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72

This Wikibooks link lists its strong points, some of which are: An extremely strong, static and safe type system, which allows the programmer to construct powerful abstractions that reflect the real world, and allows the compiler to detect many logic faults before they become errors. Modularity, whereby the compiler directly manages the construction ...


68

Well, gee, this question may as well have my name printed directly on it! Spacecraft protection from the orbital debris threat comes in two flavors: Shield and withstand Detect and avoid To start, page 5 of this NASA paper presents a good first-order approximation of the general LEO orbital debris threat. You'll see some variation with altitude and ...


54

Timing. Ada was developed in the 1970s and 80s with the intent of replacing the plethora of languages used in the US Department of Defense's realtime systems. NASA (and also organizations from Europe) were active participants. The DoD mandated Ada for all major development in 1991. NASA did much the same. The International Space Station had been a paper ...


48

It's safe. The ISS is about 100 meters across at its widest, and it's 400km away; this calculator tells me that makes an angular size of ~0.014 degrees. The sun's angular size is about 0.53 degrees. If both the ISS and the sun were square, the area ratio would be some 1400:1; the aspect ratio of the ISS is in roughly the ballpark of π/4, so the non-...


40

Let's start with the "Statement of Problem" in the anomaly report. ...the service module, upon being jettisoned on a lunar return flight, should have entered the earth's atmosphere, then skipped out into a highly elliptical earth orbit. Thus, the risk of recontact with the command module during entry would have been eliminated. However, on Apollo 8, 10 ...


36

The Merlin-1D engines are now tuned to use the super cooled fuel and oxidizer. Thus you would be running the engines in an out of normal state, if not using it the same as all other launches with warmer propellant. It would imply different software to handle the different performance levels. Last thing you want to do is run things differently, if you can ...


30

There's a few pieces of information that are needed to explain why one might be wary of 1 cm objects: Objects as small as 4 inches (about 10 cm) can be seen by radars or optical telescopes on Earth Oops, can't see 'em. There are also millions of pieces of debris smaller than a third of an inch (1 cm). In Low Earth-orbit, objects travel at 4 miles (7 ...


28

No problem, even with a telescope Not only is it perfectly safe with the naked eye, it's also not a problem at all with a large aperture telescope. At first, I tried looking at the ISS with a 80-200mm f/2.8 Nikkor attached to a scope converter. Handheld, it was pretty hard to find the ISS at all, let alone track it for more than 0.1s. I then bought a ...


27

It depends on how you count. Flights or individual astronauts: 302 manned spaceflights, 4 of which ended with a total of 18 fatalities: 1.3% of flights. 544 people have been in Earth orbit, 18 fatalities: 3.3% of astronauts have died during spaceflight. But many astronauts have made more than one flight. Thanks to @Eoin: the number of person-...


26

Practice. It's unusual for the same fault to cause more than one rocket launch to fail. Flaws are found and corrected, and launchers get more reliable. In all our history, there have been something like 5000 orbital launches. Each one of those was an opportunity for things to go wrong, for a flaw to be exposed and eventually corrected. Today, airlines ...


24

The leak is in the Orbital Module (OM), which is jettisoned prior to re-entry, so there is no concern there. Source: link in the question. Image source: spaceflight101.com


22

The Apollo Operations Handbook, Caution and Warning section, identifies the alarm tone as "a square wave that is alternately 750 cps and 2000 cps, changing at a rate of 2.5 times a second" Perhaps someone can gen that up? It appears to me to be more like an alternating type sound rather than a buzzer. If the Shuttle copied this sound for its master alarm (...


21

In some Mercury flights, the astronaut had a personal parachute with them. The Gemini program used ejection seats, which could be used during launch and reentry. Later on, they realized that igniting a rocket-propelled ejection seat wasn't a good idea in a pure-oxygen atmosphere. The Vostok capsule also had an ejection seat, but not as a backup: the ...


21

The Space Shuttle Orbiter had a flight mode whereby, at or below ~50,000 feet of altitude during the reentry (or, in the event of an ascent abort, the gliding, unpowered phase of flight), the commander could command an autopiloted, wings level glide at about 190 knots equivalent airspeed (KEAS). The plan was then, while the Orbiter was gliding, that the ...


20

Just another analogy to maybe help explain why #EverythingIsTrickyNotJustRockets (in addition to the great answers already here). Take Formula 1 racing. It's a sport with some extremely complex machines, built to the very edge of engineering and manufacturing capabilities to give as much performance as possible. Just like rockets. Others have mentioned ...


