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About Empiro

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    Sr. Spacecraft Engineer

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  1. I've only done one such mission, and tried both the sky-claw and rover design. The sky-claw is really challenging because you're essentially attempting a docking maneuver with very limited time before running out of fuel, and you'll need to be constantly adjusting the thrust to maintain altitude. At the end, I went with a rover that was essentially a rocket with a claw in the front. To land, it had wheels and radial engines that lands it horizontally. I also had a horizontal probe core on the side to help with the horizontal landing. For most of the way, it uses the efficient engine in the back, and when it's just about to land (maybe 100m off the ground), I deactivate it, switch to the radial engines, and control from the horizontal probe. After landing, I drove over to the target and clawed it. To get back into space, I turned off some of the radial engines (because the CoM shifts after you grab your target), and just used the engines to pitch the nose up so that I could use the rear main engine to boost into space. All in all, it was fun and challenging, but so time consuming that I haven't done such a mission since.
  2. Yes and no -- it comes down to whether both engines have enough delta-V to get you where you want to go. I don't know what your entire rocket looks like and I don't know where you're planning to go with it, so I can't tell if both engines will work or not. However, you're right that 310 vs 350 isn't *that* huge of a difference, so in many cases, both would work. If the ISP difference were 221 vs 350, then it's highly likely that either: the 221 engine wouldn't have enough delta-V, OR the 350 engine has so much excess delta-V that I can remove fuel and get the same TWR. A slightly more advanced tip is that efficiency becomes more and more important the later your stage is. The design of a stage not only affects that stage, but also the performance of every stage before it. It's critical that your upper stages are efficient and light, while low ISP solid rocket engines are totally OK for the 1st stage. For a 2nd stage, it matters some, but in my experience you have some flexibility in your selection.
  3. You generally don't need to calculate exact ISP and TWR values at specific altitudes -- for example at anything 20km and above, I simply use the vacuum values (even if you start burning at 15km, you'll gain altitude very quickly). The ISP and other guidelines are there to help you whittle down the engines you should be looking at different stages, but the actual TWR of your rocket and delta-V determine the construction. If both the Poodle and Bobcat have enough delta-V, then I would go with the Bobcat -- the better TWR means less burn time, and a more forgiving flight trajectory (I don't need to worry about falling back down). If I have to go with the Poodle to get enough delta-V, then the low TWR also helps inform me of my choices for the 1st stage -- I know I would need a rocket with better TWR and fly a slightly more vertical trajectory. For your first stage, your choices of engines are all pretty good, and I think each design could be viable. My final choice will depend on my 2nd stage choice (if Poodle, then higher TWR). Real-life rockets like the Saturn V had an on-pad TWR of only 1.15 or so. In KSP, a 1.15 TWR rocket requires roughly 3800 m/s to make it into orbit, compared to a 1.6 TWR rocket that only requires 3500 m/s.
  4. This is just a general guideline on how engines in KSP compare, so you'll want to do some exploration and studying on your own (the KSP wiki is helpful). The two most important stats of an engine are the TWR and ISP. The other stat to look at is mass, but it's much less useful. ISP is important because as we've discussed above, it's the basic efficiency of an engine, taking both thrust and fuel consumption into account. Vacuum ISP is typically used since you spend most of your time in a vacuum (as soon as you're 20+km high, the ISP is very close to vacuum). If you compare all the engines, you'll notice that engines with really high ISP in vacuum tend to have very poor ISP in atmosphere (the lower ISP comes from having lower thrust, while still consuming the same amount of fuel). KSP doesn't provide the TWR, but you calculate it by dividing the thrust by just the mass of the engine and nothing else (so for the Twin Boar, make sure to subtract away the mass of its 36-ton tank). An engine with great TWR on its own will also provide great TWR attached to a rocket. TWR is important when taking off and landing, and you don't want it too low in space (<0.1 in space is quite problematic. I generally have more than 0.5 to avoid long burns. If you compare all the engines, you'll notice that engines with really high TWR in vacuum tend to lose less ISP and thrust in atmosphere, so high-TWR engines have good TWR nearly everywhere. The VAB also has a TWR display that shows you atmospheric and vacuum TWR of your craft in different environments. Note that raw thrust is not something I look at on its own. This is because TWR is a more useful stat that encompasses both thrust and mass/weight. If an engine has a great TWR but not enough thrust on its own, you can easily double or triple-up an engine to get the oomph you need. Finally, mass matters, but ONLY because you can't have half an engine. TWR already takes into account mass. Engines like the Spark get used on small crafts because you can't have a quarter-Terrier with 1/4 of the thrust and 1/4 of the mass and same ISP. All this provides us a basic way to compare engines and summarize the important points: You want engines with both high TWR and high ISP, but those don't exist -- engines with great TWR tend to have relatively lower vacuum ISP and vice versa. Low TWR engines have really low ISP in the atmosphere, which