[Why my spacecraft tumbling when i try to insert it on orbit]

I didn't watch all your videos, but your ascent profile was much better on that last video. Keep trying to stay within the prograde marker until around 15-25k or so. Try to time it so that your prograde marker is around 45 degrees in the 10-15k range. These are all general though, different TWRs will warrant different ascent profiles.

It's your game and I don't want you to play with rockets you don't enjoy building or flying, but you are still bringing too much engine at launch, at least at the beginning of your last video, which was a far as I watched. I aim for an off-the-pad TWR of 1.2 using atmo thrust. This way you shouldn't have to lower your throttle so much. By the time your thrust increases with altitude and fuel burn-off, you should be able to maintain a decent TWR without going too fast. Not only are you spending funds on rather expensive-ish engines, you are burning excess fuel to accelerate their mass. Reaching terminal velocity ASAP isn't as big a deal as many players make it out to be.

[Are EVA landings a science mining exploit?]

I'd say it's an exploit as far as using an inexhaustible amount of fuel. Using EVA packs to orbit/deorbit? No. That's using the game's physics. If you could do that on any body, then it'd be an exploit too, but it takes TWR and Dv into account (at least the amount of Dv a Kerbal can take with them) so it's not cheating. However, good for you that you can eyeball rendezvous with EVA and can get 2100-some science off your first launch!

[Do you use maneuver nodes?]

I voted use them a lot, but only one at a time. Except going to Minmus, I put out a second one at the AN/DN to see if my original node was placed correctly. I'm not to the point of IP travel in my career yet, but I imagine using a second one to deal with inclination to make sure my first one has been placed right too. I don't set up a series of them to plan out my Dv, I use a Dv chart to do that.

However, I don't use them ALL the time. I'll eyeball my maneuver to place my PE right where I want it after a SoI change. I eyeball many inclination changes too, but I like to put a node down if I'm going to use any radial burns for corrections. I also put a node down for circularization burns because I don't fly with a standard ship. My acceleration values vary enough where I like to put a node down mainly for getting the correct burn times.

I've been trying to learn to use them better for timing landing burns. Haven't nailed it perfectly yet, but they definitely help getting much closer.

I think they are a very important part of the game. I can appreciate those who do not need them, but I pretty much do need them and I think it can reduce small amount of Dv usage vs. not using them.

[Cannot Warp While Under Acceleration]

When aerobraking, you are under an acceleration. A negative acceleration produced from the drag of the atmo. As sal_vager said, use alt+ to use physics warp. It's only x2, x3, and x4, but it's better than nothing.

[Interplanetary transfer from Kerbin orbit with Mechjeb]

I hope five months is not too much of a necro, but I have a related question: what's the best way to time a launch so that step 5, waiting for the ejection node, doesn't take too long? I went to Eve last night, and every time I'd launch, the ejection node was about a year into the future. Worse, when I took the advice in MJ's manual about recalculating far-future nodes, by cancelling and re-creating it 20 days in advance, it said I'd need to wait another year-plus for the next ejection window!

I tried waiting for the phase angle to be -54.whatever, and that didn't help, but maybe I just barely overshot and had to wait a full cycle? Is there any function of MJ that will ensure a launch during the transfer window?

Most likely you just overshot it by a bit. I'm pretty sure MJ's new warp helper has a phase angle mode now, but I haven't used it yet so I cannot comment on its accuracy. Otherwise Otis has a good suggestion. I mainly use Kerbal Alarm Clock. I cannot remember exactly right now because I haven't done any interplanetary stuff in a while, but there are two modes to calculate transfer times. I think MJ uses one mode for inward travel and the other for outward. I wish I could log on right now and check to help out more, but I can't.

[Landing on airless bodies]

Think of it this way: how much delta-V would you need to get from the surface to the orbit, that is, do the maneuver in reverse?

This. It always takes more delta-v to get to a higher orbit, so it'll always take more delta-v to come back down from that orbit. Also, due to Oberth's you will get more delta-v per unit of reaction mass burned in the lower orbit. In many cases this won't be very much, maybe even unaccountable, but the math is still there.

