Hannu2

It looks like plastic bag or part of cardboard box or some scrap like that. Wind from engines lifts it in air. It seems to be so far that flow speed and temperature are relatively low.

Every superpower states have effective warning systems for ICBM launches. Therefore it is practically impossible to launch secretly rockets to orbit. Every launchpad would get some cruise missiles soon after launch. Such mobility would be quite hard and expensive. Probably it would be more productive to sell honest launch services if you have such resources.

It is quite difficult in space industry because there are practically infinite amount of asteroids and resources in Solar system (compared to current production levels or deposits on Earth) and no realistic means to prevent others to utilize them. Even some corrupted government would give monopoly to prime minister's brother's company there are many other countries which would certainly compete.

It is ridiculous to take current metal prices and multiply mass of large asteroid and get insane numbers. Space mining will work because it may crash prices of platinum group metals and rare earth metals. They have interesting properties and if they were cheap like aluminium it would be possible to make new mass products with better properties and lower prices and grow economy indirectly. Unfortunately it makes beginning of mining business even more difficult. There is no easy and fast revenues but whole industry must change.

You are right, in my opinion unfortunately. I think that common attitude must change before humans can take great steps in manned space activities. Technological development is not enough. We have to learn to accept that manned space exploration is dangerous pioneering work which is impossible without deaths and failed missions. Currently it is not possible and this kind of things take generations to change. But they may change. Maybe possibility to safe working conditions for average workers are so new achievement (after WW2 many common works, for example in factories, were very dangerous in modern standards) that people overdo it. But maybe after 50 or 100 years safety is obvious for everyone who want it and daring individuals are allowed to take higher risks.

I do not see great value of testing that kind of process in LEO instead of laboratory on Earth. LEO environment simulates only low gravity, but as far as I know (however, I am not expert on that area) gravity is not significant in reactions of gases. Effects of smaller gravity would be easy to calculate. Effects of actual Mars atmosphere, its weather and other variations, dust and other surface phenomena are much harder to predict without tests. It is true what you say about redundancy. But it is very hard to predict better than guessing what will be chosen strategy. We are so far from it. I am sure that when tests begin they give many surprises which affect the mission and all current ideas will be changed. Is it better to make direct landing and make all fuel for ascent on Mars, or should we use separate landing and ascent module and maybe utilize only local oxygen as you suggest? Unfortunately hydrogen is almost impossible to store for long periods. It boils off in few hours if tanks are not refrigerated continuously and there is not practical refrigeration technology suitable for space.

It is very different to do things on another celestial bodies. Sabatier reaction and following refining stages have been made in huge industrial plants under possibility of immediate service if problems arise. It is obviously impossible option on first Mars trips. Reactor and purification stages must be developed to very lightweight, compact and sturdy package which is possible to transport on Mars. And it must be able to produce and store tens of tonnes of fuel without any service. Any problem means mission failure. It is huge engineering problem which takes decades time and billions of dollars before we can even talk realistically about manned missions. And it is only one small part of whole Mars mission. There are as large and even larger problems in another sectors. Propulsion, habitats, crafts etc. must be developed. We may know at scientific level what they need but all actual devices must be funded, planned, built, tested and certified to use. We know about the history of space tech that it will be very hard and time consuming task.

I do not want to underestimate fuel production problems. They certainly need several test missions to Mars to finalize all details before actual manned mission. But still I think that it is easier way to achieve the first manned mission than trying to overcome the terror of rocket equation by brute force. Nuclear propulsion may be another route, but as I wrote, I do not believe that any government in the world will allow it in foreseeable future and I do not count on that.

