Northstar1989

MechJeb is actually great for precisely controlling your Angle of Attack with its ASAS function (in "Surface" mode), and fine-tuning your SAS torque (so you don't over-steer when delicate maneuvers are needed) with its Altitude Adjustment function... I use it all the time for LONNNGGGG, relatively stable flights, such as the speed run on one of my Thermal Turbojet spaceplanes... (TTJ's are from KSP-Interstellar) @XOIIO Give MechJeb a try. It sounds like you might be setting too high an Angle of Attack- real planes achieve maximum lift at an Angle of Attack of around 20 degrees... You might also want to try building the wings in at a 5 or 10 degree upward angle (use Shift + WASDQE to rotate parts 5 degrees) so that you can point the intakes and engines more level to the horizon during your speed run. That should raise your altitude ceiling under jet power quite a bit... (especially since intakes work best when pointed along the prograde vector) Built-in wing angle also makes it easier to get off the runway on takeoff... Regards, Northstar

Get more money set aside for space exploration, so there will be more cool things going on to interest the public... How? Send a politician or two on a mission to the International Space Station... Tell them we don't have the money to bring them back for three weeks (it wouldn't be a lie- many astronauts stay there for over a month) when they get violently space-sick as soon as they enter zero-G... Regards, Northstar P.S. I know that wouldn't work- I'm just being snarky...

Where did you get the figure for Kerbin's mass from? Regards, Northstar

You're not the only scientist here, you know *self point* I'm a biologist in real life... Just learn to relax and go with the slang a little.. I'm perfectly aware of the technical "inaccuracy" of many of the terms used here too... Regards, Northstar - - - Updated - - - Awww, I'm sorry- what other typos do you want me to fix? Regards, Northstar

He *might* be thinking of FAR- where you want to break the sound barrier to reduce the drag coefficient on your rocket. But with FAR, generally you don't want to stall at Mach 1, because the most difficult part is breaking the sound barrier, and after that drag increases a lot less with speed- whereas you will still see strong benefits to reduced engine burn-time if you fly faster... Regards, Northstar

There's kind of that whole "hurtling around in space" part to deal with. Comets, unlike some asteroids, tend to be on highly elliptical orbits- and thus actually would cost a LOT of Delta-V to get to or capture in Earth orbit... I was pointing out that In-Situ Resource Utilization (which isn't a thing for many KSP players) is actually likely to become a thing sooner than fuel tankers launched from Earth (which *is* a thing for many KSC players). And actually, there is already a working Sabatier Reactor on the International Space Station, being used for life-support. It's not much of a stretch to use the same reactor on Mars to make methane for an interplanetary mission's return-trip to Earth... (you send the reactor ahead of the mission, and make the return fuel before the astronauts ever leave Earth...) http://www.nasa.gov/mission_pages/station/research/news/sabatier.html My computer's older than most out there, and it somehow manages to handle it (admittedly, my game *is* a little laggy). Don't be so sure yours couldn't before giving it a try... Regards, Northstar

Metals don't necessarily need smelting. Not if the form they come in is already re-usable, anyways... For instance, there's no reason you can't tear apart a metal hull, and re-use the sheet metal as micrometeorite shielding on a space station. Or metal engine components as spare parts for an interplanetary mission (someday). Or even re-use half an empty fuel tank as a bin to hold some of the junk you've just salvaged... And, when it comes right down to it, small-scale smelters aren't necessarily impossible in space either. Difficult to engineer, yes, but not impossible. Regards, Northstar

Not really an option to quickload at this point, if that's what you meant. And even with the extra reactor fuel, it was perfectly capable of atmospheric flight on Duna, and even suborbital hops like the one I used to place it into a holding pattern while I try and get it some front-end cargo to balance out the extra uranium. The problem is it can't land with the extra weight in uranium in the rear... I decided a while back I'd just try getting it some cargo, and see if it could land safely then... But, if it can land with the cargo (I imagine it will still be a very difficult landing)- do I have permission to edit or dump out the extra uranium with TAC Fuel Balancer? (if it will let me when landed- it doesn't let me do either in-flight) Regards, Northstar

