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110

In my former job I was writing educational software. In short, it's exactly what you described: we offered a paid version of what you could get for free by looking out on the internet, going to class, going to the library, ... And yet, I'm still incredibly proud of it, knowing I made a difference. What is the difference between well written software and a ...

91

In several press conferences, employees of NASA or private space firms have been asked if they played KSP, and some answered with "Yes". NASA used patched conics to find candidate orbits for Apollo back in the days. With that being said, KSP strikes the balance between accuracy and simplicity. Patched conics give a good idea how space works, without being ...

71

A 25m diameter rotor has a perimeter of around 78 meters. At that size, at 500rpm, the rotor tips would be going in excess of 1,400mph. At those kind of speeds, even though it doesn't take much power to get a very light rotor going, there is still an awful lot of force involved which has to be handled by the materials to prevent them literally tearing ...

57

At 100 km altitude, you get to the Karman line. This is the altitude where you have to fly at orbital speed to get sufficient lift. This definition is based on the lift equation, which applies to all airfoils including that of a helicopter rotor. So in a helicopter at 100 km altitude, your blades have to travel at orbital speed (27,000 km/h or 17,000 mph) ...

53

3753 Cruinthe ranks as target number 16832 in JPL's list of near earth asteroids that might be worth visiting, someday. With 16381 better targets, that "someday" most likely will be a long time from now, if ever. The problems with getting to Cruinthe are twofold. One issue is that its orbit is rather eccentric (0.51485). Changing an orbit's shape is an ...

50

I'm wondering if there were any test missions to get unmanned ships to the moon and safely back to Earth? There were no uncrewed round-trip missions to the moon prior to Apollo 11. Several one-way missions landed safely on the moon without crew before 1969, but did not return, including the American Surveyor series. The first of these, Surveyor 1, landed ...

34

Space is really like this (XKCD What if) In theory a plane could reach most of the way to space, but it won't be able to reach orbital speeds. Bottom line, it just isn't practical. Maybe someday a helicopter could lift a rocket up high, which would help a bit, but it really just isn't practical. Also, a balloon might just be better in any case, it can go ...

31

I purchased "The Apollo Guidance Computer: Architecture and Operation" to answer this question (an excellent read). And the answer is yes it might be possible to land on the moon unmanned. However, a number of checklist items would need to be skipped, mostly numerous inertial system checkouts/alignments, most importantly for the gyros. They need to be within ...

29

No, not yet. The Parker Solar Probe became the closest ever artificial object to the sun on October 29th, 2018, surpassing Helios 2 which held the record since 1975 [1]. No other human-made object has been closer to the Sun. The probe will repeatedly touch the outer corona until mission end in 2025, with the closest approach being 3.83 million miles [2]. It ...

29

Soviet planetary probes sometimes had pressurized compartments, so I suspected that they might contain fans. This answer confirms that Venera-8 had a fan. The illustration in the answer has the inner parts mislabeled, though. The fan is really #15 in the drawing. Reading through the source linked in that answer also confirms that Venera-5 had a similar ...

25

In a sense, you're correct; KSP does not teach you any of the math involved in orbital dynamics. But it gives you an incredibly good intuitive sense of how they work. For example, one of the first things you learn is just how much fuel you need to get to orbit. You quickly have to come to grips with the tyranny of the rocket equation if you want to get ...

24

The propellor needs to be strong enough not to pull itself apart via centrifugal force. If you go through the math, you find that the maximum stress on the propellor blade will be halfway along its length, and will have the value $$\sigma = \frac{1}{4}\rho L \omega^2,$$ where $\omega$ is the blade's angular velocity (usually measured in radians/second) ...

24

It doesn't really work that way. We can use the Sun to change direction, but we need rocket thrust to increase speed with the msneuver. To begin with, the closest stars (apart from the Sun) are not close. If we were somehow to reach escape velocity from the Solar System (which this method won't do, see below), we would still be moving at only a small ...

23

Ascent G-Forces The Apollo 11 AS-506 launcher flight report contains a nice graph of the G-force curve of that famous Saturn V launch: From this chart you can see that, off the pad, the Saturn V first stage is doing about 1.2g; this climbs rapidly as atmospheric drag falls and fuel mass is consumed. The center engine is intentionally shut down to limit ...

22

The "gravitational" (slingshot) maneuvers space probes are performing are actually not so much about gravity. The gravity is method to "tie" temporarily these two bodies, but you could (purely hypothetically of course) use something else, some superstrong tether or so ... "Slingshot maneuver" is in fact much better name in this regard. What actually happens ...

