RECYCLING ROCKET EXHAUST
This is a concept for lunar industrial development.
Concept description
- It seems technologically possible to produce a space based solar power (SBSP) system for Earth from lunar materials, but the economics cause difficult constraints and the current geopolitical situation is very difficult.
- Investment in costly infrastructure is necessary to take full advantage of the potential low cost of achieving orbit from the moon. Many launches to orbit for a large customer are necessary to pay for the infrastructure. So, committing to infrastructure for launching to orbit and the building of SBSP should be a package deal. One or the other by itself or half-way measures do not make much sense.
- Industrial production of oxygen on the moon with depot storage should be an early step. Then depots orbiting the Earth and moon. This technology is difficult, possible, and certainly possible to get wrong. Then there is the recycling of rocket exhaust into rocket fuel by having the acceleration to orbit on Luna occur in a tube that is horizontal along the equator with the tube in a semicircular cross section ditch in the lunar regolith with an air-lock door at the downrange end of the tube. The air-lock door must be closed after the rocket leaves the tube to allow the rocket exhaust to be captured by vacuum pumps. The regolith on which the tube rests should be built up enough so the craft exiting the acceleration tube misses any landscape features. The rocket flies free down the center of the tube with guidance from RFID tags mounted on the walls. The guidance of a free flying rocket would need to have about the accuracy that is achieved in acrobatic formation flying of jet airplanes. Jet airplanes have routinely flown as close as three feet from wing-tip to wing-tip while in formation flying. This suggests that three feet clearance between the rocket and the tube walls can provide room in which the rocket can maneuver to avoid hitting the walls. The choice between rocket-sled cargo launching and free flying rocket is a matter of which technology is most easily verified by development of models on Earth.
- If acceleration in the tube averages about 30 meters per second squared then the tube on Luna needs to be about 48.3 kilometers (30 miles) long. I find "30 meters per second squared for 30 miles for orbital speed" easy to remember. A rocket-sled can use one of various deceleration techniques to use fuel recycling. A free flying rocket continues on in orbit to an orbiting depot where another tube would exist for providing delta v to deorbit and return to the moon with the deceleration rocket exhaust recycled to rocket fuel on the depot. For orbital stabilization the orbiting depot would need large, high specific impulse electric thrusters with low thrust to weight ratio which are possible with various technologies. The mystery to me is why these technologies have not been already employed, since they were all available since 1985. The low thrust to weight ratio for the orbital maintenance thrusters on the orbiting fuel depot would not be something people would strive to achieve. It would be a natural result of releasing a weight constraint in design and using every means possible to increase exhaust velocity.
- The horizontal acceleration of a rocket in a tube should start with electric acceleration of a movable launching pad for the first 4% or so of orbital velocity. The moving start of the rocket prevents the rocket exhaust from having too much erosive effect on the tube, prevents excessive pressure build-up behind the rocket, prevents the rocket from flying in its own exhaust, provides ullage thrust for the start of the rocket engines and a portion of mission delta v. A larger diameter section of tube to collect exhaust behind the launch spot may also be desired. Six feet larger in diameter than the rocket should be about the minimum diameter for the launching tube to provide the clearance to avoid the rocket smashing into the tube wall. Rocket scientists can calculate whether the tube needs to be larger at some parts of the tube to accommodate the volume of exhaust. As the rocket continues down the tube at increasing speed, the mass of exhaust gas deposited in the tube per unit length decreases. So, the diameter of tube needed to accommodate the exhaust gas decreases with distance traveled in the tube to where it is less than the diameter needed to avoid crashes into the tube wall.
- Recycling rocket exhaust provides a way of storing the electrical energy needed for launch of a cargo carrying rocket. The energy is stored as rocket propellant. That compares to the use of the amount of energy for achieving orbit as electricity in the short time that it takes a rocket to accelerate to orbital speed (about 56 seconds), a task that is undemonstrated and, I feel quite confidant, would require much more expensive infrastructure.
