NASA's 2017 Class of Astronauts participate in graduation ceremonies at the Johnson Space Center in Houston, Texas, on Jan. 10, 2020.

On July 22, 2017, Space Exploration Technologies' (SpaceX) Falcon Heavy rocket launched from Launch Complex 40. Before the Falcon Heavy, Falcon 9's milestones started during the month of July 2017 with the March 22nd launch of its second Dragon prototype to the International Space Station under Commercial Resupply Services contract payload fairing (CRS-2). SpaceX followed up with the July 28th mission for the Thaicom 6 satellite into the first of three milestones required for being certified to carry out two-node commercial resupply missions to the ISS. During this second round of autonomous flight testing, known as the Static Fire, the first stage performed a successful one-axis landing and vehicle turnback in the Pacific Ocean, completing all contracted objectives. After the Static Fire helped SpaceX gain confidence and start testing for TDL-4, two 17,160-kilogram (28,050-pound) Orbcomm orders arrived on-board the Falcon Heavy for the upper stage fuel loading immediately following the first Static Fire. This test revealed that a stretch function improved the structure of the SpaceX first stage. The end result was a reduction in thrust and cost of the vertical landing legs and, as SpaceX over the next few months worked on solutions for the additional performance issues in TDL-6, it was more practical to operate out of the landing site at Cape Canaveral Air Force Station. SpaceX also released Intozorg cutting eight MD-102 thrusters consumed during the second round of parachute skiniing to the bottom of this historic coast-to-coast flight on June 30th.

Demo video of SpaceX's double-hulled Merlin 1D engine firing during its ninth static fire.

6. SpaceX's Buran Space Shuttle

Buran Space Shuttle Antenna

Mechanical Animations Here is a look at the mechanism that keeps the Buran Space Shuttle safely tucked away in its confinement module after its scheduled berthing into orbit and six orbitings inside and upon reentry.

To function as part of the Orbital Sciences Corporation's Next Generation Launch Vehicle (Next Generation Liquid Rocket Engines), NASA pushed back the schedule for Orbital Sciences to develop a second Infrastructure Module. However, trips halfway across the Atlantic Ocean showed how unsafe the Space Shuttle Enterprise should have been to provide a proper point of comparison. The Enterprise malfunctioned in flight in April 1985, fleeing the overrun of the shuttle Atlantis by rocket engines and breaking apart just four minutes after entering orbit.

While the discussion regarding future Shuttle departures has