GoSlash27

- - - Updated - - - That didn't work so well. Let's try this:

I'm not going to bother using the science labs unless there's a serious rebalancing. Although they convert data into lots of science, it's simply too grindy to set up and run. Best, -Slashy

Hmm... curiouser and curiouser. I guess it must be version- dependent. I'm running 1.04.861. Perhaps they noticed this bug and closed the loophole? Best, -Slashy

Jolly_Roger, Not true in my case. I have a clean stock install and it shows up for me in the VAB but not the SPH if I follow the OP's instructions. Perhaps this is only in sandbox. I haven't dug into it that far. Best, -Slashy

A late late update! I have integrated thrust requirements in my application of the reverse rocket equation, but haven't talked about that here. Designing a stage with a minimum acceleration requirement involves a couple additional steps, but it's all pretty logical. First, you figure out how much mass one of your proposed engines can lift at the desired acceleration rate. Next, you figure out how much of this theoretical rocket needs to be fuel in order to achieve your DV budget. Given the required fuel mass (and thus tank mass) and the mass of 1 engine, you figure how much payload one of these engines could handle in this mission. Finally, you scale this to your actual payload requirement and proceed as usual. It works like this: I wish to design an upper stage for a 20t payload. It needs to generate 1800 m/sec DV at no less than .7g acceleration. I will simultaneously check all engines, but for this exercise I will look at the Terrier. Specs: Isp= 345s T= 60kN M=0.5t Since this is an upper stage, I will assume vacuum figures. How much mass can a Terrier lift at .7g? M=T/(g0*a) where M=theoretical rocket mass in tonnes g0= local surface gravity (9.81 m/sec^2 in this case) a= acceleration requirement 60/(9.81*.7)= 8.74 tonnes How much of this theoretical rocket needs to be fuel in order to achieve 1800 m/sec DV? Rwd= e^(DV/9.81Isp) Rwd= 2.718^(1800/(9.81*345) = 1.70 Fuel fraction= (Rwd-1)/Rwd Fuel fraction= (1.70-1)/1.70 = .412. 41.2% of our theoretical rocket is fuel. How much of our theoretical rocket is tanks to hold the fuel? Fuel fraction/ Rfe= tank fraction .412/9 = .0458. 4.6% of our theoretical rocket is tankage. Adding them together yields 41.2+4.6= 45.8% of our theoretical rocket is fuel and tankage. Multiplying it by the mass of our theoretical rocket, .458*8.74= 4.00 tonnes of our theoretical rocket is fuel and tanks. How much payload could one of these engines handle in this requirement? Total mass- fuel and tank mass- engine mass= payload mass. 8.74t - 4.58t - .5t = 3.66t payload. This needs to be scaled up accordingly to meet our 20 tonne payload requirement, so we need (rounding up to the nearest whole number of engines) 20/3.66= 6 Terriers to do this job. Given this figure, we proceed normally. Best, -Slashy

GigaG, Yeah, it's not that big a deal from the Mun. Just keep your Pe above 47km until you've bled off sufficient speed. You don't really need a heat shield until you go interplanetary, but you do have to be cautious. Also, take care not to run out of electrical power. If it looks like that's going to happen, set your chute to 0.5Atm and trigger it. That way it will still deploy safely and automatically. Good luck! -Slashy

^ Seconded. "Minimum DV to orbit" doesn't get you anything. What you want is minimum mass and minimum cost. Vehicles that are designed to achieve orbit with minimum DV accelerate rapidly while following a gravity turn. Because they require bigger engines to do that, they are neither mass efficient nor cost efficient. I design my stuff to use cheap boosters (you're gonna throw them away) and light upper stages. It carries a penalty in total DV to orbit but pays off in higher payload fractions and lower $ per tonne. Best, -Slashy

Rthsom, Try it in the VAB. It only works for me there. Best, -Slashy

322997am, Here's one way: Best, -Slashy

It works on totally stock installs as well. Advance filtering > Filter by cross- section > surface attach. Best, -Slashy

^ This is true. Refer to the "Caveman challenge". It's amazing what can be accomplished without any upgrades. Best, -Slashy

Clear Air Turbulence, I do this: Then this and eventually this Best, -Slashy

Gooru, Well, you established a fix for it. That's more important. Best, -Slashy

Steven Mading, I don't disagree with any of this, but I don't watch live streams for that reason. I'm mainly watching for educational purposes, so while sloppiness and mistakes are expected... I'm still a lot more likely to turn it off and watch something else. Best, -Slashy

