The SLS Block 2

https://en.wikipedia.org/wiki/Space_...-_Post_CDR.jpg

puts 130 metric tons into LEO.

The 30.5-meter (100 ft) diameter balloon was made of 0.5-mil-thick (12.7 µm) metalized 0.2-micrometre-thick (0.00787-mil) biaxially oriented PET film ("Mylar") material. Echo 1A was easily visible to the unaided eye over most of the Earth. The spacecraft was nicknamed a 'satelloon' by those involved in the project, as a portmanteau of satellite-balloon.

It had a total mass of 180 kilograms (397 lb).

Echo 1A was originally loosely estimated to survive until soon after its fourth dip into the atmosphere in July 1963 but possibly until 1964 or beyond.. It ended up living much longer than these estimates and reentered Earth's atmosphere, burning up on May 24, 1968.

Echo 2 was a 41.1-meter-diameter (135 ft) balloon. Echo 2 used an improved inflation system to improve the balloon's smoothness and sphericity. It was launched January 25, 1964, on a Thor Agena rocket.

Instrumentation included a beacon telemetry system that provided a tracking signal, monitored spacecraft skin temperature between -120 and +16 °C (-184 and 61 °F), and measured the internal pressure of the spacecraft between 0.00005 mm of mercury and 0.5 mm of mercury, especially during the initial inflation stages. The system consisted of two beacon assemblies powered by solar cell panels and had a minimum power output of 45 mW at 136.02 MHz and 136.17 MHz.

In addition to the passive communications experiments, it was used to investigate the dynamics of large spacecraft and for global geometric geodesy.

Echo 2, being larger than Echo 1A and also orbiting in a near polar orbit, was conspicuously visible to the unaided eye over all of the Earth. Echo 2 reentered Earth's atmosphere and burned up on June 7, 1969.

Unlike Echo 1, Echo 2's skin was rigidizable, and the balloon was capable of maintaining its shape without a constant internal pressure. This removed the requirement for a long term supply of inflation gas, and meant that the balloon could easily survive strikes from micrometeoroids. The balloon was constructed from "a 0.35mil (9µm) thick mylar film sandwiched between two layers of 0.18 mil (4.5µm) thick aluminum foil and bonded together." The balloon was inflated to such a level as required to slightly plastically deform the metal layers of the laminate, while leaving the polymer in the elastic range. This resulted in a rigid and very smooth spherical shell.

http://dspace.mit.edu/handle/1721.1/84399
http://www.lgarde.com/assets/content...ns/scaling.pdf
http://www.travisdeyle.com/files/pub..._TermPaper.pdf

https://goo.gl/m1I4Oi

At 1600x solar intensity, using solar pumped multi-spectral lasers, attains 62 grams per square meter of sunlight. This is 22,064 Watts/kg of payload..

At this specific output the solar collector intercepts 2,868.3 MW of power and the size of the solar collector is 1,634 meters - a little over a mile across. 2,150 MW of useful power is available, and 150 MW is used by the spacecraft itself, and the ground stations.

A station placed in a 1,688 km high orbit with a 77 degree inclination, will be visible 3.5 hours before sunrise or sunset, until 3.5 hours after sunrise or sunset. Charging takes place during a 35 minute period when the satellite is high in the sky, once every 12 hours - for any spot on Earth!

A 2,000 MW beam delivering energy for 30 minutes every 12 hours, delivers 2 million kWh per day. With 1 million kWh storage and 0.1 kWh/kg

http://batteryuniversity.com/learn/a...er_lithium_ion

We need 10,000 tons of batteries for each 83 MW (average, 2,000 MW peak) station. There are 24 stations served around the planet. At 8cents per kWh each ground station is worth $794 million when funded by a green bond, and the collection of 24 ground stations with a single power satellite in SSO is worth $19 billion. Well worth the $500 million launch cost, and the $500 million. At $0.47 per Wh a 1 million kWh battery pack costs $470 million each at today's prices. Each half billion dollars adds $0.04 per kWh to thecost.

Using solar powered, or laser powered, ion rockets in Low Earth Orbit, payloads may be boosted to GEO in a 28 degree orbital plane, along a transfer orbit, and then circularised at altitude, and the orbit inclination tilted to zero degrees.

So, a satellite in Low Earth orbit moves at 7.9 km/sec. To attain a transfer orbit requires it increase its speed by 2.52 km/sec achieving 10.42 km/sec. When it attains geosynchronous altitude, 35,786 km 5 hrs and 14 minutes later, its speed is slowed to 0.20 km/sec but must attain 0.39 km/sec to stay at that altitude. It must also be directed along the equator, with no north/south component. However when it arrives it is moving at 0.20 km/sec along its 28 degree path, and that means 0.1766 km/sec is moving along the equator, and 0.0939 km/sec is moving perpendicular to the equator. To get the velocity vector to move along the equator at 0.39 km/sec means that 0.2134 km/sec must be added to the equatorial velocity and 0.0939 km/sec must be subtracted from the north/south component. A total delta vee of 0.2332 km/sec directed 51.74 degrees away from the direction of travel. A total of 2.76 km/sec delta vee to go from LEO at 28 degrees to GEO at 0 degrees.

To impart 2.76 km/sec to the payload using a 8.2 km/sec exhaust speed requires that 28.23% of the mass at LEO be propellant. So for a 130 ton satellite 51.14 tons must be propellant. About what a Falcon Heavy could lift.

The added cost of the propellant/solar ion stage, of say $125 million ($60 million for launch, $65 million for the stage itself) would more than pay for itself by cutting out nearly all of the batteries needed in the SSO test system. Here you'd save $470 million per ground station, $11.28 billion per satellite.

Three Falcon Heavy Launches, at $61 million each, including one solar pumped ion stage, would cost less than the $500 million SLS cost.

The advantage of a GEO based solar power satellite is that you get 1368 Watts of power 24/7 with rare exceptions that occur only twice per year for a few minutes. You can get it at a competitive price. You can also get it in adequate quantity - a reliable renewable. 3,312 satellites of this capacity provide all the electrical power currently provided by coal fired power plants. One every 6.52 arc minutes around the equator. 80 kilometer separation between each of the 1.6 km diameter stations.

With one launch every eight hours (one SLS, one SpaceX Mars Colonial Transport, one Chinese SLS equivalent) we can put up 3,312 satellites in 1,104 days. A little over three years. In that time we can improve launch rates, reliability, and reduce costs. This sets the stage for colonisation of mars, the moon and the asteroids.

6.6 TW operating continuously around the world, (replacing coal fired stations) and selling at $0.08 per kWh, generates $4.628 trillion per year. At 25% retained revenue by the launch providers, $1 trillion per year is available to expand upon the experience of these providers to help build the off world colonies that will reduce human numbers on Earth.

As the number of humans decline on Earth, the use of non-renewable fuels decline, and more reliance on renewable beamed power is made.