SDEngineer
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Everything posted by SDEngineer
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Duna Aerocapture in 1.0.2
SDEngineer replied to rcp27's topic in KSP1 Gameplay Questions and Tutorials
rcp27 - yes, the aerocapture to lithocapture window is very small these days, and varies a lot based on each individual craft. My first simple Duna satellite probe that I sent in aerocaptured anywhere between 19 and 21.5km - any higher and it failed to capture, any lower and it wound up suborbital. My second Duna satellite, larger, less aerodynamic, and carrying a lander (bound for Ike) aerocaptured between 20.5 and 23km. Clearly with the new aero, it is much more individual, and seems that it will be unlikely that there will be a single "good" trajectory to take inbound, likely to any atmospheric body. -
How efficient is your Minmus mining operation? Share your pics
SDEngineer replied to vej's topic in KSP1 Discussion
It's faster to get a match (and you can usually start much earlier) by burning target retrograde at the closest intercept node to null your relative velocity, then burning direct at the target (not target prograde) until the intercept node hits minimum and starts increasing again, and then repeat when you again get close to the intercept node until you get an intercept of <100m. Even in Kerbin orbit, I can start washing the orbits this way at 15km+ separation and have a 100m intercept within 3-4 burns. -
How efficient is your Minmus mining operation? Share your pics
SDEngineer replied to vej's topic in KSP1 Discussion
MechJeb is in fact quite awesome for nearly completely automating these types of routine missions. However, since you haven't unlocked the rendezvous module yet, you may want to watch a tutorial on rendezvous procedures. Your docking time doesn't seem too out of line for a completely manual procedure, but your rendezvous time is really really high, suggesting that you may be missing a few key points on how to do an efficient rendezvous. From orbit, it should probably take no more than 4-5 min for a rendezvous to <100m, particularly around Minmus, where your orbits are so low that a fast Hohmann transfer orbit is cheap from a dV perspective. Scott Manley as I recall has an excellent rendezvous tutorial, I watched it and pretty much instantly halved my rendezvous time, and have been refining those techniques ever since. MechJeb can probably cut the entire ascent->docking procedure down to about 4-5 min total with time acceleration. I think also, as someone else above pointed out, your mining ship may be a bit on the small side. It's Minmus after all - get a honking monster of a mining ship out there so that you can fill the ore tanks and take a huge load of ore up to the processing facility. Your efficiency will skyrocket if instead of spending 80% of your mission profiling travelling, you are only spending 25% of it travelling, and the rest of the time filling your gargantuan ore hold with rocks. -
Fueling Big Ships with Ore? Coal power FTW!
SDEngineer replied to Mister Dilsby's topic in KSP1 Discussion
Nifty idea. Hold your fuel in a common pool and only refine what you need into small holding tanks just big enough for the maximum you'd use at any time. Particularly a good idea for a mothership, since mine are always powered by LV-Ns, but carry landers with LF+O rockets, so with the 1.0 changes, this would keep me from needing to estimate the amount of oxidizer I the missions will require (and likely over-estimating wasting dV and tank space or under-estimating and not being able to complete a landing I would have otherwise been able to). -
Minmus, of course, because it's made of mint ice cream, or at least so Jeb swears.
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<ALT>+L is your friend - always lock your staging when you don't expect to be doing any soon. Fun story though. And yes, you should always send another ship. Just because it's Kerbal.
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I'm at work, so can't look at the craft files right now, but there are a few pointers that you might want to check. Your mention of "crossfeeding" and the tanks draining "oddly" suggests that you may have some fuel lines pointed the wrong way. Orientation of the fuel line matters - the side you connect first when placing a fuel line is the "fuel donor", and the side connected last is the "fuel receiver". Making a mistake when doing this will lead to all sorts of problems, particularly if other lines are actually placed correctly. You can see the fuel line orientation if you zoom in close (there are little arrows pointing the direction of the receiver). Also, generally, you want to keep the fuel line situation simple. KSP is known to do odd things if you try to connect multiple donors directly to multiple receivers. One donor to multiple receivers is usually fine (i.e. a central fuel tank feeding multiple radially attached engines works fine), as well as multiple donors feeding a single receiver (typical asparagus staging for example, where the central tank is typically going to be fed by the two final radially attached engines, or onion staging where the radial tanks all feed the central tank), but if you try something like having each of the asparagus radial stages feed the central tank, and each radial stage ALSO feed the next radial stage in the asparagus sequence, the fuel behavior will likely not behave as expected. One final caveat - never connect two tanks directly together in both directions (even through a chain). For example, Tank A feeds Tank B, and Tank B feeds Tank A, or A feeds B which feeds C which feeds A. If you wind up with a circular connection the behavior gets very unpredictable.
