PakledHostage

As a rule of thumb, air can be considered compressible above Mach 0.3. Compressibility effects such as heating are already noticeable on subsonic airliners. Readouts of "Total Air Temperature" (TAT) and "Static Air Temperature" (SAT) are available to the pilots as these values are important to engine performance. The two values typically differ by many degrees.

I know that lots of people liked the movie. Heck, even the Academy liked a lot of parts of it. But notice it didn't win for best picture or best screenplay? That, I think, is the biggest problem with it. It was, at times, scientifically accurate and the special effects were amazing, but the story was so full of cringe inducing clichés: - The "old hand" Kowalski, effortless and at ease in the challenging environment of space constantly giving unsolicited advice and encouragement to Stone. Never mind that she's a highly trained professional astronaut and PhD... I would have politely told him to **** off. - Kowalski nobly sacrificing himself to save Stone. Thanks Jeebus! - The south Asian character Shariff and the cultural stereotypes his character embodies. - The scene with Stone curled up into the fetal position in the airlock, reminiscent of an infant in a womb... What was that all about? Gratuitous artsiness? ... Uh... [strokes hipster beard] “it symbolised stone's rebirth; her beginning to get over the death of her daughter and rejoin the world of the living.†- Stone landing off the coast of a beautiful tropical location and feeling the earth with her hands when she washes up on shore… I get it. There's no place like home... But did the Lilliputians only arrive to tie her up after the credits rolled? I could go on... But as I said, I know that a lot of people really liked the movie. Irrespective of that, plenty of others hated it or disliked it. And it wasn't just for the occasional lapses in scientific accuracy. I hated the story. I feel that there are plenty of better examples in the history of film making of stories of people persevering in the face of incredible odds. Given a choice between re-watching one of those films or documentaries and re-watching Gravity, I'll pass on Gravity.

Ha ha! You fool! You fell victim to one of the classic blunders - The most famous of which is "never get involved in a land war in Asia"

I thought some here might find this interesting: A 30 metre rock designated 2014 DX110 passed within 1 lunar distance of the earth today, only 5 days after being discovered.

Good point. Of course you'd then have to also worry about flammability in the enriched oxygen environment. My point, ultimately, was that design compromises will necessitate selection of an altitute for the cloud city, and I suspect that would be somewhere higher than 50 km.

I would think that placing the city even higher in the atmosphere would be more practical, because of cooling requirements. On the other hand, you'd need to balance atmospheric pressure against temperatures. At 50 km, by your table, the temperature is still excessively high. 350 K is about 80°C. Cooling the city would be a problem. Temperatures are a more reasonable 30°C at 55km altitude, but pressures there are comparable to 5000 m above sea level here on earth. It is possible to acclimatize to that altitude, but it is also approaching the limits of human physiology for long term exposure. The highest permanent settlements on earth are at about that elevation. In short, you'd either have to actively cool the Venus cloud city, or pressurize it. Both cost weight and complexity.

If you are referring to the Tenerife accident, then to say that it was at all caused by carrying excess fuel is a bit of a stretch. So many things went wrong that day. All of them contributed to the accident in some way. KLM flight 4805 wouldn't have needed to haul itself into the air at low speed (where a lower takeoff weight due to less fuel on board might have helped) if everything else hadn't gone wrong first.

Like this? Atmosphere? Maybe occasional elevated levels of CO2, SO2, methane and/or methyl mercaptans?

OK. I'm a bit busy right now in life outside of KSP but I will think about how I could add SBAS type augmentation to the mod over the coming weeks. Maybe I'll have it ready in time for the next version of the game. The capability already exists but it needs to be implemented by the developer of kOS. I exposed the number of visible satellites plus lat, lon and altitude in response to a request from SirJodelstien for his Persistent Trails mod. Those same variables could be used by the developer of kOS to do what you are requesting.

It is an interesting idea... I need to balance realism with fun, and I am afraid that too much realism would negate some of the fun. But on the other hand, this mod is intended as a "science mod" in so far as it gets players thinking about where their navigation information comes from. Maybe having an option to improve navigation accuracy using WAAS, EGNOS, GAGAN, etc analogs would further that goal? What do you readers of this thread think?

It seems that there was a strong aurora at about midnight UTC last night. It was still daylight for most of us here in North America, but they should have been visible from northern Europe, including Scotland and the northern parts of Ireland. The map below is from about an hour or so after peak activity. Did anyone here see anything?

And because you don't need a pressure wave to nudge the asteroid. In principle, the nuclear bomb blast heats the surface of the asteroid causing surface material to ablate away on the side facing the detonation. That ablation results in a change in momentum in the asteroid. It doesn't even matter that much if the asteroid is rotating because it all happens so fast. Personally, I think it is an important experiment to try. I realise that there are political obstacles to that type of testing but we should have some sense of how well it works (if at all) before we need it.

I wasn't able to find a concise article to link to, but there is an observed spin rate barrier.

I suspect that you'd find that the amount of energy required to stop the rotation would be comparable to the energy required to deflect it by a few fractions of a m/s... You could, of course, pulse your engines every time the asteroid was oriented the right way, but then they would have to be designed for literally thousands (if not millions) of restarts and it would take a lot longer.

While I agree that nudging an asteroid sufficiently to avoid an impact is within the relm of possibility, given enough advanced warning, you have to assume that the object is already spinning at some rate. It is just as improbable that the object has exactly zero rotation as any other rotational speed. Any scheme that uses engines mounted to the surface of the object is going to have to account for the rotation. This is where gravity tractors and nuclear warheads detonated above the asteroid's surface have an advantage. And nuclear bombs have the additional advantage that they can be detonated on a flyby trajectory. This may save enough delta-V to make it possible to deliver the charge quickly using only existing rocket designs. Edit: Ninja'd by AlbertVDS... I guess I should have refreshed before replying.

