arkie87

Some great ideas! Another place to add a button is to the maneuver node icon itself in the map view, when it collapses. I can never figure out how to get the menu to show "warp to maneuver node" to appear.

Rolling resistance does increase with mass for non-rigid bodies. However, does KSP simulate it (i'd be impressed if it did). Regardless, rolling resistance still cannot increase breaking force above what is possible from static friction...

More weight shouldnt help. Friction is proportional to the normal force. The more you weigh, the more friction you get, but also the more mass you have, so your acceleration will not and cannot change. More wheels wont help. The more wheels you have, the less weight is on each wheel. Your acceleration is always related to the local gravitational constant. No getting around that (unless you use RCS or engine to provide extra downward force). The maximum angle uphill (or downhill) you can go at steady speed is related to the coefficient of friction of the wheels ONLY and not dependent on gravity, number of wheels, weight, mass, etc... http://physics.bu.edu/~duffy/semester1/c6_measuremus.html

Breaking force is proportional to local gravity (friction is proportional to weight). You will only slow down at approximately 1 local g. On Mun and Minmus, that is quite slow... EDIT: on review, it appears you are talking about breaking on Kerbin...

Try to keep your ship pointing within the prograde circle. Deviating too much from prograde will cause you rocket to flip due to aerodynamic forces. If you have them, put fins on the bottom/back of the rockets (think "arrow"). This will allow you to deviate further from prograde vector for more aggressive turning. - - - Updated - - - Or just watch this video:

Yes, i've done this many times, usually when trying to turn a craft with a large moment of inertia and weak torque, such that it takes a while. I would try turning with the a,s,d,w,e,q keys (whatever i needed to do) and then simultaneously, with my other hand, press alt+> key, to enter physical time warp. Thus, i enter time warp, but also adjust my trim by accident, since i pressed alt+(a,s,d,q,w,e) at the same time That's most likely what happened to the OP?

1.0.0 aerodynamics and heat shielding seemed fine at times, but other times, would appear completely unrealistic. I've had crafts explode at 45 km at 1300 m/s during ascent, and 65 km during descent. Something appeared to be wrong with the convective flux term. In 1.0.2, they fixed certain bugs (like craft overheating in water) etc... which leads me to beleive that 1.0.0 was buggy. It would make sense then that they had to turn down aerodynamic heating in 1.0.0 due to these (then unknown) bugs since craft were exploding when they shouldnt. I think after fixing these bugs, aerodynamic heating can be turned up...

I'm not a realism nut, but i like what they did. It's educational and creates "aha" moments when you dont factor that part into the equation... Case in point, i had a a space station that i decided to de-orbit. Since it was a space station, i never put parachutes on it. However, i had like 1600 m/s deltaV on it, so i figured i could slam it into the atmosphere, slow it down to 200-300 m/s, and then use the engine for a powered landing. I had like TWR = 3 in vaccuum, so i figured it would be easy. I entered the atmosphere, slowed down to 200 m/s, and then fired up the engines, not realizing thrust would be reduced, and my TWR actually dropped to 0.8, so needless to say, i had to launch a quicksave

Basically, what the title says: i've noticed that when using "warp to" button on my craft's trajectory, it doesnt always slow down to 1x time acceleration once it arrives at the point (sometimes staying on 100x). Does this happen to anyone else? Does anyone know what causes it or how to fix it?

I experienced both things. Sometimes, my craft was fine coming in at 3 km/s to ~36 km. Other times, it would explode at 45 km for no reason. When i used debugger i saw convective fluxes in the 10's of thousands. After 1.0.2, the convective fluxes stay around 5,000... I think there was some sort of bug in 1.0.0... Anyway, IMHO, I dont think the game would lose it's mass appeal if default aerodynamic heating was set to hard mode and every descent must be perfectly planned (though sliders to let other players make it more difficult are fine). IMHO, i think the default setting for aerodynamic heating should be something like: (1) from LKO, you pretty much just cant come straight down, since G forces will destroy craft/kerbal. (2) from Mun or Minmus, you either need a heat shield and a steep descent (say 20 km) or no heat shield and a shallower descent (say 35 km). (3) Returning from interplanetary mission, you need a shallow descent (35 km) and a heat shield. But that's just me.

