moonguy

Couples would not necessarily be chosen to 'work on the same project'. They would have different jobs within the context of a colonization effort. One being an IT manager while the other is a hydroponicist is an example.

This presents an interesting question: How much propellant is needed to get a crewed payload to Mercury if it is one-third the mass of a crewed payload used for a Mars missions? As the post notes, delta-V to Mercury is roughly three times that for Mars. A crewed payload, however, would be much lighter, for several reasons: 1) Typical ballistic flights to Mercury are about 43% as long as those to Mars. This reduces food/consumable needs accordingly. 2) The reduction in consumable mass also means a reduction in vehicle volume - hence structural mass - for the crew module while maintaining the same volume ratio per crew member. 3) Flights to Mercury are always closer to the Sun than 1 AU, requiring less mass for a (assumed) photovoltaic system compared to a Mars vehicle. 4) Crew size matters. We are used to thinking of Mars missions with four or more crewmembers. Credible Mercury missions can be flown with crews of three, though, of course this would not be a straight up, al-things-equal comparison. This reduces consumables even further for a total mission payload mass that reaches about one-third the Mars mission payload value. This issue here is not whether Mercury is 'less expensive' than Mars. It probably is not. The issue is whether Mercury can be reached for costs less than the three-fold (compared with Mars) delta-v figures would seem to indicate.

You are correct. The delta-V for the crew vehicle must be the same for the Cycler. The difference, compared to classic concepts, is that there is only the crew module to be boosted as payload. In traditional approaches, the payload boosted away from Earth is the crew module AND a stage for insertion into orbit over Mercury. In the Cycler concept, the 'free lunch' is not free, it is just paid up in the form of solar sail deliveries of propellant to the Cycler prior to the crew's departure from Earth. These require no propellant at all for Earth departure or rendezvous with the Cycler. A square sail 820 meters to a side weighing just 4000 kilograms can deliver 10-ton cargo masses (propellant, supplies etc.) to a Cycler in flights of about a year from Earth. A typical insertion to Mercury orbit might require 50 tons of propellant. This allows a fully supplied Cycler to support several crews over about five years of missions.

How would crews get to Mercury? Is there any way we can beat the high delta-V penalties for classic style ballistic flights? Yes, there is: Cyclers. Mercury’s orbital period is 87.97 days. Earth’s is 365.25 days, or 4.15 Mercury ‘years’. A cycler deployed to a 351.5 day orbit, with Earth’s orbit as the aphelion and Mercury’s orbit as the perihelion, will encounter Mercury every time it (the cycler) reaches perihelion. Crews departing Earth would still have to generate a high delta-V. In fact, cycler missions would require a delta-V around 9.5 km/sec. while some standard (‘Hohmann’) transfers can be done for 6-7 km/sec. The difference is that a cycler mission puts most of th payload mass required for the ~176 day transfer time on the cycler. This drastically lowers the payload mass injected into the transfer. In a classic Hohmann transfer scheme, a manned payload would be injected with an upper stage able to effect the Mercury rendezvous and orbit insertion. For a 10 ton payload and a stage using a J2-X engine, a mass ratio of at least 4.1 would be needed for even the most favorable MOI delta-V, which is about 6.3 km/sec. The resulting stage would be about 60 tons. Pushing this into a transfer orbit from Earth would require a stage which also has a 4.0 mass ratio – and hence masses over 100 tons by itself. The cycler reduces the requirement to launching the crew in their Earth-return capsule. This could be an Orion, A DragonRider derivative or something similar. If it had the same 10-ton mass as the first example, it would not need to be boosted with a second stage. Instead, propellant for the maneuvers at Mercury would be derived from water stored on the cycler. Food and living accommodations would also be on the cycler as well. A 15 ton cycler could easily store enough food and consumables for several mission cycles. These supplies would be replenished to the cycler periodically by the same solar sail that deploys the cycler to the 351 orbit. The water used for propellant would also be supplied using solar sails. Initially this would be from Earth, but it would eventually come from Mercury. With an orbit of 351 days, the cycler would encounter Earth every third orbit of the cycler. This is due to the synodic period of Earth and Mercury is 115.9 days. Multiplied by three yields 347.7 days. There is just over a 4 days discrepancy between an exact encounter., However, launch windows to Mercury are open for about 20 days, so it could be assumed a delta-V penalty would be incurred to make up for the 4-day difference. The cycler mission requires much less propellant be available in Earth orbit. Only one stage is used. This is refueled at the cycler for the MOI burns and again for the return to the cycler for the return trip. If the Earth-entry interface velocity is too great for the return module’s heat shield, the crewed stage could refuel a third time to execute a burn into Earth orbit. This architecture enables a crew to launch to Mercury every 347 days. Twice as frequently as flights to Mars.