That's true and I'm sure it works just as well now as it did then. But it's "old" in the sense that my designs have evolved considerably since then. I'm using a lot less engine and a lot more streamlining these days, which results in lower operating costs. Best, -Slashy

Spaceplanes that are designed that way from the outset fare very well, but in the main spaceplanes don't respond well to unplanned additions. It usually requires rebalancing and scaling up the rest of the aircraft to accommodate it. My back- of-the-envelope says that a RAPIER powered rocket needs to be 28% fuel by mass *when in orbit* in order to have 1 km/sec DV. This is not counting the fuel that's required to get it up there. If you incorporate NERVs, this percentage drops to 12%, which is a whole lot more manageable. The trouble is that NERVs are so heavy that the engine itself takes up a large portion of the total mass when built powerful enough to have reasonable burn times. IME NERVs really aren't worth the mass penalty on trips requiring less than 2km/sec DV. *edit* And I'm with Justy on this one. Why haul a mostly- empty airplane all the way to Minmus and back? It makes a lot more sense to transfer crew in LKO to a smaller and much more efficient fully- fueled spaceship for that leg of the journey. I think of a spaceplane like an old WWII "Duck". It's useful for ferrying troops and supplies between ship and shore, but you wouldn't want to cross an ocean in one. That's what ships are for. Best, -Slashy

For me, the subject matter needs to be interesting and educational. The presentation needs to be organized and concise. The presenter needs to be engaging and entertaining, but not to the point of being obnoxious. It's the combination of all these characteristics that makes a stream or Youtube channel watchable. There's a few people out there who are really good at it and a whole lot of people out there that aren't. Best, -Slashy

Tibbe, Probably not. DV is a function of your wet/ dry ratio and specific impulse. You're not just going to find another km per second DV by optimizing. You will either need a lot more of your spaceplane to be fuel or else you will need a much more efficient rocket. This will require a wholesale redesign. OTOH, you could stick with this design and simply refuel it in LKO before moving on. Best, -Slashy

They can go pretty darn cheap with spaceplanes, particularly when you ship them in bulk. But the utility of orbiting large numbers of crew simultaneously is pretty limited. This old design could do it for $65 per Kerbal. Best, -Slashy

Lord Aurelius, I'm not aware of any major mysteries about Mars other than "was there life on Mars" and "where's all the water". Does anybody know what else it might be? Best, -Slashy

1: Landing gear exhibit less drag when mounted backwards. 2: A vehicle designed to waste the minimum amount of DV isn't necessarily the most efficient vehicle in terms fuel consumption, mass, or cost. 3: Specific impulse is useful for figuring out a lot more than just DV or wet-to-dry ratios. It can also be used to figure out thrust with fuel flow rates or vice-versa. Burn timers, staging models, etc. are all possible because of this. Best, -Slashy

arugela, I think I understand what you're getting at. It used to be that thrust was constant and fuel flow varied with Isp. That changed with the 1.0 update. Now fuel flow is constant and thrust varies with Isp. If you check the info on the parts you will see 2 figures for thrust and 2 figures for Isp. This unnamed other poster is mistaken. Best, -Slashy

Red Shirt, Back in my day we designed all of our landers to use RCS. We walked 20 miles uphill to school and back both ways and we were thankful for what we had! Congratulations; you have rediscovered the lost art of RCS landers! For calculation purposes... the FL-R25 tank weighs 1/5 the mass of fuel it carries and the Isp of a thruster quad is 240 sec. You can reverse the rocket equation thusly http://forum.kerbalspaceprogram.com/threads/102809 and design RCS powered stages for landers or ascent stages for nearly all occasions. We made use of these back then because we didn't have LF&O engines small enough to be suitable for the job. We have those now although occasionally the RCS lifter still winds up being the lightest option overall. Use it in good health! -Slashy

Nothalogh, I've never played Artemis (or even heard of it for that matter) but I think I see what you're getting at. I'm not sure which position on the team I'd be best- suited for. I'm sort of a "jack of all trades" in KSP but there's somebody out there who's better in any specialized role. Best, -Slashy

Gooru, I've seen that happen before. I think you'll have to remove all the wings and reattach them. Best, -Slashy