Steps to Space
Still in progress, many errors and omissions ...
Consider the below as part of a ghost of an outline for a forthcoming book, Mind Meets Sun
Neil Armstrong's "Giant Leap For Mankind" was one step among trillions, by billions of people for thousands of years. A milestone, but there will be thousands of milestones on the way to a living cosmos. Life found ways to profit (derive benefit from) every step along the path from inert matter to an Earth filled with life; as Earth life's ambassadors to the universe, so will we.
This webpage lists a series of steps we can take to the stars. Some steps are dependent on others, but the ordering presented here is one of many possible ways of sequencing those dependencies.
Some major milestones are:
- worldwide longterm prosperity
- space biology testing
- digital immortality
- server sky
- launch loop
- apogee capture
- space solar power
- lunar materials
- complete space industrialization
- space settlement
- taming the solar system
- lunar NEO interception
- a Stapledon-Dyson shell
- preserving life on Earth beyond the Sun's lifetime
- filling the galaxy with life
Some steps to these milestones follow. Most elements and paths can be replaced with other paths; the essential requirement is that every element produces a direct profit to fund future growth.
Server Sky Technologies
Kilogram Server Sky
First experimental thinsats strung together in 250 gram "box kites". Profits from kickstarter sales, chip radiation testing, scientific data collection in the van Allen belt, particularly particle trajectories and energies. See HitchHiker for details.
Space Radar Server Sky, Space Debris Ephemerides
Thinsat arrays will make excellent transmitters and receivers for 60 GHz radar; hundreds of kilowatts of pencil-beam chirped energy and hectares of receiver area, backed by petaflops of computation and correlation. This permits a complete and precise mapping of space debris to sub-gram object size, allowing space assets to maneuver away from (or intercept) threatening debris objects.
High Bandwidth ISS connectivity
Probably the best way to move terabit data to and from ISS is with optical links to relay satellites in GEO. However, GEO is crowded; server sky links are an alternative, with shorter round-trip times to Earth. Shorter delays facilitate predictive-adaptive telepresence. Imagine complex "kilo-robot" space factory prototypes attached to ISS; perhaps a large chicken-wire cage containing thousands of robots, work objects, cameras, and telemetry links. A large server sky constellation of thousands of arrays (perhaps 100 tonnes in orbit) could send and receive terabit data from ISS, while keeping "view and control" round trip times below 200 milliseconds.
Developing World Data Server Sky in MEO
Petabit data service to the cell towers serving three billion tropical people. The goals are to provide education, global connection, and digital employment opportunities to these people. They will be able to shape the global economy and contribute their cultural wisdom to the world without leaving their families. Worldwide longterm prosperity Server sky thinsats will be cheap enough for them to own as capital goods, providing collateral for credit transactions and assets protected from local corruption. Perhaps 1 terawatt of computation services delivered from 12789 km radius MEO orbits.
Second Generation Server Sky
MEO thinsat orbital stability requires a minimum mass of 100 grams per square meter (in sunlight); however, thinsats can be manufactured thinner than 10 grams per square meter, with on-orbit ballast added to stabilize orbits. Lumps of mass from space debris and retired thinsats are a good source of this mass, providing a profitable path to debris-free orbital space. Assuming 200 watts per square meter (averaged over the orbit, including self-occultation and night-side eclipse), that is 2 kilowatts per kilogram, and 1 terawatt of thinsats would be 500,000 tonnes. That might be composed of 50,000 tonnes launched from Earth, 10,000 tonnes of space debris and recycled thinsats, and eventually, more than 400,000 tonnes of lunar regolith welded into 2 gram ballast blobs.
Cutting up debris into ballast, and the production of regolith bricks, will be the first baby steps towards space manufacturing.
Radiation Belt Remediation by Server Sky
500,000 tonnes and 5,000 square kilometers of metal foil in MEO orbit will Rutherford-scatter radiation belt particles (mostly protons and electrons) into longer pitch angles, trajectories that intercept the upper atmosphere. That will rapidly deplete the belt regions that Server sky orbits through (L=1.8 to L=1.2 or so), creating a low-radiation zone that slowly spread as magnetic storms perturb neighboring belt regions into the depletion zone.