means their TWR becomes abysmal, and are worse in every way compared to high-TWR engines in atmosphere (as it has both lower ISP and TWR). More massive / late-tech engines tend to be better in both TWR and ISP and break away from the trend a bit. For example, the Poodle is heavier than the Terrier, but actually has better ISP and TWR in vacuum. The Aerospike is pretty good in every situation (though never the best). These engines are great if you have the tech and big enough craft. You'll find that for small crafts, these engines provide more thrust than necessary and add too much to the mass. (The engines in KSP are pretty balanced these days, but in the early Beta versions, some engines clearly were outside of these trends) Putting together these stats, you can roughly group engines into three classes: Lifter engines with high-TWR and relatively poor vacuum efficiency. Mainsails, Reliants and SRBs fall into this category. They're engines you use off the launch pad in Kerbin and Eve, where there's high gravity and atmosphere. Vacuum engines with really great ISP but poor TWR. The Terrier is the most accessible example of this. Vacuum engines are great to use as soon as you're high up in the atmosphere. Even though the TWR is poor, they're still useful on landers because most places you land on have no atmosphere and low gravity compared to Kerbin (TWR of only 1 on Kerbin is 6 on the Mun). Duna's atmosphere is thin enough for most vacuum engines. Sustainer engines that are a middle ground. I find the Skipper a really useful example in this category. You can use them off the launchpad if you augment them with SRBs, or use them as a second stage that puts you into orbit. They're also really useful to keep using in Low Kerbin Orbit. Hopefully this is helpful to you. Let me know if you have more questions.
  5. Here you're calculating acceleration by dividing the thrust by mass, so your crafts will accelerate at 19.61 and 19.59 m/s/s. The TWR is a Ratio between the acceleration due to the Thrust, divided by the acceleration due to gravity (the Weight). Your TWR changes depending on your reference body and how far you are from that body, though if omitted, it's typically relative to surface of Earth or Kerbin (both 9.8 m/s/s). To get TWR, you'd divide your answers by 9.8 (or do what I do, and just divide by 10) to get a TWR of around 2. Like many folks have said, TWR matters when lifting off. Under 1.0 and you won't be able to lift off at all. In orbit, TWR matters very little unless it's extremely low (<0.1g). I think you're on the right track. I think your misunderstanding is coming from thinking that more thrust = more efficient, without taking fuel consumption into consideration. The Terrier will take 4x longer to burn, but compared to the Reliant, it will be able to use the same fuel and burn for more than 4x longer. The ISP measures efficiency. The higher the better. If you're interested in the math, it's calculated by taking the Thrust and dividing by fuel consumption per second, and then dividing by 9.8/s/s (it is by convention to measure ISP in seconds). KSP gives fuel consumption in weird units (not kg/s) so it's good that it provides you the ISP information in seconds. However, the ISP isn't the full story, because the mass of the engine matters too. The Terrier is often chosen because it both has good ISP and low mass. It is almost always chosen over the Reliant in space. Poodles have only slightly better ISP but far more mass, so its good for larger crafts. When comparing the Poodle with the Reliant, it's a bit trickier, since the Reliant is lighter, but the ISP is lower. KSP shows you the delta-V in the VAB, but by default shows you stats for in-atmosphere, which is really bad for engines like the Poodle. In the VAB, try out the two different engines, making sure to set the Delta-V mode to vacuum. If you're interested in learning the general rule about engine selection and how to judge an engine, I can help with that. It helps you determine what engines you should and shouldn't be looking at when deciding what to use.
  6. The key is getting your orbit to match as closely as possible to your target before your encounter. If you're coming in directly from a Jool escape trajectory, then naturally your orbit won't look anything like your target's. Instead, try to use gravity assists to capture into a Jool orbit, and then use more assists to adjust your orbit so that it closely matches the moon you want to get to Generally, it's OK if your AP or PE is some ways off, but you want the other side to be just barely touching your target's orbit and have the encounter happen there (so it looks like a Hohmann transfer). Having a big inclination difference is also bad. Finally, get your encounter as close to your target as possible, which will also cut down on the delta-V you need to capture (maximizing Oberth effect). Note that it IS possible to efficiently capture directly into a moon's orbit, but you'll need to follow the advice above (no inclination difference, having the orbit around Jool just touching your target's, and getting the encounter there). However, it might be hard to time the encounter just right.
  7. Drawing players out of the Kerbin system could be fixed with smaller changes (for example, if you get less and less science after the first biome on the same celestial body, it would prevent biome-hopping on Minmus from letting you fill out the entire tech tree). I definitely like the idea of a slow collective process, but tying that to the gameplay in a good way is hard. Anything that's game-clock driven wouldn't work by itself, since you have 100,000x time acceleration at your fingertips (and it's one reason the labs are not very balanced). You want the reward loop to be (do something fun/challenging -> get science to let you do even more stuff). In KSP 1, biome-hopping Minmus or time accelerating a lab are two strong ways of getting science, but neither are particularly fun nor challenging.
