November 18, 2004

Space tourism: (too) risky business?

The estimable Alex Tabarrok argues:

The vision is enticing but the facts suggest that space tourism is not ready for market. The problem is not the monetary expense, there are enough millionaires with a yearning for adventure to support an industry. The problem is safety. Simply put, rockets remain among the least safe means of transportation ever invented. Since 1980 the United States has launched some 440 orbital launch rockets (not including the Space Shuttle). Nearly five percent of those rockets have experienced total failure, either blowing up or wandering so far from course as to be useless. The space shuttle has a slightly better record of safety -- it was destroyed in two of 113 flights. There are lots of millionaires willing to spend one or two million dollars for a flight into space but how many will risk a two to five percent chance of death?
Enough to keep the rockets full, I'm guessing, if mountaineering stats are any indication. According to this website, the overall fatality-to-success rate of those who set out to climb Mount Everest is 9%, though since 1990 the rate has dropped to 4.4% -- still a very risky (and costly) proposition, and still very popular: no less than 1,640 climbs to the summit are recorded in the same period.

Everest isn't even at the top of the list; here is a brief list of the riskiest 8000m+ peaks:

Annapurna (8,091 m)
In total, only 130 climbers have summited Annapurna, while 53 have died. The overall fatality rate is thus 41%.
Nanga Parbat (8,125m)
216 climbers have summited Nanga Parbat and 61 have died. The overall fatality rate thus 28.24%.
K2 (8,611 m)
Fewer than 200 climbers have summited the world's second highest peak 198 total. 53 have died. K2's overall fatality rate is 26.77%.
Kangchenjunga (8,586 m)
To date, only 185 climbers have summited Kangchenjunga and 40 have died. The overall fatality rate is thus about 22%.
Manaslu (8,163 m)
To date, 240 climbers have summited Manaslu and 52 have died. The overall fatality rate is thus 21.67%.
Dhaulagiri (8,167 m)
To date, 313 climbers have summited Dhaulagiri and 56 have died. The overall fatality rate is thus 18%.
Makalu (8,485 m)
To date, 206 climbers have summited Makalu and 22 have died. The overall fatality rate is thus about 11%.
Gasherbrum I (8,080m)
Since 1958, only 195 climbers have summited Gasherbrum I and 21 have died. The overall fatality rate is thus 10.77%.
Shisha Pangma (8,027m)
To date, 201 climbers have summited Shisha Pangma and 19 have died. The overall fatality rate is thus about 9.5%.
NOTE: These figures are just for fatalities, which tends to understate the overall risks of mountaineering. Spaceflight risk will tend to be all or nothing, but high-altitude climbers face the additional risk of crippling injuries -- broken limbs and the like, of course; but also loss of appendages to frostbite; altitude sickness leading to pulmonary or cerebral edema, heart attacks, strokes, and embolisms; and the potential loss of serious numbers of brain cells to prolonged hypoxia.

UPDATE: While this post was essentially concerned with the issue of risk tolerance among well-to-do adventure travelers, others took issue with the underlying estimation of the riskiness of space tourism. Alex Tabarrok responds here. My take: his skepticism is well-founded for a space tourism industry running thousands of flights per year; at 100 flights or fewer, however, the mountaineering comparison will hold true.

FURTHER THOUGHTS: There's a big difference between excursion tourism ("fat guys with cameras") and adventure tourism (lean guys in boots, get insurance before you go -- if coverage is to be had), despite some scumbling in the middle. Certain places -- Everest, for example -- will never be excursion destinations, while the development of tourist infrastructure has opened up many other destinations once squarely in the adventure camp. Space tourism is sure to follow the latter path, starting as extreme adventure travel and eventually ending up as a relatively safe thrill for the masses. The real question here is not whether, but when.

Bonus topic for further discussion: The De Havilland Comet -- more detail, including full accident reports and analysis, here. The Comet may have killed the British airliner industry (along with over 100 passengers and crew), but did it even put a significant dent in public enthusiasm for jet travel?

AND NOW FuturePundit Randall Parker weighs in, with comparisons with aviation c. 1938.

Posted by David on November 18, 2004 9:37 AM


I disagree with your evaluation. You'd have to calculate fatality rates taking into account those who have tried and failed (non-fatally), in addition to those who have tried and succeeded. That would be a much more accurate measure of risk.

Although, on the flipside, you'd have to somehow account for people who showed up at base camp and made it no further. So: I think your figures are inaccurate, but I can't think of a better metric right offhand.

Posted by: Slartibartfast on November 18, 2004 10:30 AM

Space tourism and mountaineering aren't strictly comparable, obviously.
But I do think the stats cited for Everest are a good indication of perceived risk -- in this context, the most relevant factor.

Posted by: David on November 18, 2004 11:19 AM

I don't think the "tried and failed" stats pertinent to mountain climbing would be a factor in the risks encountered in rocket travel. There is the failure possiblity of failure without fatality built into the former, whereas with the latter failure most probably leads to death. Obviously, you can stop a climb at any point and descend, something you can't do when strapped in a rocket. It has nothing to do with perceived risk, unless one's perception is totally distorted.

