall you can't see through: essentially if you can see the sun, the sun's radiation can see you. Also it doesn't appear to check other vehicles, a Kerbal on EVA can't shelter in the shadow of a ship. The upshot: higher density objects are more effective for radiation shielding, but they don't need to be very high density, solar panels work well, flags are a bit flimsy but significantly better than nothing. Stacking layers of shielding is probably far more effective than heavier shielding. Enclosing the habitat inside an object with inner walls like a cargo bay is useful. Standoff doesn't literally do nothing but is practically worthless. A habitat in a base can be shielded simply by blanketing it in surface attached parts or placing it inside a cargo bay or service bay. If you don't want to know exploits don't read this next part: This is the measured in-game behaviour. It might not be the intended behaviour. RTGs: They produce essentially no radiation. Technically they do, but a Kerbal has to snuggle up against one to get an increased dose. They do nothing like 1m away. Don't clip one to the center of a habitat, don't put one on the wall of a very small habitat. Otherwise they do nothing and no shielding strategy is required. I don't have a fission reactor mod installed atm to test them. LV-N "Nerv": They produce even less radiation than an RTG which is saying something, and also produce no additional radiation when firing. A Kerbal on EVA has to snuggle up against one to get even half the dose of an RTG. Don't attach one directly to the bottom of an Mk1 lander can or something like that and otherwise they are irrelevant. I don't have any nuclear engine mod installed atm.
  4. Hey I'm a globehead and my one complaint about AA's Fly-By-Wire mode is that it doesn't pitch the nose down to account for the curvature of a planet. Is there any way that AA can do this amoung it's multitude of bewildering settings? I'm aware that AA constant altitude can do this, but the context I want it for is controlled ascend/descent not merely maintaining a certain altitude.
  5. There's actually a marginally good reason to throttle back with certain engines in certain contexts. First is core-throttling on Falcon Heavy style rockets, that is you don't throttle everything, just the core. This give you more deltav and would even do so on a vacuum world because by saving fuel in the core for after the boosters are decoupled, that fuel goes only to accelerating the mass of the core+payload, and not boosters+core+payload. If you're using a rocket with boosters and aren't using crossfeed (which isn't even a possibility if the boosters are SRBs), then it is usually an improvement to keep the TWR at about 2.0, of course you could also bring more fuel but that costs more and you could technically probably use smaller engines, but there aren't a ton of engine choices available. (like if you could custom tailor every aspect of the engines you're using, this strategy probably wouldn't be employed. But it's like SpaceX, they want to make a Falcon Heavy using "off-the-shelf" Falcon 9 boosters, without designing entirely new boosters and core, the way to maximize performance is to heavily throttle the core soon after liftoff, until the boosters have detached) The second reason you might throttle is ISP: some launch engines, especially Swivel, get a lot more thrust per unit of fuel once out of the lower atmosphere (practically, 10000m is as good as a vacuum for ISP purposes), this often has a much more significant impact on efficiency than aerodynamic drag. Now, of course, you do need to climb and maintain a good enough TWR, most likely this will only be useful when used in conjunction with the first factor I mentioned: If you're using something like a Swivel core with Thumber SRBs then throttling back the swivel means not only are you saving fuel for when it no longer needs to accelerate the mass of the SRBs, you also get more thrust out of it thanks to a higher ISP due to altitude.
  6. I think the key is understanding lift. Lift is very potent at transforming vertical velocity ("falling") into horizontal velocity ("distance"). Even with the stock aerodynamics, a good spaceplane (one which needs wings to fly, not one with enough power to do it without wings) can glide about 1/4 of the way around Kerbin further than the ballistic prediction would indicate (and that's the simple suborbital prediction, not even the ballistic-with-drag prediction of a poorly configured Trajectories). The FAR aerodynamics are more "slippery" than stock and higher lift/drag ratios are possible, meaning gliding even further. When landing spaceplanes you need to aim to undershoot by A LOT because the plane is going to glide around the world - that is assuming you are pitching up a bit to slow descent and ease heating. Trajectories mod is so useful for modeling this but it's vital to tell it you'll be gaining lift (and nice thing is, you can adjust the angle of attack you want it to use for its prediction and see the projected trajectory change in response). If you've never seen it I super highly recommend this video about how the Apollo capsule used lift to narrow down, though mainly just for inspiration, the main take-home is that it's damn hard, you descend too fast and burn up/get destroyed, or you overshoot by half a world (and it's computer stuff, not "seat of the pants" stuff):
