Tullius

There are probably two main reasons for it: The Russians believe that it brings bad luck to have women on spacecraft. Quoting from the wikipedia article on Soyuz TMA-11 (which had 1 man and 2 women on board for the landing): Also, normally astronauts are chosen to be the best of the best. However, when comparing men and women in terms of physical strength on equal grounds, usually the men come out ahead. This might in part explain why men are overrepresented in the astronaut lists.

Even if recovery is easy, it is also a problem of cost. Arianespace was expecting at the start of development of Ariane 6 a launch cadence of 10-20 per year. If one rocket can fly 10 times, it means you only need to produce 1-2 rockets per year, i.e. you need to keep production lines open for a ridiculously low number of products produced. Therefore, instead of developing booster recovery, Arianespace decided to put their development money into designing the booster to be as cheap as possible. It is only now becoming clear that these launch cadence estimates were way too low, as extremely large satellite constellations have been announced (OneWeb wants to launch nearly 700 satellites for a single constellation and SpaceX wants to launch as many as 12000, which need dozens or hundreds of launches themselves).

On wikipedia, one paragraph is dedicated to Ariane vs Space Shuttle: Designing Ariane 1 to be reusable would have also been a pretty pointless endeavour, as it only ever flew 11 times (including 2 failures).

Someone needs to pay for New Armstrong and it is certainly useful if you already have a paying customer.

If there is no crew on board, I would guess none. After all, it is YOUR rocket that blows up, if YOUR drone misbehaves.

A few hours. For the Space Shuttle (https://en.wikipedia.org/wiki/Space_shuttle_launch_countdown), the propellant loading took 2 hours, which meant that fueling started about 11 hours before launch, while the crew started boarding the shuttle about 4 hours before launch. Also during the propellant loading, nobody was at the pad. So in case of STS, NASA was expecting the propellant loading process to be one of the more dangerous parts of the countdown. Also one should not forget that it was during the propellant loading for the static fire that the Falcon 9 for Amos-6 exploded (although one can hope that the problem that caused this is now solved). It is clear that SpaceX wants to shorten the countdown of any launch as much as possible (the Space Shuttle countdown started nearly 3 days before launch), but that will of course mean that they will have to take additional risks. It all depends on how much risks you are able to mitigate and how much risks you are willing to take.

This new rocket looks a bit like their CEO saw Falcon 9 and told his designers and engineers to build something similar, especially considering the timing. However, Buran was also a 'ripoff' of the Space Shuttle, but at the same time a completely independent development.

This is something of category, where you just don't want to find out afterwards that you have been wrong, no matter how low the risk. It is the same with the quarantine measures for Apollo 11, 12 and 14. If it is really necessary to do the quarantine measures and first tests of the samples in lunar orbit, I don't know, but having some protection in place is necessary. After all, it is better to be safe than sorry. Planetary protection is more about protecting our future scientific results than the planet. After all, when did the humanity ever give a f*** about protecting a place when colonising?

Saturn V was at the time the largest American rocket by quite some margin. Choosing a two-launch scheme would have meant building a half-size Saturn V, which would have still been the largest American rocket. Only problem now is that you need to build and launch twice as many rockets.

But then the lander needs to be able to survive for a few months in lunar orbit, i.e. have solar panels etc. On the other hand, Apollo did it with only batteries and fuel cells.

If you look at the picture a bit more closely, you see that the Falcons and ITS were added later on.

Very few things crossing the orbit of the ISS will be in such an eccentric orbit, since the atmospheric drag has the tendency to circularise orbits.

And you really think that there is a single company out there that is dumb enough to jump on such a project? If NASA wanted to let a private company develop a new rocket, it is going to look much more like the commercial cargo or commercial crew programs: The project gets divided into multiple milestones and the companies get paid for reach each one of them separately. This gives you much finer control over costs, since you can stop and rethink how a certain milestone can be reached if costs explode. However, if at some point the companies decide that a certain milestone cannot be reached with the given amount of money, either NASA increases the budget or the project has to be given up. Part of the reason why the commercial cargo and crew programs have been so successful at keeping costs down was the fact that SpaceX wanted to offer Falcon 9 also on the launch market outside of the program. And Orbital ATK and Boeing had to make sure to keep costs down, since otherwise SpaceX would get the whole programs.

And what exactly does this change from NASAs usual procurement procedure, except awarding everything to one company? Orion is the result of such a competition between Lockheed-Martin and Boeing. Any government project will see cost overruns, if you don't keep a very strict eye on the contractors to stay within budget, since the government will usually pay for any overruns. A NASA backed BFR would also accumulate delays and cost overruns, just like SLS, since it would not be necessary for SpaceX to make do with whatever budget they could ensure, since it's practically infinite.

