SpaceX Grasshopper August 2013 progress

SpaceX’s Grasshopper is a technology demonstrator rocket that has been taking small steps toward a vision of a reusable rocket that takes off vertically and returns to land vertically. Each step has pushed the performance out both in terms of highest altitude reached and in flight duration.

The first “hop” took place on September 21, 2012 was 1.8 m (6 ft) and lasted 3 seconds.

The second “hop” test was a little over a month later on November 1, 2012, and went up 5.4 m (17.7 ft) and lasted 8 seconds.

A month and a half later, on December 17, 2012, Grasshopper performed a much more impressive flight than the previous two hops, reaching 40 m (131 ft) and lasting 29 seconds.

A few months later, on March 7, 2013, it doubled its previous height reaching 80 m (263 ft) and lasted 37 seconds.

Then, a little over a month later on April 17, 2013, it tripled that to reach 250 m (820 ft) and lasted about 60 seconds.

On June 14, 2013, Grasshopper reached 325 m and (1,066 ft) in a 68 second flight, this time using its full navigation sensor suite.

The most recent test as of today was the August 13, 2013 flight which didn’t go as high as the previous flight, reaching only 250 m (820 ft), but was more impressive as it displayed maneuverability by moving 100 m laterally to its launch site before returning. The flight lasted roughly 60 seconds.

In physics, the rocket equation states that as you add more propellant the maximum change in speed of the rocket only grows as the logarithm of the propellant mass. In a word, that’s not good. When you add more mass, the initial mass of the total rocket is greater so all the previous propellant has to “work” even harder. Adding more propellant mass will get your rocket higher, but the efficiency isn’t great. This is why I initially was skeptical of the idea of Grasshopper as to have the rocket burning mass on the way down means it had to carry it up to begin with, but the idea of a reusable rocket drops prices by a good bit (I imagine), so I’m happy to be gradually shown wrong with these successive tests.

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