Sab 13 dic 2014
Having pods speeding down the ribbon towards either planet is no joke. What if anything fails?
On Earth, something falling from the moon towards the Earth would reach the atmosphere at close to 40 thousand kilometers per hour. That was the speed the Apollo capsules had when they reached the atmosphere where they slowed down by friction. That is why the recent test flight of the new NASA capsule Orion was such a big deal, could the thermal shield protect the capsule? Since Apollo 17, no spacecraft has re-entered the atmosphere at such speed. Orion hasn’t gone that fast, but it was far faster than any man-rated vehicle has since Apollo.
Anyway, back to the novel, what to do with a failing falling pad? If the problem is detected soon enough, the best is to discard it. The two halves of the climber, one on each side of the ribbon, would simply separate and fall away. The easiest and lightest would be explosive bolts, frequently used when separating rocket stages, which would also provide a light push to each half away from the ribbon. From the midway point up to a certain height, the halves would eventually burn up in the atmosphere. It would help if the cargo bay opens and the contents spread, since that would ensure everything burns up faster. However, if this is done very high, the remains might get into orbit. That is not good since in that case, they would eventually return to the point where they had detached from the cable and hit it. That is in theory, in practice, it’s anyone’s guess. Due to many perturbation factors, the chances of actually hitting the cable are small.
The highest chance would be if the two halves are ejected in the direction of the ecliptic, meaning one eastwards, the other westwards. Even then, the cable is continuously vibrating like a guitar string, very slowly, but enough to move away from the debris at the right moment. By tensioning the cable or changing the speed on the remaining pods, that movement can be adjusted to avoid the debris. If ejected in a polar direction, the cable and the pod remains would meet only after very many orbits, that is, if the pods don’t slow down due to friction in the atmosphere and burn down before that happens, which is the whole point.
If the linear induction motor works all the way down and the parachutes fail, an extra set of parachutes could be sent up via a small sounding rocket or a weather balloon tethered to the cable. As the pod comes down, it would entangle itself in the tether and pull the parachute out of the rocket or balloon.
An idea that fascinated me was what if that is not enough. I remembered how the catapult of an aircraft carrier is stopped after it has released the plane. The piston runs in a tube which has injectors for water jets that swirl around the inside of the tube. The jets point towards the incoming piston but at an angle so the water remains attached to the tube, being centrifuged by its own speed. The front end of the piston is shaped so it scrapes the water from the tube and sends it back through the center of the tube. The tube is open towards the bow of the aircraft carrier so after every plane departs, the catapult spits a jet of water right behind it.
So, in the case of the ribbon, two water jets could be sent upwards one on each face of the ribbon. The pod would have its front shaped like a snowplow. Scraping the water from the ribbon and sending it sideways or, preferably, back down, would eat up a lot of the speed. Remember that this would only be used if the induction motor did work so the pod would be falling at a few hundred kph, not tens of thousands. At that kind of speed, the pod would not go fast enough to burn in the atmosphere if released. For the final stop, a net can be deployed at the top of Pinnacle or its counterpart in Heaven, like those deployed in aircraft carriers to catch plans whose landing hook is damaged.
I would have loved to put this in the novel but it seemed it would lengthen that chapter too much. It is already dense with technical details, it didn’t need any more.