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Do you run missions in serial or more than one at a time?
SDEngineer replied to Invader Jim's topic in KSP1 Discussion
In the early game, when I'm just within the Kerbin SOI, just one at a time. Once I go interplanetary though, I definitely do other things as well, but I do tend to just accomplish a few things then go back and time warp whatever interplanetary mission is closest to it's next "checkpoint". For example, current game I have a lander halfway to Eve (just finished fine tuning the intercept). I have a reasonable dV launch window to Duna coming up in about 2 Kerbal weeks, so I've launched that mission into orbit awaiting the transfer burn, and am meanwhile running a few incidental contracts (rescuing a few Kerbals, launching a throwaway solar station, etc) to pay for a new Minmus fuel mining station I want to launch to Minmus. I should have those done by the time the Duna launch window comes up, then I can start the Duna burn, and swap back to the Eve mission to time warp to an Eve rendevous - land the Eve lander and do some SCIENCE!, then swap back to the Duna probe which should be ready for it's fine tuning burn by about that point. Then head back to Kerbin and do a few more local contracts/infrastructure building, and look for another good launch window for another interplanetary mission, and repeat the cycle. -
Was the entire station brand new? If you attached missing parts to fulfill the contract requirements to an existing station it won't fire (as the "root" of the final station will be the original "old" station not fulfilling that particular contract parameter). Other than that, I can't see anything wrong with the station.
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Making orbital rendezvous less laborious
SDEngineer replied to cephalo's topic in KSP1 Gameplay Questions and Tutorials
Generally with MechJeb, you've already done what it can do well enough to become proficient at it before it unlocks the ability in the tech tree. Besides, at a certain point in your KSP career, it becomes more about building your space program, and less about actually piloting all the missions yourself. I generally personally fly all my "historically significant" missions (all my first landings, major launch of a new interplanetary explorer class ship, etc). But do you really want to do something like personally dock every single fuel tanker transport coming from Minmus to your LKO refuelling station? I don't. Those are what I fly with MechJeb fully automating, since it will go far faster. I'm good at flying and docking, but MechJeb, since it uses time acceleration so well, can fly a Minmus fuel mission to my LKO station and have it docked there in a tenth the time I can do it myself - for a mission profile I've done a half dozen times personally and need to do at least a dozen times every Kerbal year. -
Check your staging. Sometimes KSP, particularly if you're adding and removing engines, makes mistakes in how it sets up staging. My Duna probe wound up with the parachutes on the same stage as my rendevous (final) engine, so when I fired that engine to fine tune my Duna approach, it also deployed my parachutes (fortunately, my Duna entry was cool enough and slow enough that it didn't actually destroy my chutes, but if the same mistake had been made on a Kerbin re-entry vehicle, it would have been bye-bye parachutes at about 15000 ft). Please note though, the parachute does not actually deploy until it goes below a certain atmospheric level, so it visually looks like the parachute is still packed, but by default it will deploy itself quite high up while you are still moving very fast, so it is instantly destroyed by the airspeed and heat if it has already been staged. You can fix this by adjusting the atmospheric pressure it will deploy at as another poster above noted (I think you may be able to do this on the fly, but not sure - if not, you will have to wait for a rescue mission to come up and get your Kerbals and science out). I try to remember to do a staging checklist before launching any vehicles (I simply had forgotten this time, and fortunately a cheap mistake that didn't wind up killing the mission) going over the major "oops" possibilities (like launch clamp releases before igniting the first stage - this is something that KSP usually does, and if not corrected, can easily destroy a mission on the pad).