Mining the building materials
- Of course, remotely controlled equipment would be necessary to mine the moon; separate oxygen which is 44 percent of the moon's regolith; store oxygen in tanks; separate the regolith into constituents by electrolysis in a bath of calcium chloride, potassium chloride or potassium fluoride, with the potassium and chlorine or fluorine recycled; take the iron sponge from the anode of the electrolysis bath and purify it by a carbonyl process; form the iron and aluminum into pigs, alloys, and bar and sheet stock; form sifted regolith into sintered brick and fiber glass; build buildings, the orbital acceleration tubes, sheltered and shaded East-West roads and North-South roads, each type by its proper techniques; make the solar cells and ship products out. Astronauts doing any of those things on the moon by any means other than remote control simply could not be economically competitive. This is not a new idea. "THE MOON : Resources, Future Development, and Settlement"[1] described remotely controlled equipment doing industrial tasks before astronauts arrive on the moon before I did and did a better job of it than I can. Eventually there should be enough infrastructure built up to be able to support human workers on the moon doing tasks suitable for human beings in vehicles with suitable life support systems and in buildings with recycling life support systems; not in space suits. When people come to the moon they should be called passengers, not astronauts.
- The carbonyl process: The reason for the carbonyl process in purifying (and perhaps extracting) iron is that it can separate the iron from the nickel that is naturally in lunar iron that comes largely from meteorites. Nickel carbonyl and iron carbonyl plate out of vapor at different temperatures. The nickel is needed to put a corrosion resistant coating on the inside of the corrugated silicon steel tube that catches the rocket exhaust.
- A zeroth step in building a SBSP system is verifying the technologies. Step 0.1 is committing to all that is necessary for the whole chain of steps to work and finally start producing revenue. Within step 0.1 there are agreements among nations to share the financing, engineering, hardware building, electrical power sales arrangements, and revenue.
- For high specific impulse, large, thrusters for orbital stabilization of the moon orbiting fuel depot, the reaction mass should be oxygen plasma since oxygen is readily available on the moon.
- Transportation: For East-west roads on the moon the pavement could be graded regolith or sintered, and perhaps glazed, bricks separated by sifted regolith. There could be an East-West awning over the road held up by a row of pillars and made of aluminum sheet or aluminized glass sheet or material of suitable alloy containing some proportions of aluminum, silicon, magnesium, calcium, titanium or whatever available material is found to be most economic for the use. The pillars would separate the Northern lane from the Southern lane. There could be solar cells for charging batteries or recharging fuel cells that are swapped, spent for charged, by passing vehicles.
- The vehicles might be walking vehicles (four or more legged) that wear space suits holding one percent of an Earth atmosphere pressure of nitrogen thus eliminating the need for a gas tight rotary seal around wheel axles that would otherwise be necessary to prevent wheel lubricant (and all other lubricants inside the space suit) from evaporating into the vacuum.
- Alternatively, wheels could be outside of the pressure containing suit and supported by magnetic bearings, instead of a typical greased axle bearing, with only electric wire connections to the inside of the vehicle. The key to economic remote-controlled equipment on the moon is long-lived equipment.
- The North-South roads could be sometimes two-lane roads with a wall between the lanes and an awning hanging out over the lanes on both sides of the wall and sometimes a three lane road with two walls separating the center lane from the Eastern lane and the Western lane. The two walls would support an awning covering all lanes. When the sunlight comes from the East, the Western lane would be used. When sunlight comes from the West the Eastern lane would be used. Where three lane stretches meet two-lane stretches there is a provision for cross over as necessary to stay in a shady lane. Spurs going off to the East or West under Awnings would provide the battery exchange stations where the spent batteries are charged.
- Roads can be involved with bringing necessities to the tube construction area, such as sulfur to aid in sintering in a sulfur dioxide atmosphere. It would be possible to construct a solar power grid active in lunar day and lunar night by connecting distant spots on or near the 87th latitude North or South. Electric power by wire could flow from this grid following a road to where a fuel recycling depot is being built. If nuclear power is available at the construction site, a polar electric connection might not be necessary. Road construction could be delayed until necessary. If it is found to be most expedient to build the polar power grid and forgo nuclear power, then for three circumpolar points with always one of the three in sunlight, a road to connect point A to point B and point B to point C would be about 240 miles long. Nuclear power or no nuclear power there would be much construction activity before a 48.3 kilometer (30 mile) long tube to collect the exhaust of a rocket launch to orbit could be built.
