GoSlash27

Post- apocalyptic world.

Don't forget the "forgot to deploy the solar panels and ran out of power" merit badge -Slashy

Ellegon, We've all done it too. No worries, -Slashy

I built and flew a couple examples of what can be accomplished using tier 2 conventional rockets within the 140t limit. Example 1 is a triple Poodle design with a pair of strap-on Skippers. This design would get over 5km/sec DV without landers and a minimum .56g when fully fueled. Example 2 is what I was talking about earlier; series Twin-boar/ Skipper stack. This design can achieve 4,700 m/sec at a minimum t/w of .62g unencumbered. Either design would get you to a lot of bodies with landers; probably more than you would wish to use them for once the tech becomes obsolete. Best, -Slashy

Abastro, I usually design my upper stages with 0.7 t/w and my interplanetary stages with 0.5. In this case, the upper stage would be able to generate it's .5g when fully loaded and 1.2G when partially fueled. Not as aerodynamic as an airplane True, but I was under the assumption you didn't have nukes yet since you were contemplating unlocking Panthers. If you have nuke upper stages, you can take the same approach as I outlined above. Personally... I'd consider how many times I'd be using this ship. After the first mission, I'd have so much tech unlocked that I could easily build much better ships. Best, -Slashy

In addition to the above, it allows you to adapt a small Mk.0 controller to larger Mk.1 or 2.5m rockets without incurring a drag penalty. Put the small Hecs or Okto inside, and it becomes properly sized for the stack. Mainly, I use it to contain instruments, batteries, and what- not during launch in early career. Draggy bits in the nose are bad. Best, -Slashy

Nah. Nobody said you have to launch with full tanks. Using mid- career tech, you can put 24 tonnes into orbit with a 140t pad limit. That payload can be whatever you want/ have access to. Crew quarters, lab, couplers, empty fuel tanks... Let's say you use a simple 2 stage Twin Boar/ Skipper arrangement. The Twin Boar can lift up to 55 tonnes within the pad limit to the requisite 1,800 m/sec DV and initial 1.4 sea level t/w. Stage 2 becomes your dedicated spaceship, partially- fueled at launch, and capable of producing 1,700 m/sec DV before it runs dry. When it arrives in orbit, it weighs 24 tonnes. Now... if we refuel it in orbit to make use of all the empty tanks, we could use that skipper to generate 4,400 m/sec DV to 14 tonnes of payload at 0.5g. That's a massive amount of DV; adequate to get you the Mun, Minmus, Duna, Ike, or Gilly. 14 tonnes would be your guidance, lab, landers, fuel for your landers,crew quarters, etc. This ship would weigh 123 tonnes when fully refueled in orbit. You could go even more crazy with a pair of Poodles and strip-mine the entire Joolian system, but this ship will soon become obsolete as better tech becomes unlocked. Best, -Slashy

Abastro, I haven't had any problem with a 140t pad limit; it's actually very generous. If you use the ship as it's own transstage to orbit, you can save a whole lot of weight. You also have the option of orbital construction and fueling. Plus, you don't need to take the entire ship down to the surface and back at the destination. If you use these techniques, the pad limit doesn't hinder your mass in orbit. Not so much with Panthers, though. They peter out at a relatively low top speed and altitude, forcing you to use rockets to produce more of the DV to orbit. Your payload fractions wind up being in the same ballpark as chemical rocket lifters with the added disadvantage that a lot of the "payload" is actually airplane. Best, -Slashy

