Pecan

Yes, I had second-thoughts along the same lines. Probably better re-categorise SP 40 from 'light cargo' to 'heavy cargo'. Sorry to mess you about. No sweat, I have 'SP 40 B' almost ready to go anyway - lighter, cheaper, (a bit) better-looking and carrying 3 crew instead of 1 (fuel-module + 2 crew represents a complete station-rotation load for me). PS: @ all - I'm going away for a long weekend but will test others on Tuesday/Wednesday if I can.

It's pretty and, obviously, not deploying the parachutes would help (^^ I know you know that) but there's a long way from the island to orbit. Which rocket(s) do you have on there? (Wanderfound - ah, right, sorry about that. BTW - do we have a definition of 'light' vs 'heavy' cargo?).

@ Wonderfound - So how about adding my entry to the OP? @ FCISuperGuy - Your download link for Globemaster is 'undefined' and therefore doesn't work.

Thank you for the verification. As to your concern regarding TWR; yes it is possible to design a rocket with a tiny engine and lots of fuel so that it has lots of deltaV but can't actually get off the ground. The only, but simple, way to guard against that is as capi said in post #8 - total your engines' thrust, divide by (gravity * minimum TWR) and recognise that as a cap on your total mass. In a spreadsheet you'd just use a min(calculated from deltaV, calculated from TWR) function to see which satisfies both constraints best. To apply the formulae, or indeed the rocket equation itself, to multiple stages you simply apply them to each stage in turn, using the upper stage(s) + their payload as the total payload for lower stages. There is a bit more to consider in that you may want different TWRs at different points - high at launch, low at circularisation for instance. Oh, and by the way I wasn't distraught yesterday. "Tired and emotional" is a euphemism for 'drunk'; I went to the pub last night so I wasn't really in a fit state for debugging equations.

Post #34 updated to make mine an entry. Versatility is the key there, since the plane itself is just a framework for the payload.

/me nods - Kerbinside is good.

Yeah exactly - if the thing won't lift-off no advice in the world is going to help so I'd just have to live with the limits of my design. NASA make paperweights too, right?

Gah - I knew I'd forgotten my own formulae; and I still can't find where on the interwebz I got it from. Please try this; I think my mistake was in dV_Launch. The formula can work out what the rocket has from it's wet/dry masses so what it needs is the required dV for whatever you're doing - in a normal Kerbin case that's 4,500m/s. From that (has - needs) it can re-work the remainder to give a 'spare capacity' figure in tonnes. Maybe. Anyway ... stick 4,500m/s in for dv_Launch and tell me if it works. In the specific case you give it leaves 1.13t but I'm way too tired (and emotional) to see if that's correct at the moment.

Or - to put it the other way around - the "ideal" ascent profiles only fit "ideal" vehicles. Yet another good point, although several of us have stressed that 'ideal' depends on design. On the other hand, if I want to complain about all the "boring" advice when my vehicle has a TWR of 0.1 at launch I shouldn't be surprised that no-one seems to help me get off the ground. I'm not saying that's your case, but your design is, erm, stressing the boundaries, shall we say?

In anyone's terms. In vertical rocket designs they can be very cost-effective though, even if you just throw the empties away. At least ... within certain conditions. I've got a couple of Skipper-based SSTOs in the 5 - 10t range that benefit from SRBs and below that they should be useful. Above that it would seem that they become less and less useful because lots of them cost too much to throw away but mass too much to be worth recovering. Oops, sorry - derail. It's 2am, I'm side-tracking .

Very kind of you. I just looked at Stratzenblitz's though and that's a thing of beauty I haven't tried to get near yet. May chuck one in there to make up the numbers but I'm (still) just trying to work out how to explain the differences in fuel-tank cost-efficiency or, indeed, fuel-density. You know how it is with me, I'm writing tutorials or test-pieces and everything else just falls out of that; so far I'm only just messing-about with mixing SRBs into (otherwise) SSTO designs; JATO still seems months away :-(

While that is true, I know both Wanderfound and I use MJ's Smart A.S.S (SAS controller). For my flights - bearing in mind that a lot depends on the individual plane designs - I typically climb-out at 50-degrees, reducing that by 10-degree increments so that I'm at 20-degrees at 20km altitude. My horizontal speed will then be well below the 1km/s I recommend but building fast. From there up it's into speed-matching - the higher you go the faster you can go because there's less drag but the higher you go the faster you HAVE to go because there's less air to feed the engines. It's a balancing game and takes a bit of practice but once you've more or less "got it" it doesn't take much to adjust to any new design you come up with. If you enjoy flying planes then - as Wanderfound would definitely recommend :-) - FAR or NEAR are worthwhile mods, because they make atmospheric conditions much more realistic. Personally, I tend to ignore the atmosphere except to get out of it as quickly as possible, which is why I prefer rockets, even if they do use more fuel. @ FleshJeb - nice post :-)

Tavert's analysis is the only stuff that could beat your own and Kashua's, mhoram, that's why I keep it bookmarked ;-0 He made a particular comparison of LV-Ns, 48-7Ss and 909s and the 909 is only ever slightly better than the worst of those other two and only in very specific circumstances the best choice of the three. In other words - if you're thinking of 909s you almost certainly want either LV-Ns or 48-7Ss (science-tier considerations excluded). Edit: put 'could' into the first sentence.

