It's not very often that I have a new thought about space, but when I do, I should post it here, rather than debuting it at Space Politics, as I did yesterday. Here's a repeat.
In response to a comment by Stephen Metschan that "According to Dr. Neil Degrasse Tyson, 80% of the life cycle cost of space is in the spacecraft and mission not the launch system," I wrote:
"That's because we haven't been doing human exploration to the moon and Mars for the time period over which he gathered that data. The vast amount of payload delivered to orbit for a spacefaring civilization (at least initially, until we are getting it from extraterrestrial sources) is propellant, which costs almost nothing on earth, but is very expensive in space when it's put up on an expensive launch system. And propellant is almost infinitely divisible, and something that can go up on large vehicles, small vehicles, high-reliability vehicles and low-reliability vehicles. But the important thing about it is that it go up on low-cost vehicles.
I'm always amused by the absurd notion that the mistake we made in the past was mixing crew and cargo.
No.
The real mistake that we made was mixing cargo (which is high value, at least if it's space systems, as opposed to logistics, regardless of whether people are being delivered) and propellant. Once you stop doing that, the rationale for large vehicles goes away completely. It can be done with existing vehicles, or new lower-cost vehicles. But it doesn't need expensive new and large expendable vehicles. And in fact they are counterproductive."
I should expand on this sometime. I think that there's an interesting economic argument for "impedance matching" vehicle costs to payload costs.
Rand,
Good way of putting it. I've been thinking along similar lines for quite some time, but that's a very good way of explaining it.
~Jon
In practice, that works for generic transportation. One doesn't send a casino's cash receipts by moped. They want guarantees that the money makes it. If you order a several thousand dollar computer by phone or internet, you don't want the seller to send it by the cheapest method (namely, in the postal mail, uninsured, no return policy). You want quality transportation for high value cargo.
In a similar fashion, who sends a 25 cent postcard by Brink's armored truck?
I really like this "impedance matching" idea. That's the way we do things on Earth. So what makes space transportation so different? Instead, this seems to be more indications of the uneconomic basis of modern manned spaceflight.
I recall Andy Turner from Space Systems\Loral discussing something along those lines a few years back at an ISDC...
If you order a several thousand dollar computer by phone or internet, you don't want the seller to send it by the cheapest method (namely, in the postal mail, uninsured, no return policy). You want quality transportation for high value cargo.
Actually, Karl, when I order a computer, I always choose the free shipping. Which is the cheapest method. And it does include insurance and a return policy.
You're operating on the basis of a fallacy called "false economy." There is no tradeoff between low cost and high reliability. Low cost *requires* high reliability because fixing stuff that breaks due to low reliability costs money.
Almost anything you do to improve reliability also improves economy, and vice versa. Changing the transmission fluid in your car not only makes it less likely that you will be stranded at the side of the road, it also saves you spending several thousand dollars for a new transmission.
When people talk about systems with "low cost but poor reliability" they are almost always talking about initial upfront costs and forgetting the recurring costs.
Actually, Karl, when I order a computer, I always choose the free shipping. Which is the cheapest method. And it does include insurance and a return policy.
You're operating on the basis of a fallacy called "false economy." There is no tradeoff between low cost and high reliability. Low cost *requires* high reliability because fixing stuff that breaks due to low reliability costs money.
If you're getting insurance and a return policy, then you're not getting the cheapest method. The cheapest method is I put all that junk in a big box, drop it off at the post office, and never return your calls. Even better, they could skip the postage and just write your address as the return adddress. It could get to you that way.
Insurance and a return policy aren't free for the seller.
Almost anything you do to improve reliability also improves economy, and vice versa. Changing the transmission fluid in your car not only makes it less likely that you will be stranded at the side of the road, it also saves you spending several thousand dollars for a new transmission.
When people talk about systems with "low cost but poor reliability" they are almost always talking about initial upfront costs and forgetting the recurring costs.
I disagree here. We're not speaking of routine systems with standard ways of improving reliability already know. Rockets as they are now are systems optimized with a particular combination of reliability and cost. If we want to get to a different optimized combination, there will *always* be a tradeoff.
Also, let's look at the current situation. SpaceX has a launch vehicle that is currently very unreliable, but could down the road become very reliable. But under NASA's current plans for exploration of the Moon and Mars, there simply aren't any cheap payloads (that is, payloads that wouldn't cost much to assemble on Earth) to feed business to SpaceX. SpaceX has to somehow jump that reliability hurdle in order to get that business.
In contrast, the COTS resupply contracts to the ISS give SpaceX a path. They can start with the cheap cargo resupplies. And if they prove the reliability of the rocket, they might eventually fly passengers to the ISS and possibly other high value missions.