TythosEternal

My four-year-old daughter being obsessed with the movie Frozen, I told her that Minimus was the ice-and-snow-covered planet where Elsa lives. Needless to say, now it's her favorite place in KSP, too (well, right after Duna, because red's her favorite color and nothing's more important than that, right?) Follow-up: I just noticed, for the first time, that I've been spelling Minmus wrong (specifically, with a second 'i'), pretty much forever. I take some comfort in noticing here that I'm not the only one. =p

I'll go with Minimus--I feel like it's such an overlooked charmer. Easy you reach, easy to land and take off, easy to explore and conduct experiments, etc. It also has a really neat mix of surface textures! Minimus is a unique spot, and Squad was very creative with putting it into the game.

Ground testing is one way to mitigate this particular risk factor. (Risk factors, as I pointed out in the beginning of the response, are functions of their likelihood and their consequence--not testing and mitigation efforts, which are made in response to the assessment of the event.) Mitigation does not mean irrelevance, however, and many vehicles can still encounter disastrous combustion issues. (The Delta II launch of GPS IIR-1, in which a high-reliability GEM-40 developed a crack and subsequently experienced a 'structural failure', is one of my perennial favorites.) "Being shaken to pieces" is close to being the very definition of combustion conditions (even during normal steady-state and transient sequences) and effects. Considerable effort goes into mitigating vibrational modes excited by vehicle engines--including for the engines themselves. Especially for main engine sequences, there's a controlled explosion taking place at one end of your rocket, and a whole lot of shaking going on! I think you are confusing quality control, which ensures the manufacture of components within sufficient tolerances, with process and inventory control, which ensures High Bay Bob keeps track of all his wrenches. I'd be interested to see a source on the 'tens' figure, but it's irrelevant anyways: Do you know what failure mode is induced by FOD (foreign object debris) in plumbing? That's right! Combustion instabilities. (Catastrophic turbopump failures are another result, but it's the uncontrolled combustion that does the greatest and fastest damage.) I would encourage you to look at an AIAA paper written by a colleague of mine on launch vehicle failures. Only the front page is readable for non-members (well, unless you want to pay the $1065 cover charge... AIAA is ridiculous like that), but even that much is interesting and very accessible to non-engineers, actually. Lastly, I would end with a note on mitigation. As long as there have been rocket engines, engineers have been trying to control the intricate instabilities of the combustion process and its sensitivities. Even today, though, when something goes wrong after ignition anywhere in the fuel train, the typical response is to shut down the effected systems BEFORE an instability occurs. Sometimes this means you continue on other engines, sometimes it means the RSO hits the big red button and you're out the better part of a billion dollars. This is all to say that, looking at a history of launch failures, many cases in which rockets deliberately shut down were the result of efforts to avoid instabilities, trading them for a more controlled (and de-escalatable) failure mode instead.

The single highest-likelihood, highest-consequence failure mode in launch vehicle (liquid or solid) is combustion instability. Inconsistent combustion of oxider feeds in particular are very, very dangerous. This can result from a large number of causes, from pressure variations in your turbopump feeds to injector plate inconsistencies to unusual vibration modes in your combustion chamber. Poorly-controlled variations in your steady-state conditions and manufacturing defects are also frequent factors, as are operating conditions outside the design space (a la Challenger). The result of combustion instability is, simply, things blow up. Unconsumed oxidizer, at the temperatures and pressures that exist inside your combustion chamber, can actually react and combust with metallic components, induce a fatigue or rapid crack failure, or produce uncontrollable variations in thrust. Uncontrolled combustion products induce material failures in surrounding components, creating a chain reaction--and it doesn't take much for a delicate, high-energy piece of equipment operating under extreme conditions to catastrophically fail. In short, you will not be going into space today.

Aaaaaaaaahhh... That feels better. Thank you so much.

You seem to be confusing theta, the true anomaly, with gamma, the flight path angle. You can rearrange the geometric and kinematic orbit equations to cancel out the cos(theta) terms, at which point (at least in my own math) you should have: e = sqrt(1 - h^2 / (mu * a))

