Hannu2

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.

I would think, that ability to run some distance at ridiculous speed would be practical if there were problems in naval fight. Especially if it would be impossible to follow the submarine with plane. If it got hundred kilometers of distance it would be able to continue slowly and silently to unknown direction and disappear before the enemy would get some units at latest known position. But achieving that kind of speeds in real world is not credible at all, in my opinion.

The direction of force is very significant thing. I do not know exact structure of launch clamp, but I am sure that rocket's weight is on solid pieces fixed on pad before the ignition. But when engines are running, the force acts to moving parts of clamps.

Transmission depends on product of antenna efficiencies. You can also use a small omnidirectional transmitter antenna with low power and huge receiver antenna with sensitive detector, like small space probe sending data to DSN antenna on the Earth. But there is severe bandwidth limitations in satellite telecommunication. Even optical frequencies could not handle telecommunications for medium sized city. Satellite telecommunications can never replace cable and optical fiber networks in large scale but it can be used in addition to them in remote areas.

Heating power of long living isotopes are negligible. The more atoms decay during time the more heat it releases. Pu238 is technically relatively easy to make in nuclear reactor and there is well known technology to handle it and pack it in suitable form so that it is not very dangerous if it fall accidentally on Earth. It would be possible to use fission reaction of U235 or some plutonium isotopes to produce much larger power and get high power ion drives and many interesting applications, but unfortunately, it is politically impossible to make and launch nuclear reactors because irrational anti-nuclear attitudes are so common with people and politicians.

As far as I know density in Earth's core agrees what is known about iron (theoretically and experimentally). It is just hydrostatic compression. More massive elements are very rare compared to iron (parts per million instead of percents) and it is not credible that there are large concentrations of such elements or some more exotic forms of matter in Earth's core or at other planets, too. If superearth has 7 earth masses at about 4 times higher volume, I would say it has just high iron concentration.

I am quite sure that ESO's announcement has something to do with LIGO's announcement. http://www.ligo.org/news/index.php#oct16 My guess is that they have detected merging neutron stars gravitationally and optically.

I thought too, but if I look at that map the most of the east coast is nearer equator than Cape Canaveral. They can build their launch facility at peninsula near Coral sea at about 15 south latitude and fly between Solomon islands and Vanuatu.

Cassini was very great scientific project. Thanks for NASA & cooperators. I hope that we will see more such huge and incredible successful projects in my lifetime. I do not know what is this F thing but here is my official F. F

Unfortunately this may be true. However, it is quite difficult to see any other organization capable of getting enough money and engaging to such clear and risky goal. Chinese maybe, but not with current effort. Europeans can never achieve agreement of who pays and who is allowed to build everything, Russia do not have real interest at all and private companies can not get reasonable profit. Building is not actual in couple of decades. It is impossible to predict what companies are active when NASA eventually get funding and begin to order components or make development contracts. But probably they order stuff from Boeing, SpaceX, Blue Origin and several other current and new companies. I would guess that they will have also some kind of cooperation with other countries and international companies. NASA has never given such a massive project for one company.

1. NASA. It may be that SpaceX will make many critical components for the project but NASA will pay it and gets the honor. 2. After 2045. There is no credible plans anywhere in the world in foreseeable future. Many companies and organizations produce papers filled with empty promises but nobody have an idea who will pay the bill. 3. Terraforming or genetic manipulation is not possible in foreseeable future. I think that terraforming will never be reality. We have to make bases isolated from atmosphere several hundreds of years.

I do not know details. Safety limits depend on launcher type and some payloads may have own restrictions. This video shows main engine throttle of Shuttle. You can see a dip at around 1 minute to avoid excess aerodynamic stress but it runs at full thrust over burn out and jettison of SRBs. They make massive simulations for ascent profiles and take every known things into account. They have also huge number of emergency profiles for situations in which thrust is anomalous for some reason. Some of them may lead to intended or wrong orbit and some of them makes just abort more safe.

Gravity losses are the lower the faster acceleration is. Drag losses are relatively small in normal launches (about 100 m/s or less). More important reasons to throttling is avoiding too large stresses in launcher's and payload's structures. Details depend on many things, as already mentioned, but as far as I know all rockets lift off at full thrust because they want to clear the tower as soon as possible. Lift off is dangerous phase. The craft can hit launch structures or if thrust fails it does not give much time for abort. When craft gets speed the drag increases. About after one minute speed is transsonic and soon after that the aerodynamic pressure is highest. Aerodynamic forces exert to shrouds and surfaces of craft and they are also turbulent and may cause torques. At that phase many rockets throttle down to avoid too high speeds in too high pressure air. Also if launcher has SRB's they are light and push at high thrust. Thrust profile of SRB's can be changed somewhat but limits are quite narrow. Soon after max Q aerodynamic stresses decrease rapidly and typically SRBs burn out and are jettisoned. Typically rockets burn at nominal thrust because it is the most fuel economic way. Near the end of 1st stage it gets very light and acceleration increases and causes stress to payload and rocket structures. In that phase engines are throttled down to limit acceleration to largest allowed value of rocket or payload. Second stages have usually much weaker TWR and do not always need throttling at all.

It is not so simple. Finland is member of ESA and some Finnish companies and public departments make stuff for ESA (and also some components for US probes) but our country does not take part in manned programs. Therefore Finnish people can not apply for astronauts. You should check if Poland takes part in ESA's manned operations if you consider astronaut's career. I agree with tater that the first priority for Europeans should be to vote politicians who have positive attitude for ESA and are ready to pay tax money for space technology. USA will certainly not change their laws for us and it is not very fair to demand it. Unfortunately it seems that whole EU is in severe political crisis. Radical parties with negative attitude for EU (and science and high tech too) increase their power in many countries, including Finland. It may not be very realistic to expect significantly more spending to European space cooperation in next decade or two.

Laser may evaporate and even ionize material in which it hits. That hot gas or plasma expands and can make crater in surrounding material like hot gases from explosion or fast projectile. It is utilized in microscopic scale for some laser cutting applications, but such lasers which could make a large crater on ground will not exists in foreseeable future. Comparison between continuous wave and pulsed lasers are not straightforward. Effect depends on material, power level, time etc. and if we talk about power levels several order of magnitudes above anything which have ever been tested answers will be very hypothetical. Certainly both techniques can be destructive weapons if we can assume arbitrarily large power levels. But I suspect that there may be more effective and practical weapons than laser beams for those who have technical skills to handle such power levels.

What you mean bean alone? Scattered radiation? I use visible and IR laser beams with average power up to 10 W in my work and I certainly know that they are not dangerous if beam or reflection (these are much greater danger which forces to use protective goggles) does not go directly in the eye (or ignite your clothes). That does not sound quite credible that lasers are banned because they are horrible when we have huge stockpiles of such nice things like nuclear weapons, toxic gases, biological weapons and soon cheap attack robots and drones with crappy AI. Real reasons are technical and economical. Lasers are extremely sensitive devices which are almost impossible to build robust form for infantry use and they need energy and special service. And also, what you can do with laser which is impossible with an assault rifle?

Such handheld lasers have very well collimated beam which must be aimed straight to the eye. If large squad of enemies are moving it is practically impossible to product significant losses. Instead, the stray radiation reveals immediately laser soldier to enemy sharpshooters. Such a laser is also cheap and easy to avoid with cheap protection glasses. Combat laser would need wide beam which needs huge amount of energy. It leads to all other problems which have been mentioned. Automatically targeted big lasers may work in special applications, like in missile defense systems, but it will not replace firearms in standard infantry weapon in foreseeable future.