Starman4308

You do recall the bit where NASA refused to count anything other than Block 5 for validation flights for commercial crew? In software, if you change one aspect of the code, everything has to be re-tested. Man-rated launch vehicles are just about that strict. Very minor changes might be permitted, such as adding a redundant pump to prevent a repeat of CRS-16, but vehicle-wide upgrades such as have happened over the history of Falcon 9 are verboten, for good reason. Not only do you have countless parts on an orbital launch vehicles, each of them interacts with each other. For unmanned launches, if you do a thorough analysis of what a change might affect, you might get away with it. Manned launches are, for good reason, put to higher scrutiny. Either SpaceX freezes the Starship design way earlier than they should, or they're not launching people on it for many, many years after its introduction.

I'll believe a 2023 manned launch when I see it. The timelines Musk predicts are widely known to be aspirational at best and outright pixie dust in many cases. Four years is not much time to go from technology demonstrator to a mature launch system. It took eight years for the Falcon 9 to go from its first flight to a mature configuration, and that was based on much more well-understood design principles.

1) Technically you have me there. Practically, substitute almost any other system of the vehicle in, and that's still something that could cause a failure. 2) Does it matter? With experimental vehicles, half the time it's not what you anticipate might be an issue that kills you: it's what you don't anticipate. 3) Failure of active cooling to the heatshield during reentry. I don't care how. Maybe a bolt shakes loose on reentry and hits enough adjacent pipes/valves that you get a local hotspot. The key point here is that rattling off a list of technical details doesn't matter. In vehicles this complex, being run this close to engineering limits, something will be overlooked. Even in the airline industry, overlooked failure modes have caused disasters. The difference with the airline industry is that they've made so many flights that, if there is something overlooked, it's such a strange, rare edge case that very, very few flights will be affected. Orbital launch vehicles? They don't have that track record. It's not the part you can think of that will fail you. It's the insulation foam falling onto your wing. It's a worker inserting an accelerometer backwards. It's the bellows surrounding the augmented spark injector encountering vibrations in the vacuum of space, that hadn't been an issue on the ground because of condensation (Saturn V Owner's Workshop Manual, pg. 149-150). It's an improperly secured nut that the prior worker used an extra-long wrench to firmly insert, while the new worker used the prescribed (too-short) wrench. With such massively complicated systems, the only way to get reliable failure-rate data is to go out there and launch some vehicles. Until SpaceX has that, it's criminally risky to put astronauts on something that doesn't have a bone-simple and robust launch escape system. EDIT: You want to know why Challenger and Columbia killed 14 astronauts? Really, it wasn't the foam, or the SRBs failing in cold weather. It was the poor management decisions combined with an overly experimental vehicle lacking good abort modes that killed 14 astronauts. Fix one problem, and another crops up. I can only hope that SpaceX's actual engineers are a lot more cautious than that.

Independent engines-out are hardly the only failure mode imaginable. COPV fails, and ignites the tank (which, you know, happened on a Falcon 9). Control glitch cuts the Superheavy thrust half a second into flight. The active cooling on the Starship reentry fails, even on a small patch, leading to burnthrough and vessel breakup on reentry. And that's just known failure modes. Take the Columbia disaster as an example: nobody thought foamstrikes could be a failure mode until a foamstrike was a failure mode. The Starship is experimental technology, in a class known to be prone to failure. It's going to be a huge amount of effort to man-rate it.

Because the Shuttle showed just how foolish that was. NASA at that point was overconfident. Apollo had gone through with only two major incidents, of which only one killed astronauts. They'd made that very tight deadline. On top of that, with Congress shrinking their budget, they realized they needed something cheap and affordable to make their ambitious goals such as space stations, Mars missions, etc. work. Add to that Presidential pressure to come up with something impressive on a budget, and you get a project which paid little heed to safety or economic practicality. Then so be it. If it takes some extra cash to keep astronauts safe, then that's the price that will have to be paid. Manned BEO missions (and even LEO missions) are of very questionable utility, and not worth putting people into experimental vehicles flying at the razor-thin edge of engineering margins without a decent escape system or very thoroughly tested vehicle.

Because something on the scale of the Starship is necessary for those tasks does not show these two things: That the Starship can safely transport passengers to Earth orbit and beyond. That the task is necessary or economically practical given current technology. Do not let "but I want a colony on Mars" blind you to the potential issues with Starship/Superheavy. Or, for that matter, blind you to the potential issues with Mars colonies. Accept reality as it is, and hope for better... but plan for the worst. Do not plan on experimental technology working. This reminds me very, very strongly of the thinking that lead to the Space Shuttle. "We need something that looks like this to do X, Y, and Z. Therefore, the Shuttle will succeed at X, Y, and Z." EDIT: The Starship might succeed, but until the Starship has a very large number of launches under its belt, I consider it extremely risky to put astronauts on something that, to my knowledge, still doesn't have a robust launch escape system. That, and SpaceX's plans for rapid reusability are just that: plans. We'll have to see what happens when plans hit reality.

