AngelLestat

They may be lying a bit about the final cost, besides the final cost always increase from previously planned. But is not shocking for me, in fact, I guess Elon Musk was jumping of joy when NASA give him more than 2 billions for the dragon v2 development. Of course it does not look much vs 5 billions than Boing receive for the same task, but the true is that all current space cost can be highly reduced if you do the things right. This Federation ship does not have nothin fancy more than a soft landing to allow reusability. I always was very critical on the orion cost, that should not be the normal cost of space ships, so when more people realize that, more pressure will receive nasa to make the things in a more efficient way next time. If the Federation ship is finish with less than 1.5 billion, it will represent a huge slap to the Orion case.

The shuttle tank was not really insulated to prevent boiling, it last a lot due its big volume, and we are talking about hydrogen which boiling temperature is 90 degree lower than methane, also the golden rule of volume.. you need a lot of propellent for a mars trip, this require huge tanks, each time you increase the tank radius in a 25%, you double the volume and your surface only increase a 60% (tank cost and surface leak), but other think happens, volume increase by cubic and surface square, so the volume/surface ratio increase a lot, each time you double the volume, the ratio increase like this: 8, 17, 33, 67, 133. Why this is important? because it tells you how much energy needs all that mass of fuel to rise few degrees its temperature, so if your tank volume is big, (5 to 10 times the shuttle tank) then it can last years, and hydrogen leak takes a lot of time too. The missions that needs to be worry about leaks or cryo boling, are those who has small tanks (like sats or probes), or those who need to be orbiting in LEO a lot of time (because is harder to block the sunlight because you need to change always your angle and also by earth albedo) Your huge mission with several tons of fuel does not enter in this category, and 450 isp is always welcome. Yeah hypergolics can be a better choice to leave mars and save the development time for a methane engine, active cooling and ISRU, but if it will be just for ISRU alone, then it makes a huge case to save (5 saturn V no reusable launches), because savatier is nothing of other world, it may take you few years, but the total cost is much lower because all your tanks and engine scale is also reduce, but the methane engine development may take some time. Landing location? Take a view on the benefits that a pole landing can provide for a first manned mars mission: http://www.geoffreylandis.com/pole.html

My way to make money in space related to the OP will be with a "fuel depot" of 10000 Tons from a capture asteroid. How to do it: 1) search a perfect asteroid (at least 75% ice) close to 22m of diameter who also need the less amount of deltav to be capture using gravity assist from the moon and earth. 2) gather investors (promise of profit) and international government support (asteroid impact defence program) 3) sent a probe using ion propulsion for the asteroid encounter, probe payload will be 200kg of reflective paint to spray the asteroid and a small nuclear reactor that it will melt the ice and will be used as propellant to capture the asteroid, with the help of extra pipes (as RSC) it will be possible to control direction and rotation. 4) The parking orbit would be elliptical from LEO to pass GEO, you install a big inflatable tank in which you store the water and extra tanks to store hydrogen and oxygen. 5) You can sell the propellent or orbital momentum with a tether system, in which sats will stole kinetic momentum to the asteroid to reach geo. 6) You can use this asteroid as kinetic mass to hit other asteroids that menace earth, or just to provide a fast service propellent to sent heavy nuclear weapons to hit the asteroid menace.. Nuclear weapons can release more energy, but you need to detonate first the weapon and most of that energy is waste it. You can sell close to 7000 tons in propellent just with a 22m asteroid, this would require 175 falcon heavy launches. Even if something happen and this asteroid fall into earth, is small and mostly ice, it will break in the atmosphere.

Once your ears equal pressure as always does each time you change of altitude, then the problem is solve. You can get tired at higher pressures to breath, that will also depend on the oxygen concentration, but you dont need to breath so frequent at higher pressure because there is much more oxygen in each cm3 of air. I am not really sure what other issues you might have other than embolism at higher pressure, that is why I put 1000 bar as upper limit. But the main point, is that you dont implode, because you are breathing air at the same pressure.. Is similar of what happens with fishes, they can live at extreme pressures even if their bodies are ultra delicates and light. we feel 12 tons by m2 in earth, which is equal to 1,2 kg by cm2. This is why I hate of some sensational tv scientist, when they said.. if you are in venus surface, it will be like to had 100 cars above you..

You did not read what I said.. if you remove the issues of gases (like nitrogen, or in the case of higher pressure oxygen) in our blood stream "embolisms", then you dont have problem with high pressure. About low pressure, I mention 0.1 bar, this is higher than the Armstrong limit.