[Ideal atmospheric escape? (Calling the help of advanced engineering mathematics.)]

I was under the impression that staying near terminal velocity on ascent was just a by product of Kerbin's soupy atmosphere and the way drag is calculated in game. Pretty much the same reason it seems most efficient to start the gravity turn at 10k even though that's not realistic. If you use ferram, for example, you can start the gravity turn at launch, and with a streamlined rocket exceed terminal velocity by a large margin with minimal losses as opposed to stock.

Just wanted to clarify something here. Ferram does not allow you to fly faster than terminal velocity. You can always fly faster than terminal velocity, if you want to. Ferram does not allow you to save delta-v by flying faster than terminal velocity, it allows your terminal velocity to be faster. You still want to fly at terminal velocity, it's just that Ferram allows you to have a faster terminal velocity. Why?

What is terminal velocity? Very quickly, it's when the force of drag equals the force of gravity. If your rocket is more aerodynamic, it's drag generated is less, so it's terminal velocity is higher as gravity remains constant. We want to fly at terminal velocity because at that speed the sum of our losses to gravity and our losses to drag is the least. Any faster and we generate more losses to drag than we're saving to gravity. Any slower and we're losing more to gravity than we're saving to drag. It's all about balancing the losses we generate. As we know, it basically takes 4,500 delta-v to reach LKO. At 80 km, my ship is only traveling 2,279 m/s. The missing 2,221 m/s went into drag, gravity, and a little bit of steering losses. It's managing these losses that's the goal of an efficient launch.

[Delta-V and more rockets?]

is 4000 delta-v at .75 TWR the same as 4000 delta-V at 2.5 TWR?

Thanks in advance.

This matters where you're at. If you have already achieved orbit, 4000 delta-v is 4000 delta-v. Both rockets will be able to get to the same places, assuming you don't have too long of a burn with the .75 TWR rocket.

It's different when considering landing or launching from a gravitational body. If your TWR local to the body you are trying to launch from is lower than 1, you will have to burn off reaction mass to lighten your ship before it lifts off. You have lost that available delta-v because you were not able to use that reaction mass to either increase or decrease your rocket's velocity. If your TWR is above 1 but still very low, you will incur excess gravity losses during your ascent. If your TWR is too high and you are launching from a body with an atmosphere, you will incur excess drag losses. In either case, you will incur both gravity and drag losses, the key is to minimize their sum. That occurs at terminal velocity. So to reduce the amount of delta-v lost during ascent, you need to match your TWR to a value that allows you to fly as close to terminal velocity as possible. This is at least important early in the launch, it is generally too cost prohibitive to maintain terminal velocity in the later stages of your launch when you are traveling through the thin upper atmosphere.

[What is the proper way to use solid boosters?]

When money becomes a thing, asparagus is going to be seen as the false prophet, and boosters are going to be seen as the road to the future, considering that you only have 1 part for a booster, versus the 40 or so parts that go into asparagusing, a fourth of which are the motors themselves which are a bit spendy iirc.

I agree SRBs will have a stronger future when costs come to play, but I don't think asparagus will be any type of false prophet. IMVHO, one should never include SRBs with the intention of adding delta-v to a rocket. The best use of SRBs is adding TWR to a rocket that has the delta-v to make orbit, but loses too much to gravity due to too low a TWR. Here, the SRBs are not adding delta-v, but recovering lost delta-v. Tweakables help here quite a bit, as I've always felt the current SRBs have too short a burn time.

It's nice that an SRB comes with fuel and engine all in one part and thus helps lower part count, but if you are up against part count limitations, I don't think a 325 kN engine is going to give you the increase in thrust you need for that monster. Perhaps the inclusion of a 2.5m SRB would, but not the current 1.25m parts.

This is all concerning the launch vehicle. Once in orbit things change quite a bit.

[My personal breakthrough Eureka moment I did by mistake.]

Cost is important, and SRBs are cheap, but it isn't important yet.