Thinsats will detect particle flux in order to predict and compensate for radiation-induced computation errors - precise time and space mapping of those particle events will generate exabytes of radiation belt scientific data. The van Allen belts will go away, but we will have excellent scientific records of what they used to be.
War-proof Space Assets
Server sky arrays may be disrupted by megaton nuclear weapons blasts within a few kilometers, but the radiation flux from a weapon will be only a year or two worth of natural radiation. The energy and momentum flux from the blast will deposit uniformly across the thinsat and the array, so the thinsats can thermally anneal radiation damage and reassemble as an array. Since radar-mode server sky arrays can compute a precise trajectory and launch source for the weapon, the culprit nation can be identified, isolated, and data-starved back to prehistoric poverty and cannibalism. Out of mercy, I hope a wealthy and civilized world will rescue and re-educate their innocent children, while documenting the brutal self-destruction of their insane parents.
Scientific and Commercial Computation at L4/L5
Humans and automated global stock trading demand fast response times from MEO server sky, but scientific data collection and computation (and the future equivalent of block chain computation) can tolerate 2 second round trip delays, from Earth to the Lagrange points. Inverse-square attenuation at 60 times the distance from the Earth's surface permits 3600 times as much illumination for the same night-sky light pollution as MEO server sky, with rare eclipses rather than 1/6 shading of the MEO orbit. More than 4 petawatts of computation power, 50 times the 80 terawatts of electrical grid energy that a rich and optimized planet Earth of 8 billion people might consume. Orbit stability mass requirements unknown; presuming 2 kilowatts per kilogram as before, that is 2 billion tonnes of thinsat. This will benefit from in-orbit manufacturing, with microchips and beneficiated elements from the Earth, and more common elements (oxygen, silicon, aluminum, iron, sodium, magnesium, and titanium) from the Moon.
Dangerous Biological Experiments in Lunar Orbit
While we can do much with computational biology, artificial lifeforms worry many people. While some worrywarts are ignorant, stirred up by equally ignorant demagogues, peer-to-peer server sky education can cure most of that; as Justice Brandeis observed, It is the function of speech to free men from the bondage of irrational fears. We can reduce real hazards to negligable proportions by testing artificial lifeforms in kilogram-scale experimental labs in lunar orbit, connected with high-bandwidth communication to L4/L5 arrays. Lunar orbits are unstable, they will eventually be perturbed into a surface impact. While we should try to direct these impacts into small "toxic waste dumps" on the Moon, orbital mechanics will prevent this material from ever reaching Earth, while cosmic radiation and Solar UV will add additional safeguards. This may seem like extreme paranoia, but eliminating parts-per-trillion risks to life on Earth is necessary for multi-billion year planetary survival.
As we spread into the solar system, we can move these experiments to inner orbits of Jupiter, inside heavily shielded containers. Nothing can accidentally escape Jupiter's gravity well besides broadcast information.
An 50 AU diameter ice substrate statite shell of nano-engineered computation, converting sunlight leaving the solar system into computation and 60 Kelvin infrared radiation. 380 trillion terawatts are available, and this will increase as the Sun evolves.
In the distant future, in construction for perhaps 1 million years. Most of that time will be needed to disassemble Oort cloud objects without vaporizing them. Some of the mass will be ejected from the solar system as targeted interstellar probes, ejecting the excess orbital angular momentum of the source objects.
Portions of the shell will act as an X-ray scattering barrier for the Earth when nearby stars go supernova, while the rest of the statites will turn edge-om to the flux, mimimizing absorbed dose and off-axis scattering. Interstellar expeditions to supernova candidates, monitoring core neutrino flux to measure the elemental composition of the core and predict exactly when the supernova occurs, will be part of the long term strategy for protecting nearby solar systems with life-bearing planets.
