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Congratulations to SpaceX for sticking the landing

13 Apr

As someone who has been listening with some interest to the trials of SpaceX in perfecting its re-usable rocket system, I was very happy to see news that they had successfully stuck their landing on this, their fifth overall attempt.

Easy peasy, right? Try it youself:

https://scratch.mit.edu/projects/76866912/

I’m not sure it’s even possible in the game. Frankly, I would never have thought that it was possible in real life long enough to even put engineers on the project- even if I was using $100 bills as toilet paper because I just had to get rid of the stuff somehow.

The two-stage Falcon 9 rocket blasted off from Cape Canaveral on April 8 carrying the robotic Dragon cargo spacecraft into orbit for resupplying the International Space Station (ISS). Following the deployment of the cargo craft, the Falcon 9’s stage 1 rocket returned to earth to stick a perfect vertical landing atop on a floating sea platform.

The long-term purpose of this feat is to re-use the first rocket stage in subsequent launches, thereby lowering the cost of these space taxi flights, and increasing the frequency of their missions. Hans Koenigsmann, VP of flight reliability at SpaceX said, “… we hope …  to be able to launch basically every other week by the end of the year.”

The strategy employed in managing these rockets is outlined below, where the first stage executes a flip orienting its exhaust forward to allow for firings to slow the craft down and orient it towards the landing platform:

https://i0.wp.com/www.spacex.com/sites/spacex/files/16892430560_f87dff78c0_o_1.jpg

It is important to keep in mind that the landing is a great challenge, but it is not the only hurdle SpaceX has had to overcome. Delivering something into space may not seem terribly difficult. ‘How high does this need to go?’ is a reasonable first question. The ISS orbits at an altitude of 249 miles. Farther than you would want to commute on a day to day basis, but nothing like the distance to the moon or Mars (230,000 miles and 35.8 million miles away at their closest, respectively).

But another consideration is just how fast the rocket needs to travel in order to put something into orbit. Orbit isn’t just height, but requires a horizontal speed tangent to the planet such that as the craft falls to Earth, it’s horizontal movement has pushed it far enough that the Earth is dropping away below it just as quickly as it falls. The ISS travels at a speed of 4.76 miles / second, which translates to a 17,136 miles per hour. So, if it shot straight up and reached the height of the ISS orbital, there would still be this 17,000 mph speed difference to deal with, a problem that may sound familiar to viewers of the recent films, Gravity and The Martian.

To bring  cargo destined for the ISS into orbit, Falcon needs to list off, gain an altitude of almost 450 miles, and accelerate to a speed that would carry a traveler from Washington D.C. to New York City in 43 seconds.

The first stage, or main rocket engine, is designed with an array of nine ‘Merlin’ engines producing 6,806 kiloNewtons (at sea level) of force for 162 seconds of thrust. The first stage actually only fires for 180 seconds during liftoff, leaving 82 seconds of thrust for three separate return trip burns.

Following separation of the first stage, a second stage is equipped to navigate into one or more orbits for payload delivery with 8 minutes of burn. This is an unusual capability because  reigniting these large engines several times, just isn’t done in most rockets.

Ok, I’m gushing like a fanboy, but with NASA doing less and less in the way of manned spaceflight (believe me, I’m plenty impressed with their unmanned flights), SpaceX gives big kids like me something to watch and dream of a second – wait, third- career as an astronaut.

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Posted by on April 13, 2016 in Uncategorized

 

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