# Hannu2

Members

590

1. ## Imperial versus metric

Not in Finland. However, inches are commonly used in spoken language, especially in carpentry and other handcrafting. Nor example 100 mm nail is called "four inch nail" and 96x48 mm plank is "2x4 inch".
2. ## Imperial versus metric

Actually I would be happy if there were global compromise. Units could be imperial but one unit per quantity and decimal notations instead those very impractical rationals. For example an inch would be very practical unit in everyday needs. Most objects I handle have size of 1-10 inch. Kilometer would be 40 kiloinch. Megainch (25.4 km) would be quite practical for everyday traveling purposes. And I have already very used to mils (milli-inch), which is very common unit in electronic engineering.
3. ## Imperial versus metric

I understand. But in most case you buy some standard packet of meat. In my country that "normal" 4 person packet is 400 g. Next size is 600 or 700 g depending on meat company, which is practical for larger family. At least I buy very rarely arbitrary amount of food products except fruits and vegetables. Sometimes there are packets in imperial sizes but I count a pound as 500 g. It is also very common to have more complex values because companies have tendency to decrease packets for example 10 % instead of increasing price. After couple of silent decrease they can bring "new larger size" with advertisement campaign and increased price. Probably I could adapt quite easily. I am engineer and used to use and convert imperial units and also some other special unit systems used in certain physics areas in addition to metric units.
4. ## How To Safely Contain a Literal Ton Of Antimatter.....

If you could make anti-iron you could use ferromagnetism to handle it. It would be couple of orders of magnitude easier than handle plasma, but I would not like to live near antimatter storage. Unfortunately there is no stable configuration of permanent magnets able to levitate an object. A simple control system is needed. It may not be simple to make sure that it work after blackout, earthquake, military attack and all attempts to maximize the profit with simplification of system. Probably there is no need to store a ton of antimatter for any planetary use (except sterilize conquered planets from annoying semi-intelligent apes with nasty nuclear bombs). Large long term energy storage could use safer and more efficient methods (production of antimatter is very inefficient). Antimatter may still be allowed for small amounts if some technology needs very rapid release of energy.
5. ## How To Safely Contain a Literal Ton Of Antimatter.....

You can certainly buy disposable hypermagnets from the same shop from which you buy a ton of antimatter. There is a new year sale for magnetic monopoles going now. Take 3, pay 2. Please notice that shipping of antimatter may include longer delivery time and extra cost due to safety regulation.
6. ## Most popular planet in the system;

Biosphere makes the Earth clear winner, but if I think just planet without taking biosphere into account, maybe Jupiter. Those flow patterns are nice and it has also many different moons and interesting physical activity around. Neptunus has nice blue color but is little bit boring.
7. ## What If... Blood Fueled Rockets? I Am Not Joking...

It seem you also forgot how photosynthesis work. It takes water and carbon dioxide as ingredients. Photon energy is used to break bonds between hydrogen and oxygen in water molecule through complex biochemical reaction chain. Those molecules and radicals form glucose (through very complex reaction chain). Numbers of all kind of atoms is conserved and only changes in mass are very negligible relativistic effects. Photosynthesis do not make atoms from photons, it just uses photon energy to push chemical reactions. So, aluminated mylar foil would give much more push from sun than of all those fancy plants, blood generating zombie worms and waste recycling devices.
8. ## [New] Space Launch System / Orion Discussion Thread

All (practical) lunar orbit insertions for retrograde orbits needs braking burn behind the Moon. With modern tech it is easy but it was real problem during Apollo missions which had to also execute lunar orbit insertions and trans earth injections behind the Moon without communications to Houston.
9. ## Eastern European solar eclipse

In Finland there was thick rain cloud layer, as always when something interesting happens in the sky. I wait impatiently when Sun grows to red giant and blows all atmosphere away. As a bonus, we will be liberated from terror of winters too. Then we can happily see all interesting things on night sky in comfort warm conditions. Unfortunately, I can see a mild problem. There will not be total solar eclipses anymore at those times because Sun's angular diameter will increase significantly but Moon's angular diameter will decrease.

301 is so called austenitic steel. It means it has face centered cubic lattice, in which iron is not ferromagnetic. It is ferromagnetic only if it is in body centered cubic lattice (ferritic iron). However, there may be small ferritic areas due to for example lattice defects and sometimes austenitic steels may have mild ferromagnetic properties. It is far too weak effect to hold anything but you can barely feel it with strong magnet. I also think that such defects are not wanted in rocket hull because they affect structural and chemical properties too.

