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Criticism of the Space Shuttle program

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Criticism of the Space Shuttle program stems from claims that the Shuttle program has failed to achieve its promised cost and utility goals, as well as design, cost, management, and safety issues.[1] More specifically, it has failed in the goal of reducing the cost of space access. Space shuttle incremental per-pound launch costs are not appreciably cheaper than that of expendable launchers.[2] It failed in the goal of achieving reliable access to space, partly due to multi-year interruptions in launches following Shuttle failures.[3] NASA budget pressures caused by the chronically high NASA Space Shuttle program costs have eliminated NASA manned space flight beyond low earth orbit since Apollo, and severely curtailed more productive space science using unmanned probes.[4] NASA's promotion of and reliance on the Shuttle slowed domestic commercial expendable launch vehicle (ELV) programs until after the 1986 Challenger disaster.[5]

Purpose of the system

The "Space Transportation System" (NASA's formal name for the overall Shuttle program) was created to transport crewmembers and payloads into low Earth orbits.[6] It would afford the opportunity to conduct science experiments on board the shuttle to be used to study the effects of space flight on humans, animals and plants. Other experiments would study how things can be manufactured in space. The shuttle would also enable astronauts to launch satellites from the shuttle and even repair satellites already out in space.[7] The Shuttle was also intended for research into the human response to zero gravity. However, the research could have been done on cheaper expendable vehicles, as the Soviets had done.[8]

The Shuttle was originally billed as a space vehicle that would be able to launch once a week and give low launch costs through amortization. Development costs were expected to be recouped through frequent access to space. These claims were made in an effort to obtain budgetary funding from the United States Congress.[9] Beginning in 1981, the space shuttle began to be used for space travel. However, by the mid-1980s the concept of flying that many shuttle missions proved unrealistic and scheduled launch expectations were reduced 50%.[10] However, following the Challenger disaster space shuttle missions were temporarily halted pending safety review. This hiatus became lengthy as arguments over funding and the safety of the program continued. Eventually the military resumed the use of expendable launch vehicles instead.[8]

Costs

Some reasons for the higher-than-expected operational costs are:

  • The final design differs from the original concept, causing, among other things, the shuttle orbiter to be almost 20% over its specified weight - resulting in it being unable to boost the US Air Force's payloads into polar orbits.[11]
  • Maintenance of the thermal protection tiles is a very labor-intensive and costly process, with some 35,000 tiles needing to be inspected individually and with each tile specifically manufactured for one specific slot on the shuttle.[12]
  • The Space Shuttle main engines were highly complex and maintenance-intensive, necessitating removal and extensive inspection after each flight. Before the current "Block II" engines, the turbopumps (a primary engine component) had to be removed, disassembled, and totally overhauled after each flight. [citation needed]
  • The launch rate has been significantly lower than initially expected. While this does not reduce actual operating costs, more launches per year gives a lower cost per launch. Some early hypothetical studies examined 55 launches per year (see above), but the maximum possible launch rate was limited to 24 per year based on manufacturing capacity of the Michoud facility that constructs the external tank. Early in shuttle development, the expected launch rate was about 12 per year.[13] Launch rates reached a peak of 9 per year in 1985 but averaged fewer thereafter.
  • When the decision was made on the main shuttle contractors in 1972, work was spread among companies to make the program more attractive to Congress and the Senate, such as the contract for the Solid Rocket Boosters to Morton Thiokol in Utah. Over the course of the program, this raised operational costs, [citation needed] though the consolidation of the US aerospace industry in the 1990s means the majority of the Shuttle is now with one company: Boeing.

Cultural issues and problems

Some researchers have criticized a pervasive shift in NASA culture away from safety in order to ensure that launches took place in a timely fashion. Allegedly, NASA upper-level management embraced this decreased safety focus in the 1980s while some engineers remained wary. According to Vaughan, the aggressive launch schedules arose in the Reagan years as a way to rehabilitate America's post-Vietnam prestige.[14]

The physicist Richard Feynman, who was appointed to the official inquiry on the Challenger disaster, said that NASA was trying to "repeal the laws of nature" through its risky and overly aggressive launch schedules.[15] Despite Feynman's warnings, and despite the fact that Vaughan served on safety boards and committees at NASA, the subsequent press coverage has found some evidence that NASA's relative disregard for safety might persist to this day. For example, NASA discounted the risk from small foam chunk breakage at launch and assumed that the lack of damage from prior foam collisions suggested the future risk was low.

