Riding a Dragon to the Heavens


  1. Ripley's Believe It Or Not - SpaceX Crew Dragon test flight
  2. Max-$Q$! Max-$Q$!
  3. A Pioneering space probe

Current events

Huge news last night - SpaceX successfully conducted the first test launch of its Crew Dragon capsule, a crucial milestone in its goal to return manned spaceflight capability to the United States since NASA retired the Space Shuttle fleet in 2011. For the last 8 years, we've been totally reliant on Russian Soyuz rockets for access to the ISS at the hefty price of $80mm per seat. There weren't any astronauts on this launch, just a sensor-laden dummy named Ripley (from the movie "Alien"), but if development remains on track, the first crew could launch as soon as July.

Crew Dragon atop the Falcon 9 rocket on the launchpad in Cape Canaveral, FL

SpaceX and Boeing have both been developing a manned capsule since 2014 when NASA awarded them a commercial crew contract (Boeing's capsule is called the CST-100 Starliner). Crew Dragon is a significant upgrade from the existing Dragon capsule used for cargo, sporting windows, life support, touch screen displays, and an emergency escape system in the event of launch failure.

Today I learned

Continuing on the topic of rocket launches, if you ever watch a video of one, you'll hear the countdown announcer mention max-Q. For example, in the video of the Crew Dragon test launch from last night, it occurs at 1:25 ("vehicle is passing through max-Q")

Max-$Q$ is the point when a rocket experiences maximum dynamic pressure (air resistance). The formula is $Q =\frac{1}{2}pv^2$, where $p$ is local air density and $v$ is rocket velocity. Consider this:

  • $Q$ is $0$ at liftoff because although the air is thick at the surface, the rocket is stationary ($v=0$). 
  • $Q$ is also $0$ by the time the rocket is in space because although the rocket is flying super fast, there's no air in the vacuum of space. 

So if we were to plot $Q$ over the course of launch, we’d know that at some point during the flight there must be a maximum (useful diagram here). Rockets engines are designed to throttle back a bit as max-$Q$ is reached to avoid putting too much stress on the vehicle.

This day in space history

On March 2, 1972, NASA launched the Pioneer 10 space probe, the first mission to traverse the asteroid belt and reach Jupiter, returning data on Jupiter's environment, the surrounding radiation and cosmic rays, and the eventually the conditions of the Outer Solar System as it continued on its journey. 
Great Red Spot on the right side of Jupiter by Pioneer 10, 1973
Although we lost contact in 2003, Pioneer 10 is one of 5 space probes with enough velocity to escape the Solar System, the others being Pioneer 11, Voyagers 1 & 2, and New Horizons. A few artifacts of humanity that are heading for the stars!