StevenLawyer

I've made a single launch stock grand tour ship capable of putting Jeb or Bill down and back up from every single landable planet, including Eve, all without any refuel or support launches. All landings and re-ascents can be done in capsule and include a rover for exploring while on the planet. Except for Eve, which has an asparagus staging one time use ship, all other bodies are landed on using the same re-usable lander with dockable (and re-usable) rover. The mother ship also has six unmanned reusable probes with mini-rovers. I've finished the grand-tour mission with fuel to spare. .

I agree. I was unaware of that until I saw your excellent study on fuel flow. Thanks again for that. Yes. I knew about massless parts, but I keep designing with them in hoping that eventually the devs will make the physics in play match the SPH and VAB. In the real world, in any airplane, while the airplane is in level flight the center of total lift is directly above the center of mass. Otherwise, the plane would begin to either nose up or nose down. That said, traditional (i.e. non-canard) airplanes put the center of lift of the main wings behind the center of mass to induce static stability. By doing so, a traditional airplane's horizontal stabilizer (the horizontal tail) actually has to generate negative lift (downward lift) in order to maintain level flight. It is this downward lift of the tail (which is just a small wing that can generate lift in either direction) that, when combined with the upward lift of the main wings moves the total center of lift forward to match the center of mass. The reason why this set up promotes stability has to do with the relationship between lift and airspeed. Imagine a plane in level flight with the autopilot off (i.e., the plane is trimmed for level flight with no control input). The pilot now momentarily pushes the yoke forward to induce a nose down pitch and lets go. As the airplane accelerates, the tail produces an increased amount of downward lift due to the increased airspeed. As it does so, it pivots the nose upward back toward level flight. If the airplane starts to overshoot to a nose high position, the reverse happens--less airspeed over the tail means less downward force on the tail, which means the nose pitches down. I've flown lots of airplanes, from small Cessna's to corporate aircraft. They all exhibit this behavior (by design)--otherwise, the plane would be dangerous. In a canard airplane, it is just the opposite--you have the center of lift of the main wings forward of the center of mass and then the canard out front provides additional lift. for analogous reasons, this configuration promotes the same type of stability in a canard airplane. Now to KSP. As to Kasuha's comment: I agree that a center of lift exactly on top of a center of mass (i.e., in all three axes) makes an unstable plane. You're correct that it is the putting of the center of lift in line (fore/aft) with the center of mass, but ABOVE IT (higher) that makes the plane stable. I find when I do this that I can fly my planes level completely hands off. In other words, without ASAS engaged or constantly having to use WASD. In my experience, when the COL is aft of the COM, that's not the case. As to Doc's comment: Yes, in the real world, the center of thrust being below the COL will tend to ever so slightly drive the nose up (this is not necessarily a bad thing). I'm not sure that is accurately modeled in KSP--it may be that rotation on any axis due to thrust may only relate to the COM, not the COL. I'm finding no problem with having the COL higher (vertically) than the COT. Thanks to both of you for the dialogue. I love the intelligence of the members of this community!

I've been running into this in 0.242 (x64). After Jeb gets thrown from an External Command seat on a rover, he becomes frozen. Further investigation reveals that he know longer shows as Jeb, but as debris from the rover. It's clearly a bug, since he were being deemed "killed", he should go the way all great Kerbal's do--"poof!" P.S. You can edit the persistent file to resurrect your Kerbal: http://forum.kerbalspaceprogram.com/threads/75586-Master-Thread-Unresponsive-Kerbals-in-EVA

Kasuha: Thanks for your reply and the link to your article on fuel flow. I commend you for your testing. It's a very informative article that has expanded my understanding of fuel flow. I have bookmarked it. I do stand corrected on the CG of larger tanks shifting as they drain fuel. I had learned this from another poster and thought I had encountered it in a ship I built in 0.21, but some quick tests in 0.242 did not reveal any tanks in which the CG shifted with change in the fuel. So, I am uncertain whether this has changed or my understanding was incorrect. In any event, I agree that CG does not shift within a particular tank as it drains fuel--In other words, I agree that fuel tanks are modeled as single points of mass in the dimensional center of the tank. As to the your comments regarding using metal plates, they are not crossfeed capable, so I'm not sure what you are saying. In my experience, if you don't use them, then even if you run the fuel line, your engine will not draw from the tanks evenly. However, I will experiment further with this. Perhaps this has changed in 0.242 such that the plate is no longer necessary. I respectfully must correct your statement that my ship is not a balanced craft. I have built numerous VTOL ships using the techniques in this video and have flown them to fuel exhaustion--they have remained in perfect balance. I hold a degree in physics and am a semi-professional pilot who flies high performance turboprops in which a clear understanding of the change in COM wet to dry is important. The way you make sure that the COM of the vessel wet (i.e., full of fuel) and the COM of the vessel dry (i.e., out of fuel) are in the same place (i.e., the COM doesn't move), is to make sure the COM of the fuel by itself is exactly on top of the COM of the vessel as a whole (whether wet or dry). It is impossible to have a stationary COM from wet to dry if the starting COM of the fuel alone is fore or aft of the COM of the vessel as a whole. If you need me to provide you the mathematical proof of this fact, I would be glad to do so. So, while what you say is true--namely that the COM wet and dry must be in the same place--what I say is also true and is the practical way in which you accomplish a matching wet and dry COM. The COM of the fuel alone must be centered on the COM of the craft (wet or dry), or else the overall COM will move as fuel is burned. Again, thanks for your comments and for your research on fuel burn!

Fellow KSPers: For those having trouble building Space Planes that maintain balance throughout their fuel burn, I put together a quick tutorial:

In 0.22 I found the Mun monolith in the large hole near the south pole (82S 102E) hovering about 2000m above the bottom of the hole.

Taking inspiration from Scott Manley, I decided I wanted to make a ship that could take two Kerbals in capsules (no hanging on the outside of the ship or using an external seat) down to sea level on Eve and bring them home. After several permutations, I came up with the Eve Explorer. It's a large (and thus laggy) ship, but a heck of a lot of fun. It includes a robust two man rover (parachutes down next to the Lander) and six probes that can be sent to explore potential landing areas or other parts of Eve. If you decide to mod the ship, take head of the instructions to prevent a VAB bug from breaking it due to its size. Stock Eve Explorer MechJeb Equipped Eve Explorer