In ordinary circumstances Klaus Heiss would have send the memo to Dale Myers, NASA Associate Administrator for Manned Space Flight.
But these were not ordinary times, so he decided to go to James Fletcher directly.
Heiss bypassed Myers because the NASA manager was still obsessed with two stages fully reusable shuttle concepts.
He had a reason for that: the lower booster would go to Marshall, the orbiter to Houston. The two center were devoted to manned spaceflight and they hated each other.
Document title: Klaus P. Heiss and Oskar Morgenstern,
Memorandum for Dr. James C. Fletcher, Administrator, NASA,
"Factors for a Decision on a New Reusable Space Transportation System,"
October 28, 1971
Source: NASA Historical Reference Collection, History Office, NASA Headquarters, Washington, D.C.
... the key question raised in our May 31, 1971 report is: Does there exist a precise and detailed NASA and national space program for the 1980's?
We did receive detailed mission models of OSSA (NASA scientists), OMSF (manned spaceflight), the DoD, non-NASA applications and others. Yet these continue to change substantially. A space program consists of individual missions which must be specified and integrated into an overall plan of not negligible firmness, though some flexibility must also be allowed for.
To allow the space shuttle decision on the basis of the Two Stage Shuttle funding requirements, many of the important missions were postponed recently by NASA to fit the shuttle development into the expected funding limitation.
A far more sophisticated analysis needs to be done that allows the scheduling of types of payloads. The importance of payloads, the interdependence among payloads within missions and between missions, as well as an analysis of resupply, updating, maintenance, and reliability. Utilizing programming tools that are available today in operations research, substantial work can be performed, some of which is incorporated in the present ongoing work by our group.
Thus, within these constraints an acceptable Space Shuttle development program is indeed difficult: budget limitation by year, total program costs, the timing of different components of the system, the need for a Space Tug and an early full operational capability, and comprehensive and justified national space program alternatives for the 1980's.
Our Major Conclusions Are as follow
1. In the May 31, 1971 report by MATHEMATICA, Economic Analysis of New Space Transportation Systems, the overall economic worth of a reusable space transportation system was examined. The study was based on the two-stage fully reusable concept then under investigation by Phase B contractors and NASA.
That report has demonstrated how an economic justification of a space shuttle system, including a space tug, with an IOC date of 1978 has to be made. The report was not concerned with identifying the most economic choice among alternative space shuttle configurations to be considered.
2. The Baseline, fully reusable, space transportation system had attached to it a non-recurring cost of between $10 and $14 billion when the costs of all systems were included. This large investment outlay would be largely independent of the time span within which these funds are expended. These high non-recurring costs coupled with a relatively high risk led to the study of many alternate configurations.
Among the many other approaches studied by NASA and industry, our calculations show the emergence of an economical and acceptable solution to the question of the best strategy for NASA to achieve a reusable space transportation system for the 1980's at acceptable costs.
3. Over 200 space programs were analyzed by MATHEMATICA, comparing
(a) the Baseline two-stage fully reusable system,
(b) the Baseline, external hydrogen tank system,
(c) the Mark I-Mark II (reusable S1C) system,
(d) the RATO system of McDonnell Douglas,
(e) the TAHO system of Grumman-Boeing,
(f) the Stage and One-Half of Lockheed Corporation, and
(g) the Identical Vehicle Concept of McDonnell Douglas.
The Thrust Assisted Orbiter Shuttle concepts (TAOS) which include concepts like RATO and TAHO, emerge as the most preferred systems within the space programs so far analyzed, using the economic methodology as exemplified in the May 31, 1971 report.
The common feature of TAOS concepts is a single orbiter with external hydrogen/oxygen tanks and rocket assists in the form of solid rocket motors or high pressure fed unmanned boosters. This eliminates the need to develop a large manned, reusable booster.
(...)
(c) Timing of the Space Tug should be such that its IOC date comes closely after the IOC date of the Space Shuttle. If European countries undertake the tug development --after assurance that NASA will have a Space Shuttle System!--then tug funding becomes a problem outside the NASA budget and these expenditures should not affect the shuttle decision itself. They were, however, fully allowed for in our analysis.
(…)
The Thrust Assisted Orbiter (TAOS) concepts emerge as the most economic systems within the space programs analyzed. TAOS with external hydrogen and oxygen tanks, a 60 x 15 payload bay, and a 40,000 pound polar orbit capability, if possible by 1979, clearly dominates any other configuration.
The TAOS concept foregoes the development of a Two Stage Shuttle System. With the use of thrust assists of either solid rocket motors or high pressure fed systems--which can be made in part reusable for low staging velocities-
The detailed economic justifications of the TAOS concept--when compared to any two stage reusable system are:
1. The non-recurring costs of TAOS are estimated by industry to be $6 billion or less over the period to 1979 or to 1984-85, depending on the objectives and choices of NASA. The TAOS concepts promise a reduction of the non-recurring costs (RDT&E and initial fleet investment) from about $9 billion or more (two stage systems, including reusable S-IC) to about $6 billion or less, with a minimal operating cost increase, if any, in the operating phase of the TAOS system.
2. The risks in the TAOS development are in balance lower but still substantial.
Intact abort with external hydrogen and oxygen tanks is feasible; lagging performance in the engine area can be made up by added external tank capability. A large reusable manned booster is not needed.
3. The TAOS's that were analyzed promise the same capabilities as the original two stage shuttle, including a 40,000 pound lift capability into polar orbit and a 60 x 15 feet payload bay.
4. The TAOS can carry the Space Tug and capture high energy missions from 1979 on.
5. The most economic TAOS would use the advanced orbiter engines immediately. Our calculations indicate that among the alternative TAOS configurations an early full operational capability (i. e., high performance engines on the orbiter) is economically most advantageous, and feasible, within budget constraints of $1 billion peak funding.
6. The TAOS can use J2S engines on the orbiter for an interim period.
7. The TAOS abolishes completely the immediate need to decide on a reusable booster and allows postponement of that decision without blocking later transition to that system if still desired. Thereby, TAOS eliminates or lowers the risk and potential cost overruns in booster development.
8. The TAOS can use "parallel burn" concepts, which, if feasible, may change the reusable booster decision.
9. Technological progress may make tank costs, and thrust assisted rocket costs less expensive, thus further aiding TAOS concepts when compared to two stage concepts.
10. TAOS assures NASA an early program definition, and a purpose to the agency. An agreement on TAOS will allow NASA Headquarters a quick and clear reorganization of major NASA centers to meet the TAOS development requirements economically.
11.The TAOS funding schedule make an early Space Tug development possible. The space tug is an important part of the space shuttle system. A 1979 Space Tug should recover its complete development costs before 1985 even with the stretched build of Shuttle missions from 1979 to 1985.
12 A clear policy on TAOS development will give an incentive to European countries to undertake and fund the space tug development – threbypossibly even eliminating Space Tug from NASA budget.
13.The cost per launch of TAOS can be as low as $6million or even less on an incremental cost basis, with reuse of parts of the thrust assist rockets (either SRM or pressure-fed). With Point 9 realized, the costs of TAOS would practically match the costs per launch of two stage fully reusable systems.
14. TAOS practically assures NASA of a reusable space transportation system with major objectives achieved.
RATO AND TAHO SHUTTLES