Thanks for the informative reply. I will review your source. Based on my derivation from my source, i arrived at T_atm (static temperature) is in the equation. it is not a mistake. please double check my derivation. I am aware that T_aw is not T_atm... Yes, the source i posted ignored recovery, apparently (i'm not an aerospace engineer so some of these equations are new to me). We can assume Pr is 1 for simplicity and still be more accurate than what KSP does now. The main benefit is convective flux not spiraling out of control...(it seems in the forums, other people are starting to complain about re-entry heating difficulty) - - - Updated - - - Your source says: q=h(T_w-T_r) with T_r = T_atm +1/2* r*V^2/Cp My formula is: q=C0*rho*V*(V^2 - 2*Cp*(T_w - T_atm)) if we make the simplification that r=1 everywhere (an overestimate), then we can substitute T_atm = T_r - 1/2*V^2/Cp q=C0*rho*V*(V^2 - 2*Cp*(T_w - T_r + 1/2*V^2/Cp)) q=C0*rho*V*(V^2 - 2*Cp*(T_w - T_r) - V^2) q=2*C0*rho*V*Cp*(T_w-T_r) so our formulations are equivalent and your h = 2*C0*rho*V*Cp

Until just now, i wasnt sure if there was a bug, or if there was, what it was or how to fix it... That's why i posted this, hoping someone could help me pin it down or explain that there isnt one... If you dont have anything nice to say, please dont say anything at all

I found a good reference for the convective flux relationship: convective_flux = density*velocity^3*convection_constant See Page 22 Interestingly, the derivation assumes that the wall temperature is much less than stagnation temperature. Thus, this formula correctly predicts heating when the wall is cold and heating is just beginning, but as T_wall approaches stagnation temperature, convective flux will not approach zero, as it should... NathanKell: how difficult would it be to make a mod that corrects this incorrect assumption? After reviewing the equations all that is needed is to add an additional term to the convective flux: from: convective_flux = density*velocity^3*convection coefficient To: convective_flux = density*velocity*convection_coefficient*(velocity^2 - 2*specific_heat*(T_part - T_atm)) where T_atm is static temperature (not stagnation temperature) What do you think?

I found a good reference for the convective flux relationship: convective_flux = density*velocity^3*convection_constant See Page 22 Interestingly, the derivation assumes that the wall temperature is much less than stagnation temperature. Thus, this formula correctly predicts heating when wall is cold and heating is just beginning, but as T_wall approaches stagnation temperature, convective flux will not approach zero, as it should...

I'm glad to know people do that to other people and not just me... sometimes getting answers on these forums is impossible!!!! And yes, that has happened to me too

Yes, that is exactly what i was saying (and everyone else; no one is confused about that)... have you read the whole thread? No one ever questioned why atmospheric temperature (i.e. external stagnation temperature) was so high.... We are confused why there is heating when readout for Temp_ext (stagnation temperature) is BELOW part temperature... NathanKell proposed a reason here: http://forum.kerbalspaceprogram.com/threads/117511-Serious-Bug-in-Convective-Aerodynamic-Heating?p=1886854&viewfull=1#post1886854 IMHO, there is still a bug since Temp_ext is not used above Mach 2 or so, so it is misleading, to say the least... Futhermore, I'm not convinced that the form of hypersonic convective flux is correct. convective flux = density*velocity^3*convection_constant What is the physical basis for this form (any sources?)? Regardless, there also seems to be a numerical problem: at hypersonic velocities, flux is independent of part temperature so part can be heated to infinity, even above the stagnation temperature of the compressed air. this is clearly not physical The only hand wavy explanation i can give is that since radiation heat transfer coefficient grows with T^3, (flux grows with T^4), radiative heat transfer coefficient will be dominant anyway... though i'm not really convinced that is the case (for example: h_radiation(T=2000K)~=5.67e-8*2000^3=450 W/m2-K.... that is not large at all...)

Thanks! That is consistent with everything we have observed. Since external temperature isnt used (i.e. bypassed when doing convective flux calculations), it has been a bit misleading. Marked as answered! I would like to know what the effective Temp_ext, given the flux and heat transfer coefficient to see if that is realistic... Thanks again.

that's what ive been saying Unless it's just a display bug, and the game actually simulates atmospheric compression to 20,000 K - - - Updated - - - The main reason this is a problem is because it seems to be acting up even when it shouldnt... i.e. everyone would be fine with the plane getting superhot at sea level and going 1500 m/s. However, at 65 km, there shouldnt be any convection even at interplanetary velocities... and my ships have had trouble returning at orbital velocity...

