GoSlash27

Cairol, If there's a way, I don't know about it. I think reaction wheel torque and control surface deflection range should be tweakable like we do with gimbals. Best, -Slashy

More Boosters, Keeping true to your name, I see The Kickback is definitely the best SRB in the game (and for what it does the best engine in the game). It has the lowest cost per payload tonne and highest specific impulse. As for it's raw thrust, it has more than enough for it's intended role. If you want something disposable that will get a payload halfway to orbit for cheap, the Kickback is unbeatable. 2G off the pad and only 800 m/sec DV is an odd requirement. Most designers want a much lower initial thrust (it's going to get hectic as the fuel drains) and more DV. I'd imagine you could unload propellant to do that, but it kinda ruins the entire point of the Kickback. Best, -Slashy

RoboRay, A lot has changed since my last reply in this thread back in May. Now spaceplanes are up to 40% payload fraction and extremely economical. They're definitely the way to go. IRT your question, if you use a spaceplane the airplane is the tank, so you don't have an empty tank to get rid of. 1) launch a big honkin' tank 2) Build a station around it Bonus: Having a station means convenient orbital assembly. 3) Refill it from time to time with the spaceplane tanker. 4) Profit! Best, -Slashy

dresoccer4, The lights themselves will always appear white, but if you shine them at something you will see that the light they cast is actually changing color. Best, -Slashy

More Boosters, Not generally. Usually when I see something inspiring it's because somebody else has figured out a potentially beneficial solution to a problem. So I scamper off to KSP to experiment with it. I don't mind at all if what I wind up with looks generic. Pretty much all of my stuff looks generic. But if it's a more efficient way for me to do the job, then I'm happy with it. And if it doesn't work out, then figuring out why often leads to another breakthrough. Best, -Slashy

Well... the companies actually create the parts (or more often find them by the side of the road/ in each other's backyards filled with water/ etc). R&D figures out how to attach them with left handed metric wingnuts, stash snacks in them, and make them extra- explodey. Best, -Slashy

Frozen Heart, The standard approach is to clip a couple small tanks into the rear tank where the actual shuttle's OMS pods live and then attach the thuds to them. The thuds will draw from those tanks when activated but the SSMEs won't. It's "legal" clipping since the rear tank doesn't contain any fuel and is merely empty structure. To be super- accurate, you'd use O-10 engines and monopropellant. Anywho... glad to hear you've added your STS to the fleet and kudos on the achievement. This ain't an easy undertaking! Best, -Slashy

Nah. It's actually quite rigid; way less flimsy than the LFB, since the thrust vectoring tends to make it oscillate. The reaction wheel is adequate. Adding fins would tend to make it overly- stable. That's also why I don't add nose cones to the boosters. It is important to dial back the thrust to an appropriate level. Otherwise you can lose steering authority. Best, -Slashy

Kegereneku, The original question was about cyclers in KSP, not RL. Kerbals do not need life support or comfortable habitat, so cyclers aren't useful at all *in- game*. In addition, the transfer shuttles burn more fuel to match a cycler orbit than they would need to establish a Hohmann transfer and the trip is longer. Best, -Slashy

There you go makin' me grin again! -Slashy

OhioBob, Oh, I realize that was never your intent and I agree with all of this. There was just some confusion (not on your part) about whether SRBs were cheaper or more expensive than LFBs and I was trying to clear that up. I think your response here does a much better job of that than mine did. *edit* to clarify, SRBs can be surface attached to each other or a central part, so radial decouplers (or stack adapters) aren't actually necessary. For example: And I've found it's rare that the RT-10 can outperform LFBs even in this manner. Best, -Slashy

Frozen Heart, I'm sure you don't use them; you wouldn't be able to because their alignment would spin the orbiter. My point is that tank should ideally have no fuel. Variations in piloting and mission profile mean that it will wind up with varying fuel levels once orbit is achieved. The fuel will be left in a tank far from the CoM with no way to counterbalance it and nowhere to shift it to. That's why the rear tank is left empty and the OMS engines have their own dedicated supply. Extra fuel is carried in the external tank and any unneeded fuel is jettisoned with it. I'd recommend rearranging the fuel allocation as above and then adjusting the wings to rebalance it. I wouldn't count on any of the engine stats in the preview. Best, -Slashy

A-Name, Actually, I don't have a specific recommendation. It depends on your wing loading and t/w ratio. Basically you want to get it up to Mach 1 and see where your prograde vector is. Adjust the incidence so it's straight ahead aligned with your forward marker and that should about do it. Best, -Slashy

Gaarst, The docking/ payload adapter is something every shuttle needs IMO. Aside from giving you the ability to dock and release a payload, it moves the CoM forward. This allows you to build your shuttle with the CoM and CoL closer to the pressure center. The other 2 points clearly don't apply to you, so you can disregard them. Best, -Slashy

