GoSlash27

EmanonP, I'm on day 2 of my "caveman" career, and I've got offers for satellite contracts. All basic facilities and I haven't done a Munar flyby yet. Perhaps it's related to which nodes you have unlocked? IIRC, you need to have the 48-7S before they are offered... Here's my tech tree: Best, -Slashy

AeroGav, All true, and an ideal space plane ascent will try to circ at 45km before coasting up to 70+ for the final orbital burn. I've done this with as little as 0.5 t/w, but it's rare that I ever have to add an engine to hit 0.7. I prefer to have the higher t/w so I don't have to dawdle for 20 minutes in the high atmosphere worrying about the heat. In the case of RAPIERs, you should never have a problem with achieving the necessary closed cycle t/w if you've got enough thrust to get supersonic in open cycle. As for "carrying RAPIERs to Duna", I have no experience with that, as I would never design such a ship. I believe space planes make lousy rockets, so I never design them to do anything more than ferry supplies and passengers between a surface base and low orbit. There are lots of folks around who do interplanetary missions with space planes. They may have some insight into this. Best, -Slashy

Back in LMO with 947 m/sec remaining. The burn back to Kerbin shouldn't take any more than 270 m/sec. Reentry with plenty of leftover fuel. Recovered Jeb and the science without incident, so the ship works as designed. I didn't use a max- efficiency technique for the Mun landing, but rather a more expensive "pinpoint landing" technique. So here's what you should be seeing for DV remaining: At LKO, about 3,600 m/sec. At LMO, about 2,450 m/sec On the Munar surface, 1,500 m/sec Back at LMO, about 950 m/sec Stage jettison for reentry, about 680 m/sec remaining. Wherever your numbers diverge from this is where you're having a problem. You will either have to add DV to that stage to compensate, or I can give you some pointers on how to improve your technique. Best, -Slashy

I second what @Plusck and @WanderingKid said. Forget about that "climb to 10km and hang a right" nonsense. It no longer applies in KSP. Using the rocket shown, here's the easy way to do it: At 50 m/sec, tip it East to 85° pitch. Turn off SAS and stage the SRBs when finished. Keep your t/w to 2cos(pitch). At 70°, t/w= 1.7 50°, 1.5 and so-on. Once you clear 27km altitude at around 800 m/sec, turn SAS back on and fly prograde. It should pretty much fly itself to orbit. Best, -Slashy

I agree with what the others have said above; getting to orbit with minimal DV expenditure isn't the same thing as getting to orbit with the least stage mass, fuel consumption, or cost. I design my boost stage to have 1.4 t/w off the pad if liquid fueled, and 1.2 if SRB. Upper "transstage" is initially 0.7 t/w. If your t/w is too high while in atmosphere, it won't want to cleanly follow the gravity turn. You may also run into heating issues. I taper my thrust in the boost stage so that t/w= 2cos(pitch). It costs a little in DV, but makes up for it with controllability and precision. AeroGav, It really doesn't translate to spaceplanes. There, your mission is to get as much velocity out of the air breathers as possible before transitioning to rockets. Rules for the rocket portion of the flight is the same as conventional rockets; 0.7 t/w minimum so Apoapsis stays 45 seconds ahead. For the air breathing portion, you simply want to get hypersonic. If you have enough thrust to overcome your drag and accelerate in level flight at 360 m/sec, that's all you need. Minimizing drag is far more important than raw thrust because you're not following a gravity turn. I've built successful SSTO spaceplanes with an initial t/w as low as .32. Once it gets past the Mach wall, drag drops and thrust increases, allowing you to top-out after that. Best, -Slashy

That's okay. We'll get through it If you had your core stage almost out of fuel in Munar orbit, then you're fine up to that point. It's probably your descent to the surface that's killing you. This is what I ended up with at touchdown: This is 1,566 m/sec DV on the surface. How much do you have at landing?

Update 4: It's in a 25x25 LMO with 53.6 m/sec remaining. Plenty to put the stage on a collision course with the surface. No, you should have over 2,400m/sec when entering Munar orbit with this design. 1,000 isn't going to cut it. You're losing nearly 1500 m/sec before you reach Munar orbit. We need to back-track and figure out where... How much DV do you show remaining when you reach LKO? Best, -Slashy

@The Space Dino, It's kinda hard to tell what you have going on from that pic. Are all of the engines in your asparagus arrangement LV-T30s? What about your vacuum stage? Is that an LV-909? When you say "it didn't work", what exactly do you mean? Did it run out of fuel? If so, when? Can you describe the points in the mission at which you executed each staging event? Thanks, -Slashy *edit* I'm attempting to recreate your ship from the pic. It looks like your vacuum stage has 2,400 m/sec DV (depending on what's in your cargo bay). That's enough to do the entire mission from munar circularization to Kerbin intercept. If you attempt to do the Mun intercept on this stage, you'll run out of gas later. *edit 2* I built a replica of your ship. I figured out that you were using LV-T45s. It got to orbit comfortably with 1,233 m/sec DV remaining. This is more than plenty for the Mun intercept and even circularization if you choose to do that. Are you seeing similar numbers? *edit 3* It made Mun intercept with no problem on the core LV-T45 stage. With 345 m/sec DV, it's also good for circ and beginning the descent (which will help dispose of unwanted space junk). Incidentally, I didn't notice any solar panels on your ship. If you don't have them, you need to fix that. Best, -Slashy

What LaytheDweller said. Your best bet in KSP would be a kraken drive. *IF* you can figure out a way to make one in 1.2, you can go pretty much anywhere without expending any fuel. The devs have worked hard to eliminate phantom forces, so making one would be no easy task. Best, -Slashy