  7. Better yet install the Mod "Better Burn Time", fixes that issue and adds some other minor utility.
  8. I'm sorry but this advice is almost completely invalid when using FAR. The FAR atmosphere is a lot more "slippery" and lift is a lot more effective, if you try a "looney toons stop" then for one you'll retain more velocity because steering tends to be very effective in changing direction without losing velocity, for two you probably won't be able to because of the air restraining the plane's movement or you'll succeed but rip the wings off. Because lift is a lot more effective (i.e. lift/drag ratio is higher) by adjusting the angle of attack you can glide very long distances, much further than in stock. It's hard to bleed off velocity and overshooting is a very realistic possibility. Because of the slipperiness of the atmosphere heating can also be a serious constraint, you can get down to lower altitudes where it's hotter without slowing down enough. Even in stock, but moreso in FAR, with the right plane it's possible to glide further than the ballistic trajectory would indicate, with a high enough lift/drag ratio the vertical velocity can be converted into horizontal velocity effectively enough to more than compensate for drag - to the point where you can fly at least a 3rd of the way further around kerbin (than ballistic impact point) through the power of gliding. If you're re-entering a capsule then aim to overshoot, if a plane then aim to undershoot and glide to make the distance. (and if using trajectories it's essential to set a positive AOA so it knows you'll be gaining lift, the 0 AOA prediction is nearly meaningless for a plane)
  9. Use the Trajectories mod (it works with FAR). You need to tune it a little bit, tell it you'll be entering prograde and estimate your angle of attack at different regimes (or use 10%). Naturally the prediction made by trajectories is not perfect, it's probably not perfect even if you maintain the angle of attack you told it you would, but the prediction is much more useful than not having it, generally speaking if the prediction is undershooting the target you can pitch up a little, and if it's overshooting you can pitch down.
  10. Yup. For spaceplanes wings make by far the most mass-efficient liquid fuel storage - that is assuming you need the wings. This is because wings with fuel capacity are identical in terms of mass per lift/drag as wings without fuel capacity, the fuel capacity is a freebie in terms of mass.
  11. Hiding stuff inside fairings and cargo holds DOES work, though when things are attached to the walls the game might convince itself that the thing is really not inside the cargo hold. But if anything is offset deeply into the cargo hold it'll definitely be removed from the airstream. To clear up any confusion here is how it works: Node attachment: What a thing is attached to and relative node sizes matters*, offsetting and clipping doesn't matter in the slightest. Cargo holds/fairings: The things physical location relative to the cargo hold/fairing matters, the part it is attached to does not matter in the slightest. (yaaaay!) * There is a limited exception when dealing with truncated cone parts, for whatever reason you can stack parts like mk1 command pods on top of each other or place a part matching the bottom node on the top node (i.e. putting a 1.25m fuel tank on top of a mk1 command pod) and the game considers this to be properly streamlined.
  12. Some interesting alternative landing gear include decouplers / hard points and radiators. Radiators have an especially odd interaction with the terrain, they aren't exactly bouncy, but they will slide up on impact helping to absorb the shock. Service and Cargo Bay doors can also be used as landing gears particularly if you adjust how far they open. Doors are rigid, indestructible and deployable.
  13. Nose intakes are typically less draggy than nose cones, the Shockcone particularly has unnaturally low drag but all nose intakes are less draggy than comparable nose-cones. Intakes are typically heavier and (much) more expensive than nose cones and sometimes have less thermal tolerance. Surface attached intakes can be quite draggy because in general the drag model hates surface attachment, but there are only two of them and neither of them are that good. Certainly given the choice between a surface attached intake or inline/nose-intake you should not go with surface attached.
  14. The main reason to use a precooler is if you want an intake with reasonable performance and you can't use a shockcone on the nose of the ship because it will burn off (or other reasons, like wanting a shielded docking port). Shockcones have good thermal tolerance but bad other thermal properties, one factor which determines how easily something burns is "cross section exposed to heating" vs "skin area available to radiate heat", the Shock Cone being a short and stubby part can't radiate much heat. A reasonably pointy fairing makes the best nose cone for thermal tolerance and you can put stuff inside it like batteries, reaction wheels, probe core, antennas etc. A single shockcone can supply 6 RAPIERs with air with the right ascent profile, so is very much overkill for a spaceplane with only 1 or 2 engines - which a precooler will suffice for. Using a Precooler + Fairing Nose with light/cheap 0.625m parts inside it can be a nice optimization for smaller planes.
  15. It is possible but it's hard. You have to use some combination of leaving early in the transfer window to Duna and a fast transfer (low trip time), when using Transfer Window Planner it's arrival date you care about, you want it to be as soon as possible. This will result in you arriving late in the Duna->Kerbin transfer window, allowing you to (nearly) immediately transfer back. The deltaV requirements are not absurd, I can't remember exactly what, but budget maybe 2000m/s extra than for perfect Hohmann transfers.
×
×
  • Create New...