Build a better rocket. Or do you have deltaV stats to break existing records?

LV-10-1 is still the simplest SSTO I know for a decent payload (in its case 10t, hence the name) LV-10-1 + Cartographer Heavy Launch Chapter 5 of the tutorial in my signature.

"There is no in between. You either space or you don't." Now I've got that out of the way ... Stop trying to go 'up' and read all the tutorials about spaceplanes that tell you to go "FAST". It sounds like you're trying to get a plane to space using a normal rocket ascent-path, which is possible but not efficient. If you want to take all those wings and things to space the best way to do it is to be flying almost horizontal - less than 20m/s or so vertical speed - until you get near orbital velocity (~2,000m/s). What that means is spending a lot of time go sideways faster and faster until gravity just can't keep you down. As a rule - get above thick, draggy, atmosphere by going up to 20km as fast as you can. Then adjust your pitch so that you get 1km/s at 20km, 1.1m/s at 21km, etc. That should mean 2km/s at 30km and you're basically at orbital speed. ETA: Oh - and 909s are almost never the right answer to anything

Is the amount of fuel the only thing that you care about? It doesn't take as long for my ship to get to the station that is already there, with the fuel that is already there. - that's more time-efficient. It doesn't take as many journeys to put 'spare' fuel in place than it does to send a refuelling tanker every time my ship needs topping-up. - that's more launch-efficient. It doesn't take different vehicles to supply fuel and crew if they are all in the same place. - that's vehicle efficient. It doesn't take a new scientific instument for every experiment if you have a single lab (if you can be bothered with science). - that's part efficient. If you think about launching EVERY ship from Kerbin then, no, a spacestation is not useful. If you think about starting ANY mission from space then stations are very useful ("motherships" possiby even more so").

Thank you for your kind assessments. I'd assumed this would look too scruffy for this challenge but I'll edit the post above into a proper entry later this evening (going out at the moment). Those images are imgur's 640x480 thumbnails but you can click on them to see them in 1680x1050.

Which is another good point for the OP - the ideal ascent profile also depends on what you're trying to optimise. If you want to minimise the deltaV used to orbit you'll have as little fuel as possible in the launch vehicle to try to follow the terminal-velocity curve. If you want maximum deltaV remaining once you've got to orbit you'll pack your launch vehicle with as much additional fuel as it'll carry as well as the payload, giving a lower TWR (my SSTOs are designed that way). If you're using non-stock aerodynamics (eg; FAR) you just can't go too fast or turn too sharply or drag will tear you apart. etc.

Yep :-) Simplicity is the only advantage of that advice - though it does still work for most ships, of course. I was just wondering why you kept the thrust so low, since that increases gravity losses.

I suspect it was an old design-decision that made sense at the time (and might still make sense internally) but, yes, it can be confusing.

I take it you're using FAR? Without it anyone will do much better to reach and maintain terminal velocity, which requires a TWR over 2 on average, during the course of each stage. Circularisation stage, being space-only, doesn't need anything that much thrust, of course, but if you've got it you might as well use it ^^. mhoram did a lot of work on calculating ideal ascent profiles so hopefully he, and Kashua, will pop in soon ...