Good luck to apply license to use all those environmentally friendly and very safe fuels. Do not forget chlorine trifluoride. If it is too weak stuff for engines you can use it to ignite campfire on Moon or Mars. Maybe you could jump straight to the deep end of pool and build an Orion (that original version form 50's, not modern capsule).

That green flame is spectacular. Maybe they should add little bit copper containing chemical in fuel in those missions do not need 100 % capacity. Do you know was that unexpected anomaly or did they some destructive or intentionally risky testing?
13. ## Ionizing Air Going Through A turbojet engine... could it increase thrust?

Energy of normal ionization methods, like corona discharge or radioactive source, is negligible to energy of combustion. Ionized intake gas would give no benefits but corrode engine parts. Highly ionized gas is used for plasma cutting.
14. ## Imperial versus metric

Imaginary unit is usually written as j in electrical engineering. i(t) is instantaneous current (as a function of time) and I is usually RMS-value. You write that sinusoidal 50 Hz AC current I =10 A which means i(t) = 10A * sqrt(2) * exp(2*pi*50 Hz*t*j), where j is imaginary unit and t is time. Calculations use complex currents which arguments is phase in relative to some reference. Actual physical current is real value of complex current.
15. ## Could the SuperHeavy booster be SSTO?

At what price level? If passenger capacity is few people and trip takes thousands of tonnes of propellants and need special rocketports it need pretty scifi-ish assumptions about economy to be profitable. Environmental issues are also very severe and probably many companies avoid such trips due to reputational damage.
16. ## Could a Moon/Planet/DeathStar Spin Faster Than it's Own Orbital Velocity

It is practically the same thing. Calculation of Roche limit assumes that bodies have no structural strength. It is very good approximation for planet size objects, because structural strength of solid materials are negligible compared to gravitational forces present in near flybys. But smaller objects can rotate much faster. For example rotating space stations are based to that. You have to have some means to grab on surface or use engines to push ship against surface. Net force to object on surface is out from center. However, you can land on pole if you have same roll rate than planet and can somehow manage controls. I would not like to try it with hand control id spinning rate is noticeable.
17. ## Plasma Airlocks For Spin Launch.... Possible?

No. For some strange reason those guys with limited sense and high level of tech enthusiasm (including me) rarely have dollars for investments.

It is on easy to keep public interest. But Apollo was "easy". It here had been few failures before first success and then clear development (and failure now and then, maybe thrilling rescue operation) it would have been more interesting. I think Mars will give much more challenge. But of course pace of program will be very slow which decrease public interest. On the other hand, I can not see much other options. Billionaires do not have enough resources to develop systems capable of manned operations on another planets. They have so high personal ambitions and tendency to compete against each other that meaningful cooperation is impossible. Musk talk much about Mars but has not actually made anything Mars specific yet. It is very speculative if Starship will be ever used in any kind of Mars-operations, or even in manned flights, but it will certainly be very profitable rocket for next generation satellite constellations if development succeed nearly as intended. New Shepard is just overhyped test article without any meaningful use except testing. I do not see why they keep it running. Few flights per year means few millions of profit. It is less than nothing in Blue Origin sized company. And less than less than nothing for Jeff Bezos. I have tendency to think that Mars is not visited before there is some kind of cultural shift. People should have more ideological objectives and will to use resources for them instead personal pleasure and entertainment or invest to short term profits. It has been the situation on most of humankind's history. Most of historical monuments we admire sign of high level civilization have build primarily for ideological reasons and not to produce direct profit. Industrialization changed the game. People ceased to build cathedrals and monuments intended to last forever and began to build factories intended to short term profit. We have not fully adopted to industrialized society yet but I think it will change and we get new ideological motivations to do things. Now there are couple of billionaires who has ideological thoughts instead of just building of new cheap consumer scrap factory in developing countries. Now there are governments who think environmental and health issues in addition to GDP and tax income during their electoral term. Now there are citizens who seek alternative ways of live. But of course it will be slow change and unfortunately I can not believe that I see manned Mars-operation in my lifetime (statistically about 35-40 years). I do not believe current projects. Neither expansion of Artemis or any other governmental operations nor private operations.