Space Dino, We would need to know why it didn't work. A Mun lander is feasible in 1.2 career, even under "caveman" conditions, so this is a design/ execution problem rather than an unrealistic goal. Can you share a link to your craft file? Best, -Slashy

Finally getting around to Caveman for 1.2. This is my status at the end of the first day: http://s52.photobucket.com/user/GoSlash27/slideshow/KSP/Caveman challenge/120 Check out the mission flag All difficulty settings are default. Best, -Slashy

All, This is too short for a tutorial, so I'm going to just leave this here. Are you having problems with reentry packages tumbling? Part placement and stacking order matters in KSP. There are some things you can do to reduce or even eliminate the tendency to flip. Principles for aerodynamically stable reentry: 1: The center of gravity should be as close to the ablator as possible. Stack your capsule so that physically compact and dense components ride near the ablator, while large and light components with high surface area are far away. This creates a torque moment that tends to self-correct deviations. To determine the correct order of series stacked parts, simply multiply their mass by their height. Highest values go closest to the ablator. Lowest values farthest away. 2: If you have solar panels, mount them as I have here. Slightly rotated, tucked in to keep out of the heat, and as far away from the ablator as possible. This will add drag to the "back" of the reentry capsule, acting like a drogue. Remember, physicsless parts such as surface mount panels don't apply mass and drag to their own center of gravity, but rather the center of gravity of whatever part they're attached to. This is a nice, stable design for an early career science capsule. If you folks have stable designs, feel free to share! Best, -Slashy

My $0.02: - Space planes are time consuming to develop. Accordingly, they should only be used for flights that you do regularly. Shuttling crew to/ from orbit, delivering fuel, that sort of thing. - Space planes make lousy rockets. I don't recommend using them for jobs beyond LKO. - Space planes restrict the size and shape of their cargo unless built with a shroud instead of a cargo bay. I don't use space planes for cargo haulers. - Space planes are in their element when low operating cost to orbit is the most important factor. They should rely more on low drag than high thrust for best results. - Low drag means keeping attitude changes to a minimum. Wings should use static incidence to keep the nose prograde at Mach 1. You should also use minimal control surfaces to keep maneuverability down. Best, -Slashy

Interesting... In that case, nevermind. Best, -Slashy

Aegolius, You're doing it right. Plane changes cost proportionally to the orbital velocity. The one thing I'd recommend changing: After the plane change (or even concurrently), I'd recommend raising your Pe to 680 km. It sounds counterintuitive, but that should save you about 40 m/sec on the final kick. Best, -Slashy

It was. Typo corrected. Thanks, -Slashy

If you're going to Minmus, your best launch is into Minmus's orbital plane. If you have to choose between polar and equatorial, equatorial is closer. Less DV to correct for inclination. Usually though, your first orbital launch isn't going to Minmus. It's just orbit and recover. Either way, equatorial is the better option. Best, -Slashy

I would budget 6,150 m/sec DV for a Mun shot. 1,700 for boost 1,700 for LKO injection 900 for TMI burn 350 for circularization 1,150 for descent/ landing 600 for ascent/ rendezvous 350 for TKI burn Keep in mind that while there are many ways to shave mass and cost on a mission, there is no way to "save DV" on a mun shot. If it were me, I would calculate DV myself using a spreadsheet. Best, -Slashy

Jestersage, I agree, but we have access to more advanced avionics than the kerbals do. Without an active alpha hold control loop, the Hermes would've suffered the same problem. Best I can recommend is "hiding" your tail wings by rotating and clipping them inside the tank. I'm not certain that will still work in 1.2. I gotta try it. Best, -Slashy

Jestersage, A space plane on a stick means that the center of pressure is ahead of the center of mass. As a result, the rocket wants to weathervane backwards from it's direction of travel. Picture an arrow with the fins at the front. Fixing this will require bigger fins on the back, assuming you want to keep the "plane on a stick" configuration. You can also make it more manageable by accelerating more slowly, but that means your DV budget must be higher to account for the increased gravity losses. Best, -Slashy

Rule #1: Never ask others if "it's okay". Single player game. Play it however you like. Best, -Slashy

According to the changelog, g0 has been changed to 9.80665 m/sec2 and G is now 6.67408x10-11 km3/s2 Does this now mean that Kerbin's mass has been changed to 5.28971x1022 g, or is there still a discrepancy between g0 by convention and g0 by calculation? If the discrepancy exists, do I now use g=9.80665 for physics calculations, and g=9.810118 for flight planning? Confused... Thanks, -Slashy

p1t10, Thanks for the response, you're right; I asked the wrong person but you did a fine job explaining it. Thanks, -Slashy

I guess I'm just not getting what this complaint is about. @p1t1o, could you please elaborate? Thanks, -Slashy

There's a difference between "inaccuracy" and "imprecision". The inaccuracy in my model is due to an error on my part, which is correctable. How many times have we seen people led astray due to false assumptions in KER and MJ that left them stranded? At least by my method, the current inaccuracy is toward the safe side. If my model suggests a design, it *will* work 100% of the time. The big differences between our two approaches are 1) you have to actually build a stage to ascertain what it will do and 2) you can only build 1 stage at a time. I am not constrained by such limitations. All I have to do to model a stage is enter the parameters of the job. It will construct stages using all engine types simultaneously, allowing me to cross- compare mass, cost, and complexity at a glance. And frankly... I find "faffing about" in the VAB tedious. If you enjoy that approach, more power to you. As I said earlier... to each his own. Best, -Slashy