The following section shows the data found for risks and costs associated with current launch systems, second generation concepts, and space elevators. It also contains a brief summary of market research done by Andrews Space & Technology⁴ and Information Universe.⁵

Risk Analysis:

Current Launch Vehicles:

Current launch vehicles include traditional chemical rockets and the space shuttle. Reliability and associated risks vary greatly by launch vehicle.

For rockets, the most reliable types are medium sized rockets like the Delta II (97.0%) and the Atlas II (100.0%). The small Pegasus rocket is the worst at 50%, while large rockets like the Proton (87.7%), Ariene IV (87.5%), and Titan III & IV (93.0%) are in the middle. All data is based on 1997 statistics.⁶

The space shuttle had a mission reliability of 97.4% in 1997. ⁶ I found no new data for mission reliability since the Columbia disaster. A great deal of data on probabilistic risk analysis for the shuttle was also found. The current shuttle (after several engine improvements) has a probability of loss during ascent of 1/483.⁷ This is up from the original shuttle’s value of 1/262.

The space shuttle is nearing its service life, and maintaining the fleet with the current levels of risk will become increasingly difficult as the designed retiring age is exceeded.

Second Generation Launch Vehicles: 

Data is not as readily available for second generation concepts, as the concepts are still in the design phases, and many projections are still proprietary or classified information. What is known is that the benchmark for a viable system is a 1/10,000 chance for loss of crew per mission,^8,9 or 1/100 chance of failure for uncrewed missions.⁹

Space Elevators:

Data for risks to space elevators is even sparser than for second generation systems. What is known is that the greatest single contributor to the chance of damage will be micrometeoroid impacts. The values vary by size of the particle and by the cross section of the elevator. The results are summarized in Figure 1, which is reproduced without exact data points.¹⁰

Figure 1: Space Elevator Debris Impacts per Year

Particles would have to be over 10.0mm in size to be capable of severely damaging or severing a lift cable. Smaller particles could still do damage, and the number of impacts is high. Still, only a direct hit on a lifter would cause loss of life or cargo, and particles would need to be much larger than the numbers listed here to destroy the elevator beyond repair. One must think of an elevator as a 36,000 mile road which would need constant “pothole” repair and maintenance.

Summary:

The benchmark for reliability of second generation systems is at least two orders of magnitude better than current space launch capabilities. While more research is needed into specifics for space elevator operation risks, the biggest contributor to risks will have at most an equal chance to the second generation systems chance of loss of crew. This risk will also not necessarily result in unrepairable damage or loss of life.

Table 1: Risk Analysis Summary