For Jeff King: Why are Interplanetary Robots So Expensive?

One of the downsides to having multiple blogs all on the same system is that I sometimes put my post on the wrong blog. This was first put on Rocket Scientist (where The Mother commented: "Two words: R and D." It should have obviously been put here. Sorry about the confusion.


Jeff King asked: The mars rovers look simple to build, so why do they cost so much to build… actually I thought they would look cool and very complex?

That's actually an excellent question. I think a lot of people wonder how space equipment comes to be so very very expensive. And it is. Even simple straightforward equipment is often an order of magnitude more expensive than it would be in a retail outlet.

There are several reasons for this, but those reasons are driven by two other reasons: extreme environment and reliability. The first reason drives design and it's easy to underestimate the impact of environment on hardware.

To rove around on Mars, a vehicle has to be able to withstand dust and unknown terrain.

It must be able to withstand a radiation environment that is far harsher than we have on Earth (thanks to the protection from our magnetic field), which is hell on electronic equipment, computers and data storage. Most electronic hardware made to withstand high radiation environments are created for military and frequently go through extensive testing and/or "rad-hardening" that exposes them to radiation, testing and often redesign so that they can reliably withstand more extreme radiation environments. This not only increases development and testing time, it might increases material costs if different materials are required to reach an effective design. That increases costs enormously, especially given that there are often only a handful of vendors for a part - which means they can charge nearly anything they want for those consumers who must have them.

The electronics and batteries and all other equipment must also be able to withstand temperature extremes, particularly cold which is very hard on many aspects, including lubricants, batteries, electronics. The extreme in cold can affect tolerances for mechanical interfaces. Which means all equipment must be tested in environments colder than most electronics on this planet need to survive for months if not longer. Vacuum (or, rather, the very very low pressure) adversely affect lubricants as well and complicate thermal characteristics as convection effects are limited. That means you might need some form of heating and cooling for electronics that are cold-sensitive or heat-producing.

For reliability, there are design considerations as well. The design has to be restartable and redundant, in case something goes wrong, or the cost of the whole mission (hundreds of millions, mostly on the trip to/from) is lost. Batteries must be lightweight, high density, resilient to radiation and cold, reliable, and long lasting. Solar arrays must also be lightweight, efficient, reliable and able to use the reduced light available on Mars (compared to here).

Because so much hinges on the functionality of these parts, each part must have a "pedigree" - i.e. been obtained through vendors that have certified processes and materials and who ensure that each part is tracked and verified to be clean and functional. And that makes those parts more expensive.

But, what frequently costs so much is verification and analysis. Hardware is tested, exhaustively, through dedicated use (often months) in testing facilities. Often flight-like prototypes are destructively tested to ensure the flight hardware meets requirements. In addition, a great deal of time and manpower is spent performing reliability and safety analyses, fracture control analyses, fault trees and failure mode and effects analysis, safety assessments.

Frequently, complex (and it can look simple without being simple) devices are one-of-a kind and require exhaustive and unique software that must also be exhaustively tested and retested.

No one's going to sue us if a rover fails, but years of design and planning, years of flying through space, and, literally, hundreds of millions of dollars are at stake, not to mention quite a few reputations.

If it's gotta work, you gotta do it right the first time and that costs a lot of money. But it's cheaper than doing it over. Better more money spent on testing than a second flight because the first one failed.

And that's why they cost so much.

And kudos, I think, have to be offered to the teams that built both Opportunity and Spirit for surviving >20X their expected lifetimes. That design overkill meant we got our money's worth.

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Quadmama asked: Blog pages?

Quadmama asked: How do I add a "page" to my blog... for instance a disclosure policy or other info that I want people to read but don't want the entire thing right on my home page?

I can't answer this readily. Truth is, html isn't my strong suit. However, I'll tell you what I did as an html idiot and hope that one of my many computer savvy readers will pop in with more details if it doesn't answer your question.

I use blogspot and it's pretty uncomplicated. It's got a standard form and, to make a "page" I put in a post with a forced date earlier than my earliest post so it went to the "beginning". Then, I just have to put a link up in the setup. I'd love to tell you how I did that here, but I had someone build my website and she put in a button for me. I don't think it would be hard to do, but I haven't done it so I don't have the specifics.