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Post 1.0, the most cost effective way to refuel anything is probably to build a fuel refinery on Minmus (or in Minmus orbit, with ore ferried by a mining ship from Minmus itself). Fairly cheap to set up the infrastructure, assuming you have the appropriate tech nodes unlocked (maybe a half million to set up a fuel depot in orbit, a miner/ore carrier for the ore, and a fuel tanker to move fuel wherever you need it). Drawback of course would be the time to set it up and the time it takes to mine and move the ore - but the dV savings over time is frankly enormous. You only spend a few hundred dV to get the ore (and therefore fuel) to the Minmus fuel depot, and then (assuming you aerobrake properly) another few hundred dV for the fuel transfer vehicle to get to LKO to actually do the refuel, and aside from the initial launches to put those craft in orbit, no further wastage as those craft will never need to return to Kerbin. Essentially at that point, it's free fuel forever for anything that has made it to LKO. Given that you're looking at 5 orange tanks, the savings will be huge, and it's likely cheaper to set up a Minmus fuelling operation than to find a way to launch 5 full orange tanks worth of fuel into orbit (my 40t launches to LKO, which is roughly equivalent to 1 orange tank, are typically well over 100K/launch). However, if you're dead set on lifting that much mass from Kerbin, you're right, it's not an easy answer. What you're looking for is the payload that you can lift to LKO expressed as tons, then divided by the cost of the total spacecraft to get a kerbal kredit/ton cost. While I haven't done any math on this, simply based on my own designs I think the "cheapest" way to do it is with a ton of relatively small launches - I can get 5t into orbit at well under 10% of the cost for a 40t launch, even though my payload fraction for a 40t launch to LKO is definitely higher.
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Bases,Rovers,Satelites and Stations have purpose now
SDEngineer replied to 95tiger59's topic in KSP1 Discussion
Already always used them. True, bases/rovers/satellites didn't really have a lot of purpose in vanilla .23 and before (stations were quite useful as staging/refueling points), but I used them anyway for pure RP value. They were just fun to build and set up. -
Airplane doesnt fly well
SDEngineer replied to Jetsim's topic in KSP1 Gameplay Questions and Tutorials
For 2, he means any off-centered mass. In the case of your aircraft, you have a number of engines (heavy mass parts) that are mostly distributed on one side (the bottom side) of your aircraft. In air, not a problem (or at least, not an insurmountable one), but once in space, it means that your craft will "push" towards the bottom side, since it is bottom-heavy - the mass isn't evenly distributed. For 4, you need to monitor the air intake of your engines (you can see it on the fuel status tab), once it drops to just above the point at which you will start having flameouts (which depends on the engine) you will need to shut off the jet engines simultaneously, and then switch on the rockets (generally use action group keys - one assigned to enable/disable the engines as a group, the other to enable/disable the rockets). Most of the time, if you're doing a SSTO (single stage to orbit) you will level off at below the altitude your engines will flame out on, and start building speed in a level trajectory - as you speed up, your air intakes get more air - then you can gradually start gaining altitude again. Still, at some point, you will have to switch over to rocket power. -
As others noted, the problem is in your fuel lines - it looks to me like what you are trying to do (based on the staging) is have the external 4 tank/engine combos be a orbital insertion/landing stage, then have the central vehicle be the return stage. If this is the case, here is how you want to lay the fuel lines out: You'll want just a single set of fuel lines from the side mounted tanks running to the central vehicle: .....T..... .....|...... .....v..... T->O<-T .....^.... .....|...... .....T..... Make sure the arrows on the fuel lines are pointed the correct way - fuel lines only conduct fuel in one direction. When you connect them, you attach them from the tank they are transferring fuel FROM first, then connect to the tank they are transferring fuel TO. The above arrangement will ensure that the central tank is completely full when the outside tanks are empty, since it will draw from the outside tanks first. However, I agree with the others on this thread - your vehicle is seriously over-engineered for a simple Mun lander - and it will get you into trouble as-is. The problem with it is that since it has been so over-engineered, it masses a ton (or rather many, many tons) - and will be difficult to land on the Mun intact for