Exoscientist

Key points about a propellant depot based Mars architecture, once the propellant depots are in place at both departure and arrival points: 1.)A single medium-lift booster first stage, Falcon 9, Atlas V, Delta IV, etc., delivered empty to orbit can then do ALL the propulsion from LEO departure, to Mars orbit insertion, to Mars landing, to Mars liftoff, to return to Earth. No Saturn V, Constellation, Ares V, SLS, Mars Colonial Transport, or even Falcon Heavy required. The required boosters are already existing IF those propellant depots are already in place. 2.)SpaceX has shown that you can do reentry burns in the hypersonic airstream with the F9 first stage reuse tests. Then the problem of landing large masses on Mars is solved by doing a fully propulsive burn to Mars landing once that one, single stage is refueled in Mars orbit. 3.)That one single mid-lift stage could also be used to make an approx. 30 day flight to Mars. No VASIMR, solar electric, or nuclear propulsion required. However, very high reentry velocity heat shields, ca. 20 km/s instead of ca. 6 km/s, would need to be developed for this. 4.)The most important point of all: getting the propellant depots to cislunar orbit is easy using near Earth asteroids. You don't need to use the Moon's proposed water ice deposits or develop a manned lunar base. This was the most surprising calculation of all: a single Centaur upper stage, of ca. 20 metric ton(mT) gross mass, could drag a 500 mT asteroid to cislunar space. See: Propellant depots for interplanetary flight. http://exoscientist.blogspot.com/2015/08/propellant-depots-for-interplanetary.html Bob Clark

Any of the entrants use liquid fuel? Bob Clark

My favorite has always been Noctis Labyrinthus because of its frequent low lying fogs: Bob Clark

Yes. A major problem with this is normally scuba divers don't use pure oxygen. Usually it is compressed air with a normal mix of oxygen and nitrogen. In fact pure oxygen at too much of a depth can be toxic to divers: What Scuba Tank Gas Mixture do Divers use? Posted by Sandro Lonardi | October 05, 2013 | http://www.elitedivingagency.com/articles/scuba-tank-gas-mixture-divers-use/ However, as you stated astronaut's spacesuits do use pure oxygen So instead of using heavy tanks to hold the compressed oxygen it might work to carry water which would be electrolysized to produce oxygen. Bob Clark

BTW, running some numbers I think it would be doable technically to do electrolysis to separate the oxygen out of water at a much lighter weight than a scuba tank, which run about 15 kilos for about an hour's worth of breathing time underwater. To chemically separate the hydrogen and oxygen in water takes about 16 million joules of energy per kilo of water. This is at 100% efficiency. I don't know what the best efficiency actually is now but we'll see the amount that can done be using batteries is so high that likely it can be better than using scuba tanks for the same weight. The ratio of oxygen to hydrogen in water by mass is 8 to 1. So using 16 megajoules of energy you get 8/9 of a kilo of oxygen. This means 16*(9/8) = 18 megajoules gives 1 kg of oxygen. As a rough estimate take the amount of oxygen someone needs in 24 hours as about 1 kilo. Now for the weight of batteries. See this table for a list of energy densities per weight: https://en.wikipedia.org/wiki/Energy_density#Energy_densities_of_common_energy_storage_materialsy The best energy density among the commonly available batteries is the lithium battery (non-rechargeable) at 1.8 megajoules per kilo. Then to provide the 18 megajoules to get 1 kilo of oxygen you would need 18/1.8 = 10 kilos of the lithium batteries. I'll assume the weight of the system will be dominated by the weight of the batteries since electrolysis can be done simply by placing electrified wires in the water. So at 15 kilos of the batteries, the same weight as the scuba tank for 1 hour of breathing time, you would actually get enough oxygen for (15/10)*24 = 36 hours, a day and a half. Or said another way, to get enough oxygen for 1 hour would only take 10/24 = .42 kilos, less than a pound. Practical problems of course are for one how efficient is the electrolysis procedure? Also I believe the lithium batteries catch fire when wet. You would need to insure the battery casings are super-waterproof. Then there is the weight of the electrolysis components, and the weight of the tank to hold the oxygen as it is being produced. You would also need to dispense with the hydrogen in a way to insure it does not combine with the oxygen to catch fire. It might be sufficient for this to mix it with surrounding water.