[spoiler=SP 40 ( Don't work in 0.25] The SP 40/SP 40 B designs are withdrawn from the challenge as changes in 0.25 prevent them taking-off. .craft files and information are still below for anyone that wants them. SP 40 B Craft File <- Update to equally-unimaginatively named SP 40. Stock aerodynamics and parts. Categories: heavy cargo, tanker, passenger, all-stock parts. <- The only difference is the payload you choose to fit. SP 40 B is designed for low part-count and versatility. As such it can carry a variety of payloads (up to 40t) to orbit. Fuel lines run from inner rear tanks to outer and then to the inner forward ones. As with the original SP 40 only the inner forward tanks carry oxidiser. Performance and handling vary quite a lot depending on the payload mass (if any); with a full load some (30-40 units) of the liquid fuel that 'should' be reserved for the rockets may be required for the jets during ascent, but this is unlikely to materially affect in-orbit operations. With a lighter payload - or a better pilot than me! - the rockets each have a full FL-T800 fuel tank for space-based operations, giving moderate range. Principle changes from the earlier model are replacing the LV-N rockets with 48-7Ss and the single-seat cockpit arrangement with the 3-seat Mk1-2. This version is both lighter and cheaper at the cost of vacuum endurance. SP 40 B with Fuel Module payload SP 40 B itself: 38.394t wet/22.67t dry. 278 parts, cost 287,843.2 Action groups: 1 = 'outer' jets, 2 = 'inner' jets, 3 = rockets, 4 = shielded docking port cover Payloads dock behind the cockpit. Whatever you want up to a mass of ~40t (hence the name) as long as it maintains the CoM. Although held at the front by the docking-port payloads should also be supported towards the rear by struts from just ahead of the LV-N engines. With any payload, or none, takeoff with full jets (action groups 1 and 2) and throttle, rotate at 100-110m/s to 20-degrees pitch to start climb, retract landing-gear and then rotate further to required climb attitude. I haven't tried landing with a full orange tube but without a payload, or with a light one, land at 75m/s+ horizontal, about 1/3 throttle for approach/lineup and one set of jets, reducing and adjusting pitch (probably 5-10 degrees depending on your flying) as required. SP 40 (A) is still available if anyone wants it. Operation is more or less identical and it is shown here just to illustrate different payloads. Sample Fuel Module - docking-port, orange tube, docking port With a heavy load like this climbout at 50-degrees pitch to ~15km then reduce to 20 degrees by 20km. Speed-balancing from there to between +/- 5-degrees at 30km and ~2,100m/s. Shutdown one set of jets (action group 1 or 2) when air-limited around 33km. Maintain thrust with the other set, reducing throttle as required, until space. Cut throttle, shutdown the remaining set of jets, activate the LV-Ns and perform circularisation burn (35 - 40 m/s at 75km). Sample Passenger Module - docking port, 4 x Hitchhiker containers, docking port With a lighter load the ascent profile is similar - you know this, you spaceplane experts! - but you will probably want to throttle-back or shutdown one set of jets during the climbout, shortly after takeoff, simply because the plane has too much thrust (see picture/caption below). Variations on the theme are easy (eg; Mixed Load Module: docking port, hitchhiker, X200-32 fuel tank, hitchhiker, docking port) and structural support can be built for shorter loads to centre their CoM with the plane's. A science load is quite good (docking port, hitchhiker, science lab, science juniour, goo and all other science eqpt) but then the LV-Ns don't really have the fuel for a return trip to anywhere interesting. Much flexibility is, however, still available - such as adding oxidiser to the rear/outer tanks to provide more in-space performance. Almost tearing itself apart (this image is a bit dark but I hope you can see what's happening): I forgot to strut the back of the payload when I took off with this and, since the 4 hitchhikers mass so much less than a full orange tube, the acceleration 'almost' tore it apart. I wondered why MJ was applying left-rudder and why the payload wasn't aligned properly. It turned out that the docking-ports were only just maintaining a connection, despite not even touching. KSP still counted it as one ship and it flew to orbit quite happily, re-connecting as it should when the acceleration/drag weren't so strong. NB: Only half the jets are required for this mass ^^. Planned extra: a service rover to load fuel/pax/other modules Bantam craft file Stock aerodynamics and parts. Categories: Best sporty pleasure craft Bantam is low-part, fast and agile. It handles well at low-speeds and altitudes (~60m/s take-off and landing) while also being able to reach orbital speeds and altitude on less than 50 units of fuel, leaving ~50-60m/s for rocket circularisation. Should you be scared of space for some reason there is enough jet fuel to circumnavigate Kerbin entirely within the atmosphere (I did it at just under 30km and a touch under half throttle, just to check). Bantam light spaceplane Bantam: 5.65t wet/3.61t dry. 53 parts, cost 44,350 Action groups: 1 = jet, 2 = intakes, 3 = rockets, 4 = shielded docking port cover Take-off and landing at ~60m/s or just let it lift on its own, since it sits on the runway with positive pitch. Retract gear and pitch-up to whatever you like, it has a lot of power for the mass. Aim for 2km/s and prograde around 30-33km altitude and then climb to space and circularise as you prefer. Land with around 1 'tick' of throttle or so.

Yes it would be fun to have the minions and other voices. It's unlikely the copyright owners would do anything about it even if they minded and even if they knew ;-0 At least trying to do it the legal way isn't that hard though. (Hint: a letter to them will almost certainly be ignored, since there's nothing in it for them and too much work to answer. If it includes something like "unless you say otherwise, I'll assume this is OK" you can at least show that you asked, and had grounds to believe it was allowed. It's very cheeky and you won't fool anyone, but it's probably good enough to put responsibility for saying 'no' back on the company).

I think our posts crossed, I have now edited the formula above. EXP is the exponential function, which nearly every spreadsheet and scientific calculators should have. Funnily enough, in LibreOffice which I use, and Excel it is EXP(...)