Simple was compared to overall complexity of Mars mission. But certainly it is possible with enough accuracy. Methane and oxygen must be liquified and stored in insulated tanks with small pressure. Gaseous storage would be enormous and totally impossible to land on planet. Water must be removed from air very carefully before liquefaction. Otherwise it freezes and blocks the liquifier. And if there are overpressure in tanks atmospheric water can not go in. ISRU system must be planned do that all freezing stuff is removed. It is simply necessary prerequisite for manned mission. Probably practical time scale would be maybe 1.5-2 years of manufacturing. That would keep process in sane scale. After 26 months crew would land on planet (if telemetry tells that fuel is ready), make few months research and ascent during next return window. Probably nuclear reactor is only suitable energy source for such resource utilization. Unfortunately, it is currently politically impossible. I believe that all forms of nuclear propulsion are far more impossible. It is one thing which would need change of attitudes before manned Mars operations will be really feasible. Without nuclear power best option would be insanely expensive Apollo-like propaganda trick but not real long term research. ISRU will not certainly be an easy solution and it will need much more decades and billions of dollars than some overoptimistic scenarios suggest now. It is certainly totally impossible to get ready for 2030's. But I do not see realistic choices for first missions. Nuclear propulsion would work technically, as you mentioned, but when will world's governments and safety nitpickers allow research and utilization of nuclear power for space nerds? Maybe after WW 3 when (or if) they notice that "hey, we did not extinct yet".

It is relatively easy to detect fuel quality. There are many options. For example fuel refinery can be with return craft and use return craft's tanks as a storage. When astronauts leave they remove ISRU unit and use the craft. In any case it needs much development and tests. I do not believe manned Mars expedition in my lifetime (about 40 years if it is average). if ISRU is not used for manufacture fuel for return, mass budget explodes to ridiculous numbers. Far beyond any foreseeable technology. Such projects is possible after some (or many) sudden breakthroughs, which may take hundreds of years. Who is guilty? That is the attitude which practically prevents manned exploration. Therefore I said, that before it changes there will not be significant steps in manned exploration. Laws must be written so that everyone know risks and no-one is accused in case of emergency and crew loss. Like no one was accused if someone died during last centuries expeditions. Every technically possible methods must also be accepted, like nuclear power in all forms. That is much slower than technological development, it is main reason why I do not believe success in many decades. Methane and oxygen can burn even they have much impurities. And liquefaction removes most impurities (like water). Of course ascent motor would be the type which would have large enough tolerances and the craft would have much larger marginals than normal stages. I think that would be small problem in that huge project.

As far as I know, the idea is that ISRU unit goes first and begin to make fuels. Crew leaves at next window if telemetry tells the fuels are ready. If some problems arise during trip towards Mars, landing is aborted. I am sure that humans can never go to Mars with current safety cavil and insane bureaucracy. We have to get the same pioneering attitude as kings had during great expeditions. We have to be ready to send spaceships to daring expeditions and accept that everyone will not come back. As far as we require that risks of astronauts can not be higher than risks of office bureaucrats, we will get only empty words, fancy "plans" and gorgeous animations. Something must really change in out attitudes (all of us, regular taxpayers, politicians, authorities and rich entrepreneurs) and unfortunately there are no real signs of such change. Any leaps in technology will not help. We can not develop technology for manned space exploration without risking crews.

Maybe it would be possible to make some tests for some components, but it would be no sense to test whole system. You can not test raw resource gathering in LEO and conditions are very different. Atmosphere and dust are very significant planning parameters for everything intended to work on Mars.

Here in southern Finland weather is partially clear today, which is quite improbable in January, but Moon rises after full phase of the eclipse is over. So no photos or stories for next generations.

If I remember, propellants were in rubber balloon in metal tanks. I think there had no reason to specify it last decades. Mass budget of LM was extremely tight. Therefore they had to use lightest possible materials in engines instead of corrosion resistant materials, which are used for example in engines and RCMs of deep space probes, which use same hypergolic propellants and have to last decades.

Rubber and plastic parts have become brittle due temperature cycling, residual fuels and oxygen may have corroded some parts, batteries have destroyed and maybe corroded their environment and so on. Modules are certainly in very weak condition, except the metal frame which is probably quite intact. Cosmic radiation does not make materials significantly radioactive. Astronauts took rocks which had been billions of years on surface without any problems with radiation.

They have continued deadline many times already. If you have startup, you should not accept the deal that you make something almost superpower level space tech by blatantly overoptimistic deadline. But I agree that this was nasty and probably also stupid decision from Google. 30 millions is less than nothing for them and prize would have given lots of positive advertisement. But as far as I have understood, budgets of teams have been tens of millions and they have had other sponsors. Let's hope that at least someone of them are able to continue.