I assume that was from the failed mission? (it looks like it's not going to make it back to orbit) Even so, that was a nice screenshot... Ways to increase mission viability/decrease mass: (1) Consider if you can't get by with OX-STAT solar panels. They are the most efficient producers of ElectricCharge per ton when facing the sun, and it looks like you already have some radial extensions from the main body you could stick a few on to provide front/rear sun coverage... (2) Make sure you can detach the extra fuel tanks you no longer need after the transfer burn to Duna, so you won't have to haul them back with you. A great place to dump them is just after your aerobrake- your periapsis should still be in the atmosphere of Duna, so if you load them up after you circularize, you can ensure they crash into the surface so you don't have to worry about orbital debris... Alternatively, you can design the extra fuel tanks as a detachable section with a docking port to leave in Duna orbit (after circularization) as structural elements and fuel storage for a future Duna space station... (3) Winged lander for Duna! (works best if the Kerbals ride down on External Command Chairs) You can get away with a lower TWR if your lander ascends back to orbit as a spaceplane, instead of like a rocket. This will enable your lander to ascend to orbit more fuel-efficiently, and provide your lander with a lot more freedom to select its landing spot on Duna's surface (so you don't have problems coming down over a mountain). Just remember to ditch the wings after you exit Duna's atmosphere on the way back up, so you don't have to haul the wings to Ike when you use the lander there... (attach the wings to decouplers rather than directly to the body of the lander) This would also give you the opportunity to knock out the Flying Duna Challenge while you're carrying out your mission... (4) Consider sending a fuel tanker AHEAD of the main mission. That way, you can build a heavier mission vehicle, with just enough Delta-V to get to Duna and rendezvous with the tanker, and have your return fuel already waiting for you before you return. It also means you don't need as much tankage on your main vehicle, because you can refill and re-use the same tanks that carried the fuel to get to Duna for the return trip... Obviously this doesn't work well if you drop empty tanks like in (2) (5) Consider how much Monopropellent you really *NEED* for your mission- I saw you packed an awful lot. Many new players make the mistake of packing entire 2.5 meter tanks full of Monopropellent when all they REALLY need is a couple small radially-attached tanks of the stuff. Once you get REALLY good at docking, you might even find you can get by with just tiny bursts of thrust at low throttle from your main engines instead... (precisely match velocities with the vehicle your are rendezvousing with, and then have both vehicles point their docking ports at each other, and one give a tiny burst of thrust towards the other such that they approach each other at 0.3 or 0.4 m/s...) Regards, Northstar

Ugh, and while I resent the comparison "Minecraft in Space" (MC doesn't even come CLOSE to realistic physics), it certainly should attract some attention considering what a cultural phenomenon Minecraft has become... (I even played it myself) Oh, and yes, this was published today! Regards, Northstar

Awesome! KSC, and by connection space, can always use more PR... Regards, Northstar

It depends how much fuel you added. What this did to the average ISP of your remaining engines (did you remove the least or most efficient engines? How was their TWR?) and a lot of other things... Additionally, I made no secret of the fact that you get more Delta-V with lower-TWR rockets in many cases- so you're not saying anything new. The thing is, that extra range comes at the expense of higher fuel-consumption, so if you can get the rocket to orbit with a TWR closer to ideal, you will often expend less fuel that way (which is in some ways better if you re-use just the engines, salvage them, or re-use the entire lower stages of the rocket- but inferior for a "throw-away rocket") That's generally a bad assumption to make. IF your payload has engines, and you have a way to use them in your ascent and thus save engine mass on lower stages, why wouldn't you? It's almost always best to take an integrated approach to rocket design... It's up to you how you want to play the game. If you want to design general-purpose rockets, and try and get other players to use them (though I don't see the fun in using somebody else's rocket design- the pride of seeing something you designed soar through the sky is half the fun in KSP), then that's your perogative. Personally, I prefer to design my own specialized rocket for each mission where possible. In a worst-case scenario, I usually at least design a general frame and then make extensive modifications (a drop tank here, a lighter launch engine there due to the ability to use payload engines, etc...) based on my mission profile. As always, KSP is about learning and having fun, and open to many play styles- so do what you like, and enjoy! Regards, Northstar