The Earth is finite. Whether it can support 8 billion people over billions of years, or less, if we choose to have children, we either die or go elsewhere. Meanwhile, the neurons in unmodified human neocortexes are not replaced after development (pregnancy and a few weeks after birth), so even if we keep every neuron alive somehow, we face hard limits on the capacity of those brains.
However, we will someday internalize our digital tools, connecting them directly to our brains, speeding input and output, and more importantly conveying sensory data and adding manipulation capabilities that natural brains lack. Perfect memory, predictive-adaptive telepresence, the list of possibilities are endless, and plenty of early adopters willing to risk their lives and their sanity to try the new technologies first. The rest of us will learn from their mistakes and their successes.
In a few decades, there will be people who are mostly enhancement - as their bio-brains decay, their enhancements remain and fill in the gaps, until the bio-brains and bodies fail and the enhancements continue. Again, a dangerous and error-prone process, but so evolution, and biological life in general.
The Earth is a hot, corrosive, confined, resource-limited place to keep electronic intelligence; digital personalities will soon escape the Earth and into the abundant resources of the Stady shell.
Because the Stady shell is cold and stable against thermal damage, it can operate with 5x lower power per logical operation than the best possible electronics on the 300 Kelvin Earth. Neural operations are perhaps 25,000 electron volts each, and a "Shannon limit" digital operation might be 0.02 electron volts at 300 Kelvin, so a stady shell operation might be 0.004 electron volts, 1.6e-7 of the energy used by a neural operation. Even with 600 times the power (mostly for signal propagation, error and damage repair), a 20 watt human brain might be emulated with less than 2 milliwatts. There's room in a solar system Stady Shell for 2e29 human-scale minds, enduring for 10 billion years; in the whole galaxy, perhaps 1 billion times more.
There is no need to damage the Earth to do this; indeed, a vast amount of the shell can be devoted to protecting and enhancing the Earth into the distant future. That is 1 digital mind for every 25 living bacterial cells on Earth - even if only a tiny fraction of those minds focus their attention inwards, they can blanket our home planet with enough love and attention to keep it alive for a very, VERY long time.
Launch Loop Technologies
Diamond-coated iron pipes ("rotors") moving in moderate vacuums at 8 to 20 kilometer-per-second velocities can store enormous amounts of energy and momentum, and be deflected by Tesla-scale magnetic fields into loops and structures above the atmosphere. Magnetic attraction is unstable; measurement, computation, and electronic control is required for stability. However, control frequencies range from 1 to 100 KHz, and chips can perform trillions of computations per second, distributing the results over fiber optics 10,000 times faster than the rotor moves.
The vapor-deposited diamond coating will be thicker than diamond hard disk platter coatings, and thinner than tool coatings. This is a well-understood industrial process; the purpose is to reduce "spalling yield" from small particle collisions. The Launch Loop website has much more information.
Terrestrial Power Storage Loops
The energy densities of fast moving rotors are high; an iron rotor (density 7870 kg/m³) moving at 8000 meters per second stores 70,000 KWhr/m³, the output of a gigawatt power plant for 4 minutes in about $100 worth of iron.
A practical exaggeration - the iron will be formed and machined into bars or pipe perhaps 5 to centimeters in diameter, and positioned with electromagnets and above the track and inside the turns. The electromagnets, sensors, vacuum containment and tunneling to hold the rotors will be far more expensive.
Small loop ring velocities are limited by magnetic field strength, rotor mass, and turn radius. A 9 kilogram per meter, 5 centimeter diameter round rotor in a 1 Tesla control field moving at 8000 meters per second has a turn radius of 14 kilometers. If the rotor and tunnel are in a racetrack oval, two "D" magnets at the end with 100 kilometers of track between the ends, the total length of the rotor is 288 kilometers, the mass is 2600 tonnes, and the power storage capacity is 8.3e13 joules, or 23 gigawatt-hours. Many rotors can share most of the same tunnel, though care must be taken to prevent "fratricide" in case one of the loops fails catastrophically. Occasional diverters and "mass dumps" along the path will allow one power loop to fail without damaging neighbors.
