Navigation – Destination Signs in Space

Australian National Fabrication Facility’s Laser Labs

Destination Signs Will Pave the Way in Space.

by Robert brand

In the last day a comment by a well meaning reader condemned Project ThunderStruck for lack of information. In any project’s early days, that will always be the case, no matter how much funding you have and how real any project may turn out to be. The skeptics will always put down a project publicly based on their measurement system, lack of knowledge of the team’s capabilities or previous experience and a large number of other factors.

I cannot table what I don’t have as so much is fluid at the moment. We are tabling the Phase One tests and other facts as they are both allowed commercially or announced by the group with the appropriate permission of the stakeholders. Commercial-in-confidence will dictate these matters as in any company. None the less there are components of the craft that are solely my property at the moment. I can give you a snap shot of a typical day in my life at the moment that may show the strength of this project.

The title of this post is about Space Destination Signs and conversely avoidance signs or safe passage signs. So who is building these new modern signposts for the difficult environment of space and a navigation system to use them. We Simply I am and it is part of the Thunderstruck Navigation System

Laser Tag

I am not speaking about kids with toy guns, but a serious business in space that will create new auto-navigations systems and will keep track of objects that are on the move of change their location such as survey craft.

The concept is simple, but the solution is hard. If it was easy, we could all create it. My next words make me shudder as a recent detractor said that the term “Quantum” was not on the site and that was a plus. He said that was the realm of scientists, so I have some breathing space here because some of the solutions will probably have the word “quantum” somewhere in there, but scientists’ words, not mine.

There are two essential components of this project:

  • A spacecraft mounted laser transmitter and a laser receiver with a steerable mount.
  • A passive but easily identifiable laser reflector (Retro-reflector + ID).

You can watch the video below that both debunks any thoughts that we have not landed technology on the moon and also shows a small basic bit of essential info on retro-reflectors. Hey, it is Mythbusters – a great show anyway.

There must be at least hundreds of variations of these reflectors for our use, but each ID can be reused, just not in that locations. Lighthouses do that too. Many have the same rate of light bursts, but they are so distant from each other, there is no confusion. The laser reflectors can be made larger to give it “gain” and a longer range, but at this stage I would be happy with a 100,000Km range. Again I cannot give details as we have not selected the passive ID system and thus the weight, distance of operation and wavelength is not yet available. Nor is the polarisation and other factors, but whatever system we use, playing with the polarisation will give us three times the number. Left hand, right hand and no polarisation. We cannot use horizontal or vertical polarisation as we don’t now the orientation of the reflector, but we could use it as a forth multiplication factor if needed.

I am hoping that we will not have to delve into polarised reflectors simply because polarisation drops the reflected  light levels a lot, but they could be could for close up navigation systems.

There are a few candidate technology solutions for the system and I hope to finalise the selection of the core system in the next few weeks, ensuring a low cost, low mass system that is small enough for a good signal return.

Yesterday I visited the photonics labs at Macquarie University in Sydney. It is part of the Australian National Fabrication Facility – a group of high tech facilities in universities around Australia. Everything from clean rooms to heat shield fabrication. It could be R&D or it could be simply renting and using the equipment. It was the first step in assessing the capability of the group to produce the solution. I was very impressed by their range of equipment, services and people.

A nice side story here. The Sydney Olympic torches were incredibly successful due to their help. One of the problems with most torches is that there is a huge variation in the flame height and thus the burn time. You really don’t want a flame too small that gets blown out or a flame too big that the gas runs out before being transferred to the next torch. The lab fabricated a component by burning a bore hole though glass (or similar substance) that had a very precise bore hole that regulated the gas to burn at a very precise rate. It was a huge success and although you will not hear it officially in the real world another country contracted the lab to do the same for their Olympic torches.

I will revisit the labs in a few weeks and discuss the findings of the research and how we can engage the laboratory to build and test the systems for sale to the space sector. The ThunderStruck craft will have the active scanning unit as part of its plug and play design. Add it or leave it off, the decision is up to you.

Why Bother to Tag.

Spiral Search Pattern

Spiral Search Pattern

In the real world of space, there are no sign posts, but let’s say an asteroid has been tagged or even tagged a couple of times. Our craft will start looking for the reflector in the area of space that it is expected to be found. A simple spiral search starting at the expected location (centre of search) should locate the reflector if it is in view.¬† The search may have to be repeated many times if the target is rotating. Its rotational speed with determine the number of searches required and their interval.

In the event that the target is not found, a series of overlapping search patterns will need to be conducted around the outside of the original pattern and may require the craft to maneuver slightly. One found the information reflected distance to the destination and the angle of the search unit and the attitude of the craft will give the direction of the target reflector.  This is helpful to the extreme and you can then plan you trajectory to get there and the braking force required to stop at the destination without wasting fuel. Fuel is one consideration and so is time. This system leaves nothing to chance.

If you use an ion engine to brake, then you need exceptional information to get the flight just right and preserve fuel for the return flight (if there is one). This system is ideal for ion engine slowing and stopping. In fact the ideal slowing may be planned to just miss the target so that any failure or overshoot will not be an issue. Thrusters can correct the slight difference once stopped.

Other Reasons to Tag

There are many, but here are a few:

  • The target object is spinning
  • The target object has moved
  • The target is a spacecraft that is in a new location
  • The target is moving (a relative measurement of course).
  • The object is big and the target is a precise area of interest.
  • The target is to be avoided (a lighthouse style beacon)
  • The target is to be monitored (spin rate, speed, direction).
  • The target spacecraft has lost power and rendezvous is only possible with a radar reflector.
  • Staking a claim to a rock or body. International Space Law needs to be involved here.

There are many more, but the passive signpost is a feature that we can expect to see in space soon if we get the price and size right.

I expect to be a regular at the labs as we will be working on laser comms, but more on that in the near future. There is absolutely no reason that the navigation unit cannot be also a laser communications link. Once the first craft locates the second, the ability to for the second to “lock on” is made a lot easier with a constant laser pointed at it. The laser will be brighter than a reflected laser beam. Once locked, they will be able to talk to each other making the approach much simpler if they are to rendezvous. If you are concerned about the tag reflecting the signal, a voltage controlled shutter can be activated, diminishing the reflection or even steering the reflection away. There are options. More on our new technology later.

Robert Brand and Warren McKenzie at the Australian National Fabrication Facility's Laser Labs

Robert Brand and Warren McKenzie at the Australian National Fabrication Facility’s Laser Labs

Australian National Fabrication Facility's Laser Labs

Australian National Fabrication Facility’s Laser Labs