All that said, there are lots of rich folks who would pay to ride the rocket at those odds. Those risk odds run about parallel to going into Goob's Tavern on Saturday night about 10 p.m.

Posted by: Buster on November 18, 2004 11:34 AM

If anything, I would say the attraction of an activity equally as risky as mountaineering will only be enhanced by the marked lack of physical effort and discomfort required for space flight. Also, the all-or-nothing approach to risk will also be more appealing than the potential to spend the rest o fyour life disabled. As much as everyone admired Chris Reeve, noone wants to be the next notable injury.

Posted by: submandave on November 18, 2004 11:48 AM

There may be enough passengers, but what about pilots? They are not taking that risk once, like the passengers or the mountaineers and shuttle astronauts cited above, but are expected to take regular flights.

If the rocket has a five percent chance of blowing up on each flight, and the pilot is supposed to make a trip a week, odds are that the pilot will be dead in under three months. Even if he only makes one flight a month, the odds are against him surviving a single year.

The Space Shuttle odds (2% failure) are better, but would still have him dead in about six months of weekly flights.

While the rocket failure odds may be acceptable for a "once in a lifetime" tourism opportunity, they certainly don't provide for much job security.

Posted by: Joe Zwers on November 18, 2004 11:48 AM

I believe Alex Tabarrok's analysis of space tourism's risks is flawed because he is only looking at boosters launched from the ground. Rutan's SpaceShipOne was air launched, as will be his follow on vehicle for Virgin Galactic. Those are wildly different flight profiles with different degrees of risk. The energy levels involved with a surface launch are much greater than for air launch. Many of those failures cited since 1980 happened within the first stage burn.

The flight profile of SpaceShipOne more closely follows the 1960s X-15 research plane which flew 199 missions with one fatality. That fatality happened when the pilot lost control during reentry - an issue Rutan resolved with his shuttlecock mode.

Even comparing the X-15 to SpaceShipOne has its limits. The X-15 was designed for hypersonic research missions as well as high altitude flight. It was powered by a liquid fueled rocket engine that was sometimes tempremental. The design factors for very high speed flight usually lead to high landing speeds, something that is less an issue when the objective is to fly vertically. Rutan has designed a vehicle strictly for the high altitude mission using a less risky hybrid rocket engine. While SpaceShipOne was designed to win the X Prize, the Virgin Galactic vehicles will be designed with even greater safety in mind.

Posted by: Larry J on November 18, 2004 11:54 AM

Mountain climbing risks are beside the point. The real problem is that Prof. Tabarrok's extrapolations are based on an incorrect premise, namely that rockets is rockets. For purposes of estimating safety, they aren't.

Consider. From the dawn of the Space Age until the recent flights of SpaceShipOne, every manned or unmanned rocket was fueled by two liquids, one or both of which is a normally gaseous element rendered liquid by cooling to cryogenic temperatures. In some configurations, there are also booster stages involved that burn a solid fuel consisting of a mixture of a fuel and an oxidizer mixed with a binder and cast into one or more "grains" that are loaded within a basically tubular casing.

Both conventional liquid fuel and solid fuel rockets pose non-trivial risks of catastrophic explosion for essentially similar reasons - unintended and uncontrolled mixing of fatally large quantities of their propellant chemicals.

With liquid fuel rockets, the two propellants are carried to engines through a complex and failure-prone system of plumbing and pump hardware that has to withstand huge temperature differentials, internal pressures and vibration loads. The pump hardware is usually high-speed, high-pressure turbines which add their own rich pallette of catasrophic failure modes to the overall picture. As both propellants are liquids, even relatively minor leaks can quickly lead to a sufficient quantity of both propellants coming together and igniting outside of their intended rendezvous in the combustion chambers of the rocket motors. A small explosion, of course, quickly produces more structural compromise, larger volumes of propellant meet "out of school" and in a fraction of a second, the entire propellant load explodes at once. This type of failure cascade is intrinsic to bi-propellant liquid rocket motors.

Solid fuel rockets are, in many ways, even more problemmatical as the entire fuel-oxidizer load is in rather intimate contact from the get-go. If the propellant grain does not burn in the intended controlled fashion, internal motor pressures rise quickly to the rupture point and an equally catastrophic explosion destroys the rocket and its payload.

At least as bad is the fact that once ignited, even if it burns as intended, a solid rocket motor cannot be shut down. If there is some reason other than propulsion failure to abort a mission, a solid fuel rocket booster makes shutting off thrust impossible. One is faced with either riding the booster until it burns out, or with trusting to some sort of separation-under-boost system. The latter cannot, itself, avoid being risky to use. Sudden major configuration changes to a vehicle which may already be moving at hypersonic velocity is not something to contemplate lightly.