Abastro, Okay. This is what I was afraid of. Bad idea. A spaceplane is like one of those "duck- boats" from WWII; it's a truck that can float or a boat that can drive (depending on how you look at it), but it's not a good truck or a good boat. It's strength is that it bridges the gap between both because it can do both. Likewise, a spaceplane does *not* make a good spaceship. It's hauling around wings, air- breathing engines, control surfaces, landing gear, and structure to make it fly well in atmosphere that never gets used in space. It's more expensive, less efficient, and more cumbersome for the job of "spaceship" than a purpose- designed spaceship would be. This is coming from a guy who's a big proponent and fan of spaceplanes: They are really good at their assigned mission and it's an important one... but don't confuse that role with one that something else can do better. A spaceplane gets your people or supplies from a point on the surface of an atmospheric planet to low orbit and back again. It is not the best option for anything other than that. If you need a plane, build a plane and leave off the stuff that helps it be a spaceship. If you need a ship, build a ship and leave off the stuff that helps it fly. The spaceplane is what you use to connect crew and supplies between the two. Best, -Slashy

Sorry, I need more info. I should rephrase. To travel where?

^ Agreed. The real question is whether turning an engine *on* is a waste or not. Or more importantly, whether it was a waste to bring it in the first place. Best, -Slashy

Abastro, I must be misunderstanding what you're talking about. Get it to space only one time and use it over and over again... to do what? Scratchin' mah head, -Slashy

Cephalo, You'd be better off without the Dart. Ditching it saves you a tonne and costs you 10% of your fuel efficiency on orbit, which is a very small DV budget. The Dart is actually adding weight to your ship overall, which means more fuel, more wing, etc. Moreover, using 3 engines instead of 2 means you need an additional parallel node to mount it, which means more drag. Best, -Slashy

Abastro, That's kind of the point of SSTO spaceplanes; the only cost is the fuel... theoretically. As a practical matter, the R&D and cost to build are higher than a comparable disposable lifter, which raises the risk of using them. If you lose one during a mission, it will erase the savings you might've seen. I found (back in the day) that Panther based spaceplanes weren't worth the risk and effort. Not because of the Panther itself, but because of the other tech that's available at the time. Too many "puzzle pieces" for a good spaceplane still missing. Moreover, spaceplanes aren't very adaptable for mission roles. They restrict the size and shape of their payload in ways that vertical lifters don't and are sensitive to changes in CoM, which makes them a PITA to use as cargo haulers. This being the case, it's not really worth the time, cost, and effort to develop a spaceplane unless you plan on using it regularly. I basically use spaceplanes as crew taxi or tankers, Both of these roles presuppose either a space station or orbital construction. Neither is going on when the Panther is unlocked because critical pieces for those operations are also missing. By the time you develop the tech to do things that would make spaceplanes useful and viable, you've also unlocked better engines than the Panther. Best, -Slashy

This, basically... except I have a spreadsheet to show me my options. Which engine is "best" depends on what you're doing. What's the payload mass and DV budget? Best, -Slashy

NSEP, I follow the Von Braun STS infrastructure concept, and it works really well for me in KSP. Crews and fuel are sent to LKO aboard space planes. Interplanetary vessels are assembled in orbit from modular chunks sent up aboard disposable rockets. Once the whole system is in place, everything is reusable. The space program essentially becomes a system- wide transportation network to move Kerbals and experiments from the KSC to any of the planets and home again. Swap crews, refuel and refurbish, and the same ships are off to explore other destinations. Best, -Slashy

Martian Music, Yeah, they're mainly talking about the engine itself. Thrust comes at a price. In pure vacuum, it's additional engine mass, lower exhaust velocity, and/ or a higher price tag. In the atmosphere, you add drag, heating, aerodynamic instability, and more complicated assembly, We try to strike a happy balance that minimizes cost, mass, and complexity while maintaining acceptable t/w for safety, player sanity, and minimal cosine losses. Generally speaking, my rockets look like this: Booster (LFO): 1,800 m/sec (1/2 ATM), 1.4:1 initial sea level t/w at liftoff Booster (SRB): 1,800 m/sec (1/2 ATM), 1.2:1 initial sea level t/w at liftoff Transstage: 1,700 m/sec (vac), 0.7:1 t/w (vacuum) at ignition. Ejection/circ: 0.5:1 t/w (vac) with respect to local body Lander: 1.5:1 t/w (vac) with respect to local body Launcher: 1.5:1 t/w (vac) with respect to local body. HTHs, -Slashy