Those of us living far enough north in the northern hemisphere may be treated to active auroras tomorrow evening. According to the University of Fairbanks Geophysical Institute Aurora Forecast, auroral activity may be sufficiently strong that they will be visible as far south as the northern parts of the continental US. Presumably Scandinavia, Iceland and northern UK could also get a good show. Let's keep our fingers crossed that it actually pans out this time? Maybe post your photos if you do manage to see them?

The simplest method is to patch together two orbits at their periapsis or apoapsis points. You can then estimate the delta-V required to transfer between them by calculateing the difference in speed between the two orbits at the point where they intersect. For example, if your hyperbolic trajectory has an orbital speed at periapsis of 3500 m/s and your elliptical orbit has an orbital speed of 2250 m/s at a periapsis that matches the hyperbolic trajectory's periapsis, then you will need about 1250 m/s to enter the elliptical orbit from the hyperbolic trajectory. In reality you will need a bit more delta-V than what you calculate with this method because you aren't executing your manoeuver instantaneously, but the estimate will be close.

As a point of interest, the solar panels on the ISS do contribute significantly to its orbital decay. Re-orienting the panels into an "aerodynamic" alignment with the direction of travel while in the Earth's shadow (where they don't need to face the Sun) significantly reduces drag on the station's solar arrays. According to a paper cited in Wikipedia's Night Glider Mode article, carefully orienting the solar panels in this way reduces average drag on the ISS' solar panels by 30% and saves about 1,000 kg of orbital-maintenance propellant per year.

I wasn't aware that software exists to predict iridium flares until I read some of the posts in this thread a week or so ago. I was a bit skeptical about how precise they were, but I figured I'd go out and see what I could get on camera. Clearly the predictions are pretty spot on because I was able to photograph one, where and when it was predicted to occur. They only last for a second or two, so I figure it is actually a pretty impressive demonstration of the predictions that I was able to capture one.

Kryten has a long history on these forums of posting informative and well written responses. It is obvious to me from that history that Kryten has a solid background in space technology. I am willing to forgive an occasional spelling mistake and focus on what is being said.

You necro'd an eight month old thread to provide us with a link to a Wikipedia page?

That story did get a fair bit of media coverage about a year and a half ago or so. Maybe it just depends on which media outlet you pay attention to? Fox probably focuses on stories like how Coke desecrated the US "national anthem" during the Superbowl by showing people singing "America the Beautiful" in languages other than 'merican, while the opposite end of the spectrum (i.e. NPR , etc) would be focusing more on real news and science.

Not really a physics calculation, but I once tried to calculate the size of the Kerbol system by using the Lazor cam mod to observe a transit of Eve from two locations on Kerbin (one near the north pole and the other near the south pole). Unfortunately it didn't work out so well; I was out by about 20%. I suspect because the graphics engine wasn't designed to render objects in the sky that accurately. Even so, I learned a lot about how transits of Venus were used historically to calculate the size of our own solar system.

IIRC, the Isp was constant in v0.15 and prior versions of the game (i.e. it did not vary with altitude). Looking at an old copy of v0.15 that I still have on my computer, here's some relevant data for the mini-challenge rocket: 1. The Isp of the engines was 579.4 seconds. 2. The thrust was 200 kN. 3. The engines had a mass of 2 tonnes each. 4. The fuel burn was 8 litres per second per engine at full throttle. 5. The two tanks had a capacity of 500 litres each and contained 2.2 tonnes of fuel. The empty mass of the tanks was 0.3 tonnes. The full fuel mass of the tanks was 0.3 + 2.2 = 2.5 tonnes. 6. The tricoupler had a mass of 0.8 tonnes. 7. The ASAS module had a mass of 0.8 tonnes. 8. The command pod had a mass of 1.0 tonne.

@K^2: Very interesting analysis. I have some questions though: 1. Your model appears to have optimized the rocket's pitch angle in the region between ~130 seconds and ~205 seconds while the rocket was coasting. What is your model attempting to minimize in this flight regime? Is the aerodynamic drag a function of the rocket's angle of attack in your model? If so, why wouldn't it be most efficient to simply maintain a 0° angle of attack while coasting? 2. If I understand correctly, you are optimizing an artificial launch profile where the rocket launches vertically, abruptly pitches over to 45° at 8000 m altitude and then proceeds to climb to orbit. Your optimized profile does not appear to have strayed very far from your initial seed profile. A real-life rocket flown this way would be subjected to very high transverse aerodynamic loads and may even break up as a result. (See videos of the recent Proton-M launch failure for an example of a rocket breaking up in flight due to transverse aerodynamic loads.) Even in KSP, many rocket designs would not have the control authority to execute such an abrupt maneuver. Even ignoring those considerations, an abrupt turn is easily demonstrated to be sub-optimal. How does your model perform if you use it to optimize a launch profile that uses a true gravity turn? Does it find profiles that are more optimal than those flown by competitors in Tarmenius' Launch Efficiency Exercise challenge? 3. How does your model compare to the optimizations calculated by TheDuck, et al. in Closette's Mini-challenge: max altitude with this supplied spacecraft challenge? I would think it would be fairly straight forward to run your model with the same parameters that they used. Would it be a good benchmark test for your algorithm?