Impacts of mining on the Moon
- People have complained that so much industrial development would ruin the pristine nature of the moon but people need to dig to get the scientific truth of the moon's composition. Where there is soil dug up and pushed around for industrial development, it will be first photographed then analyzed as much as is necessary to get a good idea of the moon's nature. The opportunity for exploration will not be missed. There are more than 9,370,000 square kilometers of lunar surface. A few hundred thousand square kilometers reserved as parks here and there might be reasonable, but not the whole 9,370,000 square kilometers.
Political context
- It is essential that peaceful use of the moon be guaranteed with treaties forbidding any weapon based on the moon or in space that would reasonably have potential for damaging targets on Earth. Treaties must include a means of verification by inspection with robots for the inspecting nation given access to a reasonable environment and electrical power sold at rates equivalent to what it costs the operator of an industrial establishment to provide this for its own robots. The plans for industrial establishments on the moon must not be allowed to be secret. It would be nice to get Russia and China to a situation in which they would cooperate with an international group of nations to everyone's advantage. There is precedent for the cooperation of enemies in the numerous treaties the U.S. signed with the U.S.S.R. and China in the past referring to the launching of satellites, the sharing of radio broadcast frequencies and the elimination of smallpox.
- With a war going on between Russia and Ukraine, there must be peace before we can have cooperation from these countries in providing SBSP to Earth. President Volodymyr Zelenski has been quoted as saying that Russia should not receive control of the Crimean peninsula in a negotiated peace. That is a proper negotiating position to start from but it seems unlikely that there will be a quick settlement that fails to leave Russia controlling Crimea. The administrative assignment of Crimea to the Ukraine Soviet Socialist Republic by the USSR[2] would indicate that Crimea should be part of Ukraine. The history of Russian military forces fighting to control Crimea, the considerable number of ethnic Russians living in Crimea and the Russian military occupation of Crimea since February 2014 tend to suggest that it should be Russian territory. The Russian invasion of Ukraine is inexcusable and terrible. There have been terrible elements of Ukraine's response which is more likely to be excused because of Ukrainians defending their home territory. The significant point is that both sides need to stop fighting without regard to assigning blame.
- We have a situation in which Russia and Ukraine are enemies. It did not need to be this way but we cannot change history. Both Russia and Ukraine have Christian backgrounds and Christian teaching favors dealing charitably with enemies when possible. Proverbs 25:21 states: "If your enemies are hungry, give them food to eat..." Mathew 5:44 states: "But I say to you, love your enemies..." Romans 12:19 states: "Beloved, do not look for revenge but leave room for the wrath; for it is written, 'Vengeance is mine'..."
- It may be difficult for people in Ukraine and Russia to imagine cooperating peacefully after the harm and destruction that has been done but if all that can be imagined is continuing war, war will go on for a long time.
- One does not need to believe Christian teaching to see that it could be a basis for these countries with a history of Christianity to reach a peace agreement acceptable to many of their people. Scriptures respected by the Jews predate the exclusively Christian scriptures on this point so Zelenski should pay attention as well.
- Things that a peace treaty might include would be: 1) an agreement to not seek prosecution for war crimes that may have occurred in this invasion by Russia and defense by Ukraine 2) a return to their original countries of anyone captured or deported to another place who is willing to return 3) interviews with any persons unwilling return, which interviews are to be monitored by neutral parties 4) provisions allowing international trade with reasonable cross border trans-shipping procedures to help both countries to return to economic productivity. There is some potential use to be made of Putin. He can carry the blame for "Putin's war". Leave him under house arrest in his dacha outside Moscow with the Kremlin controlling who does or does not visit him. It does not matter if ruling class in Russia forced this war on Putin or not. Only Russians can determine if this is practical or not.
- Other nations trying to assist in peace making will have the task of making reasonable analysis of the likelihood of Russia and Ukraine abiding by terms reached at any stage of negotiations and advising negotiations to bring about a successful end to fighting.