I did some delta-v calculations. First, let's assume I have a 10 ton ship powered by an LV-T45. I do not have enough delta-v to complete my mission, so I add reaction mass to my orbital stage. For this specific scenario, I have two options:

A) Add two Rockomax BACC Solid Fuel Boosters on TT-38K radial decouplers or,

Add two liquid fuel and oxidizer boosters consisting of an FL-T800, an FL-T400, and an FL-T200 on TT-38Ks. They are cross fed to the base ship with fuel ducts.

This is a nice comparison because both the BACC and the stack of FL-T tanks add up to 7.875 tons full. Using this delta-v equation:

delta-v = ln(start mass / end mass) x Isp x 9.81,

For option A I have a starting mass of 25.8 tons, an ending mass of 10.05 tons, and a vacuum Isp of 250. I add 1,671.6 m/s of delta-v to my base 10 ton ship using option A.

For option B I have a starting mass of 25.9 tons, an ending mass of 11.9 tons, and a vacuum Isp of 370. I add 2,822.8 m/s of delta-v to my base 10 ton ship using option B.

If I indeed did these calculations correct, I add more delta-v per ton of mass lifted to orbit by adding liquid fuel and oxidizer than I do solid rocket boosters. I don't have the numbers for the SRBs you used form KW, but the point I'm trying to make is adding more reaction mass for an efficient liquid fuel rocket will gain you more delta-v than adding that same reaction mass for inefficient solid rocket boosters.

I hope I did the maths right! LOL

[My personal breakthrough Eureka moment I did by mistake.]

The thing is, during mid stage, my "true" mid stage is more or less just the rockets, since I use virtually no fuel from the tanks, or nearly none.

I consider boosters not part of the ship, since they are a 1 shot all use, and can't turn them off. Instead of using fuel which I can use for other things and fine tune maneuvers, etc. isn't being used.

They are still thrust generating devices that spend reaction mass to add or subtract velocity from your ship. Even if you decide to not use them until you are already in orbit, they took the expenditure of reaction mass to lift them to that point. They are ever so much part of the ship.

As for your Mun encounter, I don't see a PE tag on your orbit. Looks like a surface impact incoming.

Glad you are reaching new milestones in your space program. Keep it up!

[Fuel Lift concepts]

You have to remember to include the fuel burned to lift the re-fueling fuel from 80 km to 600 km. It's the cost of the entire space program, not just any individual ship.

[Getting Rovers from the SPH to the VAB]

Start out with a piece you will not use. That's your root part. Build your rover extending from that piece and then copy it to the sub-assembly. Just remember that you'll attach the sub-assembly from whatever part was attached to the root in the SPH to wherever you want to attach to your rocket in the VAB.

[running 4 nukes at 25%]

False. It all depends on the mass of your ship. Try to do a burn with 1000t and a single LV-N, it'd take you a year. Even in less extreme cases it makes precision impossible and you waste fuel on correction burns.

This is how I view it. I don't want to take the time to plan out ahead of time when to start my PE kicks and at what ejection angle to start so that I'm in the correct position by the time I make my last burn. What a pain in the butt. I'll lose a couple 100 m/s of delta-v to cut my burn times in half, or more. If my delta-v budget is really that close, adding fuel tanks to ships this size is not a very big concern anyway.

[Power without control is nothing]

But, that's not the whole story... More engines means higher dry mass, which means lower total Delta-V. So rocket designs also need to balance thrust-to-weight ratios against bringing useless empty mass. Given this factor, sometimes the optimal configuration isn't one that peaks at terminal velocity, but something lower - because the total Delta-V is higher due to less empty mass. <- That can really only be sussed out through test launches though.

Note: Configurations that are capable of going faster than terminal are always sub-optimal. You are simply carrying extra mass (in the form of powerful engines) that go unused fully, which will always reduce your total Delta-V - a double whammy: dV lost due to going faster than terminal and dV lost by having extra mass.

Exactly. It turns out that the 4,500 number is pretty spot-on for fuel efficient ascents.