You would not implode in case the air you are breathing is part of the same atmosphere (all directions as you said), our bodies are incompressible. Only gases can change its density by pressure, unless we are on pressures higher than millions of bar. The only problem with pressure comes from the fact that nitrogen becomes narcotic in our blood under certain pressure. If we ignore that fact, we would be ok no matter how thin or thick would be our atmosphere.. 1000 bar or 0.1 bar. The problem with forces on our body only matter if they are not uniform.. a gravity field produce uniform forces, so in free fall nothing happen. Pressure produce uniform forces.. but if something hit you as a stone, you are receiving a force just in one part of your body and is not uniform.. so you get hurt.

no, is not possible, because all the mass of the atmosphere above you it will produce a gravity field in opposite direction which is closer than the gravity field caused by the atmosphere of the other side of the planet, but we are talking of gases, so distances here are larger. In the same way that if you travel to the earth center, each time the gravity is lower, it would not be much difference here. And the pressure and mass of the atmosphere should be huge to add some significant gravity field. Just imagine saturn gravity and going down, the only thing that rise is pressure, gravity will be lower, and I guess it does not matter if it has a solid or very dense core, because at that level gases are also highly compress which increase its density. ---------------IGnore, you already explain your question-----------------------

sabatier reaction is like a children play for chemist.. gas separation very easy using different frozen point temperatures, etc. You can carry your h2 from earth or just get it from the water, (a way to get water on mars using ISRU will increase the survival chances of the mission. ISRU= Lower risk Also why you always said "massive" machine.. massive filter, massive sabatier.. etc. I understand, you want to make the point against ISRU, but these machines are way far from massive, in the worst of all cases, all your elements will weight 1000 kg, that is several times less than the fuel you need to carry in case you dont use ISRU. Here is a NASA site speaking on ISRU: http://nssdc.gsfc.nasa.gov/planetary/mars/marssurf.html Here is another link but it seems too old: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120001775.pdf Is not really need it, if you design 2 or 3 types of landers in which one of those is able to make methane and return to earth. The other 2 will carry extra supplies, vehicles and other ISRU tools just in case (mostly for water). You send them first.. you test methane production and quality with many sensors, you test the engine fire and thrust, if something doesn´t work, you can fix the problem and launch another one in the next launch window, then you test again, if all works fine and they had full fuel, then you launch the human mission using the same design that also is ISRU capable in case something happen or that would stay and work for the next explorers, you can also exchange fuel between vehicles in case something happen and you need to launch using your arriving ship. Why human lives are in "risk" if you are already test all this from earth? And you have many contingencies solutions that you will no have with a no ISRU approach. Is cheaper.. is more efficient.. and is more safe. You are also sending the humans in a ship that already did all the trip and land in mars, because you use a copy of the one that already is there. There is no point to sent a rover to test something so simple as the savatier process to mars, because it can be test it here simulating mars conditions. You will be doing triple test for nothing, when in fact the most hard about mars is aerobraking and landing (and that risk increase proportional to your lander mass)

I just mention 747 because it is the most common airplane, of course you can use another airplane that will fit better in cost for the payload size. Thanks for the link.. but I am shocked with that new ISP number.. I thought that a jet turbine engine designed for lower speed would be more efficient. Maybe that isp depends on speed and altitude. remove lox will help a lot. If in the future if we see more cryo fuel airplanes as it should if we want to solve the co2 planet issue, then it may had more sense.. but we would still need lox.

Those 50W are for few grams of propellant with low isp (less than 100s), the thrust seems fine for that scale (0.1N) This discard even rocket hobbyist uses and even put into question how good can be for microsats, because we already have many option in thrusting with better numbers: http://www.tethers.com/HYDROS.html http://www.busek.com/technologies__ppt.htm Take a look to the other kind of thrusters too. I know that solid thrusters can have a benefic in cost, but the product is not developed yet so we dont know nothing about its final cost, but I can agree that it will be cheaper for sure. Many of the products on that page already include subsystems and stabilization. But if you reduce your thrust for higher isp, it allows you extra deltav and extra precision. I know.. it may be still had some niche.

Ok, but even if you plan to kills all your deltav with propulsion, you have to know that this is not as easy as the moon, due the supersonic co2 flow that is trying to extinguish your burn. Maybe is not a problem, maybe it is.. we just try it with modern engines at lower speeds and with a mix of nitrogen and oxygen. The mars case would be much worst. Those 2500 tons is the why NASA is trying to search other alternatives to reduce the deltav, managing such huge rocket with so many stages and trying to land such heavy vehicle on mars surface is not the way to improve safety, in fact increase the risk, each kg you save in your final stage it has a huge impact in your first stage. In those cases ISRU, high isp fuel and even hard aerobrake techniques are welcome. You can have sensors to measure the quality of the fuel before you sent people there, those kind of sensors are super lightweight and you can add redundancy. You can even test engine firing, hover and landing before you send someone. This will complete the test that your engines work and the fuel is fine. In the other way, if you sent someone there carrying your return fuel from here, you dont know if the engines will work when you need them, plus the risk to land heavier payloads and how much that impact in your amount of required launchers from earth.

