Part 4 of 4: the pros & cons of Capturing an Asteroid to deliver raw materials to orbit

The first three posts in this series have discussed the advantages and disadvantages to using rockets, mass drivers or the “PR method” to deliver raw materials to orbit.  This post will describe the pros and cons of using a lunar space elevator to achieve that goal.

First, what is a lunar space elevator?  The best, most succinct answer to that question can be found on Wikipedia:

A lunar space elevator is a proposed cable running from the surface of the Moon into space.

It would…be constructed with its center of gravity in a stationary position above the surface of the Moon, providing a controlled means to transport people and/or materials between the surface and lunar orbit.

Here are a few videos of how the system may be built and how it might work (h/t LiftPort).  Bottom line: the lunar space elevator will allow a continuous flow of lunar regolith to be delivered to orbit for a very low price per pound.

Bottom line: a lunar space elevator will regularly deliver thousands of tons of raw materials to orbit for very little money.

That is, if it works.

Let’s start with the good news:

• Highly efficient – once in place, delivers lots of material with low operating costs (lunar ground ops, ribbon maintenance, interorbital transport, etc.) relative to other systems
• Easy access to large supply
• more technologically achievable than an Earth space elevator

And now the challenges:

• deployment/maintenance on target totally unknown, orbital debris/micrometeorites/radiation destroying/degrading the ribbon
• slow rate of lift – probably not able to carry people
• the giggle factor
• pr issues surrounding excavating the moon i.e. “scarring the surface of the moon”

Part 3 of 4: The pros & cons of Capturing an Asteroid to deliver raw materials to orbit

The first two posts in this series have focused on the pros and cons of using rockets and mass drivers to collect raw materials in orbit. This post will discuss the merits of capturing an asteroid using what I’m calling the Planetary Resources (PR) method. As far as I can tell, PR will capture whole asteroids (small ones) and somehow drag them back to more convenient orbits closer to Earth for processing (as opposed to strip-mining them or processing the ore on-site).

How PR will (probably) capture asteroids. Credit: Planetary Resources

Let’s start with the advantages:

• Easier transportation to destination – The more accurate way to state this is that it takes less of a change in velocity (delta-v) to move asteroids around the Earth-Moon system than it does to haul materials up from the Moon or Earth. This is because asteroids are already at the top of the cislunar gravity well. In other words, one should expend less fuel moving a typical asteroid from its orbit into, say, geosynchronous orbit, than one would on moving an equivalent mass from the lunar surface to geosynchronous orbit.

This is a HUGE advantage. Perhaps an Earth-bound analogy will drive home the point. Consider two mines on Earth. In one, the ore is laying on the surface and just has to be picked up and trucked to the processing facility. This is the PR method – snagging an asteroid and sliding it to where it needs to go. Now, consider another mine where the ore is buried deep underground. First one digs up the ore and hauls it to the surface and then it has to be trucked to the processing facility. Obviously it’s a lot more work to move all that heavy stuff around but this is what happens when ore is collected from the Earth or the Moon and then transported into orbit. By eliminating the need to haul the material up out of a gravity well, Planetary Resources has a great advantage over the other methods.

• Provides massive infusions of raw material – Thousands of tons of material will be delivered immediately upon the arrival of a near-earth asteroid at the destination. No other technology known today has the capacity to deliver thousands of tons in one delivery. Rockets can, at most, deliver tens of tons of material. Space elevators and mass drivers provide a continuous trickle of material that, over time, can add up to thousands (even millions) of tons –but it requires patience.  If you need a lot of space rocks and you need them right away, asteroid capture may be the way to go.
• Provides goodies – Asteroids could more easily provide resources that are not known to exist in great quantities on the Moon and are difficult to haul up from Earth e.g. rare platinum group metals, volatiles or even hydrocarbons.

But what about those disadvantages:

• Lots of unknowns – No one has ever captured, or barely even landed on an asteroid. Pristine asteroidal material has never been examined on Earth. The composition of different classes of asteroids is essentially unknown and manipulating asteroids is, at this point, a best guess. Can a rubble pile asteroid be de-spun without it falling apart? Can a volatile-rich asteroid be “bagged” without all the water and oxygen boiling off and popping the containment unit? Mastering the capture and processing of asteroids will take many years, as well as the coordination of the swarms of robots it will take to accomplish these tasks. It may be decades before these techniques are commercially viable, especially when compared to the more familiar technologies required to exploit lunar resources.

“A mine is just a hole in the ground owned by a liar”

– Mark Twain

• Long delays between deliveries – While a mass driver or space elevator provides a steady continuous trickle of material to orbit, asteroid capture provides huge shipments once every two or three years. This time lag will  complicate processing as facilities will have to be designed to store or digest a huge amount of material when the asteroid arrives but will then lay fallow while they wait for the next shipment. It could lead to inefficiencies.
• Potential public relations problem – I’m not going to spill too much e-ink on this topic but it is possible that the same Luddites who oppose nuclear-powered space probes could oppose and potentially derail or delay asteroid mining because they fear “killer space rocks” being positioned closer to the Earth. Even though putting them into a more convenient orbit makes it easier for them to be deflected and diverted should something go wrong.
  

So, lots of pros and cons for this item. Stay tuned for the final installment regarding lunar space elevators.

 

Part 2 of 4: The pros & cons of using Mass Drivers to deliver raw materials to orbit

In a previous post I described the pros and cons of using rockets to deliver raw materials to orbit. And, in the post before that, I explained that this part of a series of posts discussing the best ways to amass raw materials in orbit needed for space development. In this post, I will discuss the pros and cons of using mass drivers to accumulate a resource base in Earth orbit.

The biggest advantage to using mass drivers is that they are very efficient. That is, once they are set up and functioning well, no fuel is required to launch payloads into orbit. In theory, the mass driver can launch hundreds of times its own weight using only electricity.

Furthermore, extensive research has been completed on mass drivers, and their earthbound cousin, the railgun. The Space Studies Institute and Gerard K. O’Neill himself built a small mass driver in the 1970s basically proving that this idea will work. And today, the US Navy is working on an electromagnetic railgun to fire artillery shells which is basically a mass driver.

Gerard K. O’Neill and his team with a working mass driver prototype in the 1970s. Courtesy: SSI

In practice, however, one cannot be sure that a mass driver will function as promised. It is, after all, a machine and machines require maintenance and upkeep. I am skeptical that mass drivers can function anywhere near their peak performance without a human presence on the moon to maintain them.

Which brings us to the biggest disadvantage to using mass drivers: they require a massive upfront investment in infrastructure. This infrastructure includes not only the kilometer-scale mass drivers but also megawatt-scale power systems (probably nuclear due to the long lunar nights – which means additional headaches), loading machinery, canister processing machinery and all the subsystems needed to make this structure work. Essentially, one must build a minor lunar base in order to construct, and possibly operate, a mass driver on the moon*.

So, bottom line, mass drivers are extremely efficient, but require a massive upfront investment in order to work.

*The fact that a mass driver may require a lunar base could be construed as either a positive or a negative, depending on one’s point of view. Positive because, hey, who doesn’t like moon bases, right? Negative because moon bases are expensive and, in this case, would simply be an overhead cost as we establish our raw material delivery system.