Remember OP, delta-v is not fuel usage, it's merely change in velocity. We can get to orbit by flying at terminal velocity as long as we can, and in doing so we can reduce our losses to gravity so much that we may be able to get to orbit using 4,300 delta-v. Maybe even less. Problem here, as EtherDragon has mentioned, is that we are carrying massive amounts of thrust high into the gravity well in order to keep up with the ever-increasing speed of terminal velocity. More thrust generally comes at the expense of more dead-engine mass, lower specific impulse, or a combination of both. These require us to pack more fuel to re-achieve our delta-v goal.

By using less thrust and smaller, more efficient engines we are capable of getting a given tonnage of payload to orbit using less fuel, even though we "used" more delta-v. The trick is finding that middle zone that gives us enough TWR and delta-v while using the least tonnage in our lifter. Payload fraction is more important than delta-v usage. As payload mass is constant, the only way to increase payload fraction is to reduce lifter mass. The majority of lifter mass is fuel. Of course, that only matters when costs become important.

[Power without control is nothing]

Deployed parachute or not, any object falling in the atmosphere will be traveling at terminal velocity. The only thing to watch is whether it has a drastic change in velocity when it passes through 10 km.

[Power without control is nothing]

...Unless are you playing with Ferram Aerospace Research. Maybe you know that KSP hasn't a realistical drag model that makes you ships very unaerodynamics at low altitudes, and this mod furnish a more accurate one that allow you to go faster and save Delta V (=fuel).

Anyway, I think you can go a little faster also in stock KSP than speeds listed above. Remember that every second spent in vertical ascent means fuel wasted to counteract gravity. The goal is to find a speed that don't waste too much energy both in drag and gravity. In stock KSP I used to keep speed...

>150 m/s if >3000 m

>250 m/s if >6500 m

>400 m/s if >10000m

The you can throttle up and go for the gravity turn.

But you are still want to travel at terminal velocity. Remember, terminal velocity is where the drag acceleration equals the gravity acceleration. In stock KSP, all things have the same drag coefficient, except nose cones and parachutes, but their mass is usually a very small percentage of the total ship's mass. In the real world, aerodynamics play a more important role. Their purpose in this case is to increase the value of terminal velocity for any given altitude, because the ship has a lower drag acceleration.

In KSP we associate terminal velocity as a constant relative to the planet with the atmosphere we are trying to escape. In the real world terminal velocities vary depending upon the aerodynamics of the ships, in conjunction with the attributes of the planet with the atmosphere. I've never played with FAR, but what it should do is raise terminal velocities of ships as they are designed more aerodynamically. At this rate, you are requiring less delta-v because you can lower your losses to gravity. But, you should still want to limit yourself to the terminal velocity of your specific ship.

[Is asparagus the best staging system? (might contain science)]

Actually, in the given case where all 7 engines are identical and there is more than enough thrust from 6 of them, then the onion staged version can't possibly out perform the serial stage. best case scenario would be break even.

Onion staging would only be an advantage if the boosters didn't have enough thrust to maintain terminal velocity on their own, or if the core stage had a more efficient engine than the boosters.

I think I essentially said that, didn't I? In theory, the cross-feed could accelerate to terminal velocity faster, at the cost of increased fuel usage during that brief increase in acceleration, which happens to take place at a lower altitude where the engines have less Isp. After reaching terminal velocity, if six engines can do it the seventh isn't helping. Whether or not it is worth it? That particular test proved it wasn't.

Talking about asparagus in real life and why NASA doesn't use it, has anyone given any thought to the physics needed to pump fuel the the very bottom of one tank, to the top of the other, all while continually accelerating? I'm not sure the physics of gravity would allow the liquid to be pumped in that fashion. It's like trying to lean forward in a car as it is accelerating. Now do it vertically. Just a thought. Any ideas?

Unless I'm mistaken, fuel doesn't "fall" out the bottom of the tank into the engine, it is still pumped from the tank to the engine. In the case of cross feed, we KSP players attach from tank to tank. In possible real-world applications, I think they'd still pump from tank to engine, it's just that they're pumping from one tank to an engine in a different stack. So there should be no reason to pump that fuel "up".

