A Reply to "Can Hyperloop Be Adapted As Launch Loop?"

• https://forum.nasaspaceflight.com/index.php?topic=40280

The simple answer to this simple question is NO.

Hyperloop

Hyperloop is Elon Musk's idea for running hyperspeed trains between San Francisco and Los Angeles in a vacuum tunnel.

Hyperloop won't work as described, for many reasons; the main reason is turn radius. There are a lot of east-west mountain ranges between SF and LA, seismically unstable, so it will not be practical to drill through them. Going around them involves a lot of wiggles to avoid terrain, and the maximum turn radius of those wiggles limits speed to well below Shinkansen speed. The idea might be patched by running the tunnels off the coast, underwater, but to the average reader that sounds crazy. Unless the northern terminus is Gilroy and the southern terminus is Fresno, hyperspeed trains are incompatible with California topography.

Besides, as we transition from the Combustion Age to the Second Information Age, we will use predictive-adaptive telepresence to get around, at the speed of light, not at the speed of weight.

Surface Coilgun Launch

The first good technical description of a coilgun space launcher was in Edwin Fitch Northrup's Zero to Eighty, published by Princeton's Scientific Press in 1937. Northrup built some formidable prototypes, much more impressive than O'Neill and Kolm's benchtop "mass driver" forty years later. Earth-to-space coilgun launchers have 3 big fails:

• 1) The air at the Earth's surface is a trillion times denser than the air at 400 km ISS altitude, and ISS orbit drag is inconveniently high there. Imagine trying to dive through 10 feet of rock at mach 30. Air drag is halved at the top of the tallest mountains ... 5 meters of rock. You will need a very dense vehicle to penetrate that, even with substantial velocity loss. Rockets climb to very high altitudes before going full throttle, and lose about 1000 meters per second doing so; a full-velocity-from mountaintop launch might lose "only" 2000 m/s IF the vehicle is very long and skinny and dense.

• 2) curving up the slope of any mountain will subject you to horrendous gee forces, far worse than a hyperspeed train. The centrifugal acceleration formula is V²/R - for a 30 degree exit angle at 8000 meters altitude, the turn radius is 75 km. V = 10000 m/s, R = 75000, so the acceleration is 13000 m/s², of 13000 gees.

• 3) Coilgun electronics cost scales as the payload mass times the velocity cubed - the electronic drivers at the end must pulse with enormous power levels. If a 1 kilogram 100 m/s benchtop coilgun costs $1000 (WAG numbers for the Kolm/O'Neill 1974 Princeton model), then a 10000 m/s 10 tonne mass driver would cost 1e13 dollars.

Why is launch expensive, anyway?

Launch is very difficult, involving the hard work of thousands of clever specialists, who want to be paid. If rockets fail and fall on a city, they can kill many people, so a big chunk of launch cost is insurance. We launch about 400,000 kilograms to orbit per year. Divide salaries and other costs by kilograms, and you get a huge $/kg number, even larger than what launch customers actually pay. The difference is paid by government subsidy, because domestic launch contributes to national prestige. If you want cheaper launch, go to India or Russia, where the clever specialists work for tiny wages.

Or, increase launch volume. 10x the volume does not need 10x the specialists, more like 5x. That cuts the cost per kilogram in half. It also adds experience and reduces accident rates, lowering insurance costs. If you can't imagine 10x more applications for expensive space launch, get a better imagination, or go to http://server-sky.com and borrow mine.

That said, while I would love to have cheap rockets. I would also like free ice cream and a pony.

Developing practical and reliable rocket launch cost the world trillions of dollars ... and thousands of murdered prisoners in the Nordhausen V2 factory. Millions of prisoners starved in concentration camps, because harvests were turned into alcohol to fuel the V2s. If we had started with coilguns in the 1940s, we would have evolved to launchloops half a century later, and we would be launching billions of kilograms into orbit per year in 2016. We are paying dearly for our war-making belligerence, the ghosts of millions of murdered slaves, and our slavish devotion to the ideas of the Nazi monsters who murdered them.