Methane is not corrosive on human skin. LIQUID Methane is a no-no on human skin, but that is not at issue here. Human lungs cannot convert Methane into anything useful. Alveoli in the lungs require a very narrow range of pressure and humidity so the question of whether humans could operate with just an O2 mask is dependent on that. My guess is 'No' because Methane can saturate human tissue to toxic levels. I have something in my files about all this and will dig up the figures if you need. For now, I recall at least one source that indicated Earth's atmospheric pressure was somewhere between 1/2 to 2/3 what is now. There are other sources with different estimates. Storms? Tornadoes? Hurricanes? Definitely. This is not particularly dependent on chemical content of 'air' but energy balance (or lack thereof) between solar heating and cooling. A Methane atmosphere would definitely have a different cooling rate from the current atmosphere but at this distance from the Sun - and the extent to which volcanic dust was present in the air -its likely Earth was much warmer than now. People might want to live anywhere. There was a TV show, 'Terra Nova', about a group of people who chose to live on an earlier Earth - with dinosaurs. Go figure. Said TV show is available on Netflix. A colony's feasibility is really about the ability of inhabitants to understand and deal with challenges from an environment and the extent to which they are equipped to. So I'm thinking 'Yes', an early Earth colony could be feasible. Perhaps the earlier Earth was where Isaac Asimov's 'Founding Fathers' landed - not realizing they had broken the time barrier.

Agreed. I never bought the logic of doing one or the other.

As usual your post has a lot of good perspectives on the Aquarius Colony idea. There are a number of particular points that should be detailed for perspective. . . Skylab had a total ‘working’ volume of 330 m3. The Aquarius’ Liquid Hydrogen tank alone was 23 meters long by 4 meters in diameter. It had a volume of 272.2 m3, or about 82% of Skylab’s. When you add the volumes of the gaseous Hydrogen tank (33.6 m3) and the 8.4-meter long LO2 tank (88.7 m3) the total working volume is 394 m3, exceeding Skylab’s by 64 m3. As a visualization, the LO2 tank alone presents more habitable volume than the two decks of the Space Shuttle crew module combined. Yet NASA was totally comfortable with seven-person crews flying missions up to two weeks on Shuttle. If you consider just one LH2 tank/module as a bunkroom only, like a Pullman car way back when, with three tiers of bunks to each side of its centerline, you get 110 bunk spaces. Only nine modules would be needed to accommodate 1000 people. Though that better describes a space station of the type Von Braun had in mind where crews had temporary tours of duty and private space was not considered so important. It should be noted that the 100 module figure only defined the modules in the habitat ‘ring’. Also, that was not ‘100 flights to supply the ISS’ as a program. That was the expected production/launch rate per year for the rocket as stated in the company’s business plan. Most of those would go to support ISS, but they expected other customers as well. The rationale behind the use of Aquarius is that the standard mission profile puts the rocket into a stable, if temporary, orbit. It is almost like having a small (23-ton) space station launch itself into orbit. The Bigelow modules you mentioned still need a separate launch vehicle and they also need retrieval in order to be integrated with other modules. In that sense, they are no improvement over Aquarius tankage. Also, I doubt these modules can be built for the $4 Million cost of the Aquarius. I agree with your suggestion about several revenue streams being possible. From a business point of view, this colony would be applicable to an orbital hotel. We have already seen people spend real bucks for short stays on space stations that were in no way designed for ‘tourist’ applications. Aquarius colony could offer more and accommodate more people. Another revenue stream would come from modules being rented out to NASA. If the colony is designed along a Mars gravity level, it would be a natural for training Mars-bound astronauts. Space Systems/Loral estimated a development cost for Aquarius of about $200 Million, which included construction of a factory and purchase of a barge fleet to launch the rocket. Transportation costs are a concern, but if you review concepts such as the ‘Phoenix’ system developed by Gary Hudson and others in the 1980’s, the prospects are not so dismal. They had projected development costs for Phoenix that were about $600 million in today’s dollars. By comparison, Boeing’s 777 aircraft was developed for about $4 Billion in the 1990’s and was considered high risk due to its innovative technologies. This suggests to me that if there is a place for such a system to fly to, there can be sufficient grounds to execute loans for development of a Phoenix-type system. Aquarius can provide that ‘place’ sooner, faster and at less expense than any other option.