Just like the Shuttle! I am reasonably confident the engineering will work out. The SpaceX team isn't stupid. What concerns me is what comes after the first few flights, on whether SpaceX can maintain their highly ambitious goals in turnaround time, minimal refurbishment, launch cadence, and the overall economics of the Starship/Superheavy. I'm also skeptical of plans to use the Starship/Superheavy for manned launches. Personally, I'd strongly prefer it if the astronauts were sent up on a separate F9/Dragon II, which is generally much more proven technology.

While a perfect resonance generally doesn't happen, approximate resonances do. If, for example, you have an orbital period of 1.01 local sidereal days, it will take nearly 50 local days to map the body in question. This can be a factor if time is a significant factor.

So, out of likes today, but: Thanks for your analysis. It's not a field I have much knowledge in, so what you provided was quite illuminating. So, I'm guessing your analysis would be "there are probably companies with more reliable data and estimates... but they're not giving up that information without some dollar-signs attached"? I will confess: I was weirded out by a few of the choices made, but comments in this thread were what took it from "that's weird" to "okay, this might not be totally kosher".

Not incredibly surprised. AFAIK, the transonic regime results in high aerodynamic stress, and if I did the calculations right, it has a 1.2 launch TWR. Combine that with the high specific impulse of hydrolox, and it gets going quite slowly at first.

Complexity is just as bad in software engineering as hardware engineering. It's something where the chance of this being necessary has to be weighed against the cost of developing and validating the software, plus the risk of the propulsive landing routine accidentally activating on a nominal landing, plus the risk of it somehow interfering with the parachute landing software, plus NASA bureaucracy.

While I can't comment on many things, since this thread is probably about stock launches (and not Realism Overhaul), this point I can address. The Saturn V shutting down its central F-1 had very little to do with efficiency, and everything to do with not squishing fragile astronauts and cargo. Granted, the Titan-Gemini stack was much worse at that, but even 4G accelerations can be hard on people.

Courtesy of Ars Technica's recent rocket report, I am now aware of the Spacefund Reality Rating (SFR). This appears to be an effort to provide information to potential investors on which companies are real, which companies are still developing and may not work out, which companies are likely investment scams, and which companies have been part of the space-industry bedrock for decades but you haven't heard about until you found them on this website. I'm looking at the Swedish Space Corporation, which is apparently huge, but nobody talks about because they don't operate their own orbital launches, just... like all the less glamorous stuff, apparently. As to the poll: I think this is a positive development for an industry crowded by startups, which have to be distinguished from scams or really bad ideas, but I am perfectly aware that good-sounding initiatives can be useless to actively harmful. EDITS: It's also interesting to note that Relativity Space, despite having just gotten launchpad clearance on the Cape, are a 6. As I understand, plenty of ex-SpaceX engineers on staff as well, so I'd given them a solid chance of making it to orbit... even if it's premature to figure out if they're going to survive the small satellite launch bloodbath... I mean small satellite launch business. Also, as a personal gripe, I'd give Blue Origin an 8, at least when it comes to New Glenn (New Shepard-based services are a 9). Sure, their chances are excellent... but until you have payload in orbit, I consider top-flight reliability rankings premature.

I know I'm not nearly fit enough to be qualified for being a real astronaut... though if I make enough money, Blue Origin might make me a fake astronaut. Both mission control and being an astronaut appear like they'd be fun intellectual challenges, and one of those two jobs can be done from a comfortable chair with no threat of exploding oxygen tanks.

On the topic of trying to SSTO the Starship, I'll take this quote from a chapter of Right Side Up: “A marginal SSTO is a great TSTO.” “By extension, a marginal TSTO is a great 3STO.” Hand-written notes on NASA MSFC memo during STS planning, 1969 The challenge of trying to build a reusable SSTO for Earth is immense. Every time people have tried, the design doesn't work as planned, and increases in dry mass cut the already marginal payload to negligible levels. Cut things in half, though, and recover the halves separately, and the challenges become much more tractable. I doubt there'll be a shortage of Superheavies for the Starship; they're basically overgrown Falcon 9 boosters. The recovery challenges are much less severe when you're talking about merely hypersonic speeds; even ordinary aluminum can take that sort of heat load. If space launch really picks up and they simply can't turn them around fast enough, SpaceX can... build more Superheavies.

The factors driving the Falcon Heavy's late debut aren't there for New Glenn. Falcon Heavy was an adaptation of the extant Falcon 9, which was in a state of continual upgrades for five years. It wasn't a wise idea to solidify the Falcon Heavy design until the Falcon 9 settled down... many years after Elon Musk decided "what if I tried more boosters?"