What you're after is commonly called the 'shape' of an orbit--apoapsis and periapsis--which are both easily computed if you know the semi-major axis and the eccentricity of the orbit. We already have three orthogonal values for the 6-value system (the other three are for plane orientation, irrelevant to this problem), so this is actually pretty simple. I'd recommend the following approach: * Compute h, the magnitude of angular momentum, from r, the known radius (altitude plus radius of the orbited body, which we assume is spherical); v, the magnitude of the orbital (inertial) velocity; and gamma, flight path angle (the angular separation between your current heading and the nearest horizon): h = r * v * cos(gamma) * Compute the semi-major axis using the expression for orbital energy: a = (mu * r) / (2 * mu - r * v^2) * Compute the eccentricity from h, mu, and a: e = sqrt(1 - h^2 / (mu * a)) * Compute radius at apogee or perigee from a and e: ra = a (1 + e), rp = a (1 - e) Most of these are simply derived from geometry and basic orbital properties. Here's an example: r = 1.6e6 (altitude = 1e6, radius of Kerbin = 6e5 m) v = 1.2e3 m/s gamma = 10 deg (~0.175 radians) mu = 3.5316e12 m3/s2 Here are the steps: * h = 1.6e6 * 1.2e3 * cos(0.175) = 1.8907e9 m2/s * a = 3.5316e12 * 1.6e6 / (2 * 3.5316e12 - 1.6e6 * 1.2e3^2) = 1.1873e6 m * e = sqrt(1 - 1.8907e9^2 / (3.5316e12 * 1.1873e6)) = 0.3841 * ra = 1.6433e6 m rp = 7.3126e5 m I do need to run these against the previous example, though--likely after I've cooked (or while I'm cooking... =p) dinner.

I'll even take it one step further: Science: The art of figuring out how miracles happen. Engineering: The art of figuring out how to make miracles repeat on demand, and then selling those solutions for money!

I'll drink to that! Thanks for sharing a fascinating experience with us. Unfortunately, if my own encounters are evidence, too few directorates actually took your advice!

I happen to be an aerospace engineer, and my dad happens to be a neurosurgeon. (Guess which one pays better, by a factor of five...) My poor younger brother always moans about having a rocket scientist and a brain surgeon in the same family and how expectations are so unreasonably high for him. Then again, he's the Marine, and knowing his luck, hell probably get a Medal of Honor or be elected president or something. This is all to say that I hate the (anti-?) stigma people attach when they learn my profession. Suddenly, nothing I do is average, acceptable, or good enough. Good grief--it's really just engineering, you just get to engineer the really shiny toys. Yeah, I know, poor me.

"Optimization" can mean many things. Let's say you want to breech the Karman line with minimal delta-v expenditure. It becomes primarily a tradeoff between a minimization of "gravity drag" (how much delta-v you use trying to move directly up in a gravity well) and atmospheric drag (delta-v lost to air resistance). We can furture constrain the problem by stipulating a gravity turn after some pitchover conditions are meet. This is now a local optimization problem, and there may be solutions you won't capture, but in exchange we now have a fully-deterministic ascent profile, given certain boundary conditions. Lastly, for a given vehicle configuration, we can search this well-formed space (altitude, pitchover angle, and turn control parameters) to converge on an optimal solution. At this point, the biggest problem is accounting for the staging characteristics of each unique vehicle--you've entered a min-max problem space, constrained by subjective measurements like separation risk. The last sensitivity I should point out is that of models. How high are you shooting (i.e., what model determines your objective), what kind of atmospheric/drag/gravitational models are you using, how are you modeling and/or integrated control through the beginning, pitchover, and throttling sequences, etc. If you are a controls scientist or systems engineer, "optimization" means something very specific. With a problem with these qualitative sensitivities and discrete/discontinuous behaviors, analytical optimization is a pipedream. However, proper constraints of your design space and selection of appropriate models will let you find a near-optional solution numerically.

Minimus is actually easier to safely land on, and safely return from, than Mün--and it has higher science multipliers, too! In career / contract mode, target Minimus first for a better return on vehicle investment.

That model was a structural-and-systems prototype; the interior will look very, very different by the time manned rating has finished and we have better mission specifications and CONOPs. For my own $0.02, there are many, many more (and better) things that can be done with the interior. SpaceX had a novel chance to redesign a capsule from the ground up, but they appeared to have more dreams and science fiction fantasies than practical human interface and mission experience. That having been said, it's still early--I have no doubt things are only going to improve.

The cancellation of the JIMO (Jupiter Icy Moons Orbiter) program still makes me cry a little bit inside every time I think of it. Not only was it the first serious (more-than-imaging) exploration of Jupiter's moons, it was very ambitious. Why just explore Europa when you can take a look at Callisto and Ganymede, too? There were also a number of new technologies, such as a deep-space fission reactor plant, high-impulse Hall thrusters, ice-penetrating radar, and high-bandwidth interplanetary data transmission. Much of this was enabled by the unprecedented power availability provided by the power plant. Despite all this, it was very do-able and had even started preliminary mission planning and acquisition contracts before it was cancelled. The rationale at the time was that manned space missions were more important (thanks, Constellation). Every NASA mission since then seems incredibly dull, unambitious, and risk-averse.