The rotors are NOT under high tension; the stiffness of the pipe simplifies the control system in the D magnets. Energy is added and subtracted with linear motors, whose losses are proportional to thrust, not speed. Linear motors can be 99.9% efficient at high velocities.
8000 meters per second is a "magic" number; an 8000 m/s rotor following the curvature of the Earth is in orbit. Forces will increase to full gravity as power is removed and the loop slows down. The upper magnets must be strong enough to hold up the rotor against full gravity, and plus or minus perhaps 5 gravities in case of an earthquake, with accommodations for shear faults along the path.
Small systems are not nearly as efficient and cost effective; if the turn radius is small, the maximum speed is limited and the energy density is too. On the other hand, rotors moving much faster than 8000 meters per second must be held down to follow the Earth's curvature, dissipating power in deflection magnets along the entire length of the straightaway. Above 20,000 m/s, the spalling yield of a loose atom in the plenum between rotor and track can exceed unity, leading to a hypervelocity spalling cascade. This is the reason for the diamond coating - diamond is very strong, and carbon atoms are relatively light, compared to iron or steel.
A better location is deep underwater, far from shore at the edge of the continental shelf. The water provides mass shielding. Floats can hold the rotor above the sea bottom, anchored with cables that can be adjusted for shear faults. Very large power loops can encircle the Pacific Ocean, injecting or withdrawing power from the western or eastern hemispheres at appropriate times of day. Indeed, since the turn radii are so small, the rotor can be made evem more massive compared to the deflection magnets. The power used for normal deflection can be a tiny fraction of stored energy, so the power loop can store energy efficiently for years. An 8000 m/s Pacific ocean loop perhaps 30,000 km in circumference and massing 100 kg/m can store 9.6e16 joules, 36 gigawatt-months. 1000 such loops could supply the northern hemisphere with 9 terawatts for 4 months.
Rotor dumps can boil sea water mixed with iron vapor. The dissolved iron might cause a small algae bloom, increasing fish populations. Hopefully, these expensive events will be rare.
These are huge systems, though the cross sections are a fraction of a meter. They are assembled out of millions of identical units, so they can be mass produced and deployed robotically. They can store peak load from summer overproduction of terrestrial solar photovoltaic farms, and deploy that power in winter for heat pumps in hundreds of millions of homes.
Powerloop is a profitable way to earn money, develop technology and manufacturing capability, and provide power in midocean.
Earth Launch Loop
Mid-ocean power can be used for launch loops near the equator. The launch loop stores power and momentum in a 3 kg/m rotor loop moving at 14,000 m/s. This is faster than orbital velocity, so significant downwards force is required to hold the rotor in a curve around the earth, supporting about 7 kg/m of stationary track and stabilization cables to the surface. A sled with long rails of permanent magnets can extract momentum and energy from the rotor (slowing it a bit, and heating it a lot), and push a 5 tonne space vehicle up to escape velocity.
This can "throw" payloads into transfer orbits with up to 11 km/s. In plane with the loop; inclination changes and apogee insertion will require still rockets. However, most of the interesting "destinations" are in near-equatorial orbits, and specialized loops can be inclined to launch into high inclination (sun synchronous, ISS, or globe-coverage constellation orbits like GPS.
The 1980s version of the loop extracts both energy and momentum from the rotor, resulting in significant rotor heating. This reduces energy efficiency to about 40%, and limits burst launch rates to 400 tonnes per hour (global launch rates in 2016 are less than 400 tonnes per year). However, the kinetic energy of an 11 km/s launch is 60 Megajoules per kilogram; at a wholesale power cost of $0.12 per kilowatt-hour and 40% efficiency, that is $5/kg energy cost. If launch services are sold for $30/kg, and the loop launched 3 million tonnes per year, that is $90 billion revenue and and a $6 billion power cost every year. Construction costs and operating expenses are difficult to estimate, but if large scale loop manufacturing and ocean deployment capabilities already exist for the power loop, launcher construction is far less risky.
