Hannu2

I think that there are extremely low number of scenarios which would turn Earth worse than any other celestial body. Maybe a huge collision which melts whole crust. "Normal" asteroids, geologic catastrophes, climate changes etc. can not change Earth worse than Mars. If we can build colony to Mars we can make isolated caves and artificial food production in Earth with much less cost. But it will be some kind of curiosity and technical ambition which will motivate to build space colonies. There have been huge building projects without straight profit thorough history. I think and hope that current extreme capitalism where income of next quarter year is only thing that matters for powerful people and possibility to buy loads of cheap, practically useless and fashionable stuff and entertainment is only thing that matters for common people is just short period of mankind's history and after couple of generations humans have again more noble and ambitious objectives, like colonization of solar system.

Technically yes, but politically I do not think so, because problem is that Nasa (or US government) does not want to pay missions even for smaller version.

In such situation I think that there will not be permanent space colonies before medicine gives solutions to human restrictions.

Electrolysis of water takes about 300 kJ/mole. It gives 0.5 moles or 16 g oxygen gas. It can burn 0.25 moles (4 g) of methane which gives 0.004 kg * 55.5 MJ/kg = 220 kJ. External energy is clearly needed and only possibility in Titan is a nuclear reactor. Of course it is not technical restriction and in any case many political attitudes must change thoroughly before mankind will be able to establish any space colonies or even manned temporary visits to planets. Pressure on Titan is 1.6 atm. I thought habitat pressurized to 1 bar but of course it would be possible and practical to pressurize habitats to little over ambient pressure to ensure that leaking gas flows from inside to out. As far as I know 1.7-2.0 atm is not a problem to humans if oxygen partial pressure is suitable. However, leaks of oxygen containing air can be dangerous in hydrocarbon atmosphere. But probably they are not largest challenges in colonization of Titan. As far as I know every proposed fusion technology need massive structures. Typically they need also some exotic metals and complex structures which can not be manufactured without advanced industrial infrastructure. Maybe we have ultralight space fusion devices in 30th century but I think that then middle class people goes to Mars cities as tourists. Nitrogen, phosphorus and potassium, the most important fertilizer elements, are relatively common all over solar system. They will not limit agriculture in space colonies.

I know but where is the advantage over Mars which have also plenty of water? Titan have harsher conditions (temperature, pressure, toxicity), lack of solar energy (nuclear energy is only option on Titan) etc. problems but I can not see any real advantages over Mars. I am sure that boring bureaucrats would even prohibit flying with muscle powered gliding suits by astronauts.

There are carbon dioxide and water in Mars. It is possible to product methane and oxygen. I do not see situation on Venus or Titan significantly better. Titan have hydrocarbons but lack oxidizers and Venus's atmosphere have nothing ready to burn.There can not be significant concentrations of fuel and oxidizer on any planet. Such atmosphere would burn until either compound would be exhausted. There are high pressure atmosphere of toxic gases in Venus (carbon dioxide, sulfuric compounds) and Titan (large variety of organic molecules). It is much more difficult to prevent gases leak in atmosphere of habitats than to keep overpressure compared to atmosphere.

Every real "probe core" have protection measures against such problems. If they detect that there will be emergency situation, for example battery charge becomes too low, they interrupt all scientific observations, turn off all devices but necessary avionics and communication equipment, rotate itself to an attitude where solar panels get power and communications to Earths is possible and enter into safe mode until mission control resets them and begin to investigate situation. I think that it should be default function on KSP cores too. It would be relatively easy to program (except attitude changes if ship is not active). Game could halt possible timewarp and show a message in such situation. But I think that SQUAD has another opinion. It is possible and relatively easy to use safety battery or "cheat" by editing save file.