Exactly; it's what makes me think the game is using the wrong formula for convective heating i.e. adding a separate heat source term when velocity gets too high, rather than just make air temperature increase, and part temperature approach air temperature via convection.

I would agree with you if velocity always equaled temp_ext, but that isnt the case always (for low mach numbers or in space), so i dont think thats the root of the problem (or at least, not the ONLY problem). - - - Updated - - - Fair enough. If possible, if its not just a display bug (which i dont think it is for the reasons ive given above), i might even consider writing a mod to fix it... though i have little experience with that. - - - Updated - - - Since you've written your own mods for re-entry, do you think it is still behaving physically accurate (not 100%, but at least order of magnitude)? Clearly, 20,000K for 1500 m/s at sea level is a bit high....

i'm seeing the same thing-- it usually happens with the okto probe, since its max temp is relatively low (so it splodes first). I think it might be a bug with convective heating...

I like to post things in science forum since people here generally are more willing to discuss physics/science rather than just giving me an answer and get offended when i argue why their answer makes no sense. So i think this is the perfect form. I didnt place it in bug reporting because i think we might be making progress i.e. discovering that velocity = Temp_ext...I might post it in bug forum once i am more confident that there is definitely a bug... First of all, no, i didnt get a good answer. Everyone just gave an explanation ignoring the equations, like you are here, saying crafts explode when they overheat and hypersonic craft get hot. That is not helpful, which, once again, is why i came here. For some reason, everyone on Gameplay Questions and Tutorials just wants to give answers, and get insulted when you argue with them, instead of defending their positions (like you are doing here). Second, I didnt mean to be insulting (my use of emoticons were supposed to convey i was being playful). But calling me a troll I think is insulting. ... I realize that. That is not the issue we are discussing. This is condescending and unhelpful... He admitted he had no idea what newtons law of cooling was, but was participating in the discussion anyway... that is not helpful... If there is a bug, then it is a HUGE problem... Just because others havent noticed it, doesnt mean its not a problem. Other, inexperienced players (or players who never played with deadly re-entry) might not be familiar with what can and should cause re-entry problems, so they might have assumed they were doing something wrong... - - - Updated - - - Yeah, i dont know. I would love to see the source code, or a Wiki on how KSP handles re-entry heating (convective, radiative, and conductive heat fluxes). - - - Updated - - - Good find! It seems to always be the case above Mach 1-2... Below Mach 1-2, i think temp reads normally...

It's not entirely a matter of convention. The relative signs matter. Q=h*A*(T-T_fluid) -- if T < T_fluid, Q is negative, so heat is leaving the part, but that is clearly not what is shown here. For low mach number, Q is negative when T_fluid > T. The problem only occurs at high Mach numbers... The effect of Reynolds number, attitude etc... cannot influence sign, just magnitude of the value of "h". I think i will post it to the bug reports... but first i wanted to see if anyone was aware of this or had a logical explanation. If there was proper implementation, turning off temperature damage wouldnt matter, since Q would be negative and T would approach T_ext... I dont think you understand how heat transfer is supposed to work.... - - - Updated - - - Anyone notice how 1505.6 is both the value for surface velocity as well as T_ext?

I posted this in gameplay questions, but did not get an answer... So, i've noticed that some of my craft appear to explode for no reason due to overheating in 1.0, so i decided to debug a bit. I think i've found a serious problem: When i look at the ram intake temperature, it is larger than air stream temperature, and yet, the convective flux is still positive (when it was below air stream temperature, convective flux was negative)-- why? This obviously violates Newton's law of cooling ( Q=h*A*(T-T_fluid) ). Yes, h might be a complicated function of Reynolds, attitude, Mach etc... but these only effect magnitude, not sign. Thus, if T < T_fluid, T cannot become larger than T_fluid... To highlight this point, another user, Windy_Skunk, performed an experiment of hypersonic flight at sea level with temperature damage turned off. Here are his results: Temperature approaches 20,000 K while air temperature, even after all the shock heating, approaches 1505.6 K. Incidentally, 1505.6 is EXACTLY the same value as the surface velocity... so something is fishy...

Let me google that for you If you arent familiar with Newton's law of cooling or convective heat transfer, why are participating in this thread? (not trying to be rude, but...) Yes, the air heats up a lot. If you look at the debug menu, the air temperature (Temp ext) is 1505.6 K-- that's how hot it gets from heating. So how exactly is the part almost 20,000 K?