Note: The 1980's version of the launch loop specified a launch path at 80 kilometers altitude. Atmospheric density at 80 kilometers is 18 ppm of surface density, which causes significant drag and vehicle nose heating. However, the "thick" atmosphere also deorbits smaller space debris rapidly, reducing tangential debris flux at low altitude, and the probability of catastrophic impacts, a protective effect. However, Radar Server Sky (see above) can detect and characterize potential impactors. Thick robot shields can travel along the sides of the loop and block incoming impactors; in addition, the loop can move up or down to dodge them if their paths and decay rates can be accurately characterized. Debris orbit decay rates (and associated uncertainties) are proportional to atmospheric density. Although debris flux is higher at higher altitudes, with an accurate ephemeris it is easier to avoid. Hence, the 2016 version of the loop (work in progress) will have a launch path at 120 kilometers, where the residual air density is 18 parts per billion of surface density. The power flux at the blunt nose of a vehicle moving at 11 km/s is 15 kW/m², corresponding to a black body temperature of 1700 Kelvin; fortunately, much of the heat will end up ionizing air and radiating away, so the nose temperature will be lower.
Other recent upgrades studies explore coupling energy and momentum from the rotor through thin flat coils in the track, pushing the track backward as well as slowing down the rotor. This will use rotor energy more efficiently, reduce heating, and increase launch mass and frequency for a 3 kg/m rotor. Perhaps that could increase energy efficiency above 80%, while tripling the burst launch rate.
Note 2: In the science fiction novel The Last Theorem by Sir Arthur C. Clarke and Fred Pohl, the "Lofstrom loop" is claimed impossible because of friction. Hence, Sir Arthur is guilty of violating Clarke's first law, When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.. What an honor!. Fred apologized to Keith Lofstrom in a private letter, but hey, for a chance to co-author Clarke's last novel, most science fiction authors would strangle and eat their firstborn child. I gladly forgave Fred, given the Sir Arthur's inadvertent complement.
Laser trajectory correction
The launch loop is a precision instrument, but not perfectly accurate. Some velocity tweaks will be needed. If the vehicle has ablative rubber panels on the sides, the surface can be ablated with powerful orbiting lasers to produce correction thrust. With server sky radar and vehicle retroreflectors providing micrometer interferometric accuracy and μm/s velocity estimates, vehicles trajectories and destination location can be adjusted to millimeter precision. We measure LAGEOS satellite positions to micrometer accuracy from ground observatories through a refracting atmosphere; in vacuum, optical measurements will extremely accurate, and laser ablation thrust exquisitely adjusted. Space launch can become a 12 digit precision technology.
A large fraction of the cost and risk of operating a launch loop is apogee insertion, a delta V of 1500 m/s for GEO with a 5% plane change. Done in the traditional way, this involves a chemical rocket (also known as an explosive bomb) strapped to the back. With millimeter precision delivery, payloads can be delivered to capture systems, such as capture rails or tethers attached to relatively heavy destination stations. This will remove momentum and energy from the destination station; however, if the station has large solar energy collectors, and heavy but propellant-thrifty electrically powered engines (such as VASIMR), it can restore a few meters per second of velocity change using small amounts of propellant. For VASIMR engines, the propellant is argon (plus, practically speaking, occasional replacement electrodes), which is 1% of the atmosphere, and can be shipped from Earth as a -200C cryogenic solid on a 10 hour trajectory. Assuming an Isp of 5000 seconds (including electrode replacement), equivalent to an exhaust velocity of 49 km/s, and 75% "packaging efficiency", then 4% of the upbound payload stream might be argon payloads.
Space Solar Power Technologies
Space Solar Radar
Airport radar uses S band frequencies and wavelengths, 2.7 to 2.9 GHz, with wideband Low Noise Amplifiers (LNAs) amplifying dish-collected incoming energy BEFORE it reaches the first filter in front of the main amplifier. This works very well for radar receivers; the thermal noise of the dish and the receiver is spread over the whole band, and amplified, and only after amplification is most of the noise power filtered out. If the filter was in front of the first amplifier stage, then the thermal noise of the filter itself would be concentrated in the filter passband, and the power reaching later amplifier stages would be much noisier. Clever folks, those radio engineers.