It doesn't matter which direction your rocket is "pointed" (that's entirely a construct of our own analysis), or even which way a rocket is thrusting (which is what has actual physical significance), it matters which way a rocket is actually MOVING. A rocket that is thrusting parallel to the horizon, but still has a prograde vector 20 degrees above the horizon is, first of all, losing some potential benefits from the Oberth effect (which only acts on thrust in the direction of your movement- *NOT* any component of thrust perpendicular to it). Second, such a rocket is still experiencing loss of kinetic energy to gravity (and to drag if it has not yet exited the atmosphere). The higher your acceleration at this altitude (which should not necessarily be parallel to the horizon), the more quickly you will raise your apoapsis while thrusting in this direction. You will be able to get in more of your thrust before gravity has managed to slow your rocket down as much, allowing greater utilization of the Oberth Effect, and less energy spent raising your apoapsis at a higher altitude... (from a perspective more familiar to most players- you are closer to periapsis at 36000 meters than at 42000 meters if the final orbit you are aiming for is 100 km- as a suborbital trajectory can be modeled as a highly elliptical orbit that passes through the atmosphere and the planet itself...) Indeed, vacuum ISP is a major thing to focus on for upper stages. But you can't neglect TWR either. And, as always, it depends on the particulars- for instance the upper stage of a Space-X style reusable rocket (my new favorite launch profile) requires a MUCH higher TWR than the upper stage of a conventional rocket, as it will have almost no horizontal velocity when ignited, and won't have an apoapsis terribly high above the atmosphere in most cases... There's no reason the central "stalk" needs to be the same as the outer stalks in asparagus staging. In fact, in some cases it may behoove you to use a lower-thrust, higher-ISP engine for the central stalk than for all the other engines. For that matter, the central stalk doesn't even need to be your upper stage- it's not uncommon to park an upper stage on top of an asparagus-staged lower stage. Though, generally speaking, asparagus staging of the type you are describing is never a very efficient design during an ascent in the first place- you waste a lot of fuel bringing the engines on the upper stalks up, only to throw them away a soon as the fuel tanks above them run out. Generally, it's more advisable to make use of asparagus-staged drop-tanks, and use radial boosters on the central stalk for extra thrust... Eve is a stinking kraken-hole, that I never intend to visit again due to the horrendous lag it puts on my computer. But if I *were* to visit it, and even try to send a Kerbal to the surface and back, I wouldn't bother with rockets- you simply expend too much fuel fighting Eve's high gravity. On Eve, it would be much better to go with a NERVA (or KSP-Interstellar Thermal Turbojet) powered spaceplane (with chemical rockets to kick it into orbit), lots of drop-tanks and really large wings, and let lift hold your vehicle up instead of thrust... (you *might* want to put the giant wings on decouplers though- so you can detach them when the atmosphere becomes too thin for them to be useful any longer- as you don't want to haul those heavy/draggy things all the way back to orbit...) Regards, Northstar

Because your terminal velocity is usually higher in FAR, you want a TWR *MUCH* higher than 1.6 or 1.7 on the pad (if you can get it) in order to catch up to terminal velocity quickly... That won't EVER bring you up anywhere close to terminal velocity- you need a TWR of at least 2 to even maintain terminal velocity in level flight (more when ascending), FAR or not... Even though you won't reach terminal velocity in FAR, TV is not a "magical number"- the greatest benefits actually come from the first 10 or 20 or 30% of the way to terminal velocity, with or without FAR- the fuel savings from faster ascent speed steadily drop off the closer you come to TV, until you actually reach TV, at which point you start spending more fuel as you go even faster... (this is ignoring Mach effects, of course- it can be assumed any reasonable rocket should be going quite a bit faster than the sound barrier...) The challenge is, as stated, structural failures (I assume he means due to aerodynamic loads- the actual G's due to thrust shouldn't be any higher with FAR than firing the same rocket in a vacuum- and most rockets can withstand a TWR of at least 4 there...) and having enough surface area on the bottom of your rocket to obtain high TWR... I imagine you could try radial thrusters to bring up your TWR, but they might wreck too much havoc on your aerodynamic profile to be worthwhile... Regards, Northstar