20

In addition to not wanting to change anything for crewed launches (as geoffc mentioned), adding crew to a fueled vehicle is a seriously dangerous move. If you look at the AMOS-6 failure you'll see that the launch abort system probably would have saved any crew that was already on board. However, if the crew was actively being loaded, we would have lost not ...


19

While the launch escape system (LES) is important for getting the crew away on ascent there are other thing required for human-rating a craft/launch system (and you do need to pay attention to the entire system and mission, not just the rocket during ascent). Specifically for Atlas V they needed to: space.com upgrade the emergency detection system (your ...


19

The probability and consequences of a release of Pu-238 from an RTG in a launch accident are very low, due to the protections in place for such an incident. It's not like they never thought of that. The radioactive material is not "widely dispersed". As for the numbers, the rate of decay is inversely proportional to the half-life. The half-life of U-235 is ...


19

The problem is that the transition produces enough energy to boil the LH2. As explained on the old sci.space.history group: Skipping the gory quantum-mechanical details... there are two energy states of the hydrogen molecule, ortho and para. At room temperature, hydrogen is about 3/4 ortho. At liquid-hydrogen temperatures, the stable state is ...


18

NASA has made a list of requirements for spacecraft approaching the ISS. SSP 50808 is an ITAR controlled document that identifies the requirements for rendezvous, proximity operations, and physically meeting the ISS interface. An excerpt is available online: Trajectories must be designed such that ISS safety is preserved ... Safe ...


18

The frame of the spacecraft is used as a common ground. See this diagram from this handbook.


18

I remember taking Computer Science courses in the late 90s. The professor of CS explained to our meager group of CS majors that he was going to teach us C, rather than COBOL or Ada, because it would be more useful in general. At the time, they were the major programming languages colleges were teaching back in the day (every major university in the area ...


17

Fission reactors can work just fine for space probes, and that will probably happen. Projects are currently underway at US agencies to develop designs for this. Notably, Demonstration Using Flattop Fissions (DUFF). Why a fission reactor? It is not highly radioactive at launch It can be compact It can have high power It's not subject to limited supply of ...


17

No. I think this is actually the May 23, 1965 A-003 test, described in my answer to the question, Could a spacecraft spin so fast that it spontaneously deconstructs? Notice that the rocket and Apollo CM are spinning. That isn't supposed to happen. In A-003, improperly installed gyros caused the vanes on the fins to deflect fully in one direction, imparting ...


16

Kennedy Space centre in Florida formerly had its own plant for the manufacture of cryogenic fuels and other liquids. This is now closed as noted earlier. The procurement for cryogenic fuel for NASA is done via the office of procurement at KSC. It was determined that the US has only one supplier cryogenics that can supply the cape with the necessary 30 trucks ...


16

In addition to Russel's answer: The ISS' albedo is far lower than 1, so the brightness is going to be less than 1/1400. Those solar panels convert 30% of the sunlight into electricity, and another part into heat. The amount of light reflected is only about 20% (less than the reflection coefficient of e.g. grass). these specific solar panels are not ...


15

The main problem is that in order to have enough thrust to get a rocket out of the atmosphere and up to orbital velocity, 85% to 90% of the rocket has to be fuel. So you have a controlled explosion, essentially, in which thousands of pounds of fuel is combusting each second and the force of that is being directed out of nozzles, pushing a rocket upwards with ...


15

What if you just carried a couple of uninflated balloons with you? If you ever get stuck, just inflate the balloon, and then hold it near your center of mass, aim it away from you, and let the air out. Repeat until you make it to the wall. The nice thing is that an uninflated balloon is light enough that you could even have a couple of spares.


15

Alright, I went ahead and skimmed wikipedia's orbital capable rockets list and put them all into an excel file along with whether their first launch was a success or a failure! They're sorted by date. Some observations: Data from the Cold War / Space Race era is pretty spotty at points In the early days Russia had many first failures and then very ...


15

There is no concern about the safety of re-entry because the leak was in Orbital Module that is jettisoned before atmosphere reached. Crew is located in Reentry Module. But if the leak could not be sealed it would be a huge problem for the Soyuz and ISS. According to this ISS was losing its air of around 0.6 millimeters of mercury (0.8 millibars) per ...


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