Unfortunately, the Low Noise Amplifier is imperfect; designed to amplify weak signals, it becomes very nonlinear with strong signals, producing third harmonic distortion. A strong interfering signal with a frequency quite different from the desired signal can cause "intermodulation" and "mix" with the desired weak signal, adding high power interference signals that pass right through the subsequent filters. Even though 2.45 GHz Space Solar Power Satellite (SSPS) power is at a 13% different frequency than the radar energy, and pointed at rectennas far from the airport radar, many microwatts per square meter of SSPS power will spill over on distant areas, vastly more powerful than the picowatt powre the radar LNA is attempting to amplify. This will blind the radars, and spectrum regulating bodies will forbid it. National air defense will also be blinded; SSPS could be considered an act of war.
If you can't fix it, feature it . What if SSPS energy was broadcast as pulses squarely in the middle of the aircraft radar band, and replaced all the radar transmitters? The sidelobe power illumination lights up distant targets with vastly more power than an airport sourced radar does, so the returns to the radar would be much brighter, and more distant objects could be detected.
Radars are inverse-square-law transmit, and inverse-square-law receive; that means an object twice as close gets 4 times as much illumination, and 4 times as much of it reaches the receiver. The nearby object is 16 times brighter. So a 10 cm² leaf on a tree 100 meters from the transmitter is a thousand times brighter than a 737 airliner (with a 100 m² cross section) 10 kilometers away.
Space powered radar (SPR) would be inverse square - the leaf and the aircraft receive the same illumination power density from the sky, instead of the aircraft receiving ten thousand times less, so the distant aircraft is 10,000 times brighter than before, and appears 10 times brighter than the leaf. The aircraft could be 10 times further away, 100 kilometers, and still be as detectable as the 10 km distant aircraft was in the terrestrially illuminated scenario. Radar range increases vastly, yet the radar is not blinded by reflections from nearby clutter.
The United States might face a disadvantage; stealth aircraft have upwards-facing angled surfaces, designed to reflect horizontally sourced radar energy into the sky rather than back at the radar. That gives them radar cross sections 100 times smaller than a normal rounded aircraft. If the radar energy is sourced from the sky, it will bounce back at the radar receiver even more efficiently than horizontally-sourced radar power; stealth aircraft become the brightest objects in the sky.
However, if the United States provides the space energy from agile space transmitters, nulls can be inserted in the pattern, areas of zero energy amidst larger lumps of doubled energy, and the null areas can be big enough to hide the stealth aircraft. In addition, the space energy can "spoof" the enemy radar receivers into seeing an aircraft that isn't there. The country that deploys Space Power Radar can give (or withhold) "free" aircraft radar energy to developing nations, hide its own aircraft from adversaries, and place its radar sources far from enemy interception.
Space powered radar, as radar, can deploy at megawatt rather than gigawatt levels. Since the power lights up whole continents, the transmit antennas can be vastly smaller. SPR is a small scale, cost-insensitive, profitable first step towards gigawatt scale SSPS, and can prototype many of the technologies the latter will use. The global strategic and diplomatic advantages of deploying SPR and selectively sharing it with the entire world could be worth hundreds of billions of dollars, vastly more valuable per launched capability than space solar power satellites feeding the electrical grid.
Space Solar Power
Many have remarked that without inexpensive launch, Space Solar power stations are unaffordable. Baroque and high-risk rocket systems are proposed to deliver material to LEO, where it is transferred by electric engine to GEO. Many separate developments must work flawlessly and dovetail perfectly. While launch loop is a very big if, it is a key to the rapid and inexpensive deployment of space solar power; launch cost constraints vanish from the calculations, and Cheap Heavy Dumb SSPS can be launched with a fraction of the total investment.
ISM band frequencies (2.45 or 5.8 GHz) are usually chosen to minimize atmospheric losses, attempting to squeeze every last drop of inefficiency out of a marginally profitable system. The 1970s assumption was that these poorly regulated bands are "garbage" and interference doesn't matter. In 2016, with hundreds of billions of dollars of WIFI and Zigbee and smart phone infrastructure deployed planetwide, the cost of SSPS must include the cost of replacing these tens of billions of devices, a number that is climbing by hundreds of millions per day as I write this. No way in hell can SSPS systems shoulder this additional cost, against opposition and intransigence from the entire population of the world.