21

As Loren Pechtel mentions, time pressure was a big part of it; also, Apollo 10 did actually test a large part of the descent, ascent and rendezvous operations even through they didn't slow all the way to 0 and touch down. It was by no means certain that Apollo 11 would successfully make a landing. A variety of abort options were available at every stage of ...

18

Sure, with enough rockets and propellant you could land there. However the mass required for all that propellant would vastly reduce the mass of your payload, for an equivalent Earth launch mass. Mars Science Laboratory was still going about Mach 17 (in Martian terms 1 Mach ~ 240m/s) when it was at the altitude of the top of Olympus Mons. So we're talking ...

18

OrganicMarble touched on this in a comment but I think it deserves an answer as well, since the question doesn't stop at the Karman line (approx. 100km if you're really defining it as the height where the velocity required to generate lift exceeds the orbital velocity). In simplest terms: just because there's a few atoms of gas present at some height doesn'...

16

The question is somewhat odd. The "Interplanetary Transport Network" may be a misleading term. When probes are sent into deep space, most of them make use of flybys or gravity assist manoeuvres. Virtually every celestial body can therefore be used for increasing the speed of a probe or decreasing it. The "network" refers to series of such manoeuvres. In the ...

16

Nearly all balloons that have been constructed have been for flights from the surface to altitude. That requires a structure that can survive tethered at the surface in a range of wind speeds in high-density air, then expand to several times their original size in order to maintain lift as the air density decreases. The minimum density ends up being ...

16

The other 4 answers here do a wonderful job of articulating what I love about KSP, but I'd like to point out one more thing from my perspective as a game designer who has logged over 600 hours in the game. While much of the game is simplistic relative to the real world, it is accurate enough to be intuitive why things failed. Rocket flipped over during ...

15

There are incredible, mindboggling distances involved in merely reaching an exoplanet. Alpha Centauri Bb, the closest known exoplanet, is 4.365 light years away. That's 41,295,000,000,000 km (25,660,000,000,000 mi), or 276,000 AU (the distance from the Earth to the Sun). Voyager 1 has left most of our solar system behind and is traveling a blistering 17.3 ...

15

We don't fly to space with helicopters because we can't. We would if we could, believe me. Aside from all the very valid concerns raised by others, the question doesn't properly account for weight*. Maybe your 32 inch diameter propeller weighs 349 grams, but the 10m one certainly doesn't. Oh no! Now 1kg thrust won't lift it at all! So you need more ...

15

Sputnik-1 was filled with dry nitrogen pressurized to about 1.3 bar and had a fan to control gas temperature between 20° and 30° C. See Wikipedia in german or english. A picture of Sputnik-1 design with the cooling fan can be found here. Korabl-Sputnik 1, an unmanned early prototype of the later manned Vostok spacecraft, had a biological cabin with a ...

14

The real problem with Martian mountains is that by landing high you forego the ability to shed at least several hundred meters per second off your re-entry velocity available in the denser atmosphere below. Thus, you are forced to build in larger EDL (entry, descent and landing) propellant reserves and, all other variables equal, forget about putting more ...

13

Time. They were coming down to the wire on Kennedy's challenge. There might also have been technical reasons look how close to the end of the timeline Apollo 12 was. It easily could have slipped.

13

To answer your second question on the astronauts' experience and how much thought went into adjusting the g-force profile of a launch, NASA published a document that contains information on the g-force survivability range of a human. Here is the Paper, the relevant figure you want is Figure 5 which is about halfway down the page. The figure is a plot of g-...

12

Proposed Russian spacecraft, for Mars, Lunar, or orbital tug missions that would have used a nuclear reactor, did provide escape tower like functionality for the reactor. But the issue is that the entire payload stack, is usually too big to save with an escape tower (and still have any payload left to go to orbit, due to weight of escape system). In the ...

12

Remember the state of computers at the time. It is very unclear that an automated landing could have been executed -- indeed, the first moon landing was under manual control, and came uncomfortably close to running out of descent fuel before landing, Remote control from Earth would not be practical due to speed-of-light issues. The moon is about 1.28 light-...

11

In November 2010, Secure World Foundation (SWF) published their X-37B Orbital Test Vehicle Fact Sheet (PDF) that is a conjecture on the purpose of the two Boeing built X-37B OTV (Orbital Test Vehicles) currently operated by U.S. Air Force. It also gives a background on vehicles, their known technical characteristics, and describes official objectives they're ...

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