At a 3 percent growth rate, its doubling time â or the number of years to double in size â is 23 years. (The doubling time for a population can be roughly determined by dividing the current growth rate into the number 69.. Therefore, 69/3=23 years.
But the attempt was scrubbed about an hour before launch due to the helium leak. Todays launch has been scrubbed due to a helium leak on Falcon 9's first stage, SpaceX officials announced in an update today. A fix will be implemented by the next launch opportunity on Friday April 18, though weather on that date isn't ideal. [ See photos of SpaceX's 3rd Dragon mission to the space station ].
Congress forcing a compromise(d) Space Shuttle design on NASA. Among other things, the space shuttle was the first human space vehicle to use solid rocket boosters. Solid rocket boosters were previously deemed unsafe for human space flight because once they're lit, they don't stop boosting until the fuel is gone. Liquid-fueled rockets can be shut off.