Shuttle operations

The original, simple, vision of Space Shuttle ground processing
Actual, vastly more complex and much slower, Space Shuttle ground processing

The Shuttle was originally conceived to operate somewhat like an airliner. After landing, the orbiter would be checked out and start "mating" to the rest of the system (the ET and SRBs), and be ready for launch in as little as two weeks. Instead, this turnaround process usually takes months; Columbia set a record by launching twice within 56 days. Naturally, the Shuttle program's goal of returning its crew to Earth safely conflicts with the goal of a rapid and inexpensive payload launch. Furthermore, because in many cases there are no survivable abort modes, many pieces of hardware simply must function perfectly and so must be carefully inspected before each flight. The result is high labor cost, with around 25,000 workers in Shuttle operations and labor costs of about $1 billion per year.[16]

Some shuttle features initially presented as important to Space Station support have proved superfluous:

  • As the Russians demonstrated, capsules and unmanned supply rockets are sufficient to supply a space station.
  • NASA's initial policy of using the Shuttle to launch all unmanned payloads declined in practice, and eventually was discontinued. Expendable Launch Vehicles (ELVs) proved much cheaper and more flexible.
  • Following the Challenger disaster, use of the Shuttle to carry the powerful liquid fueled Centaur upper stages planned for interplanetary probes was ruled out for Shuttle safety reasons.[17][18]
  • The Shuttle's history of unexpected delays also makes it liable to miss narrow launch windows.
  • Advances in technology over the last decade have made probes smaller and lighter.[citation needed] As a result, robotic probes and communications satellites can now use expendable launch vehicles, such as the Delta and Atlas V, which are less expensive and perceived to be more reliable than the Shuttle.

Accidents

SRB O-ring "blow by" is what caused the Challenger accident

While the technical details of the Challenger and Columbia accidents are different, the organizational problems show similarities. In both cases events happened that were not planned for nor anticipated. Flight engineers' concerns about possible problems were not properly communicated to or understood by senior NASA managers. The vehicle gave ample warning beforehand of abnormal problems. A heavily layered, procedure-oriented bureaucratic structure inhibited necessary communication and action.

With Challenger, an O-ring that should not have eroded at all did erode on earlier shuttle launches. Yet managers felt that because it had not previously eroded by more than 30%, this was not a hazard as there was "a factor of three safety margin". Morton-Thiokol designed and manufactured the SRBs, and during a pre-launch conference call with NASA, Roger Boisjoly, the Thiokol engineer most experienced with the O-rings, pleaded with management repeatedly to cancel or reschedule the launch. He raised concerns that the unusually low temperatures would stiffen the O-rings, preventing a complete seal, which was exactly what happened on the fatal flight. However, Thiokol's senior managers overruled him, dismissing his safety concerns, and allowed the launch to proceed. Challenger's O-rings eroded completely through as predicted, resulting in the complete destruction of the spacecraft and the loss of all seven astronauts on board.

Columbia was destroyed because of damaged thermal protection from foam debris that broke off from the external tank during ascent. The foam had not been designed or expected to break off, but had been observed in the past to do so without incident. The original shuttle operational specification said the orbiter thermal protection tiles were designed to withstand virtually no debris hits at all. Over time NASA managers gradually accepted more tile damage, similar to how O-ring damage was accepted. The Columbia Accident Investigation Board called this tendency the "normalization of deviance" — a gradual acceptance of events outside the design tolerances of the craft simply because they had not been catastrophic to date.[19]

The subject of missing or damaged thermal tiles on the Shuttle fleet only became an issue following the loss of Columbia in 2003, as it broke up on re-entry. In fact, Shuttles had previously come back missing as many as 20 tiles without any problem. STS-1 and STS-41 had all flown with missing thermal tiles from the orbital maneuvering system pods (visible to the crew). This image from the NASA archives shows many missing tiles on the STS-1 OMS pods. The problem on Columbia was that the damage was sustained from a foam strike to the reinforced carbon-carbon leading edge panel of the wing, not the heat tiles. On the same subject, a little-publicized detail about the first Shuttle mission, STS-1, was that it had a protruding gap filler that ducted hot gas into the right wheel well on re-entry, resulting in a buckling of the right main landing gear.[20]

Retrospect

Opinions differ on the lessons of the Shuttle. While it was developed within the original cost and time estimates given to President Richard M. Nixon in 1971, the operational costs, flight rate, payload capacity, and reliability have been much worse than anticipated.[21] A year before STS-1's April 1981 launch, The Washington Monthly accurately forecast many of the Shuttle's issues, including an overambitious launch schedule and the consequent higher-than-expected marginal cost per flight; the risks of depending on the Shuttle for all payloads, civilian and military; the lack of a survivable abort scenario if a Solid Rocket Booster were to fail; and the fragility of the Shuttle's thermal protection system.[22]