- Ukraine's help in setting up SBSP is desirable but Russia's help is especially needed because the international treaties needed for SBSP should be written to work with enemies being parties to the treaty forswearing use of the technologies for warlike purposes and verifying each other's compliance. Unfortunately, the attitude of Putin and the Russian leadership make cooperation with a good enemy and the whole notion of industrialization of the moon seem unlikely. We should not quit without an attempt.
- China requires a different approach. A big concern of the People's Republic is that factions of the population take the opinion that the communist party government is illegitimate and even occasionally voice that opinion. The communist party leadership correctly interpreted the Tiananmen protests as a the first step in a change of government if they were to have done nothing. The nationalist Chinese on Taiwan could offer to help stabilize dissident groups by encouraging them to diplomatically word their grievances and plead for practical relief while acknowledging the legitimacy of the current government. They could do this with trained teams of diplomats visiting groups in the People's Republic and promoting the benefit of a stable government as opposed to the chaos that can be expected in a violent change of government, acceptance of the devil one knows rather than the unknown devil to come. Teams of two trained Taiwanese with PLA armed guards and a logistics support crew could be convincing. The idea that even the Taiwanese oppose violent overthrow of the communist government would make quite an impression. In return the People's Republic would agree to no invasion of Taiwan or use of violence to take over Taiwan. The People's Republic could become the best authoritarian government that it can be. The population of mainland China would have more of its needs met. Taiwan would still be safe behind the navies of the USA and Australia. The People's Republic suspects the nationalists on Taiwan of fomenting rebellion on the mainland. Another rebellion on the mainland would not only hurt the mainland population, it would hurt the world economy. We do not need to know if the communist party's suspicions are justified. Openly and actively opposing rebellion would answer such suspicions. Give peace a chance.
- I hope and pray enough talented people of goodwill will be able to bring some sort of solution to our political troubles. I know that some groups in war have done terrible things, killing large numbers of people who had not been threatening them with violence. If it is considered impossible to make necessary treaties that can be depended upon, industrial development of the moon will need to wait until such treaties are possible.
Some alternate ideas
- As an alternative, a rocket upper stage or rocket-sled payload could leave the acceleration tube at orbital velocity leaving the first rocket stage or the rocket-sled to proceed to a deceleration track. This could accomplish a special purpose but it would introduce extra engineering considerations to be dealt with.
- Sintered brick reinforced with fiberglass cables is a possible material for building a tube to recycle rocket exhaust on the moon. A nickel coated corrugated silicon steel inner tube would be held in place by the outer sintered brick tube. It might be decided that an all-metal tube is better.
- After the acceleration tube and fuel depot on the lunar surface are completed, they can be helpful in constructing the exhaust collecting deceleration tube for the lunar orbiting fuel depot.
- People who were intent on using mass drivers to build space habitats as suggested in "THE HIGH FRONTIER" by Gerard K. O'Neill need not give up hope. Recycling rocket exhaust to make it possible to build SBSP and space habitats does not preclude perfecting better mass drivers for space transportation. The more that extraterrestrial resources become available, the more they can be used to develop more advanced technology.
- The rocket for which exhaust is recycled can burn liquid methane and liquid oxygen. Then, the Sabatier reaction could be used to add hydrogen to the carbon dioxide at the proper temperature with a proper catalyst to produce methane and water. That water along with the exhaust water could then be subjected to electrolysis to recover the amount of hydrogen added previously and the amount of oxygen that originally burned the fuel. As side benefits the lower exhaust velocity of a methane/lox rocket as compared to a hydrogen/lox rocket would result in cooler exhaust gas to collect and recycle, a smaller fuel tank in comparison to the cargo mass and a less difficult cryogenics problem handling the low temperature liquid fuel.
- oxygen gas could be used as a heat transport fluid for taking the heat from the captured hot exhaust and transferring it to shaded radiators extending from east to west along with the launch tube. Oxygen is not the best heat transfer fluid on Earth but on the moon we might take what we can get most cheaply and there is plenty of oxygen available.