^ This. In fact, a direct transfer takes *less* DV and less time. The really short answer is "no"; cyclers have no practical advantage in KSP. Best, -Slashy

abh, Best I can tell you is this: It depends. SRBs excel at being cheap disposable lower stages. Anything beyond that.... they're probably not your best choice. The best way I've devised to be sure is to put together a spreadsheet like Ohio Bob has done here. You want to take the rocket equation and turn it on it's ear. Instead of answering "how much DV will this stage produce", you want to set it up to answer " what is my wet to dry ratio with this engine for a given amount of DV". This takes the form Rwd= e^(DV/9.81Isp) where e= 2.718 DV is your desired DV Isp is the mean Isp of your engine in the given situation. You apply some algebra-fu to work out fuel, tanks, engine mass, and payload to this wet to dry ratio, then you estimate the cost to build the stage. If you do this with all engines simultaneously, you will see how much each proposed stage will weigh and cost and will be able to pick the best option. Upper stages place a premium on weight, while lower stages place a premium on cost. tl;dr: For cheep thrillz, the answer is "never". SSTO fully recoverable lifters are always cheaper than staged disposables in KSP and SSTO air breathing spaceplanes are always the cheapest option. Best, -Slashy

Gaarst, I think Frozen Heart has hit upon the answer. Those of us with working STS shuttles don't have a problem with body lift forcing us backwards. In my case I think it's the docking/ payload adapter attached to the rear of the crew cabin. This forces the CoM forward, which makes it much more stable. Also in accurate shuttles there's never fuel in the rear tank, just in the clip- on OMS tanks. Once the external tank is jettisoned the SSMEs should have no fuel source. Neglecting this can cause serious imbalance issues. Best, -Slashy

Clipper, Ain't nuthin' wrong with that. There's no fun in downloading somebody else's design. Happy spacing! -Slashy

Clipperride, I'm always glad to hear more success stories. Congrats! On my "behemoth", I attached the FL-T100s radially to the upper wing surface, then attached the nose cones/ engines and realigned/ repositioned them using the widgets. FWIW I always try to use the minimum number of wing panels for the job. Smaller panels, no matter how they are rooted, tend to be flimsy and require strutting. Strutting is the devil in spaceplanes. Oh, and since nobody's mentioned it yet: some wing incidence can dramatically improve your spaceplane's performance. Wings produce a lot less drag than fuselages even when they are making lift. The right amount of incidence will allow you to punch through Mach 1 with your nose aligned with the prograde vector, dramatically reducing parasitic drag. This means you can get more mass supersonic and beyond with less thrust. Best, -Slashy

OhioBob, IME a disposable LFB first stage can nearly always be outperformed by a SRB in terms of cost/ tonne. Even the KR-1x2 can't keep up with the Kickback or BACC. In your cost- optimized example the second stage presents a payload of 64 tonnes. Your LFB costs $33,800 according to my model. The same job can be done by 7 Kickbacks for $18,900. For 1800 m/sec DV you simply take the upper stage mass in tonnes and divide it by 9.23. This gives you the required number of Kickbacks. The throttle setting will generally be in the 75% range. You can stagger the throttle settings to maintain a more even thrust through the burn. BACCs are slightly cheaper than any LFB in smaller payloads. Not a night and day difference, but they are cheaper. IMO nearly every disposable first stage should be SRB if cost is important. *edit* having said that, I understand that it was not your intention to create a super- economical lifter, but rather to create some data points and they are very useful. Right down the middle of where I expected them to be, so that confirms that I'm not far off- course in my designs. Best, -Slashy

Clipperride, The wings aren't too small for Mk3 parts. The key to wings is to remember that all wings are equal from the standpoint of lift vs. drag so bigger is better in large spaceplanes. The wet delta is worth 5 lift rating and the airliner wing is worth 7.8. The less you have to stitch your wings together with struts the better off you'll be. Even this underpowered monstrosity can make orbit efficiently on just 6 wing parts. You're liable to be operating at more t/w, so wing area is less of an issue for you. Few builders operate in the low t/w area that I dabble in, and the higher your t/w the higher your wing loading can be. Best, -Slashy

The Kerbals occasionally try to disguise themselves to pass for human. Results are... mixed. Best, -Slashy

Well... the tank is technically recoverable whether or not you're lifting a shuttle orbiter. In fact, it's easier to recover the tank intact while still attached to an engine than it is to recover a tank by itself. The engine makes an excellent heat shield. Well... from a purely economic standpoint I would say no... But a lot of times you have other priorities than cost per tonne or limitations in the tech tree/ facilities that preclude SSTO lifters. Best, -Slashy

Frozen Heart, You might want to try replacing the single cargo bay with 2 half-size bays; see if the weird aero behavior disappears. Also, if you give the wings a little incidence it will both both improve the low speed handling and move the CoL further back. The body flap should be enough to compensate for that and give you a more stable orbiter. sal_vager, That is a beautiful shuttle! I need to steal a couple of those design concepts! Best, -Slashy