[Is asparagus the best staging system? (might contain science)]

I didn't read through the whole thread, but I didn't see this mentioned in the first few pages; am I the only one surprised and slightly confused that the simple crossfeed was outperformed by the two-stager? The only reason I'm coming up with is that it has to do with a sudden drop in TtW when the boosters cut out, but at twenty or thirty km, would that matter? What am I missing?

Unless I have misidentified the engines, Plur303 was using Mainsails. For each Mainsail he/she had two X200-32s and the payload wasn't very much. This is way too small of a ship for asparagusing Mainsails, they can lift way more than that. I saw that MechJeb was using auto-throttle, and 6 Mainsails provide plenty of thrust through most (actually all) of the ascent, let alone a seventh fed through cross-feeding. There was really no benefit to cross-feeding the center engine unless that extra thrust was actually needed. The two-stage saved what? Eight units of fuel, I think? Yes, the "onion" staged should have out performed it, but it is really close all told because it should be for this particular situation. Get a situation where that 7th engine is needed to maintain enough TWR over the entire life (or the vast majority) of that first stage, and you'll see the cross-feeding advantages more clearly.

[High TWR low ISP vs low TWR high ISP (VAC)]

TWR is not irrelevant in space and Isp is not totally trumped by TWR for launch. Clustering higher Isp engines to give your ship the needed thrust can result in less reaction mass needed to achieve a certain amount of delta-v, like the 4,500 needed for Kerbin orbit. Likewise, adding extra engines to an interplanetary ship for additional TWR can result in less wasted delta-v during the burn. Just wanted to get that out to start.

In the case you presented, you mention all engine choices give you the delta-v required to achieve your goal. In this case it would make sense to use the engine with the highest TWR to give you the shortest burns, but you've over looked something. By using the engine with the highest Isp (assuming it gives you high enough TWR) you more than likely have extra delta-v. This means two things:

you have more burn time to make any additional adjustments you may want/need to make or

you can reduce the amount of reaction mass your ship has and still have enough for your planned maneuvers.

For the second case, by reducing reaction mass, you have naturally increased the TWR of the ship. As the mass of your ship is less, a smaller lifter is needed to lift it to the same parking orbit above Kerbin. From an efficiency standpoint the second option makes more sense. Less is more in space travel.

[.23 - Just not getting the progression-path for science labs.]

I don't quite fully understand it yet either. If you are going to make multiple trips to multiple biomes, then you have to bring the fuel there one way or another. Being that you can only take advantage of transmitting 2 sets of experiments, you'll have to bring back experiments to get the full value anyway.

I was hoping the Lab Module would be KSP's first part towards giving bases (orbit and/or surface) a reason other than just for fun. The ability to gather all available science with transmissions can make long-term commitments pay, at the expense of getting that Lab Module there in the first place. I guess I just don't see only 2 sets of transmissions being worth the effort.

[So one Atomic Rocket Motor is better than four?]

Assuming your ship is large enough and you can time a spiral transfer to intercept your target, yes. Assuming you are using a Hohmann transfer with a ship with a really low TWR, you may actually have more "usable" delta-v by adding an engine. There is a point where long burns lose more delta-v than the additional mass takes away.

[Updated Delta-V cheat sheet?]

4,523 delta-v to get to 75 km orbit. Sounds normal. I get to 80 km using 4,450. That's a big difference from claiming 3,800.

[The possiblility of a Mars Cycler in KSP]

How much delta-v would one need to establish one of these cycler orbits? Hypothesize with Duna. 1060 to Hohmann transfer. Will a cycler orbit take 1100? 1500? 5000? No matter, it will be a less efficient orbit than a Hohmann, that'll be for the initial burn for the cycler, for each rendezvous orbit for the crew module, and each circularization/de-orbit burn at Duna. Then to rendezvous back up with it and circularize back at Kerbin (or aerocapture, either way it'll take another burn). How much extra d-v it takes to establish that cycler orbit would determine how many Duna missions would be necessary to economize. Or I really don't have a clue what I'm talking about...

[need an addon to calculate]

I like MechJeb's interface better, but I like KER's better when in the VAB, if only for the ability to calculate TWR in relation to the body you are gonna visit. It's amazing how little an engine one needs on places like Minmus.