It needs to be cooled if the tank face the sun, or if is on earth surface, if is on space with a sunlight bloking and you have a decent insulation between the tank and your crew module, then it does not need to be cool it because space is already much colder than lox. The future is very close.. so no sure where you will hide when arrives.

Only 20 degree of diference with methane and lox boils at 70 degree higher than hydrogen boiling point. Is still in the passive cooling range. About the mass, I dont care if is realistic or not for a manned mission.. just pointing that we need a lot of fuel and Supersonic Retropropulsion which was first achieved by spacex some years ago at lower reentry speeds. AeroBraking does not work, because the volume -surface - mass relation, you increase just a bit the surface of your heatshield capsule design (S2) and the volume increase (V3), the volume in these cases is directly proportional to your mass, this mean that every time you increase your mass, the heatshield surface does no increase in proportion to allow an aerobrake. Even drag chutes are out of the question at those speeds, so the only option is to use your whole tank+capsule in vertical to increase the surface drag (with supersonic retropropulsion), but it would be hard to keep that inclination all your way down, by hard I mean almost impossible with 1970 tech. A manned mission to venus (havoc mission style) would be much easier for that time, you have a thick atmosphere to brake and no land to hit. The ISRU part of Zubrin was no the detail of his mission considered risky, it was the time, the crew and the low payload and simplicity of the mission, and those who said it was risky does not respond to any quality review panel, they would said that no matter the type of mission, because there was no real interest from NASA and the government to go mars in that moment. Also you said: Can you show me other proposals from NASA for a manned mars mission using hypergolic fuels? hahaha, lets start pointing that this source has a doubtful quality And you did not even understood what they are talking about. He shows a leak rate, but you dont know nothing about the tank dimensions or the environment (in earth, in orbit facing the sun, or in any other place) He did not even clarify what was its unit of time. Now, lets see if you still understand the main point here, if your tank is under the boiling point temperature, it does no boil off..

When you need just a little deltav and your tanks are so small (volume) than the surface is significant (volume surface relation) and when they need to be pointed to earth no matter where is the sun, then yeah.. hypergolics sounds fine in most cases when you did not bother to develope a methane engine. I said that methane does not need active cooling.. what does means for you? it does not need also all those things in the james webb telescope which instruments needs to be close to absolute zero, again... we are talking about -160c! But you ask about active cooling as it was "THE TECH", and is something super easy. heh, is not like I present irrefutable evidence and logic.. I told you that I knew what I was talking about. But well, I guess is not on you to recognize my time to explain you.

And you mention that now? No sure from what topic this discussion is coming, but that was no mention in the OP. Really? I thought that the biggest mistake that someone can make in rocket science is sent the high density low isp fuel to orbit instead the other way around. mmm let's see what the manual says: https://en.wikipedia.org/wiki/Multistage_rocket#Optimal 1. Initial stages should have lower Isp, and later/final stages should have higher Isp.2. The stages with the lower Isp should contribute more ΔV.3. The next stage is always a smaller size than the previous stage.4. Similar stages should provide similar ΔV. The rocket rise that payload from earth dont you? Or is mining in space.. even if is the second, methane would be still a better option. Methane does not need active cooling! I repeat.. just passive and it has a lot more density than hydrogen. he should mention this before. Add risk? you know that the isru happens before the manned trip leaves earth, this also reduce the huge mass you need to brake on mars, which this is highest risk and constraint on a mars mission. Mass seems to be pretty big? can you elaborate? --------------------------------------------------------------------- But well, now that we are in 1970.. mmm... no sure.. everything seems hard in that time, the first probe landings in mars was way beyond that, and you want to land 40 tons? You can not use aerobrake with that so the amount of fuel rise a lot, which is no good for a low isp fuel.

To land in a different runaway can be solve with aerobrake parachutes, to take off with full payload will be hard, it needs some boosters for acceleration. But all those issues just to avoid payload transport to the right runaway seems silly, a 747 has an ISP of 6000s, skylon has 3600s, then risk a machine as skylon in inter country travel no sure if payoff. You still need to transport the payload to the airport, the only good point that I see for this is that you save 1 step in the shipping, many steps can damage the payload. But well, in the cases the payload is below 10t and the runaway is in the right latitude for the chosen orbit, yeah it will worth it, but you still need cryo fuels systems in that airport.

