I remain optimistic that innovation will find a solution to all the elevator challenges, not just the tether. It is now just 13 days until the 2006 X-Prize competition, which includes $200,000 prizes each for climber design and tether design. I speculate that the tiered prize structure will prove very efficient at fostering innovation from the private sector. Last week the Spaceward Foundation announced that the package of prizes has been increased to $4,000,000 over five years.
…NASAâ€™s Centennial Challenges program has increased its commitment to our project, and we now have a total of $4,000,000 in prize purse to disburse over the next 5 years. Yes, thatâ€™s right – 10 times the purse weâ€™ve had so far, and a solid commitment through 2010 – two things which will enable us to take our program to the next level.To make the most efficient and prudent use of these funds, we will follow an escalating prize purse strategy – this yearâ€™s prize purse will remain $200,000 per each of our two competitions, increasing to $300,000 in 2007, and so on, until we reach $600,000 in 2010. Any unwon prizes (and we do not intend to have a winner every year – that will mean we have made it too easy!) will automatically roll over to the following year.Still, the same catch that applied last year will continue to apply in the years to come – NASA provides us with the prize money, but not with operating funds. In order to bring our operations to a level that matches the prize purse, we need to get commercial sponsorship.
Incidentally, to frame the difficulty of the tether solution [the biggest challenge], recent calculations by Nicola Pugno of the Polytechnic of Turin, Italy, suggest that carbon nanotube cables will not work.
…In something of a “downer” for space elevator fans, Pugno has calculated that inevitable defects will greatly reduce the strength of any manufactured nanotubes. Laboratory tests have demonstrated that flawless individual nanotubes can withstand about 100 gigapascals of tension; however, if a nanotube is missing just one carbon atom, it can reduce its strength by as much as thirty percent. Bulk materials made of many connected nanotubes are even weaker, averaging less than 1 gigapascal in strength.
In order to function, a space elevator ribbon would need to withstand at least 62 gigapascals of tension. It therefore appears that the defects described above would eliminate carbon nanotubes as a usable material for a space elevator cable. Pugno will publish his paper in the July edition of Journal of Physics: Condensed Matter. Nanotube enthusiasts counter that ribbons made of close-packed long nanotubes would demonstrate cooperative friction forces that could make up for weaknesses in individual nanotubes.
There will be a live webcast from Las Cruces, NM of the Xprize competition.
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