However, $30/kilogram launch changes everything. Space systems can be heavy (there's plenty of VASIMR station-keeping fuel available) and higher frequency, less efficient microwave bands are economically viable. Many small systems of equivalent capacity are cheaper to build than one big system (robotic mass production wins), and collector and transmitter areas scale down proportional to wavelength.
Smaller scale systems are usable for more applications; tropical islands, isolated communities, even ocean-going ships.
Using 183 GHz microwaves, power satellite and rectenna areas can both be 75 times smaller area than 2.45 GHz systems. Alternately, the satellite can be 5 times smaller, and timeshared between 225 rectennas that are 1125 times smaller. Instantaneous power densities must be 5600 times higher to produce the same voltage drop in a rectenna element, but high rep rate pulsed power can achieve this, the transmitter producing short duty cycle pulses with high volts per meter on the 8 millimeter rectenna dipoles.
183 GHz comes with a big problem that is actually three big opportunities. 183 GHz is a resonance frequency of water vapor; it cannot penetrate the moist troposphere. However, the stratosphere is above the cloud tops and bone dry; 183 GHz microwaves penetrate it with far less loss than 2.45 GHz penetrates to the ground. It is also -50 C up there. A rectenna can be operated at very high average power levels where the air is very cold and often moving at high jetstream speeds, held aloft on hydrogen balloons inside a streamlined aerostat "wing". Instead of using up valuable land for rectennas and power line right-of-ways, power cables can run vertically, perhaps 20 kilometers downwards from an aerostat platform in the sky.
Since 183 GHz does not penetrate the atmosphere, it cannot be used as a weapon against surface assets. Aircraft with millimeter-wave reflective hulls will not absorb much heat, and the air flowing over flight surfaces will probably remove what little remains.
A low-probability (but fascinating!) opportunity is that the 183 GHz transmitter on the satellite could be a "water maser". I have no idea whether such a thing is possible, but a huge cavity full of very low density water vapor might not weigh very much. Star cluster-sized clouds of water vapor have been observed that as water masers with luminosities 1000 times the power output of our Sun. Indeed, the same process on the rectenna might somehow (hands waving madly here) reverse the process to produce easily rectified lower frequency power.
If the "customer" is a military forward base in hostile territory, surface rectennas and power lines are huge targets, while vertical cables are hard to hit and protectable with lasers from the aerostat platform itself (the lasers can also do a number on the attack launch site). Personally, I think such ventures should be under UN control; a unsanctioned firebase doesn't get power from space. But then, I'm a pinko commie capitalist, who prefers high profit free trade with as many global customers as possible.
Powering Launch Loop with SSPS
If 10 terawatts of incoming space energy were devoted to launch at 40% efficiency to GEO (launch velocity 9950 m/s), that is about 120 MJ/kg, a global launch rate of 80 tonnes per second, 2.5 billion tonnes per year. Assuming 50% mass fraction at apogee insertion, and Space Based Solar Power requiring 8 orbiting kilograms per delivered terrestrial kilowatt, that is a system capacity growth rate of 5 MW per second, 430 GW per day, or capacity doubling times of 2 million seconds, 23 days. A ridiculous number, other limits and costs will kick in much sooner, but it shows what an advanced non-combustion launch system can do.
The canonical Launch Loop presumes electric motors and power plants on barges on the surface. Those might be directly powered by 183 GHz aerostat SSPS. Motors are probably too heavy for structure aloft.
Expanding Into Earth-Moon Space
Lunar Launch Loop and Lunar Materials
Earth launch loop escape velocity (minus equatorial rotation velocity) is around 10.5 km/s, while lunar escape velocity is 2.4 km/s, 5% of the energy. A 3 gee launch loop could be built with a launch path near the surface perhaps 100 kilometers long, with rotor speeds of 4 km/s instead of 14 km/s. The rotor will still need a "vacuum" sheath; lunar dust is nasty. Regolith could be gathered, compacted, and launched to the Lagrange points for industrial processing. Power loops could store operating power through the 2 week lunar night, but it might be simpler to double robotic operating cadence during the lunar day.