an inexperienced pilot. My suggestion is to take the core (only) and practice landing on Minmus a dozen times - it is a little more difficult to get to orbit around Minmus (you need to match planes, and costs more dV) but it is ten times easier to learn to do a powered landing on Minmus as opposed to the Mun. Once you can land anywhere you want on Minmus surely and quickly with no mistakes, you are ready for the Mun (until I started practicing on Minmus I was hopeless at Munlanding) Advantages of Minmus vs. the Mun: 1) the "Flats" are ideal locations to learn the basics of landing. Perfectly flat and at 0m elevation. All you have to worry about is learning to kill horizontal velocity properly and manage your descent speed. You will be very hard pressed to find anywhere on the Mun that is flat or at 0 elevation, and none at all that are both and easy to target to land at from orbit. This makes it easy to practice the basics of landing before getting into more complex stuff like trying to aim for a "nice" spot while doing a powered descent, and dealing with trying to eyeball (or check in the cockpit) your "real altitude" while still managing your descent speed and horizontal velocity. 2) Much lower surface gravity. The practical effect of which is that everything happens at about one fifth the speed it happens on the Mun - giving you much more time to think about what you are doing, and much more leeway for error. A misstep that would be absolutely fatal on the Mun is much more likely to be recoverable on Minmus. 3) Because of 2 - much lower dV requirements for landing, and once landed, taking off again - making Minmus much more fuel economical even though it takes more fuel just to get there - while it may take 15% more fuel to get there and achieve orbit, it requires about one quarter the fuel to land and take off again.
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It depends on what you are using it for. It IS the most efficient, even though it is quite heavy (and in .24, also very expensive). It is, in fact, a very good choice for the purpose you are using it for (a highly reusable refuelling craft). I won't put any LV-N's into orbit that I am not planning on re-using forever (i.e. wait until you have at least one space station) - after that, I use LV-Ns quite a bit. Of course, they form the core of any interplanetary expedition - the high ISP is just too good for that purpose, but I also use them as Mun/Minmus landers (really anywhere with light gravity and no atmosphere), asteroid tugs, rescue ships, and of course, fuel tankers.
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Stupid things you've made to do missions in career mode
SDEngineer replied to lukerules117's topic in KSP1 Discussion
I got one of those too - needed to be going at least 380m/s at 7800m altitude (where terminal velocity is ~210m/s or so). My solution was to come in from my Munshot mission dead centered on Kerbin. Just barely squeaked by the velocity requirement (I was down around 400m/s when I hit the maximum deploy altitude). -
I got bored with doing docking myself quite some time ago (though I don't have a problem with it, it just is one of the games aspects that I no longer find "fun"). MechJeb has two features I use a lot now for these - Rendevous planner, which will actually go and compute the Hohmann transfer to the target (and execute it, fine tuning the approach to whatever desired distance, although I usually kill the planner and fine tune the approach myself to put myself in correct docking position above/below the target), and the Docking Autopilot which actually docks the two targets. Neither is particularly efficient if you just let MechJeb do the whole thing. Both are reasonably efficient if you do some of the set up work for them. For the Rendevous planner, I generally either establish a significantly lower orbit (~1/2 the orbit of the target ) or a significantly higher orbit (2x the orbit) - this keeps MechJeb from doing a burn to get to a higher orbit to change the periodicity of the orbit to get a Hohmann transfer orbit earlier. For the Docking autopilot, if you line up the ships as if you were doing the docking manually (N-S orientation of the desired docking ports), then do a small burn (either with the main engines or using the RCS) to get above/below the desired port), then engage the docking autopilot, I've found that MechJeb doesn't waste much RCS at all (30t heavy landers dock at my space stations using only 20-30 units of RCS fuel, 120t+ heavy interplanetary ships dock only using 100-200 units - which for a really heavy and "bendy" ship is actually probably less than I would use). It's when you use it without doing any alignment that MechJeb wastes tons of RCS getting into position, and chasing the docking port around the target (which is exactly what would happen if I tried to dock without doing any alignment prep as well).