As somebody wrote, we do not know if metallic hydrogen is metastable state in normal temperatures and pressures. If it is not, which is very probable, it can not be stored without ridiculous pressure which can only exist deep in giant planets. Releasing the pressure would convert metallic hydrogen back to normal gaseous form. Even if hydrogen have such metastable state we do not know how stable it is. What is needed to prevent spontaneous conversion from metallic to molecular state. You want to be sure that such a chain reaction can not begin before burning chamber, for example in high speed turbopump. We do not even know if metastable metallic hydrogen (if it even exists) is solid or fluid stuff under normal conditions. We do not know how to fabricate macroscopic amounts of metallic hydrogen. Actually, according to Wikipedia's references, scientists do not even have agreement how reliably whole metallic state have been confirmed. High pressure hydrogen needs probably to be investigated decades before we can answer to questions about its suitability to practical energy storage.

There are many reasons why Mars is the most habitable and practical and I think that if there will be space colonies first ones will be on Mars. 1. Travels Mars is second easiest to travel. It takes couple of months and we know that humans can stand so long microgravity with tolerable damages. Venus is easier but I do not see any real use or interest in very risky and impractical floating colonies middle of nothing. Outer planets need years or decades to travel, if we do not invent very revolutionary propulsion devices. There are some nuclear propulsions but there are no signs that political ban against them will be removed. Their development would also need decades of time and billions of Dollars after decision before they would get man rating for interplanetary purposes. 2. Surface conditions Conditions on Mars are extremely hostile but all other places are even much more hostile. Soil and rocks are hard and give possibilities to make caves (or use natural caves) to protect cosmic radiation. Water ice bodies in outer solar system may be too soft (at least those with significant gravity). Temperatures need less insulation and warming. Atmosphere gives little protection against radiation and micrometeorites and there are not highly radiative areas like around gas planets. Gravity is probable enough for humans. Soil is toxic on Mars but probably places with interesting organic materials on surface are much more toxic. Low pressure prevents leaks of atmospheric gases into buildings (unlike Titan). 3. Street credibility Humans have dreamed about traveling to Mars or Martians. Mars is probably easier to sell to taxpayers, than any other celestial body. I do not believe in any private manned Mars projects in foreseeable future. Asteroids are certainly more interesting in economic sense. However, they do not have gravity and probably there are very advanced automation AI after couple of decades when mining becomes current (at the earliest). I think that there is no need for continuous human presence for mining or refining operations. If colonies will be based it is only for governmental propaganda reasons.

Commercial water pumps use typically 3000 rpm electric motors (or 3600 rpm in countries with 60 Hz electrics). Typical car turbo works at about 100000 rpm. You should have a high speed gear. It does certainly not fit in hobby budget. However, it is possible to use a turbo charger to make a simple gas turbine. You need burning chamber in which you feed air from compressor side of turbo and suitable fuel, for example gasoline or gaseous propane. Burned gases is used to run turbo. It is useless but gives fun, smoke and noise. Larger truck turbo is even better (as always when you play with fire, the larger the better). Google gives many hobby turbine projects.

You can not use stock turbo to pump liquid. Liquid's density is hundreds of times larger and viscosity too. Pump would be very inefficient and would not work practically. Water would give extra problems because corrosion. Materials of turbos can not stand water. It would go to bearings and whole turbo would fail.

Do you mean some kind of rolegame stuff? I think that Kerbals controls manned crafts (by using MechJeb and SAS functions) and some kind of advanced computer controls unmanned crafts like real probes.

Display of coordinate axes, node detectors in every orbit (with possibility choose reference plane (ecliptic, equator of center body, target orbit (it exist already)).

That would not give much to gameplay. It would be practically a three sat contracts maybe with some instrument and mouse clicking science. It would work if there were for example extremely tight orbit tolerances and long term scientific experiment but there are not suitable maneuvering tools and science mechanics in KSP.

If that game were really an option, I definitely want them to make only 64 bit version and debug it to tolerable level and after that use all resources to develop KSP2. Unfortunately, there are far too few people who wants to accurate physics and precision flight management tools. Most want to explosions, crazy contraptions, eyeballing maneuvers and numberless spaceflight. The only hope to get spaceflight game with proper physics, good performance and usable planning tools is that there will be some kind of hobby project like Orbiter with possibility to plan missions and spacecrafts. Simple models and graphics but very high levels of realism, physical modeling and technical details.