A380 costs 500 million dollars, which creates a cost of 100,000 dollars per day, if you operate it for 20 years. On the other hand, the A380 costs 50$ per seat and hour, which makes it cost 300,000$ per day, if we assume 500 passengers and 12 hours of operation, i.e. the operational cost is what is dictating the price tag of a ticket. Doing more flights per day, reduces the former, but not the latter. In short, it doesn't matter what the BFS acquistion costs are, but how much a single flight costs. If it is less than 150,000$ for 250 passengers, it is a win. If not, it is a loss, since, as Concorde proved, very few people are actually willing to pay a premium for faster flights.

CST-100 wasn't developed for the same contract, only Boeing's CEV proposal was. Just look at the pictures provided in your links (in particular the second, the reentry capsule doesn't even have the same shape as CST-100 or Orion). The picture in your post shows most likely an early proposal of Orion, after Lockheed-Martin gave up on the idea of a space plane for CEV. And if CST-100 is a derivative of Boeing's CEV proposal, Bigelow (Boeings partner for CST-100) worked on an Orion lite proposal (essentially a stripped down version of Orion for LEO) together with Lockheed Martin. So in that sense, CST-100, a collaboration project between Boeing and Bigelow, would be a derivative of both Boeing's CEV proposal and of Bigelow's Orion Lite, and through the latter a derivative of Lockheed Martin's Orion.

Is this random enough: https://www.random.org/integers/ (Random integers generated based on atmospheric noise)

But my video contains too much entropy to be compressed into less than 5KB, since it contains 14,400 random digits, which even with the best possible encoding need more than 40,000 bits, i.e. 5KB. And we are not yet talking about encoding how these are displayed, i.e. even if you use a generic digit to display these random digits, you can't compress it to less than 5KB. So either you don't compress the video down to 4.5KB, or you lose the information about which digits I chose. This makes compressing any normal video to such a small file unrealistic, as any video content probably contains more information than my above example. Hence, while we are still very far from the best possible compression for video, there is a hard limit somewhere below which it is impossible to compress it without losing too much information. Think of compressing an jpeg image or mp3 music file with zip: No matter which zip-algorithm you use (the old DEFLATE or the much newer LZMA), you won't be able to reduce their size by more than 1 percent, because there are just not enough patterns left in their bit sequence to use for compression.

I have seen similar, but newer videos. Usually, they require a high-end gaming pc to be played, i.e. your smartphone won't be able to run them. Also these videos are created using specifically hand-crafted program code (there are even competitions about creating the most impressive video with less than a certain amount of space), it is unrealistic that we will ever have computers capable of compressing a normal video that far. Also, take a look at my post above: It is relatively easy to create a video that cannot be compressed to less than 5 KB (at least not without ridiculous compression artifacts).

Ok, I give you a 24 second video, where each frame contains 20 completely random digits. That is the whole video contains 24*30*20=14,400 random digits. Since one can encode a single digit with a little more than 3 bits of information, this video displays slightly over 5 kilobytes of information. How do you encode that into 4 kilobytes of data? At the same, modern compression algorithms already try to find patterns or how to skip non-essential bits in order to bring the size down. Otherwise a single frame of a full hd movie would already be 2 MB, bringing the size of a movie to over 300 GB.

If the above table can be trusted, a NRHO provides both a faster and cheaper access to the surface than a frozen orbit, all with the advantage that less delta-v is needed to reach it from the Earth. Looking at the above table, a NRHO seems to be the most preferable option for doing this, except for a LLO. However, a LLO requires a lot of station-keeping fuel, which is problematic considering the flight-rate of SLS, making a NRHO the second-best option. The DSG and SLS are of course backwards, but considering the long running time of any crewed program at NASA, it is not surprising that the goals change regularly due to congress and whatnot and NASA then having to make do with whatever they have got. But still, if the only restricting factor in choosing a better lunar orbit were Orions delta-v budget, NASA would certainly have already considered increasing it.

Is it really worth putting several satellites into a higher lunar orbit just to save on a relatively small amount of station-keeping fuel?

Indeed, I messed that one up. Googling a bit further, I fund this stackexchange question: https://space.stackexchange.com/questions/23992/why-is-a-near-rectilinear-halo-orbit-proposed-for-lop-g-formerly-known-as-deep , whose first answer references this article by NASA: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150019648.pdf. It provides in particular this table, which I think was already posted in this thread and I couldn't find when I wrote the previous post: In short, NRHO beats a frozen orbit, except for station keeping, although that is still kept relatively low.

This pdf provides a few reasons for selecting a NRHO over a low lunar orbit: https://sservi.nasa.gov/wp-content/uploads/ger-downloads/day1/Whitley-LunarSurface-GER3-Workshop-20171130.pdf In summary: It is not just because Orion cannot go to a lower orbit, but also because it offers a much better place for a lunar orbit space station (less station-keeping fuel needed, very few eclipses, no communication blackout, and less cooling needed), while still offering an acceptable access to the lunar surface.

Your last point is most likely on point: For SpaceX and Falcon 9, it is cheaper to do test flights, while for NASA and SLS, it is cheaper to do the paper work to skip the tests.