You mean five orbits. Remember, you scan 36° on one hemisphere, then another 36° on the opposite hemisphere. Incidentally, it's a curious optimization issue: a low orbit restricts your field of view, but also gives you more north-south angular velocity. EDIT: Just read the "daylight passes" bit. In that case, either 10, or maybe 5 if you orbit on the day-night terminator.

Would I like to see Squad create a commercial-grade, less buggy, robust version of Realism Overhaul? Yes. Would it be in their best interests, or accessible to new players? No. It would be a huge amount of work to rebalance basically the entire game to match real-world scale. Even ignoring the many additional mechanics of Realism Overhaul (ullage, boiloff, avionics limits), a relatively small scale helps players get to space with suboptimal designs and imperfect gravity turns. Overall, what I would like to see out of stock KSP: an optional 2-3x scale version of its solar system (relying on overweight parts to make up the remaining difficulty) for advanced players, bug fixes, and another pass at the aerodynamics... though the armor-plated tanks of stock are always going to mean aerodynamics are a bit wonky. Also: launches in RO can take a very long time. My last career, I was working with an F1 -> 3x RD-58 -> RL-10 stack that took probably 15 minutes to get to orbit... partially because that second stage was hideously underpowered. One minor issue the small scale of stock does impose, thinking about that, is that it's much less practical to loft a low-thrust second stage on a high suborbital trajectory to make up for low second-stage TWR; by the time you have a good loft in stock KSP, you're almost kinda in orbit.

While it's not a big enough improvement for me to bother, I think the optimal inclination would be 90 degrees plus half your field of view, such that you just barely graze the poles with each pass. This gives you a bit of additional rotation under your scanner as you pass the equator, letting you scan slightly more of the equator with each pass.

This is just going to be a straight-up polar orbit. Let Kerbin rotate beneath you, and before too long, the entirety of the planet has been mapped. Play with the ScanSAT mod, and you'll see how it goes. In theory, if your field of view is sufficiently wide, you can get it in half a sidereal day. If the FoV is more narrow, you'll get stripes that are covered and stripes that aren't, and you'll have to wait to fill in the gaps. Now, for a bit of Fun (TM), try out Venus (Real Solar System) or other mod planets with very slow sidereal rotations. Half a Venusian sidereal day is 120 Earth days.

The Li-F-H tripropellant motor is an insane product of 1950s-1960s propellant chemists wondering how far they could push chemical propulsion. Fluorine (and the hydrogen fluoride in the exhaust) is hideously toxic and a potent oxidizing agent (requiring relatively exotic materials to handle). Lithium needs to be at 180C to remain liquid... and likes to react quite vigorously with water. Hydrogen is a very low-density fire risk, but at least we've dealt with it before. Between the safety risks, heavy tank insulation and lithium heating elements, and overall complexity, it's just not worth developing. Even if we ignore the rise of reusability, there's just no economic reason to develop Li-F-H. Commercial applications, largely bound to GSO or lower-energy orbits, don't need freakishly high specific impulses: the cost of a modestly larger rocket is much less than the cost of developing a nightmare engine. Unmanned scientific applications aren't a big enough market to develop a nightmare rocket, and can largely get by on a combination of hydrolox, solid kick stages, and miniaturized probes. Current manned scientific applications are just LEO taxis. Hypothetical manned scientific applications are likely to either just use a really big hydrolox vehicle, or bite the bullet and go for nuclear-thermal propulsion. In terms of specific impulse, Li-F-H is only modestly better than hydrolox, and significantly inferior to nuclear-thermal and electric propulsion... neither of which involves having lithium, fluorine, and hydrogen all in the same rocket stage. With the rise of reusability, well, the cost of handling nightmare fuels becomes an even bigger issue. The tripropellant combinations that actually make sense are kerosene-LH2-LOX or methane-LH2-LOX. Again, marginal improvement, and most agencies have decided to cut development cost by not trying for a relatively complex tripropellant system. In terms of little green people flying rockets over toy-sized solar systems, I don't see why an Li-F-H analogue creates a meaningful game mechanic, other than slightly increasing the difficulty of ISRU operations. I could see a hydrolox analogue (trading lower thrust and much lower fuel density for better specific impulse), and possibly something a liquid fuel-oxidizer-quasihydrogen tripropellant, but an Li-F-H just doesn't seem like it'd help things. Plus, KSP already has nuclear-thermal rockets, which fit the bill for "really good specific impulse".

