Launch Probability in NASA Space Launch System
By Grant Cates, Ph.D., Senior Project Leader
Published: October 2, 2017
Launcher’s Lurgy causes space launch vehicles to be delayed relative to their planned launch date. The disorder is similar in nature to Loser’s Lurgy, a condition causing Quidditch players to perform poorly, first described by Luna Lovegood in J.K. Rowling’s enormously successful Harry Potter series. Pretty much all rockets have Launcher’s Lurgy with launch delays being all too annoyingly common. For example, a quick search on the word “delayed” on Spaceflight Now’s launch history log web page results in more than 100 matches (the search engine’s limit). There is no known cure for Launcher’s Lurgy but simulation modeling can be used to develop predictions for how many launches can be achieved over a particular time period and when any particular launch of interest is likely to launch by.
In 1999, a NASA Space Act agreement between the University of Central Florida and the Kennedy Space Center (KSC) produced an Arena based Space Shuttle Processing model intended to help NASA increase the flight rate. A detailed input analysis effort was performed in which all past launch delays were identified and characterized in terms of when they occurred and how long the delay duration was. This allowed the development of delay probabilities for various points in the reusable Space Shuttle orbiter’s operational life cycle and the associated delay duration distributions.
In late 2002, building upon the previous work, the Manifest Assessment Simulation Tool (MAST) was developed using Arena to determine when the United States core section of the International Space Station (ISS) would be completed. Following the loss of Columbia in February of 2003, MAST was used again to determine when the ISS assembly would be completed including launch of all of the international partners’ elements (also requiring launch by the Space Shuttle) and how the completion date could be improved. MAST based analyses were used to advise the NASA administrator, the international partners of the ISS, the congress and the Executive Office of the President on how many launches could be achieved by the end of the decade, resulting in a decision to set the planned number of launches in the post-Columbia era at 20. This was significantly less than the planned 28 launches. The MAST analysis showed that it would not be possible to achieve 28 launches by the end of 2010, the President’s directed Space Shuttle retirement date, but that at least 20 launches could be achieved with high confidence. MAST was also used to help the NASA administrator make a decision to reinstate the Hubble Space Telescope’s final servicing mission.
An Arena simulation is being used today to help NASA determine the launch probability for their Space Launch System (SLS). A related Arena simulation provides launch probability estimates for the Atlas V, Delta IV and Falcon 9 launch vehicles. Since the SLS is a Space Shuttle derived rocket, Space Shuttle launch attempt historical data is leveraged for the SLS model. An Arena simulation was created to understand the logistics of fueling the SLS with liquid hydrogen and liquid oxygen propellants.
Arena simulations are being used to model potential future human spaceflight concepts and exploration campaigns such as orbital fuel depots, missions to the moon,  asteroids, and Mars.   The exploration campaigns require multiple launches of the SLS, the aggregation of multiple mission elements (propulsion stages, a habitat, a lander, etc.) in earth orbit to create an exploration spaceship, and must be completed in time to depart earth orbit for their exploration destination during a very short window of opportunity. The Arena simulations provide compelling animations and have been used to provide estimates for the likelihood of missing a departure window and how to mitigate that risk.
Arena has proven to be a valuable tool in the quest to mitigate the harmful effects of Launcher’s Lurgy.
 Cates, G.R., Steele, M.J., Mollaghasemi, & M., Rabadi, G., “Modeling the space shuttle,” In Proceedings of the 2002 Winter Simulation Conference, ed. E. Yücesan, C.-H. Chen, J. L. Snowdon, and J. M. Charnes, 754-762.
 Cates, Grant R., and Mansooreh Mollaghasemi. "A discrete event simulation model for assembling the international space station." Proceedings of the 37th conference on Winter simulation. Winter Simulation Conference, 2005.
 Cates, Grant R., and Mansooreh Mollaghasemi. “Supporting The Vision For Space With Discrete Event Simulation,” In Proceedings of the 2005 Winter Simulation Conference, M. E. Kuhl, N. M. Steiger, F. B. Armstrong, and J. A. Joines, eds., 1306-1310.
 Hamlin, Teri L., Michael A. Canga, and Grant R. Cates. "Hubble Space Telescope Crew Rescue Analysis." (2010). In Proceedings of the 10th International Probabilistic Safety Assessment & Management Conference, 7-11 June 2010, Seattle Washington.
 Watson, Michael D., et al. "Use of DES Modeling for Determining Launch Availability for SLS." SpaceOps 2014 Conference. 2014.
 Cates, G. and Schmitt, K., "The Aerospace Launch Probability Simulation." Aerospace Conference, 2016 IEEE. IEEE, 2016.
 Cates, Grant. "Space shuttle launch probability analysis: Understanding history so we can predict the future." Aerospace Conference, 2014 IEEE. IEEE, 2014.
 Leonard, Daniel, Jeremy Parsons, and Grant Cates. "Using discrete event simulation to model fluid commodity use by the space launch system." Proceedings of the 2014 Winter Simulation Conference. IEEE Press, 2014.
 Cirillo, William M., Chel Stromgren, and Grant R. Cates. "Risk analysis of on-orbit spacecraft refueling concepts." AIAA Space 2010 Conference & Exposition, AIAA-2010-8832. Vol. 30. 2010.
 Cates, Grant R., William M. Cirillo, and Chel Stromgren. "Low earth orbit rendezvous strategy for lunar missions." Proceedings of the 38th conference on Winter simulation. Winter Simulation Conference, 2006.
 Stromgren, Chel, Grant Cates, and William Cirillo. “Launch Order, Launch Separation, and Loiter in the Constellation 1½-Launch Solution,” 2009 IEEE Aerospace Conference, Big Sky, MT, March 7-14, 2009.
 Cates, Grant, et al. "Launch and assembly reliability analysis for human space exploration missions." Aerospace Conference, 2012 IEEE. IEEE, 2012.
 Cates, G., Stromgren, C., Cirillo, W., & Goodliff, K. (2013, March). Launch and assembly reliability analysis for Mars human space exploration missions. In Aerospace Conference, 2013 IEEE (pp. 1-20). IEEE.
 Cates, G., Stromgren, C., Arney, D., Cirillo, W., & Goodliff, K. (2014, March). International human mission to Mars: Analyzing a conceptual launch and assembly campaign. In Aerospace Conference, 2014 IEEE (pp. 1-18). IEEE.
 Cates, G., Stromgren, C., Mattfield, B., Cirillo, W., & Goodliff, K., “The Exploration of Mars Launch & Assembly Simulation.” Aerospace Conference, 2016 IEEE. IEEE, 2016.
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