Countdown to Curiosity: launch delay by 1 day

20 11 2011

This is Ecogirl & Cosmoboy’s 100th blog post! Thanks to everyone who’s been reading and there’s more to come!

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Curiosity’s launch has been delayed from Friday November 25th to 10:02 am Saturday the 26th. The delay is due to a battery change in the Flight Termination system of the Atlas V launch vehicle. Flight Termination systems are a key part of range safety (rockets frequently do veer off course!) so this is a pretty big deal.

So rather than writing about an experiment today, let’s take a closer look at some of the launch details and any dangers that might be lurking there.

What if it all blows up? Well other than being a huge disappointment for thousands of people that have worked on the project, there are a number of hazardous materials on the rocket. From the press perspective, I’m sure the most play would be given to the 3.5 kg of Plutonium 238 that is actually Curiosity’s main power source.

But there’s really very little cause for concern. 238Pu is what’s known as an alpha emitter – it emits alpha particles (essentially helium nuclei, containing two protons and two neutrons). From a particle physics perspective, these are comparatively large objects that will interact easily with material around them. Thus they don’t penetrate far, even a few inches of air or paper is enough to protect against small sources of alpha particle radiation. That’s considerably different to say gamma radiation emitters which can penetrate inches of lead (depending on their energy).

In short, NASA estimates there’s about a 1 in 400 chance of material being released during the launch. Anyone who was exposed to this material would actually receive a radiation dose far below that we receive in a year from natural sources. For the experts, the maximum dose expected for an individual in the launch range is 0.23 rem (as compared to 0.14 rem/day being average exposure from solar and cosmic radiation). For the dose to be fatal, it would need to be over two hundred times higher, and that is simply not going to happen – there isn’t enough material on board, and it’s type of radiation is easily shielded.

It’s worth pointing out that NASA launches have to undergo an environmental assessment (here is the one for Curiosity). These issues are taken very seriously and each launch has a list of hazardous materials that are on board. According to NASA documentation each Atlas V launcher (i.e. neglecting the payload) includes 4.7 tons of hazardous waste. In case you were wondering, here’s the list!

Material                                                                         Quantity
Petroleum, oil, lubricants                                    2177 kg (4790 lb)
VOC-based primers, topcoats, coatings            145 kg (320 lb)
Non-VOC based primers, topcoats, coatings   86 kg (190 lb)
VOC-based solvents, cleaners                             627 kg (1380 lb)
Non VOC-based solvents, cleaners                    432 kg (950 lb)
Corrosives                                                                2500 kg (5500 lb)
Adhesives, sealants                                                1036 kg (2280 lb)
Other                                                                         291 kg (640 lb)
Electron QED cleaner                                            5.7 liter (5 qt)
MIL-P-23377 primer                                              2.8 liter (5 pt)
Silicone RTV-88                                                      45 liter (10 gal)
Electric insulating enamel                                    0.1 kg (5 oz)
Acrylic primer                                                          22 liter (5 gal)
Conductive paint                                                     45 liter (10 gal)
Chemical conversion coating                                0.3 kg (10 oz)
Cork-filled potting compound                              5.7 liter (5 qt)
Epoxy adhesive                                                        5.7 liter (5 qt)

So how likely is a launch problem? Looking at the statistics of the Atlas V rocket, it’s had 27 launches and 1 failure. That’s close to a 4% failure rate, which is actually pretty good. The probability of anything going wrong on the range itself is low – thankfully!

Of course there are mission risks far beyond the launch itself. The recent Phobos-Grunt problems serve as a good reminder that there are plenty of things that can go wrong on a mission to Mars – this is rocket science…

Tomorrow, provided there are no further delays :), Sample Analysis at Mars (SAM).

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2 responses

24 11 2011
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24 11 2011
Elektrische Zahnbuerste

Straight to the point and nicely written! Why cant everybody else be like this?

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