That depends a lot on the particulars of rocket design. For instance, I notices your designs used NERVA tug engines in the upper stages right from liftoff. That increases average ISP over the ascent, and reduced the redundant engine mass (utilizing upper-stage engines from liftoff is generally a very good idea), and may actually be responsible for your increased payload fraction rather than your low TWR. It also depends on how you define your "payload" Rockets with a TWR closer to optimal consume less fuel during their ascent, and thus will be able to carry more dry mass to orbit. While more of that weight may be tied up in upper stage engines rather than "payload", in some cases the engines from your (mostly spent) upper stage actually are part of your payload- such as when they can be detached from the upper stage and re-attached to another vessel (via docking port), essentially turning the upper stage into a giant drop-tank (no reason for the payload to pack its own engines when they can steal them from the upper stage), or when you recycle the spent upper stage with an orbital scrapping/salvaging operation... There are also other considerations- for instance, a rocket with heavier lower-stage engines may weigh more than a rocket of approximately the same total size with lighter engines and heavier fuel tanks- and thus have a lower payload fraction even though it may actually be capable of carrying a slightly larger payload to orbit than a rocket of comparable size (not mass) with lower TWR... And if you use Solid Rocket Boosters to bring up your TWR, forget about a direct comparison of payload fractions- SRB's are MUCH heavier than LFO fuel tanks and engines for the amount of Delta-V they provide- their chief advantage is that they pack a lot of thrust and propellant mass into a very compact profile... Regards, Northstar

The rocket needs to accelerate faster and faster as it climbs, but it is experiencing less drag- which means the same TWR provides a greater net acceleration on the rocket... Also, if you are performing a gravity turn as you climb, the steeper you enter into your gravity turn, the more gradual your ascent through the atmosphere- meaning less TWR is necessary to keep up with Terminal Velocity... Though, as I stated before- I'm not actually sure if ideal velocity *IS* Terminal Velocity if you are climbing at a 20-degree angle to the horizon... A rocket with sub-optimal TWR (from a fuel-consumption standpoint) will often reach orbit with more Delta-V leftover, because it had more fuel and more Delta-V to work with in the first place. From a roleplaying perspective, low0TWR rockets also make sense, as fuel and fuel tanks are a *LOT* cheaper to purchase and maintain than rocket engines... For a reusable launch vehicle, on the other hand, where fuel has to be replaced on every launch, but the relative cost of engines goes down (as they are re-used again and again...), it makes sense to launch with a higher TWR, closer to a fuel-optimal ascent... (you also save a tiny bit one mission control staff hours that way- as the actual ascent takes less time...) A bit of a tangent, but one point I've always been curious about, is if in real life it actually makes more economic sense to have disposable drop-tanks on a (SpaceX-style) reusable rocket rather than making it 100% reusable... Drop tanks (unlike engines) are going to be resilient to impacts and have a low terminal velocity (which also minimizes temperature increases from air resistance)- so I would also imagine it would be quite easy to slow them down to a safe touchdown speed to prevent damage to them (and allow re-use) with relatively small parachutes... The question is, would the extra payload capacity (and thus reduced number of required launches) on each launch be worth the extra expense of recovery and re-packing the drop tanks' parachutes, or of adding disposable drop tanks to each launch? Regards, Northstar

You can fix TWR at 2 by throttling down (MechJeb has a handy readout on your TWR than you can use as a guide for when to throttle down- using the "maintain terminal velocity button won't throttle you down to 2 because you need a TWR above 2 to keep up with Terminal Velocity...) Regards, Northstar

If you go too fast, the fuel-cost penalty tends to be a little less steep than if you go too slow, but the penalty to your Delta-V budget when you make stable orbit will be even greater because you had less Delta-V to work with in the first place... (lower fuel fraction, higher engine mass) Minimizing fuel expenditures is most practical with a reusable launch vehicle (especially once budgets come out), or if you are operating on another planet with an atmosphere like Duna (keep in mind that terminal velocities will be much higher there, and you need a lot less thrust for a given TWR...) Maximizing Delta-V available after you reach orbit, on the other hand, is more practical for disposable rockets and one-off missions, and should lead to use of sub-optimal TWR from a fuel-expenditure perspective (it's better to spend more Delta-V to orbit if you have more Delta-V in the first place...) Regards, Northstar

