On July 25-27, 1995, a Technical Interchange Meeting (TIM) for the Highly Reusable Space Transportation (HRST) Advanced Concepts Study was held at the University of Alabama, Huntsville. The objective of the study is to define 2-3 approaches to space launch that could, if developed successfully, credibly provide transportation to LEO for payloads in the 10,000 to 20,000 pounds class at costs of $100-$200 per pound-payload. The concepts identified must not entail major environmental drawbacks. Launch services based on these concepts must be viable as privately financed and operated business.
The study is addressing the challenge of reducing space launch costs to approximately $100-$200 per pound-payload. This study project is being conducted by the NASA Headquarters Office of Space Access and Technology (Code X) and the Advanced Concepts Office (Code XZ), responsible for the definition and refinement (including selected research experimentation) of innovative, far-reaching new systems concepts that have the potential to revolutionize the future US space program. It is being led by the Advanced Concepts Office in the Program Development Directorate at NASA's Marshall Space Flight Center and will involve substantial participation by various other NASA centers, other Federal Laboratories, industry and several universities.
The NASA Reusable Launch Vehicle (RLV) program is planning to demonstrate technology to allow US industry to develop a new generation of space launch systems. These systems will be capable of delivering payloads in the 20,000 to 40,000 pounds class to low Earth orbit at costs of approximately $1000-$2000 per pound-payload: a factor of 5-10 below US launch prices in 1995. However the 1994 Commercial Space transportation Study (CSTS) Alliance report stated that prices of less than approximately $400-$500 per pound-payload (and hence costs less than $200-$300 per pound payload) will be needed to enable significant expansion of non-traditional commercial space industries such as tourism, industrial space parks, space solar power, etc.. Taking into account the inflated levels of return on investment (ROI) needed when new enterprises entail significant risk, still lower launch costs - on the order of $100-$200 per pound - may be necessary to engender the large commitment of private capital that must be made to create these new industries.
At the TIM, principal objectives included (a) arriving at a common understanding of the mission model and functional requirements to be met by HRST system concepts, (b) formulate principal desirable characteristics for these concepts, (c) formulate the trade space of options and identify system concepts from that trade space which might meet HRST study goals, (d) identify emerging technologies and provide a preliminary assessment of technologies that could contribute to those system concepts and (e) identify macro-level issues for HRST systems and for the study project itself, and to suggest potential approaches to resolving those issues.
The following are some personal observations and notes I've assembled following the workshop:
The "market elasticity", how much more and at what rate demand for space launch services increases as price goes down, is an issue key to any RLV and HRST. It was a frequent topic of discussion at the TIM. The Commercial Space Transportation Study attempted to define the nature of the market and answer the question "if we build it, will they come?" Some figures from the executive summary follow. Similar curves were developed for other areas.
A key conclusion of the CSTS report is that elasticity does exist. However, significantly lower launch prices than those of current vehicles are required for the growth of the market to begin to manifest.
A related subject discussed centered on whether or not current rocket technology would be able to reach the HRST price/cost goals. The use of S-curve's in predicting the maturity of technology, whether the "plateau" has been reached for example for current rocket technology, was a subject of discussion in one of the breakaway sessions. Is it arguable "performance derived" (cold war, mission first, affordability second if at all) technology has peaked in it's ability to deliver payload units per unit of time? If so, is it arguable that "affordability derived" technology (market creation, competition and profit oriented), that which is developed with an eye on total recurring costs of operations, is still at the bottom of the S-curve with plenty of growth to go? S-curves describe natural growth patterns. For example, it has been used by biologists to describe the growth under competition of a species population such as the number of rabbits in a fenced-off grass field.
A principal focus to the workshop was the process of developing system concepts and architectures as well as the totality of options in the tradespace. Preliminary technology assessments will also be required. Much work lies ahead in determining top level architectural issues. This should lead to an investment portfolio of on the order of a half dozen strategic lines of investigation to pursue during phase 2 of the HRST activity. These should be areas capable of reaching TRL 6 in 10 to 20 years
Another subject of discussion centered on the inevitability of redundancy in systems for space access due to diverse needs. A future architectural mix may include ELV's, assorted RLV's and assorted Air-Breather Rocket Based Combined Cycle Systems as well as perhaps some more exotic approach. Also discussed was whether or not RLV technology will achieve HRST goals and as such whether or not a single course is a high technology risk. On this note, the following from Nebojsa Nakicenovic in "Dynamics and Replacement of U.S. Transport Infrastructures" would seem relevant.
All in all a variety of topics were reviewed. Discounted rates of return, artificial evolution, market elasticity, balance sheets, cost modeling, designs for operations, lightcraft, rocket based combined cycle propulsion and cash flow were just some of the topics of the Highly Reusable Space Transportation TIM. However the focus was well kept - again - "to define approaches to space launch that could, if developed successfully, credibly provide transportation to low earth orbit for payloads in the 10,000 to 20,000 pounds class at costs of $100-$200 per pound-payload"
Edgar Zapata
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Edgar Zapata, NASA Kennedy Space Center
Shuttle Process Engineering Directorate, Fluid Systems Division