If probe loses all fuel it loses ability to point solar cells to sun, antennas to Earth or make maneuvers to keep orbit. It would die and hit in some body in relatively short time, because there are typically no stable orbits around planets with significant moons. In end of the mission probe has probably only few m/s left so it can not maneuver itself to more stable distant orbit or leave the system.

If there were a (very fictional) situation in which crazy genetic scientists would have hatched some living T. rex individuals, would you like to test that theory in practice in tyrannosaur's cage? It would be nice win-win game. Lots of scientific merit if theory was right and certain Darwin award if it was falsified.

This may be true (except long term observations over years). But one week for one human would cost many orders of magnitude more than flagship class rover. Using same amount of money for dozens of rovers, orbiters, sample returners and maybe more exotic probes, like drones, we could get much more comprehensive understanding of Mars than one short manned mission to one spot can give. Reason of manned lunar research will be more political prestige than scientific research or economic benefits. Honestly, I do not believe that any projects, which are under planning now, will actually realize. No Space organization have got special funding for manned Moon activity from their governments and there is no reasons to expect it in near future. In such conditions any company would not develop anything special for Moon exploration, because no one will get no other income from Moon than contracts with governments (in our lifetimes). We have almost heavy launchers, but no landers, surface habitats, research equipment or anything special stuff. It will take at least decade to build, test and certify all them before anyone can even try manned mission.

No. New structure will be more heavy than current aluminium tank, which means less dv.

There are certain electron states in solid matter. Ion lattice determines them. Discrete states of single atoms becomes to broader electron bands and there may be gaps without states between them (band structure determines many electronic and optical properties of matter). Holes are single vacancies (empty states) on such band, which are normally fully occupied (so, there are an electron in every possible electron state in the band). These empty states can be approximated as positively charged particles with certain mass (may depend on direction in which the hole moves in crystal) and other properties. It is often practical and it is used much in semiconductor physics. However, the holes are special properties of special electron states, which depends on lattice structure (atoms). If there are no atoms, there are no electron bands and the hole has no reasonable meaning in electron states of such system. Actually that kind of system is negatively charged and very unstable. Electrons repel each other and there are no attractive forces to keep system stable.

Do you know is there any typical order of magnitude what to expect? Has this kind of shutdowns lasted days, weeks or even months? It is not long time ago when time constant was half year. Hopefully this is a modern version of Zeno's paradox, story of Achilles and the tortoise. There will be some time what can not be exceeded and launch actually happens in finite time. Future generations will probably call it as Musk's paradox.

Maybe. But on the other hand, we can not be sure that such leak is not intentional disinformation. It is probably quite easy to organize that SpaceX says something, Northrop something else, some politician says something "accidentally" and official authorities does not say anything. What I wonder is against who that kind of security measures are really intended. Probably all other major states know exactly is Zuma on orbit and they can track it from launch to the end of mission. I do not believe in such stealth technology which would hide a satellite from advanced military radars on Earth and on orbit. And I believe that major states leak that information to smaller states too, which are involved to conflicts with USA, if there are reasons to expect that the satellite has something to do with them. It is possible to confuse interested people some time, but I do not see why. In my opinion some kind of re-entry testing or other very short lived mission, like quick testing of some kind of electromagnetic weapon against test target on Ocean, sounds more credible, because other states see that there is no new satellite but they can not distinguish it from failed separation. But of course I know that I can not think with such paranoid way, which is typical for security authorities.

I do not think that USA attacks against Russians with illegal space weapon. That would give very little benefits but be a huge risk. At least it would lead to aggressive and insanely expensive race to launch weapons to space (with also China). But how about some kind electromagnetic weapon which can temporarily block or disturb some important radio communications in North Korea?

It would be futile to try to keep a radar satellite as classified as Zuma. There are many reconnaissance ships of other countries on oceans and they would detect the radar satellite immediately it pass over and try to scan ocean.