In order to get the Shuttle approved, NASA over-promised its economies and utility. To justify its very large fixed operational program cost, NASA first forced all domestic, internal, and Department of Defense payloads to the shuttle. When that proved impossible (after the Challenger disaster), NASA used the International Space Station (ISS) as a justification for the shuttle. Some speculate that, had NASA avoided the Shuttle program and instead continued to use Saturn and commercially available boosters, costs might have been lower, freeing funds for manned exploration and more unmanned space science. In particular, NASA administrator Michael D. Griffin argued in a 2007 paper that the Saturn program, if continued, could have provided six manned launches per year — two of them to the moon — at the same cost as the Shuttle program, with an additional ability to loft infrastructure for further missions:

If we had done all this, we would be on Mars today, not writing about it as a subject for “the next 50 years.” We would have decades of experience operating long-duration space systems in Earth orbit, and similar decades of experience in exploring and learning to utilize the Moon.[23]

While the general concept of a reusable manned launch vehicle was good, some have argued that the shuttle program is flawed.[24] In the beginning of the program, to achieve a reusable vehicle with early 1970s technology entailed several design decisions that compromised operational reliability and safety. For example, an early point in the design phase, reusable main engines became a priority. This necessitated that they not burn up upon atmospheric reentry, which in turn made mounting them on the orbiter itself (the one part of the shuttle system where reuse was paramount) a seemingly logical decision. However, this had the following consequences:

  • a more expensive 'clean sheet' engine design was needed, using more expensive materials, as opposed to existing and proven off-the-shelf alternatives (such as the Saturn V mains);
  • increased ongoing maintenance costs related to keeping the reusable SSMEs in flying condition after each launch, costs which in total may have exceeded that of building disposable main engines for each launch;
  • less absolute tonnage available to be lifted into space, since the mass of the SSMEs attached to the orbiter necessarily cut into the craft's 'payload budget' (more payload launched at any one time, by definition, reduces launch costs per pound).

Some[who?] maintain that the Shuttle program advanced the State of the Art, while others say the shuttle program made only incremental advances and pushed the early 1970s technology excessively to build a new capability. Some[who?] argue the high costs of the Shuttle program caused the cancellation of other manned (X-38, DC-X, X-33, X-34, etc.) and unmanned programs. The shuttle program also caused all other US boosters (ELVs) to be discontinued until the Challenger accident, thereby costing the US initiative in ELV technology.

The ninth concern expressed by the 1990 Augustine Commission was that, "the civil space program is overly dependent upon the Space Shuttle for access to space." The committee pointed out, "that it was, for example, inappropriate in the case of Challenger to risk the lives of seven astronauts and nearly one-fourth of NASA's launch assets to place in orbit a communications satellite."[25]

Future

Designers look to more economical and reliable launch systems for the future, with lower maintenance and operational costs. One approach is Single Stage To Orbit (SSTO), which would be 100% reusable and use a single stage. NASA evaluated several concepts in the 1990s, and selected the X-33, which would eventually have been the VentureStar. During design that program increased in complexity and development cost, encountered problems and was finally canceled.

Another variant of SSTO is a hypersonic, scramjet-powered, airbreathing vehicle. This would be launched and landed horizontally like an airliner. It would achieve much of orbital velocity while still within the upper atmosphere. It was originally investigated by the U.S. Department of Defense, but passenger-carrying civilian versions were planned, sometimes called the "New Orient Express". The official name was the Rockwell X-30. Like the X-33, the X-30 encountered major technical difficulties, primarily due to the system complexity and materials required for hypersonic flight, and was also canceled.

Another approach is lower-cost expendable launch vehicles. NASA currently uses commercial ELVs for unmanned launches, and could use commercial ELVs for future manned launches. This would fit with NASA's mandate to promote commercial access to and use of space. However, NASA plans on rejecting the low-cost commercially available boosters, and instead, designing their own similar but competing boosters using modified shuttle components to build an expendable Shuttle-Derived Launch Vehicle. This technology would be used to develop two separate launchers, one for manned missions and the other for unmanned heavy cargo. This contrasts with the current shuttle where astronauts and heavy cargo are launched in a single vehicle. Unlike the shuttle, this future launcher and associated crew exploration vehicle will have a launch escape system to greatly improve the chances that the crew can be saved in the event of a disaster.

The proposed CEV and CaLV bear a strong resemblance to the Saturn I & V rockets respectively, even to the point of the proposed launchers being numbered in honor of their predecessors, Ares I & V. In terms of flight profile, hardware design concept, and mission capabilities, there is actually little to choose between Ares and Saturn - though the proposed CEV is larger than the Apollo CM. Some critics have seized upon this as a serious indictment of the shuttle program. They argue that if a Saturn-type mission architecture is technically and economically viable for missions currently performed by the shuttle, then the Saturn launchers should never have been abandoned in the first place, and that the shuttle has been a massive waste of time and money.