The solid fuel-liquid oxidizer hybrid motor used by SpaceShipOne suffers from neither of the above-described sets of explosion/loss of vehicle risks. All of the oxidizer is tanked external to the engine. All of the fuel is inside the engine case. The only place oxidizer can meet fuel is within the combustion annulus of the motor. Further, the only place the two can burn is the exposed inner surface of the fuel grain. There is no way that all of the oxidizer can instantly come into intimate contact with all of the fuel and cause an explosion.

The fundamentally different nature of the engine system on SpaceShipOne and any of its follow-ons or competitors that also use liquid oxidizer-solid fuel hybid engines, make them fundamentally different in kind than the delicate and cranky machinery that has heretofore been employed to boost people and payloads into space. Extrapolating the probable safety of the former by just extending curves of data based on the latter, then, amounts to mathematical malpractice.

Posted by: Dick Eagleson on November 18, 2004 12:13 PM

Larry J nails it. Rutan intends to demonstrate that NASA went down a blind alley with the Space Shuttle. And Alex Tabarrok's analysis is flawed not only due to the ground launched issue, but because the rocket technology used by SpaceShipOne (nitrous oxide and rubber) is inherently safer than the hydrazine or LOX & hydrogen of the older rockets.

Posted by: Jack Okie on November 18, 2004 12:16 PM

David: the comparison isn't completely valid, since none of those mountains is in the U.S., so U.S. standards of liability and litigation don't apply.

Also, what percentage of those who died were led by a professional guide service, versus informal teams? With an informal team, there's no one to sue. With space tourism, there's definitely someone to sue.

Posted by: Les Jones on November 18, 2004 12:52 PM

Submandave: There have long been a number of flying professions which invloved rather high risks. Airmail in the early days was a terrible killer, and bush flying today remains quite risky, with an estimated 10% chance of death in a 30-year career. Herring spotting in the Gulf of Alaska was far worse still, with mid-air collisions happening on a weekly basis during the season. But somehow there was never a shortage of pilots...

I suspect that if Galactic offered pilots, say, $25,000 per flight, they'd have military pilots lined up at the door to run trips. And that's probably far more experience than is really needed. From what I've read (and I'm a pilot) what SS1 demands is mostly a cool head that's good at following procedures. There's a lot of young folks out there flying commuters and bizjets who could do this quite well.


Posted by: Colin K on November 18, 2004 1:46 PM

Nice discussion, all.
One thing to add: There is a certain sort of person who finds mountaineering risk much more acceptable than some other high risk activities -- and that is, people who feel safer when they are in control. This is the sort of person who may not like flying in airplanes (although it is much safer than driving) because of the lack of control.

Also, more important (I think) than actual risk is perceived risk or felt risk. I recall reading an article some time ago that crash performance in SUV's and trucks is generally worse than that of well-designed small cars (I think I remember the specific comparison of a Ford Explorer with a Cooper Mini), yet people tend to "feel" safer in SUVs and big vehicles, because (a) there's a lot of material there, and (b) those small cars look so tiny!

Of course, there's another side to that, too. Airplane and rocket/space shuttle crashes tend to get lots more media attention than certain other risky activities (such as driving and car crashes) so perceived risk may be higher (how many people do you know who are afraid of flying versus the number afraid of driving?) when in fact it is not.

In summary: I suspect perceived risk would be effectively higher for space tourism after accidents happen, as media attention would undoubtedly be very high compared to other, similarly risky activities (as it is for airplane crashes). Additionally, people may be afraid as they are out of control. Space tourism operators could help with this at least somewhat by building ships which look and feel safe, if the auto example holds true.

Posted by: David M. on November 18, 2004 3:24 PM

To the whole risk analysis issue at this stage, my response is:

Your point being?

I was an avid white-water rafter some years back (my recreational choices are somewhat tamer now-a-days). I didn't do it because it wasn't risky. Quite the opposite. Risk added to the thrill.

No, of course I wasn't looking to kill myself (I wouldn't have been able to enjoy white-rafting nearly as much dead now, would I). But there's an "edge" where life can be quite exhilirating. You weigh the balance.

Space? ...Umm, I don't think the tourists are going to be lining up because it's safe.

"Safe enough" will do just fine for most anyone looking to add a bit of zest to their existence is my suspicion ...and I doubt there's going to be some commonly shared perception of a certain statistical percentage of safety that will be applicable to individual traveler's decisions to purchase their ticket. Folk are going to measure their perception of the desire to ride into space in highly individualized ways.

And I just wouldn't expect "safety" (within reason) to be an overly high consideration on that perceptual balance.

...and if there was ever a case to be made for the journey itself being the purpose, this has to be right near the top of the list.

Now. If I was going to be commuting to an orbital factory on a fairly regular schedule, I might want to re-think the safety estimate issue though. (My automobile purchase was based almost solely on crash safety considerations ...seems foolish not to extend your odds in that situation, eh?)

Posted by: brandon davis on November 19, 2004 4:30 AM
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