Criticism of the Space Shuttle program
Criticism of the Space Shuttle program stemmed from claims that NASA's Space Shuttle program failed to achieve its promised cost and utility goals, as well as design, cost, management, and safety issues.[1] Fundamentally, it failed in the goal of reducing the cost of space access. Space Shuttle incremental per-pound launch costs ultimately turned out to be considerably higher than those of expendable launchers.[2] In 2010, the incremental cost per flight of the Space Shuttle was $409 million, or $14,186 per kilogram ($6,435 per pound) to
When all design and maintenance costs are taken into account, the final cost of the Space Shuttle program, averaged over all missions and adjusted for inflation (2008), was estimated to come out to $1.5 billion per launch, or $60,000 per kilogram ($27,000 per pound) to LEO.[4] This should be contrasted with the originally envisioned costs of $260 per kilogram ($118 per pound) of payload in 1972 dollars (approximately $555 per pound adjusting for inflation to 2019).[5]
While the shuttle did serve a purpose servicing satellites and space stations in orbit, it failed at its original goal of achieving routine, reliable access to space, partly due to multi-year interruptions in launches following Shuttle failures. It was never as economical as expendable rockets for the task of launching satellites.
Two out of the five spacecraft were destroyed in accidents, killing 14 astronauts, the largest loss of life in space flight.[9]
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
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.[13] 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%.[14] Following the Challenger accident in 1986, missions were halted pending safety review. This hiatus became lengthy and ultimately lasted almost three years as arguments over funding and the safety of the program continued. Eventually the military resumed the use of expendable launch vehicles instead.[12] Missions were put on hold again after the loss of Columbia in 2003. Overall, 135 missions were launched during the 30 years after the first orbital flight of Columbia, averaging approximately one every 3 months.
Costs
Some reasons for the higher-than-expected operational costs were:
- NASA secured funding from the US Air Force's budget in exchange for USAF input to the design process. In order to fulfill the USAF's mission to launch payloads into polar orbit, the USAF insisted on a very large cross-range requirement. This necessitated the Shuttle's huge delta wings, which are far larger than the stub wings of the original design. Besides adding drag and weight (almost 20 percent),[15] the excessive number of heat tiles needed to protect the delta wings added greatly to maintenance costs, besides increasing operational risks such as those that resulted in the Columbia disaster.[16]
- At Vandenberg Air Force Base in California, the USAF duplicated the entire infrastructure needed to launch and service the Space Shuttle, at a cost of over 4 billion dollars. Following the Challenger explosion, the facility was dismantled after never having launched a single Shuttle mission.
- Aerospace engineer Robert Zubrin describes the Shuttle as having been designed "backwards" in that the Orbiter, the harder-to-recover portion, is made recoverable, while part of the booster (the liquid fuel tank) is thrown away even though it is easier to recover since it does not fly so high or fast.[17]
- Maintenance of the thermal protection tiles was 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.[18]
- Due to the complexity of the RS-25 engines, following each flight they required removal for thorough inspection and meticulous maintenance. Prior to the delivery of the Block II engines, the primary engine component, the turbopump, had to be removed, disassembled, and overhauled after each use.[19][20]
- The toxic propellants used for the OMS/RCS thrustersrequired special handling, during which time no other activities could be performed in areas sharing the same ventilation system. This increased turn-around time.
- The launch rate was significantly lower than initially expected. While not reducing absolute operating costs, more launches per year gives a lower cost per launch. Some early hypothetical studies examined the possibility of making 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 in Louisiana that constructs the external tank. Early in shuttle development, the expected launch rate was about 12 per year.[21] Launch rates reached a peak of 9 per year in 1985 but averaged 4.5 for the entire program.
- 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, such as the contract for the Morton Thiokol in Utah. Over the course of the program, this raised operational costs, though the consolidation of the US aerospace industry in the 1990s meant that the majority of the Shuttle program expenditure was now with one company: the United Space Alliance, a joint venture of Boeing and Lockheed Martin.
Cultural issues and problems
For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.
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, sometimes called "go fever". Allegedly, NASA upper-level management embraced this decreased safety focus in the 1980s while some engineers remained wary. According to sociologist Diane Vaughan, the aggressive launch schedules arose in the Reagan years as an attempt to rehabilitate America's post-Vietnam prestige.[22]
The physicist
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 still persisted. For example, leading up to the Columbia disaster, 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.[24]
Shuttle operations
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The Shuttle was originally conceived to operate somewhat like an airliner. After landing, the orbiter would be checked out and start being mated to the
In practice, before the loss of Challenger, about half of the turnaround time after a mission was unplanned tests and modifications based on unexpected events that occurred during flight.[25] The process usually took months; Atlantis set the pre-Challenger record by launching twice within 54 days, while Columbia set the post-Challenger record of 88 days. The Shuttle program's goal of returning its crew to Earth safely conflicted with the goal of a rapid and inexpensive payload launch. Furthermore, because in many cases there were no survivable abort modes, many pieces of hardware had to function perfectly and so required careful inspection before each flight. The result was high labor cost, with around 25,000 workers in Shuttle operations and labor costs of about $1 billion per year.[5]
Some shuttle features initially presented as important to Space Station support have proved superfluous:
- As the Soviets demonstrated, capsules and uncrewed supply rockets are sufficient to supply a space station.
