Flow Resolution

News in 2015-2016 from Prof. Poggie's research group.

AIAA Video Series on Hypersonic Aerodynamics

Courtesy of the AIAA Thermophysics Technical Committee, you can watch an old hypersonics short course on YouTube, featuring John Anderson, Kevin Bowcutt, and Mark Lewis: Hypersonics: Basic and Applied

Should you blow your airlock to rescue Mark Watney from Mars?

For the Fall 2015 semester, we had an interesting extra credit assignment for AAE 334, the junior-level aerodynamics class. In the novel The Martian by Andy Weir (Crown Publishing, New York, 2014), and in the recent movie (20th Century Fox, 2015), the crew of a Mars-bound spacecraft need to decelerate their ship to rescue their lost crewmate. As a desperate measure to do this, they use an improvised bomb to blow a hole in an airlock, and that produces thrust via a jet of air into space. I asked the class to analyze this problem, and to assess the realism of decelerating a spacecraft in this way.

  • The Assignment
  • J. Poggie's Solution
  • Long story short: Stills from the movie portray a ship about 100 m long and 3 m diameter, for a volume of about 700 m3. There isn't enough air in the ship to produced the required change in velocity. An analysis assuming a uniform, isentropic state in the ship, and choked flow at the hole, gives a change in velocity of Δv = 3.4 m/s. (Interestingly, the size of the hole in the ship has little effect on the net change in velocity.) Even if the thermal energy the air in the ship were completely converted to kinetic energy, you still only get a change in velocity of about Δv = 6 m/s. On the other hand, if the volume of the ship is an order of magnitude larger, 7000 m3, you get Δv = 35 m/s, as in the book.

    Nonetheless, this leaves me with a couple of questions. Did they have enough air left to get home? Why did they have to blow up the airlock? Why didn't they just open it?

    DoE INCITE Award

    My research collaborators (Nicholas Bisek and Ryan Gosse at AFRL) and I have won a 2016 DoE INCITE Award. Our project to study separation unsteadiness in compressible turbulent flow was highlighted in the DoE Office of Science Press Release. Our work will be carried out on the Argonne National Laboratory Computer Mira, which has 786,432 cores and is No. 5 on the Top 500 Supercomputer list. INCITE Awards