While the Moon requires 1/20th of the energy for loop launch, if lunar material quality is lower and the cost of operations is much higher, the 20x energy advantage might not be enough justification for lunar operations in the short term. The quality and variety of materials on Earth, plus 7 billion clever humans inventing new tools there, suggests that lunar operations will not be profitable for some time.
lunar NEO Interception and Asteroid Materials
A more compelling argument for lunar material operations is that we can use the Moon to shield the Earth from large Near Earth Object impacts. Moving asteroids to the vicinity of Earth from the belt between Mars and Jupiter requires a huge amount of delta V. Fortunately (or very, very unfortunately), billions of tonnes of asteroids are in orbits that can potentially collide with the Earth, stirred by Jupiter's gravity until sooner or later, they hit our planet (or Mars, or Venus, or each other). Launched into matching orbits by high velocity versions of the launch loop, kilogram-weight electric-engined probes can rendezvous with the hundreds of thousand of objects up there, and deposit laser retroreflectors on every one. We can build a super-accurate ephemeris for every meter-scale-or-larger up there, and predict future Earth impacts for thousands of years.
Better, we can identify the problem objects, and with very small nudges from slightly larger electric-engine probes, we can place them in millimeter-precision orbits targeting the Moon, perhaps centuries in the future. An object bound for Earth impact in 300 years (10 billion seconds) can be nudged with a 3 cm/s delta V to hit the Moon instead, when it is 300,000 kilometers to the side. The "collection area" of the Earth-Moon system to 2 Moon radii out is 140,000 times that of the Earth; for every object that hits the Earth now (a Tunguska or Chelyabinsk-sized object once per century), we can (over a very long time!) deliver 140,000 objects to precise locations on the Moon; perhaps 4 per day.
Most objects will arrive at velocities hot enough to melt them; for the valuable ones, like nickel-iron asteroids, we can dig deep shafts and line them with crucible ceramic and iron, which the asteroids can thread on their way to impact at the bottom. Whamo, a big pool of liquid nickel-iron ready for processing into Invar thinsat substrates. About 6% of meteorites are "irons"; assuming asteroids are similar, we might harvest 7 irons per month.
Robotic Space Industrialization
Mars and Beyond
Phobos is in a low orbit, and a space-elevator-style tether hanging straight down and skimming the top of the Mars atmosphere (relative velocity around 540 m/s) could release payloads for a much slower reentry that the arrival velocity of an interplanetary Hohmann transfer from Earth. A tether reaching up from Phobos could have an end velocity equal to that arrival velocity. So, objects could be captured from above and winched down to Phobos, then lowered down for fast reentry. The reverse path is a way to travel from Phobos back to Earth. An Aldrin Cycler (with shielding and centrifuge) might be the safest way for humans to travel between the vicinity of the planets, and the launch loop might be a relatively inexpensive way to launch lots of cyclers.
IMHO, Phobos should be the end destination for humans. Shielding and centrifuges will be easier there. This also minimizes contamination of whole-planet paleontological exploration for signs of early life. Photovoltaic power collectors on Phobos will be illuminated with with 36% of Earth orbit luminance. However, concentrating mirrors sturdy enough for Phobos 600 microgee gravity can be gossamer, and adjust the Sun pointing angle as Phobos turns relative to the Sun. They might even be on powered tracks, rolling 70 km around the equator of Phobos at 10 km per hour. A power loop can store energy to use during the 50 minute Phobos-Mars eclipse, probably a period of low activity, as the Martian surface directly below will be at local midnight.
Mars Launch Loop and Martian Settlement
It may take decades of careful robotic exploration to eliminate the possibility of early Martian life, or characterize it so completely that contamination is no longer an issue.
taming the solar system
preserving life on Earth beyond the Sun's lifetime