Bottom line, "page" is just a post. It's the link to it that makes it useful. If that doesn't help, I'll hit up one of my knowledgeable buds and hopefully they can get you more steps.

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For Flit: What Was Your Answer?

Flit asked: What sort of system did YOU design ...and did he recognize your brilliance and give you a decent mark for it?
OK, I was hoping someone would ask me. :)

So, we come in with our projects. Now, this was an upper level class and had a prerequisite (which no one told me about) so it was my first design project. It was not the first one for the other students.

The project which I described yesterday was a "personal fire escape device" for high rise buildings (~10 floors), with a 300 pound limit, a minimum and maximum speed, cost per unit, etc. It was pretty clear, although not said out loud, that the teacher was looking for a braking system for a cable/harness system. Ostensibly this was in response to tragedies like the MGM Grand Hotel fire and to reduce insurance liability. In case of fire, the hotel guest would strap on diaper attached to a cable in a black box and leap from the window, confident that the device would save him.

I went into the reasons why the proposal as written didn't work for me on yesterday's post. Feel free to check it out. So, if I didn't like the proposal, what did I do instead?

Well, I completely scrapped the "personal" fire escape device. I couldn't see a way for it to be flexible enough to work for families, be inaccessible for nonemergencies but reliably available for emergencies and be maintainable. So, if I, the scaredy cat, wouldn't want to jump out the window tied to a harness, I thought, what would work for me?

So, I came up with a notion of a rotating net on each side of the building, which one could reach out,grab, and ride right down. Hooks could be provided to help you stay on. You could move out of the way if there was fire directly beneath you. It was not inherently limited to weight. It was easily maintained (four winches on the roof with a backup generator in case power was discontinued), and the net, nominally rolled around it's rotor was only released in case of emergency. It addressed most of the issues I had with the original premise. As an added bonus, a fireman could actually ride the net up and over (or the net could be reversed if necessary) to help rescue people who are trapped or too afraid to come down. See my quick sketch from memory.

The winches were sized appropriately. The net was made of Kevlar (fire resistant) with a wire core to help it hold it's shape if it were exposed to direct flame.

The response to my idea was not what I expected. "That isn't what we asked for." The teacher was confused. The other students were confused. No one had any idea why I chose something different.

"I know," I said, "the other idea wouldn't work and here's why." (I had sketches demonstrating the problems). When I questioned those that provided solutions where they hadn't accounted for the issues, I got a lot of perplexed looks. No one had thought of them. No one understood why I was asking those questions (although those questions - gasp! - get asked in the real world).

Now, I mentioned that say 36/40 students did the cable/braking design, but there were a few that did something a little different. I remember three of them.

One involved jumping into "some sort of panty-hose" like material that would slow one down. The person who proposed it had no understanding that the forces required to slow a person don't just disappear - it's friction and that creates heat. Falling ten stories, it creates a lot of heat. Also, how do you size it? If you get a fat person, you can plug the whole thing up (he had them on every corner of the building as opposed to each room so multiple people would use them). Someone too skinny could slam into the ground (or someone below them). Nor could I think of any pantyhose-like material that could withstand fire or heat. The designer couldn't either.

Another involved a winch in every room that would allow escapees to walk backwards down the side of a building at 4 mph (because Boy Scouts can walk 4 mph), a building covered with windows. Asking if that wasn't a bit challenging got me a blank look and the designer had given no thought to the maintenance (or cost) of a winch in every room.

But I have to give top laurels to the parachute material design though. One individual (who deserves credit for originality) proposed tubes made of parachute material pleated into a tube kept in the ceiling that would shoot out the window at 45 degrees so that people could slide down. There would be a trickle of water to help with friction, but we were missing a method for entering said tube. But more than that, again the physics weren't fully thought out. What happens if the tube gets water (or a person) but the end isn't weighed down? So much for the 45 degree angle. A little water and the tube will end up flat against the building unless you weight the ends. Why not weight the ends? Imagine if you will, tubes shooting out of the building in every direction, heavily weighted.

So, now you know. I got a C, but I think I surprised everyone. Also, I was apparently missing pieces of the project I didn't know about. If it makes you feel better, I ended up with an A in the class and the respect of the professor. And I learned a valuable lesson that I have seen played out a hundred times.

Now I play to my strong suit and professionally ask the hard questions so that our designs end up better than they might have otherwise. So, it's all good.

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