Military Considerations
- An important point is that a desirable industrial infrastructure on the moon would be quite vulnerable to attack from Earth. A rocket with small warhead consisting of metal grains surrounding small explosive could ruin industrial equipment on the moon over a considerable area. The velocity of any rocket capable of reaching the moon would be sufficient to impart to metal grains in the warhead sufficient destructive potential to ruin photo-voltaic cells, electrically conductive wire, or gas filled tubes for radiation of waste heat. The explosive charge in the warhead would spread the grains out over the target area. Since there is considerable potential to use the moon for military purposes, an enemy of the United States (for example) could claim that if the United States is involved with its allies in industrial development of the moon it must allow examination of that industrial development to insure its non-military nature. Failure to allow such examination could be taken as evidence that the industrial development is military in nature and so require its destruction.
- Building industrial infrastructure resistant to such simple attack would likely make the industrial development prohibitively expensive. The more reasonable policy would be for the United States to include enemies in industrial development of the moon so that all can mutually benefit as with the treaties mentioned above.
Security Classification of Lunar Development Information
- Since there is potential military application for the industrial development of the moon, should the study of such development be classified? What would we gain from such classification? There are some techniques of using the moon for military purposes that are so simple that any halfway decent training in an engineering field make them obvious. No one can prevent the Americans or Russians from understanding some military potentials by classifying them secret. No one can prevent suspicion that industrial development will serve a military purpose by refusing to discuss such development with enemies. Rather, engaging in some industrial development on the moon without demonstrating what it is, provokes suspicion on the part of enemies that it is military development.
- It would be better to have a policy of "trust but verify" that industrial development is nonmilitary. Verification can be accomplished with robots acting on behalf of enemies of the operators of the industrial facility and on behalf of neutral parties. Just who operates which robots is a matter to be determined by treaty.
- As for myself, I can discuss the use of lunar industry for military purposes, nuclear fission weapons, thermonuclear fusion weapons, or advanced aircraft with secret features all without any restraint because I do not have an active security clearance. I have never been exposed to classified documents on any of these topics. It cannot be made illegal to discuss nuclear fusion weapons, the laws of nature that make them possible, the means by which and places from which they might be deployed. It is only illegal to reveal the contents of classified documents or discuss classified activities of and locations of the military about which a person has come to know by virtue of employment requiring access to such documents and knowledge of such activities and locations. I have no access to any classified documents, activities or locations. So, I can discuss them all. If some military official cannot understand the need for some information to be openly demonstrated, that one might reasonably consider other employment.
- However, if officials in charge of classifying documents related to lunar industrial development, for reasons known to themselves, insist on making such development secret and making open discussion by professionals in the field impossible, I must accept their decisions. I cannot even learn of their decisions.
- The apparent obsession with security classification has to do with the illusion that one nation can improve its position in the world by militarily dominating other nations. We see an example of this in the world situation about the time of the revolution of the British colonies in North America which colonies declared their independence to become the USA. England on one side with the world's most powerful military fought against its own colonies, France, Spain, the Dutch Republic and the Kingdom of Mysore in India. The military giant was brought to exhaustion of its resources by the five less powerful entities acting in consort against it; and England sued for peace. One could take as a lesson that military action against other nations leads to their looking for a chance to get back at the oppressor when the oppressor comes to difficulties. However, it is inevitable that military domination of others will ultimately only waste resources and make everyone poorer. For example, the Russians spent considerable effort with secret agents and secret police in the nations they militarily dominated after World War II. Russia lost much opportunity for economically competitive industry because they did not develop the network of cooperating industries using market price as information to govern the distribution resources. Workers and managers resorted to falsely reporting good production, more so than is common in Western Europe and the USA. Large blocks of industry in the USA use political influence to get preferential treatment through tax loopholes and loopholes in laws governing the use of labor. So, these industries get locked into inefficient practices to use these loopholes. Actually, honesty is the best policy.