While I agree with the basic sentiment of your point about nuke waste, the practical issue is that unless we boost nuke waste to solar escape velocity, we will have to deal with it again. Hmmmmm. Change 'nuclear waste disposal . . .' to 'Solar sail manufacturing'?

CORRECTION!!!! That was not a large Helium sphere on the Aquarius. . . It was Nitrogen. My apologies!

Five things to do with a Lunar Base: 1) Incoming asteroid detection & interdiction. 2) Earth satellite retrieval, repair, refurbishment and repurposing. 3) Very much upgraded Deep Space Communications Network. 4) Nuclear rocket development facility. 5) Nuclear waste disposal/treatment facility. These are not glamorous, high-ticket tasks for a Lunar Base. But each of these tasks are important and can potentially be money makers or at least be self-sustaining financially. They all require at least a few people. This goes beyond 'flags and footprints' or spending billions 'just to collect rocks.' We have to start somewhere. . .

I see your point. Ironically, this is a subject of one of my future postings regarding Mercury colonization. I wonder if we would do it if the best planet we could find was a lonely outpost planet no better endowed than Mars for survival?

I seriously doubt we would attempt interstellar colonization with just one ship. That said, we should reconsider strategies that have people in deep sleep or hibernating or frozen for the journey. This actually multiplies the chance for failure as it takes the anticipatory and reactionary capabilities of the human mind out of circulation. Human history is all about meeting challenges - but not while we are sleeping.