Then there's this: Oxygen absorbing material may allow us to breathe underwater. By Colin Jeffrey - October 4, 2014 http://www.gizmag.com/crystalline-material-absorb-oxygen-denmark/34064/ Bob Clark

Just released today: Bob Clark

Interesting idea. I wonder how much power would be needed to extend through say 5 km to 10 km of ice. Bob Clark

Perhaps someone could do a Kerbal simulation of this: after a Hohmann trajectory flight to the Jovian system, a spacecraft can be put in an elliptical orbit around Jupiter at Europa's distance for less than 700 m/s delta-v. To limit the total delta-v required, we want the spacecraft to be gravitationally captured by Europa. Assuming we arrange the elliptical orbit around Jupiter to come very close to Europa, how long would it take for it to be captured by Europa? Bob Clark

The next survey mission, HAMO, at a closer distance to Ceres is scheduled to start at August 17th: Dawn Journal | July 29 by Marc Rayman http://dawnblog.jpl.nasa.gov/2015/07/29/dawn-journal-july-29/ Bob Clark

Thanks for the image and the calculations. Note also measurements by Mars Curiosity suggest that thin films of liquid water might exist temporarily near the surface on Mars: Evidence of liquid water found on Mars By Paul Rincon Science editor, BBC News website http://www.bbc.com/news/science-environment-32287609 Bob Clark - - - Updated - - - Correct. Clouds don't have to have liquid water. Clouds on Mars consisting of ice crystals have been known on Mars since the earliest telescopic observations of the planet. But these images are known by the infrared signatures to be clouds not dust. Here's another famous image from the Viking missions: Clouds in Noctis Labyrinthis. This image shows early morning fog in the Noctis Labyrinthis, at the westernmost end of Valles Marineris. This fog, which is probably composed of water ice, is confined primarily to the low-lying troughs, but occasionally extends over the adjacent plateau. The region shown is about 300 kilometers (186 miles) across. http://www.solarviews.com/cap/mars/noctis.htm Bob Clark

The New Horizons mission to Pluto further confirms the great interest the public has for planetary missions. The Mars Curiosity mission got over a billion hits to the NASA web page over a year. And New Horizons mission web page got 10 million hits on July 14th alone. A lander mission to Europa to explore the subsurface ocean could result in the most revolutionary scientific discovery in human history: the discovery of life on another world. Such a discovery would dwarf even the Apollo missions in importance. Then it is notable that following the commercial space approach such a mission could be privately financed at the few hundred million dollars range. This would be low enough considering the great interest such a mission would get that it could even be profitable from advertising. Then I have changed my sig file to indicate such a revolutionary mission could be accomplished at such low cost and in a near time frame. Bob Clark

Actually Valles Marineris quite frequently exceeds the pressure triple point of 6.1 mbars. For instance even at the Viking landing sites this was frequently exceeded. The problem is the pressure is still so low that when the temperature rises just a little above freezing the water will boil away. So it would be just a tiny window of temperature where the water could be liquid before either freezing or evaporating. However, the presence of salts could extend this temperature range. Do you have the link to the images ? Bob Clark

This might recatalyze the boon of space startups that arose at the beginning of this century to launch the large number of satellites that were expected to be launched then. Bob Clark

Good point. Bob Clark

You are correct. I was mixing up distance and resolution. Here is a chart showing the mission schedule; notice there is about a factor of 10 difference between the distance and resolution for the metric units: Dawn just entered into the Survey portion where the resolution will be at 410 meters per pixel. Looking forward to the next image release at this improved resolution. The best will be in December though at only 35 meters per pixel. Bob Clark