- NASA's initial policy of using the Shuttle to launch all crewless 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
- The Shuttle's history of unexpected delays also made it liable to miss narrow launch windows.
- Advances in technology have made probes smaller and lighter. As a result, many robotic probes and communications satellites can now use , which are less expensive and perceived to be more reliable than the Shuttle.
- Advances in technology today happen much faster than in the years the Shuttle was developed. Thus the notion that Shuttle would be useful for recovering expensive satellites for return to Earth for refurbishment and updating with new technology is obsoleted; costs have dropped and capabilities increased so much that it is much more cost-effective to abandon old satellites and simply launch new ones.
Accidents
While the technical details of the Challenger and Columbia accidents are different, the organizational problems show similarities. 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
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
Risk contributors
An example of technical risk analysis for a STS mission is SPRA iteration 3.1 top risk contributors for STS-133:[30][31]
- Micro-Meteoroid Orbital Debris (MMOD) strikes
- RS-25-induced or RS-25 catastrophic failure (the Space Shuttle Main Engine)
- Ascent debris strikes to TPS leading to LOCV on orbit or entry
- Crew error during entry
- RSRM-induced RSRM catastrophic failure (RSRM are the rocket motors of the SRBs)
- COPV failure (COPV are tanks inside the orbiter that hold gas at high pressure)
Although many NASA astronauts criticized the payload specialist program, in part because they did not believe less-trained outsiders were fully aware of the risks of spaceflight, full-time astronauts may not have been either.[32] Charles Bolden was amazed to learn after the loss of Columbia that the "impenetrable" leading wing edges of the vehicle he flew for 14 years were less than an inch thick.[35] NASA in October 1982 predicted 37 shuttle flights by early 1986,[25] but Challenger's loss was the 25th shuttle flight. Hauck, with much experience flying dangerous aircraft at the United States Naval Test Pilot School, said "If I knew in advance that one in twenty-five would fail, I would probably think twice about flying three (as I did) out of the first twenty-six flights".[32]
Retrospect
While the system was developed within the original cost and time estimates given to President
In order to get the Shuttle approved, NASA over-promised its economies and utility. To justify its very large fixed operational program cost, NASA initially forced all domestic, internal, and
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.[40]
Some had argued that the Shuttle program was flawed.[41] Achieving a reusable vehicle with early 1970s technology forced design decisions that compromised operational reliability and safety. Reusable main engines were made 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:[citation needed]
- 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.
A concern expressed by the 1990
There are some NASA spin-off technologies related to the Space Shuttle program which have been successfully developed into commercial products, such as using heat-resistant materials developed to protect the Shuttle on reentry in suits for municipal and aircraft rescue firefighters.[43]
See also
References
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- ^ The Rise and Fall of the Space Shuttle, Book Review: Final Countdown: NASA and the End of the Space Shuttle Program by Pat Duggins, American Scientist, 2008, Vol. 96, No. 5, p. 32.
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- ^ Columbia Accident Investigation Board (August 2003). "6.1 A History of Foam Anomalies (PDF)" (PDF). Archived (PDF) from the original on August 6, 2011. Retrieved February 26, 2013.
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- Bolden, Charles F. (January 6, 2004). "Charles F. Bolden". NASA Johnson Space Center Oral History Project (Interview). Interviewed by Johnson, Sandra; Wright, Rebecca; Ross-Nazzal, Jennifer. Houston, Texas. Archived from the originalon January 7, 2014. Retrieved January 6, 2014.
- ^ "Columbia Accident Investigation Board public hearing". NASA – Columbia Accident Investigation Board. 2003-04-23. Archived from the original on 2008-10-16. Retrieved 2008-09-26.
- ^ Easterbrook, Gregg (April 1980). "Beam Me Out Of This Death Trap, Scotty". The Washington Monthly. Archived from the original on 2003-02-03. Retrieved 15 September 2016.
- ^ Day, Dwayne Allen (2011-06-27). "Gazing back through the crystal ball". The Space Review. Retrieved June 27, 2011.
- ^ Krauss, Lawrence (2011-07-21). "The space shuttle programme has been a multi-billion-dollar failure". The Guardian. Retrieved 2013-08-19.
- ^ "Human Space Exploration:The Next 50 Years". Aviation Week. 2007-03-14. Retrieved 2009-06-18.
- ^ Watson, Traci (2005-09-30). "NASA administrator says space shuttle was a mistake". USA Today. Retrieved 2008-09-26.
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External links
- When Physics, Economics, and Reality Collide: The Challenge of Cheap Orbital Access
- Review of ELV cost-to-orbit per pound Archived 2021-10-01 at the Wayback Machine
- Space Transportation Costs: Trends in Price Per Pound to Orbit
- Popular Science November 1974, "Reusable space shuttle" by Wernher von Braun