I'm pretty confident I now have it worked out when incorporating rotational velocity*. Fortunately, planar trigonometry is simpler than spherical trigonometry. Thanks to @YNM and @Delay for double-checking the assertion about north vs. south launch sites. *Plus or minus minor error caused by an increase in altitude between launch site and parking orbit. That, though, would probably require outright numerical simulation of the launch profile. Definitions: Gamma is the value solved for up above: the angle between north and your orbital track (as of the launch site latitude). L is as above: latitude of the launch site. Phi is the angle between due west and your launch angle. Re is the rotational velocity of the planet at the equator. R is the rotational velocity of the planet at the launch site latitude. Vo is the velocity of the target orbit. To minimize error caused by the difference in target altitude and launch site altitude, I recommend calculating based on a low parking orbit. VL is the delta-V of your launch, minus any gravity/atmospheric losses. The first thing is to construct a triangle of three vectors. Vector A is an eastbound vector of magnitude R (the eastwards spin at the launch site). Vector B is the orbital vector, of magnitude Vo. Vector C is the launch vector, of magnitude VL. Gamma is opposite vector C, and phi is opposite vector B. The second step is to calculate the angle between east and your orbital track. This is not Gamma, since Gamma is defined with respect to north, not east. Fortunately, it's a simple rotation. Theta = 90 - Gamma The third step is to calculate the body's rotation at the launch site. Fortunately, this is a simple cosine multiplication based on latitude. Re = diameter / sidereal rotational period R = Re * cos(L) The fourth step is to calculate VL. For this, we turn to the planar law of cosines: c2 = a2 + b2 - 2ab*cos(gamma), where gamma is the angle opposite c. VL = sqrt(R2 + Vo2 - 2*R*Vo*cos(Theta)) The fifth step is to calculate phi. Once again, it's the planar law of cosines, rearranged to calculate an angle. Phi = cos-1((R2 + VL2 - Vo2)/(2*R*VL)) The sixth step is to rotate phi into an inclination. Launch angle 2 is calculated as a function of angle 1... but in reality comes from the twin solutions to the arccosine. Launch angle 1 = 90-Phi Launch angle 2 = 180 - Launch angle 1 Now to actually complete the "First Polar Orbit" contract out of Tanegashima...

The lightweight experiments are just about a given. For a cheap no-return flyby, goo and materials bay are marginal: they are heavy and do not transmit 100%. One mod I like is DMagic's science parts (may not be updated); a lot of them have some mass, forcing actual choices in some cases. If you play with extra science parts, I recommend reducing the science multiplier.

What I'd do is find out when the next Jupiter->Pluto transfer window is. Then work back, and find the Earth->Jupiter window that best lines up with that. Transfer to Jupiter, and abuse its gravity well for a Pluto slingshot.

So, I'm starting to work through this myself, with extensive help from Wikipedia. I'm taking as the three points: the ascending node, a northern-hemisphere launch site*, and the north pole. All angles are in degrees. I am not yet including the rotation of the body you're launching from. *Empirically, the calculations I'm doing seem to be robust to southerly launch sites, and I think that's correct, though I'd have to do more math to prove it to myself. Bolded is the "I just want this quick" stuff. Some definitions: L is latitude of the launch site. N is the inclination of the target orbit. a is the length of the arc from the ascending node to the launch site. This is the true anomaly of the launch site on the target orbit. b is the arc length from the launch site to the north pole. This is (90-L). c is the arc length from the ascending node to the north pole. This is always 90 degrees. Alpha is the angle opposite a. This, I think is the difference in longitude between the ascending node and launch site. Beta is the angle opposite b. For prograde orbits (N < 90), Beta = 90 - N. For retrograde orbits (90 < N < 180), Beta = N - 90. Gamma is the angle opposite c. This is one of the key unknowns; it's the angle between due north and your target orbit. We have arclengths b and c, and angle Beta. The easiest unknown to calculate is Gamma... which is fortunately the easy value to get, with the spherical law of sines. Spherical Law of Sines: sin(a)/sin(Alpha) = sin(b)/sin(Beta) = sin(c)/sin(Gamma). Rearrange this a bit, and you get Gamma = sin-1(sin(c)*sin(Beta)/sin(b)). This simplifies a bit since c = 90 and sin(90) = 1. Gamma = sin-1(sin(Beta)/sin(b)) To get the unnecessary quantities a and Alpha, look into the spoiler and/or Wikipedia: In terms of the original variables (latitude, inclination), this means Gamma = sin-1(sin(90-N)/sin(90-L)). Now that you have Gamma, there are four possibilities*: Prograde: either launch to Gamma, or 180 - Gamma Retrograde: either launch to 180 + Gamma, or 360 - Gamma *The reason why you have two options is because the arcsin (sin-1) operation actually has two valid solutions, but most calculators only give you one solution. All of this was validated with a third-party tool... which doesn't seem to include the rotation of the body you are launching from. Presently working on incorporating rotational velocity.