Martian Music. Aye. The equation assumes infinite t/w ratio. Anything less than that will incur a penalty in the form of gravity losses. DV can be confusing because it refers to 2 different things; The change in velocity required to accomplish a job, or the change in velocity your rocket is capable of generating. When we look at the map, we're only talking about the first definition. The fact that your rocket doesn't actually generate infinite thrust isn't the rocket equation's fault. You will get to orbit with a lower total DV (talkin' about the second definition now) if you have infinite thrust, zero drag, attain orbital velocity at sea level, and pilot it absolutely perfectly. Anything other than that carries a penalty in the form of gravity and drag losses, which the rocket equation does not account for. I must caution you to be careful about how you define "efficiency". Getting the job done with less DV doesn't necessarily translate to a lighter, cheaper, or more fuel efficient design. Best, -Slashy

Kerbin's rotation is 175 m/sec. Subtract that from the 2,426 m/sec required to orbit at sea level leaves a DV of 2,251 m/sec. The Hohmann transfer to 70 km is 66 m/sec for the kick burn and 64 m/sec to circ. Adding these to the sea level DV comes out to 2,381 m/sec. Your math isn't bad, @Spricigo. Best, -Slashy

StahnAileron, DV values for atmospheric bodies vary greatly depending on launch profile, drag, t/w, engine atmospheric efficiency, and the assumptions upon which the calculation is based. 3,400 m/sec is a good ballpark figure, but only an estimate. For vacuum values, the math is greatly simplified and the DV values are absolute minimums; your expenditures will be somewhat higher than what appears on the map. For the math, start here: http://www.braeunig.us/space/orbmech.htm Best, -Slashy

Years ago, I used to make the rover the lander. The rovers contained the fuel and engines, and docked together to carry payloads. With that, I had the ability to use them as fuel trucks, cargo carriers, ascent/ descent stages, and bulldozers for colony construction. I used to send them up in great big stacks. Again... this was years ago and the game was a lot different then. Just offering it as food for thought. Best, -Slashy

Abastro, It's been so long that I don't remember, but that's not what's important. Fuel cost is pretty trivial no matter which way you go. The early Panther SSTOs are workable, but the lack of associated spaceplane tech makes them unattractive at best and catastrophic at worst. If you have just one break up on reentry, it wipes out any fuel savings you might have seen. Plus, spaceplanes are really for the mundane " milk run" missions that you have to do frequently. They don't really have a role at that stage in the career to justify the R&D effort. My advice is to wait until having a spaceplane is actually an advantage. By that time, you'll have better options. My $0.02, -Slashy

AeroGav, I'm afraid I'm the wrong guy to ask about this problem. I never design spaceplanes to go any further than LKO since airplanes make such lousy spacecraft. I can say that nukes are worth it from a mass perspective if the total vacuum DV is greater than 2 km/sec, and not worth it for smaller jobs. Since the Mun requires a lot more DV than 2 km/sec DV, I'd skip the Terrier entirely and just go Panther/NERV. I have done LF SSTOs in the past. My designs were based on the notion that vacuum engine thrust should be 1/2 of the air breathing thrust at Mach 1, so 2 nukes per Panther. HTHs, -Slashy

I built a low tech Panther SSTO way back when it was new. It was cheap enough, but the R&D time and difficulty involved in making it survive the trip back home made it not really worth the effort. The problem wasn't the Panther itself, but rather the other tech that was available at the time. The changes in the tech tree may have made it easier since then. Best, -Slashy

I concur with what @Foxster and @AeroGav said. The key is reducing drag rather than adding thrust, so always look for what you can do without instead of what you need to add. Once you get supersonic, it's relatively easy to make orbit. Best, -Slashy