You added an extra 0 to those distances. Bob Clark

Elon Musk has said the Falcon Heavy could do a Moon landing with two launches. Jeff Greason, head of XCOR, has proposed low cost lunar missions discussed here: Exploration and the private sector by Jeff Foust Monday, July 28, 2014 http://www.thespacereview.com/article/2567/1 Bob Clark

An edited version. Perhaps to leave out the most wildly gyrating portions? Bob Clark

For those who are fascinated by a possible visit to Europa: Europa Report. 2013 PG-13 CC Amazon Instant Video Available in HD (692) IMDb 6.5/10 Available to watch on supported devices. http://www.amazon.com/Europa-Report-Christian-Camargo/dp/B00DNUF7KW I enjoyed the film, though I admit it had a Science Channel semi-documentary look to it. Bob Clark

The Planetary Society is in favor of it: The Planetary Society Supports FY2016 Budget Request for NASA. CEO Bill Nye, Space Advocate Casey Dreier Comment PRESS STATEMENT 02/04/2015 http://www.planetary.org/press-room/releases/2015/FY2016-Budget-Request.html It's Official: We're On the Way to Europa. President requests $18.5 billion for NASA in 2016, an increase of $519 million. Posted by Casey Dreier 2015/02/03 02:55 UTC NASA's Mission to Europa May Get More Interesting Still. Posted by Van Kane 2015/04/11 21:08 UTC http://www.planetary.org/blogs/guest-blogs/van-kane/20140411-nasas-mission-to-europa-may-get-more-interesting.html Bob Clark

I'm all in favor of also sending lander missions to Titan. However, the key distinction is the existence of liquid water. As scientists who have studied the life question will tell you that is the fundamental question that determines whether or not you are likely to find life. Well then, Europa has more liquid water in its sub ice ocean than all the oceans on Earth. Bob Clark

Jonboy, it's a virtual absolute (that it will take place.) One of the big propellers of Mars missions is the possibility of life or even past there. But the possibility of life is significantly greater in the sub ice oceans of Europa. And it's not just microbial life that might exist on Mars. It would be large complex life that might actually swim up to our sub ice explorer and take a look. This would be THE most profound discovery in the history of mankind. Why many experts are positive on the possibility of life on Europa: All the Water on Europa Illustration Credit & Copyright: Kevin Hand (JPL/Caltech), Jack Cook (Woods Hole Oceanographic Institution), Howard Perlman (USGS) http://apod.nasa.gov/apod/ap120524.html Bob Clark - - - Updated - - - Actually, not. A Mars Pathfinder sized lander could be launched using a Falcon 9 and currently exisitng in-space stages: Low cost Europa lander missions. http://exoscientist.blogspot.com/2015/02/low-cost-europa-lander-missions.html Bob Clark

Here is a rather unpleasant new proposal, not yet approved for humans: New in mortuary science: Dissolving bodies with lye CONCORD, N.H. By Norma Love, Associated Press http://abcnews.go.com/Technology/story?id=4828249&page=1 Bob Clark

The head of the committee in Congress overseeing NASA is a strong supporter of not only a Europa orbiter mission but an actual landing mission. This means it's very likely to be approved: A Europa lander is possible, JPL scientists say, and Congress appears likely to support it. Posted on May 8, 2015 | By Eric Berger http://blog.chron.com/sciguy/2015/05/a-europa-lander-is-possible-jpl-scientists-say-and-congress-appears-likely-to-support-it/ However, rather than the $2 billion cost being estimated by NASA, such a mission could be undertaken for costs in the hundred million dollar range if we only sent a small size lander of the Mars Pathfinder/Sojourner variety. The reason why I say this is the delta-v requirements to land on Europa are surprising low once you arrive in the Jupiter system and use a Ganymede gravity assist: Europa Cryo-Ocean Exploration Submersible (ECOES) Project. Preliminary Design Report http://www.lpl.arizona.edu/~jmoores/ECOES.pdf However, when I discussed this on another orbital simulation forum, some members did some calculations disagreeing with these numbers. What do the Kerbalites think? Are they reasonable? Bob Clark