GoSlash27

Really, your best bet is to just not discuss anything on Twitter or better yet don't go there at all. That place is a dumpster fire. Best, -Slashy

Meh. using all metric didn't stop the Russians from installing their accelerometers backwards, did it? Stuff happens. Besides, last I checked the US was still the world leader in spaceflight, imperial units notwithstanding. If you work in an engineering field in America, you learn to work with both systems. No amount of crowing about metric's "superiority" will change the fact that we still have to use imperial whether we like it or not. Best, -Slashy

The best I can recommend is that you look for payload to LKO in tonnes, assuming that the creator provided that info. You're going to have to design the rest of your own mission anyway. Otherwise you can guesstimate the payload fraction of a lifter by its pad mass, assuming it's all liquid fueled. An average lifter should be able to orbit 10-15% of it's launch mass as payload, a really excellent one might hit 25%. This number goes down when solid boosters are used. TL/DR: If you want to launch really big payloads, find a really big rocket that's not a SSTO. HTHs, -Slashy

I work with both out of sheer necessity. It's not difficult to learn both or even convert between them. I do find metric easier to work with, but my society is used to/ happy with imperial. I don't insist that society must convert to my preferred system, nor do I assume that America's insistence on using the imperial system has ever hampered their ability in technological or scientific advancement. Best, -Slashy

1) I'm not sure what you mean "stop an orbit". Are you proposing to nullify orbital velocity instantaneously while still at orbital altitude? If so, I can point out a half a dozen reasons why that's a bad idea. 2) The payload issue with Skylon has more to do with the rocket equation than drag. 3) Current engine setups can already get more payload to orbit than Skylon ever could. Again, reference the rocket equation (in my sig below).

To be clear, The entire point of SSTO is that it's inexpensive to operate and rapidly reusable. If it doesn't fulfill those criteria, it's got no practical purpose for existing. Tsiolkovsky would point out that given identical tech, the 2 stage design will always use less fuel than the one stage design for an equal payload to orbit. Furthermore, we have figured out how to recycle the booster and are rapidly working out how to recycle the sustainer as well, it would seem that SSTO just plain doesn't offer enough fiscal advantage to be worth pursuing anymore. The turnaround time might have some niche applications, but most of today's launch providers and customers don't see that as a priority. Best, -Slashy

I think the landing gear and vertical fin are fine as they are. The main problems I see are 1) the wing is too far forward and 2) the control surfaces haven't been specialized to not fight each other. Also the horizontal stabilizers are a bit big and the reaction wheel hasn't been disabled, but these are minor points. On point 1... The VAB is misleading in that it thinks every horizontal surface is there to provide lift, but that's not necessarily true. The horizontal stabilizers are there to provide downforce to counter the weight of the nose, not provide lift. I'd recommend temporarily rotating the the horizontal stabilizers in the VAB so that they provide no lift, then move the wings so that the center of lift is slightly behind the CoG, *then* restore the horizontal stabilizers to a close- to-horizontal position with the leading edges slightly low. This will make your pitch response less janky and should cure your tailstrike problem. On point 2, control surfaces in KSP should be limited to provide control over only one axis in order to avoid cross purposes. Ailerons should only respond to roll, elevators only to pitch, and rudders... You don't really need active rudders in KSP and the plane will track more true in turns with SAS on if you don't have one. On the minor points: Smaller horizontal stabilizers will give you more precise pitch control and reaction wheels will simply drain electricity and lead to cross control crabbing the same way active rudders do. Best, -Slashy

Slyguy, Glad I could be of service Best, -Slashy

Slyguy, The communication ranges of antennas are given with the assumption that both antennas are the same type, but here your link is between 2 different types. Your HG-5 is good for 5 Mm, but only when communicating with another HG-5. Here you're talking with a Communitron, whoch is only good for 500 km. When talking to each other, their combined range is only 1.58 Mm (sqrt(Ra*Rb)). Thus they're out of range of each other. As for your launch instability issues, could you post a pic? We might be able to spot your problem. Best, -Slashy

All, I happened to poke my nose in the door this morning and saw that I'd been summoned I have to admit that I'm not familiar enough with the new changes to have a strong opinion either way. I've always applied a 2- prong test to these questions: 1) Does it break the challenge and 2) is it stock. I'm unclear as to how "sticky Kerbals" ascending to space and returning EVA negatively impacts the challenge, nor the transfer window planner. You're still ultimately limited by your part count and pad mass, as well as the inability to rendezvous in orbit other than using the Mk.1 eyeball. Could someone explain to me their concerns about these latest changes? Thanks, -Slashy

K^2, No, it sounds completely wrong Your total energy at the bottom of the well prior to the burn is zero (or very close to nil). You had 5GJ of kinetic energy and -5GJ of potential energy, which cancel out. You then added .5MJ of kinetic energy by increasing your velocity 1,000 m/sec, which you keep as you leave. The kinetic energy is transferred back into potential energy to pay off the debt you incurred by falling into the hole, leaving your 1,000 m/sec DV. Best, -Slashy Lislias, Again you are confusing the mathematics of Oberth with the mechanics of gravity assists. Oberth doesn't "steal" anything from the parent body, it simply generates higher kinetic energy from travelling faster. Gravity assists *literally* steal kinetic energy from the body... but that body must be in motion in order to have any kinetic energy to steal. The neutron star in K^2's example is not in motion. Best, -Slashy