I do not think so if they use an old missile. SRB does not have to be 5 m. Only simple (compared to spacecrafts) adapter is needed. You limit this discussion too tight. Certainly nobody here knows exact costs of options. If somebody knows he is not allowed to tell. We can only guess costs and reasons of decisions without knowing many things which are very important for Nasa.

I think that SRB is so much cheaper than Delta that it is no problem to make adapter. I am also sure that somebody have thought changes in Nasa. Even if it is not true there may be complex political reasons and restrictions in Nasa's decisions. Nasa uses several times more money to achieve things than for example private companies but it is government's way to support to US aerospace companies.

You need TWR of over 1 when you lift from surface. But when you are on orbit you do not have to fight against gravity. You push forward and even extremely low TWR can accelerate your ship to high velocities. Probes with a real ion engine can have TWR of 1/100000 compared to g and they are capable of high dv interplanetary travels from LEO (actually much more capable than probes with traditional thrusters). However, very long burns are difficult to time. There are not suitable tools in KSP or any mods. My thumb rules are: 1. stage (+possible SRBs): dv 1500-2000 m/s, TWR (at start) 1.3 - 1.5. 2. stage: dv 1500-2000 m/s, TWR (at start) 0.7-1.0. At this point ship is on low Kerbin orbit. If my destination is Mun or Minmus, it is typically 100 km and 300 km for interplanetary operations. 3. stage: dv depends on target and mission profile, typically from 1000 m/s (Mun) to 5000 m/s (Moho), TWR 0.25-0.35. The lower TWR you have in ejection burns the larger errors you have, if you do not calculate exact trajectory and time burn with separate software. Therefore I use 300 km orbit and TWR around 0.3. The higher parking orbit the less errors you get but you have to use more dv because you do not get Oberth effect. And the higher TWR the shorter and more accurate burn but payload ratio is hit by heavy engines.

I put it on top of the Mk1 pod and execute first kerbal rescue missions. Later I use it sometimes in contract satellites for aesthetic reasons (with MJ controls). It is sad that it has been chosen to be the most primitive pod without SAS and reaction wheels instead of for example boring cube shaped one.

I think that this would not fit very well in KSP's current scope. Railgun would be optimal for very frequent launches of hundreds of payloads, for example automated supply transports to colonies or sending automated mining systems to bring resources from asteroids to kerbin. But there is not such possibilities in KSP. KSP concentrates to earlier phase of space technology where single missions are important and player plan them and execute them. Railgun would fit better to game where basic piloting is automated and player manages larger scale logistic operations in solar system.

Or one step further. At this time it seems that gravitational waves behave very accurately as general relativity predicts. https://www.newscientist.com/article/2077162-revolution-in-physics-as-gravitational-waves-seen-for-first-time/

It is difficult to justify from here that solutions of space companies are completely wrong. However, it seems to be extremely difficult and expensive to develop and build huge engines to the point that their scale economics begin to benefit. There are few historic examples and they have had large problems. F1 was a propaganda machine far too expensive for all commercial use. Four chambered RD170 had not much users even smaller 2 chamber versions were more popular. It seems that also SpaceX has severe difficulties to plan large Raptor because engine shrinks in every new rumor. 9 engines gives also benefit in return. They use only one of them and it is "too powerful". It can not be throttled so low that stage can hover. Landing with such engine must be extremely accurate and well controlled.

As far as I know there are not other stable orbit around Earth than Moon and its trojans. Minmus would be ejected out from system or crashed to Moon in relatively short time (astronomically). It is also impossible to use artificial satellites as time capsules (except maybe trojans).

Part 10:First return to home. In this part we follow return trip of first crew. At next time kerbals get a new toy, large space telescope.

I agree. Mun is so large that inclination of couple of degrees does not make transfers more difficult for beginners who do not care where they land. You get just somewhat inclined orbit. For example, I have to avoid Mun when I go to Minmus from parking orbit in Minmus's plane. 6 degrees is not enough to avoid Mun's SOI. It is time to learn little orbital mechanics when you are more advanced and begin to make pinpoint landings or use orbits with defined inclination and LAN.