  8. I think the science system definitely needs to be greatly revamped. Part of it is that it's just obtuse -- clicking on various parts, then doing the take-experiments-store-experiments dance. We all know how to do this, but none of this is intuitive to newer players and it's not fun for serving of gameplay in any way. The game should automatically perform science when the situation is right. Breaking ground helps gives you more reasons to bring rovers and bringing large, somewhat unwieldy instruments, which is also a good thing. In the basic game, sticking a thermometer or barometer on the side of the rocket doesn't really add much to the gameplay. I think that having science unlocking information about the planet would be a nice addition, especially if you can add a bit of randomness to every game start, so that players get to discover new things each playthrough. There are already mods that let you map biomes, resources and so on. Having other information be available (like temperature or whatnot) would be pretty awesome, and can lead to some interesting challenges (for example, a planet that is very hostile to life/colonies except for small safe pockets). It also gives you a reason to have science instruments in sandbox mode. Having tech progression more tied to achievements could work, if the achievements were reasonably free-form. For example, my favorite part of the existing contracts system are the first milestones achievements. You don't have to explicitly take these contracts, but just happen the first time you do something. Combining that with a bit of guidance (suggesting the next steps), or giving you an extra bonus for doing something difficult (if you can land on the Mun, but do it this way, you'll get even more science/money).
  9. Having unique music for different situations and planets would definitely go a long way to making KSP 2 better. I already have the soundtrack editor for KSP1, but I definitely don't want to have to take the time to select each track for each planet / situation separately. It would also be nice for KSP 2 to have a composer creating unique music just for the game, rather than using free music.
  10. I think that the game does the right thing even with reverse-pointed winglets if you are going forward, so another solution is to mount a backward-facing control point somewhere.
  11. Some parts of these results are definitely surprising to me. The full throttle being lower than the other two in particular seems to suggest that drag losses are significant when moving too quickly, yet the fact that the more aggressive turns did better seems to imply that minimizing gravity losses is still the way to go. Can you give us an idea of how far the AP went ahead? I think the biggest takeaway here is that you really don't need very high TWR to be efficient.
  12. The optimal flight path is a pretty difficult problem to solve. Generally speaking, the most efficient ascents will balance between minimizing gravity losses, minimizing drag, and minimizing mass (not carrying too many engines). An efficient ascent has you thrusting at full power for most of the burn (if you're not at 100%, you might as well take fewer engines or more fuel). You also want to point at prograde as much as possible to minimize steering losses. So the ideal ascent would look like: Launch, 50 m/s or so, tilt slightly to the east Lock to prograde, continue to burn. Your nose will come down naturally (gravity turn) At some point, you want your time-to-AP to start decreasing, even as you burn at 100%. You typically do this by staging into efficient, low-thrust vacuum engines. Just as you reach AP, you circularize your orbit In practice, you'll never be able to get #5 perfectly (I typically will need to cut thrust or coast), but the fortunate thing is that even if you don't the difference in delta-V is minuscule. Getting 1-4 down will be the biggest difference. At only 1 km, I'd just burn directly toward your target and then slow down. If the difference is much greater, there are a number of approaches, all with different fuel costs and time to intercept. What you described would indeed work -- by thrusting down (radial in), you're "rotating" your orbit so that you'll traverse the next part of your orbit at a lower altitude and faster before slowing down. This will catch you up to your target. If you do it just right, you'll intercept your target at your initial altitude. The most efficient way (that requires a lot of time) is to burn retrograde (even a minuscule amount). This put you in an orbit with a shorter period, and when you make a full orbit and come back around to where you are now, you'll be slightly closer to your target. After enough orbits you'll be right on top of your target, and you'll only need to burn the same amount to match velocities. In practice, I tend to use this method most often, though I will burn more so that I can get an encounter more quickly.
  13. Ideally not a static texture box at all but dynamically rendered. In KSP1, stars look noticeably bad and texture-like if you zoom in. Dynamically rendering would let you take into account things like local lighting conditions, how zoomed in you are, and other things. I'm not familiar with games like Universe Sandbox and so on, but there must be stuff out there that does similar things. Parallex effects for nearby stars would be an optional, but nice feature (you'd probably never notice it unless looking specifically for it). Wouldn't be too expensive since you'd only rarely need to update the parallex calculations.
  14. You don't really need an LES in KSP. When playing without reverts, I bind my abort key to shut down all engines and decouple the pod. Generally, parts don't really explode in a way that will cause damage to a pod.
  15. It's mostly about the TWR you need. Dropping tanks reduces your mass be a small amount while dropping engines reduces your mass by a large amount, but also reduces your TWR. Drop tanks are useful for something like a Tylo lander, since TWR matters the most toward the end. If you use stack staging set ups, it does mean that some of your engines aren't firing the whole time, which means that they're basically dead weight. Asparagus staging kind of gets the best of both worlds -- all your engines are firing at all times.