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...then it becomes more wobbly.
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Is asparagus the best staging system? (might contain science)
SDEngineer replied to Pbhead's topic in KSP1 Discussion
All it takes is a sufficiently powerful pump to do it. It's really no different than pumping a liquid up a steep hill. I'd think that for most of the ascent, probably enough to avoid needing much of a pump, gravity would actually help more than hurt you, since the mass of the fuel itself will provide a LOT of the necessary "push" to overcome gravity (remember, while the rocket might be accelerating at, say 2.5g, and needs to push the liquid up that 2.5g gradient to the top of the next fuel tank, at the very same time, that 2.5g is pushing DOWN on the entire mass of fuel remaining in the "donor" fuel tank, thus providing an enormous amount of hydraulic pressure. -
Is asparagus the best staging system? (might contain science)
SDEngineer replied to Pbhead's topic in KSP1 Discussion
You need to use more thrust on the center stack. Although, if your payload is light enough (<15t) it's usually more trouble to build an asparagus launcher than it's worth. But I launch complete, fully fueled, multi-Kerbal (10+) interplanetary mission craft with 5K+ dV and weighing around 100 tons into orbit with my heaviest asparagus launchers - and no major tweaking required. For anything really heavy, it's definitely more efficient to do a full asparagus. I've built literally hundreds of different launch stages (playing since 0.18), trying various methods, and in the end, my asparagus launch stages get more to orbit, with more dV remaining than any other design. They are simply a bit more complex to build. I don't quite use as much rocket science as Temstar on the first page did, but I have about a dozen different launch stages saved, capable of getting anything from 15t (my smallest true asparagus - anything smaller there's really no need) up to just over 100t into 100km orbit without touching any fuel in the payload (my 100t launch uses a clustered design of 6 LVT30s surrounding a central LVT45 in the center stack, and 6 mainsails in the outer stacks - it's actually well below a 1.0 TWR when the final boosters drop off, but by then, it's high enough and going fast enough that it makes 100km circular orbit with enough dV left in the tank for the center stack to do a deorbit burn once the payload has been dropped off). All of them are capable of a payload to weight ratio (to 100km) of at least 14%, which you won't match with any other form of booster staging. -
Definitely the way to go. I have somewhere around 10 subassemblies ranging in capability from 15t up to 120t (all rated to 100km orbit). Saves so much time setting up the asparagus staging, fuel lines, and struts on what is generally the largest and most fragile part of the final rocket (and most prone to catastrophic failure if you forget a crucial set of struts or make a mistake setting up the staging), letting me concentrate on the payload that is actually new construction. I can't count the number of launch failures I had due to hastily constructed launch stages before subassemblies.
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My usual orbital station is semi-modular, but generally assembled in Kerbin orbit at around 850km and then flown intact to the desired planet using a very high dV tug. Typically, it's a core 70t station (1 orange fuel tank, a large RCS tank, 3 hitchhiker modules, 1 cupola, arms for smaller docking ports/solar panels, and additional large docking ports for later expansion and fuel storage). Generally add 2 additional orange fuel tanks in orbit to two of those docking ports, giving a total station mass of about 150t. Once there, I dock my heavy interplanetary tug (1.5 orange tanks of fuel + 8 NERVA engines in a skycrane format) to the top of the station, which brings the mass up to about 240t. The interplanetary tug gives nearly 4000 dV without touching the fuel in the station, which from an 850km assembly orbit around Kerbin is enough to get it most places (Duna, Eve, Moho, etc). Haven't found anywhere that tug couldn't get that core station yet, although I've yet to put stations into orbit around the Joolian moons, but clearly, given the 3 orange tanks of fuel on the station, it should be able to be put anywhere given use of the station fuel. As most of the station is a single piece (except for the two side orange tanks), and the tug is in a skycrane "pull" configuration, it's actually pretty stable to fly to other planets without much wobble at all. Generally I ditch the tug into the planet when it's done, but if you really want to reuse it, it'd be very easy to return it to Kerbin orbit after placing the station.