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Everything posted by Hannu2

  1. It is not a binary thing is person dead or alive. You can think execution in guillotine, which cut head very rapidly. What do you think is actually time of. Usually death is defined as stopping of EEG activity but brain cells stay alive couple of minutes without blood circulation. But of course the blade cause irreversible fatal injury in less than a second. I guess that explosive evaporation of water at 5800 K ambient temperature would cause some kind of shock wave, which would proceed at about 1.5 km/s, which is speed of sound in water. Such a shockwave would clearly reach any point of
  2. They can not travel to same direction. Otherwise at least one of them should be on hyperbolic orbit, i.e. not bound on Earth. They must have quite large inclination difference, I would say at least tens of degrees without calculations.
  3. What is the difference in this case? Methane and liquid oxygen are common chemicals in industry and they are used in enormous quantities in many processes. Spacex's tank farms are small and trivial compared to for example those of LNG ship terminals or oil refineries. As far as I know they must obey the same industrial standards set by laws. I do not see any good reason why very standard off the shelf liquefied gas tanks would not work for SpaceX. It is strange decision to build own tank, but maybe they developed something in welding process and decided to make a tank instead of dummy tes
  4. That rocket seem to have some kind of transparent nose. Maybe there is an elite compartment with maximum view and crazy high ticket prices. Those tourists must be brave if the rocket hits the tube at couple of hundreds meters per second.
  5. I wonder it too. Otherwise they put so much effort to videos and all kind of PR work but video system of ship is from cheap store. I am quite sure that installing a proper video link would not cost too much compared to total PR expenses. But they certainly have too much small things to do and too little workers as all companies nowadays. Videos work, everyone see does it success or crash, and they prefer other problems.
  6. Nobody knows either how to get crews there or how to keep them alive during trip or surface operations. I think that redundant and reliable enough life support systems are more bottleneck than returning, which needs relatively simple rocket with capsule capable of re-enter Earths atmosphere. Starship will be very suitable if it achieves all objectives. Of course both things need huge development efforts and published schedules are very unrealistic. I expect that they send unmanned system to make return fuel before and send crew when it sends a message everything is ready. Probably there will
  7. I can not understand all that patriotic ideology, which is so important for americans. I am pragmatic and appreciate space operators based on what they have done. Not based on who owns them, who pays them or what they say they will do in future. I have to say that I do not have much trust on Artemis yet. There has not been any significant things or funding decisions yet. I think SLS is just political industrial subsidize mechanism, not real space program with severe objectives. I would not be surprised if US government announced that Artemis has been cancelled and they begin a new manned
  8. In my opinion advancing need success to show that ideas really advanced and not just overoptimistic daydreaming. But when company is at very high position it has tendency to slowly corrupt. Administration and bureaucracy increases and they concentrate to get more benefits from politicians than develop their products. Most important reason is probably that owners change. Owners of growing companies take more risks but expect very large profits. They have to invent new things which change markets. If company succeed to grow such owners sell their shares to more conservative investors who expect
  9. I understand the reasons. But that is why publicly traded company can never win a megalomaniac billionaire in level of "advancing". I agree. Mars may be some kind of very long time vision for Musk, but I think Starship's main reason is to be heavy lifter for coming massive satellite networks and service operations such networks need (for example clearing of orbits with some king of cleaning craft). Starship will probably be commercial success even it would never be man rated. Manned operations are bonus possibility of future. For example global satellite internet can produce so much
  10. Scrap steel is not suitable for building of high strength structures anymore, but it is very pure stainless steel (compared to many other scrapped machines which have significant part of mass from other materials) and very effectively recycled to new steel in steel factory.
  11. Of course they are tested as well as they can. But it seem there have been problems with underperforming Raptors in SN9 and SN10. Something may be going on and they have to find a solution. I hope I am wrong and they had some sporadic problems easy to fix, of course. That strange flight profile may also be engine testing. They ascent very slowly and burn engines several minutes. At apoapsis they almost hover a minute or two with very small velocity. If it was just aerodynamic test they could ascend probably in less than a minute. I do not see other reasons for such profile than get import
  12. I fear that "moar boosters" and few external struts around rocket is not so simple in real life than in KSP. I do not know easiest way to proceed to something useful, because there are many political issues which are much more important in SLS project than any possible space operation ever. But I am sure that fastest, cheapest and the most reliable way would be to cancel whole SLS and pay SpaceX and/or Blue Origin to faster development of super heavy launch vehicle.