Yeah, unfortunately that's exactly what happens in the stock aerodynamics model- drag scales directly with mass, regardless of shape; so you end up with a simple velocity @ altitude chart. Play with FAR if you want more realistic aerodynamics- though then your ideal liftoff TWR goes even higher, as terminal velocity with a well-designed rocket starts off even higher (meaning you need more thrust to catch up...) Regards, Northstar

I think part of what he's getting at, though, is that there is a certain intermediate set of TWR values where the extra Delta-V you have to work with from having less engine mass outweighs the extra Delta-V you spend getting to orbit... See what I had to say about reusable launch vehicles though- where fuel savings become a relatively bigger concern (especially if you operate a reusable launch vehicle off-planet, coupled with off-world fuel production, say with KSP-Interstellar or Kethane...) Regards, Northstar

Lower TWR gives you more Delta-V to work with in the first place because either you have more fuel or less engine mass, but you will actually spend a larger quantity of fuel with rockets with lower TWR... As a result, for disposable rocket stages, you often want to go with more fuel and less engine (lower TWR) because that will get you further for the same rocket mass, even if you expend more fuel... But where fuel consumption and higher TWR (attempting to keep Terminal Velocity) really start to shine is with reusable launch vehicles. OK, not really a huge deal just yet- but once they implement budgets, you'll WANT to cut down on your fuel consumption as much as possible, if the fuel costs you any kind of money, but recovering the reusable rocket gives you back the cost of all the recovered engines... For that matter, most of this discussion about idealized ascent really only applies to the "straight up" flight profile of a (SpaceX-style) reusable launch vehicle anyways- because once you start your gravity turn, your path length through the atmosphere changes, and your ideal velocity probably isn't terminal velocity anymore... (terminal velocity being ideal was determined a long time ago by tests where the goal was to reach the highest altitude possible- which meant a straight up ascent profile, as there was no requirement that the final orbit be circular...) Regards, Northstar

I never said TWR 2.4 was actually best, it was just a hypothetical... Anyways, the increasing ISP with thinning atmosphere is precisely one more factor that makes the ideal TWR greater than 2 at most times, so that you spend less altitude in the thicker atmosphere where ISP is less (as I said, it's not simply enough to catch up and then cut back to TWR = 2, as you'll end up falling behind terminal velocity as you climb with TWR = 2...) Regards, Northstar

You can throttle down to achieve a TWR of whatever you desire. Just because you have the extra engine mass doesn't mean you should use it... As for the table, your speeds are a little slow at the start. Here's a list I copied off the Wiki a while back... http://wiki.kerbalspaceprogram.com/wiki/Kerbin#Atmosphere Kerbin Terminal Velocity 75 m: 100.9 m/s 1000 m: 110.5 m/s 3000 m: 134.5 m/s 5000 m: 163.7 m/s 8000 m: 219.9 m/s 10000 m: 267.7 m/s 12500 m: 342.4 m/s 15000 m: 437.8 m/s 20000 m: 716.0 m/s 32000 m: 2332 m/s Note that taller rockets behave as if they're taking off from a higher altitude (their tops are already higher up), and launch clamps tend to produce a little spacing from the ground, so a better target at liftoff might be 102 m/s Regards, Northstar

