Thursday, March 19, 2015

Impact of Rotating Asteroid on Orientation of Artificial Gravity Tubes

In a NASA Spaceflight forums discussion, I had a new complication pointed out to me that I'm surprised I had not thought to cover on this blog before. The artificial gravity tubes are rotating, but the asteroid is as well. We can distill the implications into 3 options. Either:
  • the tube's axis of rotation will appear to move relative to the walls as the asteroid
  • you will have to use some complicated form of "compound" rotation
  • you will align the axis for rotation of all tubes parallel to the asteroid's axis of rotation
Aligning all tubes in the same direction is the most obvious and cheapest option. In the last post on global heat removal, I inadvertently designed this in. If you follow the implications a little bit, that implies that the majority of the heat exchangers are toward the asteroid's poles. This is intriguing because that would be the ideal place for space radiators in the first place. However, if the colony is pushing the spherical black-body limit, then it's not as good because the GEO radiator is toward the pole anyway.

Actually, an ability to precess was already designed into some O'Neil colony designs. With 2 artificial gravity tubes near to each other, they can push and pull so that they change the direction they face. This was proposed as a way to keep facing the sun, which obvious means they turn a full circle roughly every year (depends on the orbital position). For the asteroid rotation, we could be talking about rotation rates of 8 hours or less. Whether the forces involved and the unwanted acceleration on the surface are small enough is a question that is still unresolved.

This is a type of topic which I might return to sometime, but I've decide that I'm going to do a few micro-posts from the long list of things in my backlog where I introduce the subject in a few paragraphs.

1 comment:

  1. Upon review, I have no idea why I said poles. It seems like they would be all around the surface except for the poles, because the driving force is in the plane of rotation. Rotational axis is the same between the asteroid and tubes (to maintain an artificial sense of stationary-ness). Driving force for the air is perpendicular to that axis, thus, heat exchangers are on the sides.