  13. I guess that they have some severe issues with Raptors they are not willing to publish. Now engines had clearly different colored flames in ascent. I suspect it was not intentional or good sign (or could they make some strange tests, for example mixing ratios). They seem to do Raptor testing at the same time they test SNs. It is quite kerbal way to test rocket engines with flying prototypes. Fortunately radio controlled command pods was before full staged combustion in human's tech tree. Test piloting those ships would otherwise be a little bit too dangerous work.
  14. To be honest, you mean quite exotic from of "advanced" if you think some other company more advanced. Big traditional companies have great history, but they are most interested in their shares of state's pork projects and do not develop practically anything with their own money. SpaceX is clearly the biggest and most succeeded of "new" companies. It has developed commercially viable reusing and much higher throughput than any other company and got biggest share of commercial satellite launches. For example Blue Origin has really made animations and marketing repurposed bovine waste in addition
  15. Yes, but control system handled it very well. Based on my experience (not related to rockets) it is much easier to do control which makes accurate position straight than control which can handle significant last minute errors without overshooting in any direction.
  16. No, they are not. But should they? Watching competition in space would feed people's competitive instincts just like watching sport do. If space companies had millions of fans like large sport teams maybe they could get significant boost to their funding by offering fan stuff, happenings, or even organized competitions to achieve some technical or scientific objectives. According to this source market size of sport business is almost 500 billion $. It is at least an order of magnitude larger than all space business and national organizations.
  17. Best mirrors reflects something around 99.999 %. They have also a limit how high field can be. There are many applications of highly reflective optical cavities but any practical energy storage is not possible.
  18. Probably yes. As far as I know planetary dynamos (sources of magnetic fields) are not very well understood. But it is believed that weak cosmic magnetic fields act as seed fields which start magnetic processes in rotating electrically connected liquids. When process is started field amplifies itself and increases many orders of magnitude and rotation of body gives energy. But it is complicated, field may be asymmetric, it changes during time, even change polarity etc. But it there probably is not such layer on Mars because otherwise it would generate magnetic field. Mars has cooled and mo
  19. It is not enough to keep B at surface constant. Magnetic field must be large enough that it can capture fast charged particles and steer them away from base. I do not know what is practical value in magnetic moment but in any case it is huge. All my numbers was several orders of magnitude larger than current production capability on Earth. And I do not believe that all other industries will be shut down to reserve all resources for mars base in next couple of thousands of years. Such a project would encounter very soon very hard resistance. Only some special materials have relat
  20. Your underestimate needed magnetic field by huge factor. We can calculate what we could do if Earth's magnetic field disappeared. Essential parameter is not field strength at the surface of the planet but magnetic dipole moment. Earth's magnetic dipole moment p = 7.95E22 A/m^2. Let's assume that we make huge coil on equator to create respective artificial field. Magnetic moment of planar coil is p = N*I*A, where N is number of turns, I is current and A is area of the coil. N*I is N*I = p / A = 7.95E22 A/m^2 / (pi * (6.37E6 m)^2) = 6.24E8 A. Critical current density of common sup
  21. If I discuss with farmers, they hate those satellites. They do not give farmers anything but authorities use the data against them, because they see easily what grows, where and how much. I live in Finland, where all farming depend on subsidiaries from EU and the state, but I think situation is quite similar in other EU countries. Maybe large farming companies can buy the data and use it for their benefit it but farmers with small family business know better local conditions in their small area and buying the useful data from satellite companies is too expensive.
  22. I know that everything must be entertaining. I just do not like it but I know that I am exceptional in that sense. I am very happy that my job is not to sell anything to anyone.
  23. I think the most important and interesting space technology are Flagship science missions. I can not say one over the others. But like Voyagers, Galileo, Cassini, Mars rovers, Hubble, sample return missions (manned and unmanned), New Horizons etc. Next very big thing for me is probably not Starship or Artemis but LISA, gravity wave detector in space. Of course other coming planet probes are too, for example that flying drone to Titan or Europa Clipper, if they will be realized. Manned operations seem to be more propaganda tricks than real scientific work. Yeah, it is nice to be able to vi
  24. You do not need to explain a special mechanism. Instead you should explain which part of your mechanism works against known physics and show it by observing such phenomenon. General natural law called as conservation of momentum tells that it is impossible to change momentum of closed system without interacting with environment. Actually conservation of momentum is a consequence of more fundamental natural law, a translation symmetry of space. It means that if natural laws are the same at every point in space. Also other well known conservation laws are connected to symmetry properties of
  25. It is return from intentional PR work. I think it is just fun for Musk to be popular among space nerds. Development process of Blue Origin seem to be very slow even Bezos has all benefits than Musk has and he is even richer. Musk's talks about Mars and aspirational schedules are what they are but SpaceX seem to bring every year something interesting to publicity or market.
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