The reversion of NASA to the capsule/booster technology of Ares/CEV/CaLV must be viewed as a clear rejection of the shuttle concept. Burt Rutan of Scaled Composites, the company that successfully designed, built, and flew the world's only privately-funded reusable spaceplane, SpaceShipOne, has had harsh words for NASA’s Shuttle and CEV programs. Likening the agency's new Moon-shot efforts to "archeology", Rutan contends that the space program must encourage some risk in technological development in order to continue to innovate. NASA's current strategy:

They are forcing the [Ares/CEV] program to be done with technology that we already know works. They are not creating an environment where it is possible to have a breakthrough ... It doesn’t make sense.[26]

This stands in contrast to other arguments that NASA should utilize commercially available off the shelf boosters where possible, and concentrate on space exploration, space science, and research and development to reduce the cost of space access. Both arguments assume that the Shuttle program has run its course, and needs to be retired to make way for a new generation of cost effective and efficient vehicles.

References

  1. ^ Cegłowski, Maciej (2005-08-03). "A Rocket To Nowhere". Idle Words. Retrieved 2008-09-26.
  2. ^ "Space Transportation Costs: Trends in Price Per Pound to Orbit 1990-2000" (PDF). Futron. September 6, 2002. Retrieved 2010-12-28.
  3. ^ Axelrod, Alan (2008). Profiles in Folly: History's Worst Decisions and Why They Went Wrong. Sterling Publishing Company. pp. 62–63. ISBN 9781402747687.
  4. ^ Handberg, Roger (2003). Reinventing NASA: Human Spaceflight, Bureaucracy, and Politics. Greenwood Publishing Group. ISBN 9780275970024.
  5. ^ Launius, Roger D. (1997). Spaceflight and the Myth of Presidential Leadership: and the myth of presidential leadership. University of Illinois Press. pp. 146–155. ISBN 9780252066320. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  6. ^ "Space Transportation System". NASA KSC.
  7. ^ "The Space Shuttle and Space Stations". The K-8 Aeronautics Internet Textbook. 1997-09-06. Retrieved 2008-09-26.
  8. ^ a b "Critics scrutinize cost of shuttle". 2003-02-04. Retrieved 2008-09-26.
  9. ^ Lardas, Mark (2004). Space Shuttle Launch System 1972-2004: System 1975-2004. Osprey Publishing. p. 7. ISBN 9781841766911. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  10. ^ "Space Shuttle". The Internet Encyclopedia of Science. Retrieved 2008-09-26.
  11. ^ Wade, Mark (1997–2008). "Shuttle". Retrieved 2010-05-24.{{cite web}}: CS1 maint: date format (link)
  12. ^ Van Pelt, Michael (2005). Space tourism: adventures in Earth's orbit and beyond. Springer. pp. 75–76. ISBN 9780387402130.
  13. ^ "Columbia accident investigation board, public hearing". NASA. 23 April 2003. Retrieved 2006-08-06.
  14. ^ Vaughan, Diane (1996). The Challenger Launch Decision: Risky Technology, Culture, and Deviance at NASA. University of Chicago Press. ISBN 9780226851754.
  15. ^ Feynman, Richard. "Personal observations on the reliability of the Shuttle". Rogers Commission Report. NASA. Retrieved 6 August 2009.
  16. ^ "Space Shuttle history - Shuttle operations". Century of Flight. Retrieved 2008-09-26.
  17. ^ "Visual Satellite Observing - Chapter 8: What Are Some Of The Rockets Used To Place Satellites In Orbit?". Visual Satellite Observer's Home Page. February 1998. Retrieved 16 July 2010.
  18. ^ "Upper Stages". U.S. Centennial of Flight Commission. Retrieved 16 July 2010.
  19. ^ "Columbia Accident Investigation Board Report".
  20. ^ Foust, Jeff (2003-04-13). "John Young's shuttle secret".
  21. ^ "ColumbiaAccident Investigation Board public hearing". NASA - ColumbiaAccident Investigation Board. 2003-04-23. Retrieved 2008-09-26. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  22. ^ Easterbrook, Gregg. "Beam Me Out Of This Death Trap, Scotty" The Washington Monthly, April 1980.
  23. ^ "Human Space Exploration:The Next 50 Years". Aviation Week. 2007-03-14. Retrieved 2009-06-18.
  24. ^ Watson, Traci (2005-09-30). "NASA administrator says space shuttle was a mistake". USA Today. Retrieved 2008-09-26. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  25. ^ "Report of the Advisory Committee On the Future of the U.S. Space Program, Executive Summary". NASA. December 1990.
  26. ^ "Rutan Takes Aim at NASA's CEV Plans, Likens it to 'Archeology'". Space.com. 2006-05-04. Retrieved 2008-09-26.
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