First I said Methane.. no hydrogen.. -160c boiling point for methane and -250c for hydrogen. Space background temperature -270c You can loose hydrogen due leaks due how small is its molecule with old tanks and longer times, but today we already had many options (as paint) to shield against h2. But h2 is not my option, is methane which does not leak and its boilling point is much higher keeping a good ISP. You dont even need active cooling, and if you need it doesn´t add much mass neither consume energy (negligible). You dont lose proppelent, also.. Elon Musk MCT will use methane. Can you tell me how much you think it weight a active cooling mechanism? I can understand that you might have issues with hydrogen with -250c, but methane?? or liquid ox? No sure what is the problem, I can assure you that even in the hydrogen, no matter how high is your active cooling mass estimation, never would be higher than the deltav lost using hipergolics. (you are using 1970 papers and tech as guide? we are in 2016! )

@Snark I read your answer, I respect it, but I dont share it. I read those kind of arguments many times, The cost-efficiency relation base on achievements is almost null in comparison to older times, and each time is worst when it should be the other way around due all the benefits of technology. 50 years! and still we did not do nothing alike those times. Agencies still need like 30 years more to plan a mars mission. No sure if you realize how much time is that and how much our technology change in that time.. We would develope a hard IA before we can put a foot in mars (unless Elon Musk do it first with goverment´s money).

those are were concerns of the past, it does not worth it today. And I was agree with @cantab answer, there are better choices for small sats. but well, maybe there is still a niche that I am not seeing.

These kind of engines does not need pumps, they both use helium for that matter, so the only problem would be ignition, and I dont see any problem with that.. you can get 100% as I said and was tested. About boil off is easy.. we are talking about liquid oxygen (-180c) and liquid methane (-160c) boiling points.. this is not bad as -250c for liquid hydrogen in which even the albedo of earth can help to boil off. Even if you need active cooling is not hard.. in principle you just need to take the fuel and oxidant gases, you compress them inside a radiator (no facing the sun), this heat up, release the heat, and then you let expand it which liquefy the gases at lower temperature. You just need to do this once every while... each time the pressure of the tank start to rise. ?? they did not give up on crossfeed, they just are not using it yet for the first test of falcon heavy. So please stop to make up fake news. I am still waiting your answer over the canadian oil pipe

Google: water definition All the first ten results in order without skip any: http://www.dictionary.com/browse/water? http://www.merriam-webster.com/dictionary/water http://www.thefreedictionary.com/water http://dictionary.cambridge.org/dictionary/english/water http://www.oxforddictionaries.com/definition/english/water http://www.yourdictionary.com/water http://learnersdictionary.com/definition/water http://chemistry.about.com/od/chemistryglossary/g/water-definition.htm http://www.biology-online.org/dictionary/Water http://www.oxfordlearnersdictionaries.com/definition/english/water_1 You can kept searching.. in all the definitions is refers to the liquid form of h2o. The fact that you can get water if you melt ice is not the same than said ice=water. @YNM Vapor (no steam) is still liquid water, but in your example case is the same. I never hear about it.. but I am not a chemist, I just had the required courses only because my career had the "engineering" word in it.

why you choose hypergolics fuel in the first place? I dont see any trouble with methane + lox. You have big volume in the tanks which reduce the surface and you are not close to earth shine (which does not matter either because earth albedo is not enough to boil methane or lox) You dont even need active cooling or any kind of cooling, just hide the tank from sunlight and other heat sources from the ship. 400 isp is much better than any hipergolic fuel, more when you need to save until the last kg in a mission to mars.

I think is possible.. I never thought in this possibility.. love it.

Safety? so now we need to send astronauts in a 5 star hotel? where is that adventure spirit? where is that risk to the unknown and brave people who made the first step, never in the man history was so coward explorers as now, but I am sure they dont have the fault, the space agencies who had the job to be pushing into the edge of discovery are doing nothing. Right now Probes are the answer to everything and the safety and super expensive rule also applies.. we can sent few to test waters.. but we can not live our lives sitting on the couch watching everything from a TV. Then the AI will come and the best scenery will be fat guys as the movie wally doing nothing relevant in their whole lives. About pulling incredible engineering feats?? why you dont study a bit more the apollo age, no just all the steps needed of true development to sent somebody to the moon, also all the great projects that was study over that time who were rejected at the end. Many of those are the same projects that even today nasa is starting to test them again without much advance than in those days!!, no due problems on what they expect to achieve.. just due incompetence and bad funds managing. Elon Musk is the only one today showing how much you can achieve if you have that adventure spirit and if you don't accept a NO for answer. But I was in this discussion many times.. so I dont pretend to waste more time in it. That is just my humble opinion. Also.. because I realize many times that I am capable to have better solutions for some kind of missions.. so if I am capable of that, then why not a whole agency.

Skylon really needs a big runaway as Nibb31 said.. but no sure why it needs more than one...