That multiplanetary species is pure repurposed bovine waste. It may become true after thousand years of colonization attempts but it is not relevant reason in our lifetime. But your suggestions are boring. Humans are not reasonable but complex psychological beings. It is bad problem in any society that new ideas and monuments have more prestige, popularity more money than maintain of existing infrastructure. Space colonization would be very good ideological objective for technical civilization. It gives something to most of people. There will be brave heros, ingenious managers, funders and builders, monumental building projects, scientific and technical breakthroughs, sad accidents, glorious success, fascinating stories, ideological motivations and so on. Reasonable development of clean tech, peaceful and fair societies and moderate lifestyle has order of magnitude less potential of that kind of psychologically fancy stuff. And fortunately it can give most of those reasonable things too indirectly. New space tech make possible to move increasing part of mining and polluting production to asteroids and build protection systems against hitting bodies, new medical knowledge gives better life on Earth, failures increase resilience and after long time our life is not anymore in one basket. But we could never fund those things without high prestige ideology of colonization. Without it people choose to use their money for everyday pleasures or profitable investments to companies selling such pleasure instead of investments to real development.
20. ## how much deltaV can you get out of a gravity assist?

It is little bit dangerous to think absolute velocities in space. There is no absolute velocity but velocity depends always on frame of reference. Gravity assist do not change magnitude of velocity vector in the frame of reference of body used to assist. But it can change magnitude and direction of velocity referenced to common center body, which makes it useful. I have not calculated the math but have a gut feeling it is better to time encounter so that you can brake near Tylo or Laythe at optimal position relative to planet (at periapsis of spacecraft trajectory). It takes single meters per second if you adjust it in midcourse few hundreds of days before encounter. It is pretty difficult to achieve with vanilla adjustment tool but very easy with mod which gives you possibility to increase and decrease of velocity components by 0.1 m/s (or smaller) steps. I use Mechjeb. It is also practical because one of those moons is the primary target for most trips to Jool system and it can decrease number of maneuvers.
21. ## How high could you pump steam?

We change composition of atmosphere and albedo of surface and if effects how much solar energy atmosphere capture. Straight effect of human energy production to air temperature is negligible.
22. ## How high could you pump steam?

Weather effects include so huge energies that it is impossible to produce by any known technology. And if you think some unlimited scifi energy, it would be much more convenient to build greenhouses or vertical farming systems than dump cubic kilometers of water to upper atmosphere and handle all nasty unexpected side effects.
23. ## What Does It Take To Create Large Magnetic Fields?

Sorry, I probably was pretty technical. Ferromagnetism is that familiar magnetism. Permanent magnets, inductor and electromagnet cores are often made from ferromagnetic materials. Iron is the the most known example. Ferromagnetic material react very strongly to magnetic field around it. Physics behind the phenomenon is awful mess of advanced quantum mechanics. Electron spins, exchange interactions and so on. I never learned it properly because I did not need it with semiconductors. They are fortunately not ferromagnetic. There is quite often claims that ferromagnetism is somehow badly understood phenomena. It is not true. It is probably because there is no classical analog and it is therefore omitted in popular material and physics courses before master or PhD level in university. Quenching is a situation in which superconductor cease to be in superconducting state. It is abrupt phase transition and quenched part get immediately significant resistance. Superconducting coils have very large inductance and also large currents. It means very large energy of magnetic field and that energy is released as heat in quenched part. It may damage the wire straight or boil so much liquid helium that pressure bursts vessels or tubes. It may also be dangerous for user if safety measures are omitted. It may happen due to some disturbance. For example change in magnetic field around experiment. It is not the only danger that iron tool is attracted at high speed. Crash may be followed by a shower of liquid helium.
24. ## Sloped Ramps, Long Runways, and Heavy SSTO's

Why? It is difficult, expensive and dangerous to roll huge speeds on ground. What that gives over vertical takeoff? You can not have wings with reasonable assumptions so you need TWR of greater than 1 at launch. If we talk about completely fictive fusion engines, TWR can be anything. If you need visually stunning scene in scifi movie, feel free to use a ramp, but it is hard to see any use in realistic scenarios. Have you heard a physicist joke? Rich gambler asked mathematician to make a model for predict horse race winners. Mathematician thought a minute and said no, there is too much too complicated things. I can not do it. Disappointed gambler went to engineer. Same answer, there are too much unknowns. Then it was physicist's turn. Physicist said, yes, of course, it takes two days. After two days he came with a fancy program. Gambler asked why you could do what other specialists could not? Physicist said. It was not difficult. Let's assume first, that horses are perfect spheres which moves in vacuum...