Lisias, Not at all. K^2's example was given in the ship's frame. The example neutron star had no defined motion, thus no kinetic energy to steal. I'm afraid you're confusing Oberth with gravity assist, which are 2 different subjects. Best, -Slashy

Lisias, This is correct when the body is in motion. You're stealing kinetic energy from the moon. However, this doesn't apply to K^2's example. Best, -Slashy

K^2, I think this is where you went off the rails: This is not correct. The conservation of energy demands that the total energy remains the same in a closed system. You converted chemical energy into kinetic energy, adding 500 kJ. That's all you did. You should've algebraically added the kinetic and potential, which in this case is subtraction rather than addition. Whatever potential energy you have converted to kinetic energy on the way in will be converted back into potential energy on the way back out. Your total energy at the end of this maneuver isn't 100.5MJ, it's 0.5 MJ. Best, -Slashy

I get where you're coming from. I used to think the same way. But (yet again) that's not how it actually works. The goal isn't to inject energy as cheaply as possible, it's to get the vehicle to the destination as cheaply as possible. If you model the situation you're talking about, you'll see the pitfall in that line of reasoning. Best, -Slashy

HMV, No, at least not in our solar system. There's only a couple targets that have a gate orbit anywhere near the moon, and you don't need to get close to the lunar surface to hit it. Farther targets are more efficiently reached by a LEO burn and simple slingshot. K^2, Again, that's not how it works. You don't actually pick up "extra" DV, even if you do your burn scraping an event horizon. The depth of the gravity well itself doesn't help or hurt you, it merely determines how far you can bend your trajectory at a high inbound velocity. This is the illusion of the Oberth effect; you get the idea that you get a DV payoff by burning at higher velocity. You don't. The payoff comes from making the transfer more eccentric. The energy of an orbit is equivalent to the area it contains. A long skinny orbit contains less area, but reaches the same Ap. Therefore requires less energy to achieve. *That's* how the Oberth effect actually works. Best, -Slashy

HMV, "Yabut" That's what I'm trying to get across... Oberth isn't what most people think it is. It's not like "free parking", where you automatically get bonus DV for going faster. It's simply math behaving correctly, but in a counter-intuitive way. For every Vinf, there is an ideal R for the burn. Above it, and you waste kinetic energy. Below it, you waste potential energy. Going too low is *much* worse than going too high. The idea of "the lower and faster, the better" is a gross over- simplification, and leads to a false conclusion. Best, -Slashy

HMV, see below... K^2, Actually, it doesn't work that way. Any velocity you pick up from the Mun's gravity well is lost escaping it. If you come in (say) at 1 km/sec with respect to the moon, you will leave with that same 1 km/sec with respect to the moon.... even if it *temporarily* accelerates you to relativistic speeds. Think of it as coasting down a hill and up the other side, except with no drag. It doesn't give you anything for free. You leave with the same speed you had when you came in, no matter how fast you're going at the bottom. Whatever you gain on the way in, you lose on the way out. The reason gravity assists work is because the body is in motion, not the gradient of it's gravity well. Turning the moon into a black hole doesn't affect it's orbital velocity, so it has no effect on that. Best, -Slashy

HMV, It's always cheaper to burn direct from LEO unless you can refuel in lunar orbit using reaction mass collected from the moon itself. Since the moon is a black hole, that's not an option. AFA the Oberth advantage, it's offset by the gravity well. Every destination has a gate orbit; a radius where the Oberth and gravity well balance at a DV minimum. The closer destinations have a gate orbit above the current moon's surface. The more distant ones would have a gate orbit below the moon's surface, and thus would save some DV. But again, you can't acquire fuel from a black hole. TL/DR: No advantage there. Best, -Slashy

Yes, that's the advantage. It's not all that much of an advantage though, since we can get nearly any direction we want now. My point is that the most DV you can gain from an encounter is 2Vorb, regardless of whether it's a moon or a black hole. Best, -Slashy

I don't think there'd be much advantage there, since you leave with the same relative velocity you came with. Gravity assists harness the body's orbital velocity, which wouldn't change. Best, -Slashy

About the size of a gnat's head, for perspective. A gnat's head orbiting Earth with the moon's mass at the moon's SMA. But in reality, it wouldn't actually *be* that size. The gnat's head would be just the event horizon. The actual moon would continue to compress beyond that point into a singularity; beyond our ability to image, even with an electron microscope. Best, -Slashy

Ah. So we've got some time, then

Nothing, really. It might confuse the hell out of some insects (sudden loss of their navigation beacon) and cause the extinction of nocturnal hunters... Otherwise, the difference in gravity to other planets and Earth is zero. But in the long run, the moon would lose its mass through Hawking radiation. This would cause the extinction of life on Earth, since our core would cool, the magnetosphere would die out, and we would no longer have a tidal force to keep our rotational axis stable. Best, -Slashy

My second stages are usually around that t/w. First stage is 1.4 t/w and 1700 m/sec DV. It burns out at 45° pitch, 28km altitude, and 750 m/sec velocity. Second stage is 0.7 t/w, 1600 m/sec DV. It burns out right about LKO. Best, -Slashy