Northstar Kerman stood before the packed auditorium at the Kerbal Space Center, full of scientsists, engineers, and Kerbal media... "Gentlekerb's, I have good news, and bad news for you all" he announced, in a loud clear voice. "First, the bad news..." Northstar began, with a dramatic pause. "Last month, our tracking station detected a large asteroid, assigned the identifier IXX-684, possibly as large as 10 meters, on a direct collision course with Kerbin. It is predicted to re-enter on a steep trajectory near one of our major urban centers- the name of which will not be revealed to avert potential public panic. Experts predict it could take over half a million Kerbal lives with its impact and shockwave..." Kerbals gasped in the audience... Northstar steadied himself- he had been preparing for this moment for weeks. "Over the past weeks, a secret Kerbal program codenamed 'Project Amadeus' was commissioned to intercept this asteroid, and redirect its trajectory- attempting to capture it into a stable orbit around Kerbin where we can study it further." Kerbals naturally began to applaud at the news of another space mission, but Northstar waved his hand to quiet them down... "This program was, until today, top-secret. Many engineers here at the KSC were unaware even of its existence. Fewer still were subject to the full details of the plan." Northstar Kerman cleared his throat before continuing. "Massive funding was directed to this program, and a reusable launch vehicle was quickly developed to launch the segments of a large ship designed for this mission. Over the past weeks, both segments of the vessel were successfully launched and docked to each other- one disguised as a fuel tanker and the other as an orbital tug..." Northstar paused again... "The Amadeus' reusable launch vehicle- the ARLV for short- was intended for re-use in launching two unmanned fuel tankers for the vessel- which would be connected to the vessel by Kerbals launched aboard our Reusable Crew Launch Vehicle- which would also provide supplementary fuel to the Amadeus Mission Vehicle if necessary..." Northstar took a deep breath before continuing. "However, the ARLV's launch stage splashed down in the ocean East of the KSC during the recovery portion of the mission launching the second mission vehicle section. This damaged electronic components in the engine and guidance systems- which were not designed for exposure to sea water... Although damage was minor, as the vessel was quickly fished out of the sea quickly, and its interiors soon thoroughly sprayed down with deionized water to remove all potentially corrosive compounds from the vessel; it does not appear that the ARLV will be prepared to make another launch for over 2 months- by which time the asteroid will have impacted Kerbin." Loud grumbling and concerned whispering began in the audience. Northstar waved his arm again in a quieting gesture, indicating he had more to say. "In my meeting with a secret Kerbal Congress committee meeting yesterday, all this was reported. However, rather than allow this asteroid to impact Kerbin, the KSC was provided with a trio of heavy lifter vehicles built for a secret Kerbal Air Force program- the existence and purpose of which was classified, and I am not liberty to share with all audience members present here today..." Northstar reached for the glass of water on his lectern, and took a sip before continuing. The room awaited what he had to say next in complete silence. "By re-appropriating as upper stages several rockets originally designed for use as one-Kerbal reusable crew launch vehicles, which were mothballed when favor shifted to use of larger vehicles with longer range and higher crew capacity, and adding refueling hoses to them; we managed to quickly piece together three unmanned fuel tankers which were launched yesterday afternoon..." Northstar took another sip of water. "Although their guidance systems were old, and we were concerned that they would not all make orbit- hence the reason for the redundant launches- all three of them managed to make stable orbits around Kerbin. We are now prepared to refuel the Amadeus Mission Vehicle, and send it on its mission to save countless Kerbal lives..." Northstar looked sternly at the audience "Should the mission fail, Kerbal government officials have decided we will announce the revised impact location of this asteroid, and begin a mandatory evacuation of the nearby populace. Meanwhile, the KSC has been authorized to use the remaining fuel tankers as kinetics in a last-ditch attempt to re-direct this asteroid, once it enters Kerbin's gravity well." Northstar looked about the room with a faint smile. "That is all, brave Kerbals. May God bless us all- and I hope in our next such meeting I will have only good news to report about the success of Project Amadeus..." OOC: I hope you guys enjoyed the storytelling. My next post will likely be on the refueling of the Amadeus Mission Vehicle, followed thereafter by its ejection towards the asteroid (I will attempt a gravity-assist around the Mun if appropriate- the mission vehicle is going to need every drop of fuel it can get), and adjustment burns as necessary... Meanwhile, the Duna Heavy Equipment Deployment platform will arrive at Duna before Project Amadeus is complete- so expect to at least see something about my capturing it into Duna orbit as well, and possibly rendezvousing it with some of the other ships in the Duna Armada (I might save the actual colonization effort for a separate thread, and roleplay the delay as time spent actually assembling the first permanent orbital station from the components aboard the DHEDP...) Regards, Northstar

Also, here was the one successful attempt I managed before I decided that (1) MechJeb's Ascent Guidance still sucks, and (2) It would be better to aim for an 170 km orbit than a 120 km orbit with this rocket, as it would at least make the direct launch significantly easier (I have a tendency to overshoot my target apoapsis if I'm not careful) As you'll notice, due to my reliance on the MechJeb Ascent Guidance, it has quite a bit less fuel left at the end than either of the vessels that I manually guided to 170 km- despite being at a lower orbit... These are all to be used in my Career save as fuel tankers by the way- hence their lack of any non-fuel payload. Regards, Northstar