- The astronaut program as we have it today is only a demonstration of superior industrial power to impress other nations at great cost. It is the shame of USA's legislators that they force such a program upon NASA when a program based upon remotely controlled equipment could result in economic development of the moon. Such development in careful stages could in time include economic activity of people on the moon. Today's astronauts are in no way heroes. They get what they bargain for, what they risk their lives for, in floating through an expensive living space with no sensation of weight. The ISS gives experience in air-lock doors and maintaining a passage between separate pressurized compartments but not enough progress in space technology to be worth nine billion dollars a year. We know weightlessness harms people. The greater time of weightlessness, the more harm. Humanity does not need more humans as guinea pigs in outer space and the guinea pig program is blocking needed space development.
- One might suspect that a worse than worthless, counter-productive, USA human space-flight program is protected from unfavorable comparison to a program of remotely controlled development of the moon which would in time include humans doing economic work on the moon by forbidding discussion of the remotely controlled program through security classification with the rational that it could possibly include some military capabilities. This harms humanity in three ways. 1) It interferes with production of treaties that could possibly prevent dangerous military development of the moon. 2) It allows a wasteful expenditure to continue. 3) It interferes with the development of economic human space-flight.
- Such suspicion is speculative but where is a reasonable discussion of the possibilities that would demonstrate that there is no abuse of security classification to protect contractors benefitting a government expenditure?
What goes on now
- I have noticed several people simultaneously becoming reluctant to discuss lunar development. I suspect there may have been a decision that studies of such potential development should be classified. So, people who might have access to official discussion of such development can no longer openly discuss it. What can be done while keeping lunar industrial development secret? Technology verification experiments can be done. A rocket can fly through a two-mile long tube made of chicken wire and mounting RFID tags. Scientists can learn how the output of inertial sensors for inertial guidance and data read from RFID tags correlate with maneuvering controls for the rocket. They learn how the data is a measurement of how straight and level the tube is in order to use such measurements to straighten the tube to be built to actually collect rocket exhaust on the moon. They can measure the effectiveness of heat transfer by oxygen gas pumped from a storage tank to a heat source and on to a radiator and back to storage with the whole system being in a vacuum tank simulating the moon. They can test remote controlled devices to assemble a liquid oxygen storage tank, devices to produce oxygen from simulated lunar regolith and store it, devices to haul liquid oxygen to a rocket on a simulated lunar surface and make fluid transfer. They can test instrument landing systems and ground navigation aids for the rockets that will bring equipment to a lunar base construction site.
- National space agencies can learn how to build a Thermal Shelter on the moon to allow their remotely controlled devices to last longer than two weeks on the moon.
- However, if they actually start to build something on the moon, there will be people who will want to know what the plans are.
- To see some discussion of argument in favor of building infrastructure on the moon see New moon base concepts.
- For a partial transcript of the original presentation of the idea at a Moon Society meeting go to Recycling Rocket Exhaust Presented at Mare Cognitum Chapter Meeting.
The benefits to be expected from space bases solar power
- As SBSP built from lunar materials continues to be installed and promoted, starting perhaps about twenty years after the start of building a landing base on the moon, there should be many various uses of electrical power that become practical as the price of the electricity decreases. Desalination of sea water to irrigate deserts and chemical processing of the material buried in land-fills to remove toxic substances that could enter ground water are possibilities. The incorporation of Whipple shields of the proper scale to protect SBSP satellites will have the effect of sweeping small debris from the geostationary orbit environment. Larger pieces of debris will need to be removed on a per each basis, perhaps by solar sail maneuvering satellites dedicated to the task.
- The construction equipment and processes used for SBSP could then also be used to manufacture solar sails in the as-deployed condition and attach them to space habitats to make humanity finally a spacefaring species. To economically construct suitable space habitats a solar sail attached to a relatively small batch of construction equipment could be sent off to Demos or Phobos, moons of Mars, to bring back chunks of rock and piles of gravel in a bag. This material would be processed into a nonrotating shell for radiation shielding for two counter-rotating steel cylinders made from lunar materials. There would be no rocket driven start-up of the rotation of a space habitat as has sometimes been suggested by commentators. When the two steel cylinders are spun up by electric motors in opposite orientations on their tracks within their radiation shield, the whole assembly will still have zero net rotational momentum. Humanity will be at the doorway to the stars.