Mars is the big plum in NASA's manned space program. Unlike other planets, when the discussion shifts to Mars, it is not about 'exploration'. It is about 'colonization'. Quite a few environments on Earth are unoccupied even though they are easier and less costly to reach and survive in. No matter. NASA wants to go to Mars, so we are going to Mars. How can a settlement on Mercury help such an effort? Skyscrapers, football stadiums, aircraft carriers. . . They all are designed to support the habitation of hundreds or thousands of people. If only on a temporary basis. Colonies on other planets are likewise designed to support large numbers of people - but on a permanent basis. A Mars colony could easily be compared to a skyscraper - only one with very large gardens, some factories and a rocket propellant plant nearby. Think Chicago's Sears Tower and O'Hare airport combined. The point here is that for any group of people put anywhere permanently, it is absolutely certain there will be more mass required by a factor of ten or more then the person themselves weighs. Right now, the largest rocket NASA has plans for could put something close to 25 tons of actual payload on Mars' surface. It would be at a cost of about $60,000.00/kg. NASA thinks this is a reasonable proposition. Ok. But there is a problem. That largest rocket can be launched two at a time. At best - if we care about safety - we could launch two every 20 days and build an entire fleet of Mars-bound payloads - and their stages - in earth orbit. If we except the Earth-Mars synodic period of ~780 days as a working figure, divide by 2 launches every 20 days, we ultimate have 78 payloads ready to go when the launch window opens!!! At a combined cost of $117 BILLION dollars. It gets worse. If you send people, you have to subtract those flights because they only bring people, not construction material. Those are just launch costs, by the way. They do not include the operation of a station(s) in orbit that can sustain that rate of deployment. You need those stations because the departure stages have to wait ('loiter') up to 26 months to fly and they are only designed to loiter for 3, maybe 4, months. Take a breath. Pour another cup of coffee. I'm only just getting started. . . With just one exception, no in-space transportation technology known to man will help the above scenario because the problem is not the Earth-Mars transfer. It's getting the construction material off Earth in the first place. Getting the construction materials from the Moon would help, somewhat. If you built the rockets from lunar materials and fuelled them from lunar water would not help because you have to build the base first creating yet more need for Earth-launched materials. Frustrating, but how does Mercury make any difference? Mercury can do the same things as the Moon to provide construction materials. It's just there are some huge differences. . . Mercury has no launch window bottleneck. With three launch opportunities per year to Mars, Mercury would need to produce and deliver only one-seventh the mass at each opportunity to keep pace with Earth capability. Since solar sails would be the transporter-of-choice from Mercury, the demand for chemical propellants there would be very modest compared to any Earth/Moon launch scenario. Carefully note I have not specified either a payload mass or sail size. Depending on exact costs for NASA's SLS, it may prove cost-effective to use smaller launchers at Earth to deploy payloads to Mercury with solar sails. Mercury's 20-fold THERMAL energy advantage over Mars makes utilizing poor-grade regolith materials a practical proposition without resort to (billion-dollar) nuclear power systems. If we did not know how to safely utilize heat like that, we would not have steel mills. Earth could use solar sails very effectively to send payloads to Mars. This would not resolve the bottleneck problem. The only way Earth can compensate for that is to somehow put seven times the payload mass onto a sail that will be inherently less efficient than its Mercury-launched counterpart because it is starting flight from 1 AU. Or deploy seven times as many sails to carry reduced payloads. Or deploy MUCH larger sails. Either approach results in greater cost-per-kilogram delivered than the Mercury alternative. Overall, construction material for a colony anywhere will make up 90% or more of the mass to be shipped. Air and water may be the greater share of the final mass, but they are both available on both Mars and Mercury. Mercury is better able to produce and ship the 10,000 tons of a Mars colony's deadweight mass. Mercury can do this without relying on SLS elements indefinitely. Mars really does not have that option.

While I applaud your acumen in orbital mechanics, I found most of this posting unnecessary. You took great pains to elaborate on the 'difficulty' of the easiest part of the mission! Boosting hundred-ton spacecraft away from Earth so they can project themselves into an orbit over Mercury. . . THAT is the difficult part of the mission!! Making the ~3.1 km/sec. descent for a vehicle with payload well below five tons is easy by comparison. For an engine like the RL10-A-3 series,(Isp 465 sec.) using LO2/LH2 at 5.88:1, you need a mass ratio of 2 for such a mission. So what is this bizarre notion about aircraft carrier arresting gear? As for the 'business' issues, what is space transport technology all about if not cost reduction? That is a discussion I hope we have when I've completes a few more posts. . .

Settlements on Mercury are better placed to support - at reasonable costs - aggressive programs of exploration to all of the bodies in the Solar System. From Mercury, it is possible to launch probes to Venus twice a year. Launches to Venus from are possible only every 1.6 years. Mercury could send three or four probes to Venus for every one Earth could launch. For Main Belt asteroids, the ratio is three or four per year to any given asteroid. Jupiter and all other outer planets have four launch opportunities per year from Mercury. Using solar sails, Mercury could launch a program of exploration that would dwarf what has been accomplished so far from Earth. More frequent launch opportunities means a given probe can be more specialized as the capabilities of one large probe can be divided amongst a series of probes, all launched within a few months of each other. If launched from Mercury, the smaller probes require much smaller rocket vehicles for launch form Mercury's surface and no rocket after that at all of they use solar sails to get to the destination planet. If that planet is airless, they would only need a small lander stage, because all of the planets beyond Venus that have solid surfaces - with the one exception of Mars - have gravities less than the Moon's in strength. This would be important for places like Jupiter and Saturn where each have several, large satellites. Individual probes could be partially built on Mercury by having the more high-tech instrument packages sent form Earth and installed on structural frames made on Mercury. This reduces Earth-launch weight as it enables a smaller rocket launched from Earth (with several instrument packages) to support several different missions. Normally, that smaller rocket (Falcon 9? Atlas V?) would only support one mission.