Commercial nearEarth space launcher a perspective

Before there can be any space exploration, there must first be an ability to reach low Earth orbit (LEO) from Earth's surface. The required speed for low Earth orbit is given in Table 3.1. For all practical purposes 100 nautical mile and 200 kilometer orbital altitudes are equivalent.

Whether it is an expendable launcher or a sustained-use, long-life launcher, the launcher must reach the same orbital speed to achieve LEO. From here the spacecraft can move to a higher orbit, change orbital planes or do both. Reaching LEO is a crucial step because, as indicated in Figures 2.5, the current system of launchers is representative of the Conestoga wagons that moved pioneers in the United States in just one direction: west. There is no record of any wagon returning to the east. The cost of traveling west was not reduced until the railroad transportation system was established that could (1) operate with a payload in both directions, and (2) operate frequently on a scheduled basis. Both directions are key to establishing commercial businesses that ship merchandise west to be purchased by western residents, and raw materials and products east to be purchased by eastern residents. The one-way Conestoga wagons could never have established a commercial flow of goods.

Scheduled frequency is the key to making the shipping costs affordable so the cargo/passenger volume matches or even exceeds capacity. The same is true of course for commercial aircraft and even for commercial space. In this context it is worthwhile mentioning that the November 18, 2002, issue of Space News International

Table 3.1. Low Earth orbital altitudes and speeds.

Altitude (nautical miles) Speed (ft/s)

185.2 7,794.7 100 25,573

200.0 370.4

108 200

25,544 25,220

Figure 3.1. Comparison of payload costs to orbit, from 1971 to 2003.

presented an interview with the former NASA Administrator, Sean O'Keefe, that stated the projected cost for the five Space Shuttle launches per year is $US 3.2 billion. That reduces to about $US 29,000 per pound of payload delivered to LEO; for some missions that cost could rise to $US 36,000 per pound. The article stated that an additional flight manifest will cost between 80 and 100 million $US per flight. If the Shuttle fleet could sustain 10 flights per year, the payload cost would reduce to $US 16,820 per pound. If the flight rate were two a month, the cost would be $US 9,690 per pound. It is really the flight rate that determines payload costs.

Figure 3.1 shows that the historical estimates of payload cost per pound delivered to orbit were correctly estimated and known to be a strong function of fleet flight rate for over 40 years. In the same figure there are five estimates shown covering the time period from 1970 to Sean O'Keefe's data in 2002. In the AIAA Aeronautics & Astronautics article in 1971 [Draper et al., 1971] the projected total costs for a 15-year operating period were given as a function of the number of vehicles. The payload costs were determined with the information provided in the article. This is shown as the solid line marked Draper et al. One of the students in the author's aerospace engineering design class obtained the cost of crew, maintenance and storage for 1 year of operation of a B-747 from a major airline. The student used that data to establish for a Boeing 747 operations cost in maintenance, fuel, and personnel for 1-year operation of three aircraft with one in 1-year maintenance. The annual costs are fixed, as they would be for a government operation; then, assuming that same B-747 operating with Shuttle payload weights and flight frequency yields a result shown in Figure 3.1 as the line of black squares marked B 747. These results show an infrequently used B-747 fleet is as costly as the Space Shuttle.

This result shows the airframe or system "technology" is not the issue, the real issue is the launch rate. This is an important finding, as most of the current new launch vehicle proposals are said to reduce payload costs through "new and advanced technology", and that may not be correct. For the McDonnell Douglas TAV effort in 1983, H. David Froning and Skye Lawrence compared the cost per pound of payload delivered to LEO for an all-rocket hypersonic glider/launcher and a combined cycle launcher (rocket-airbreather) operated as an airbreather up to Mach 12. Their analysis showed that the total life-cycle costs for both systems were nearly identical, the vast difference in technology notwithstanding, and it was the fleet fly rate that made the payload cost difference. The Froning and Lawrence data is the line of grey squares. In 1988 Jay Penn and Dr Charles Lindley prepared an estimate for a two-stage-to-orbit (TSTO) launcher that was initially an all-hydrogen vehicle and then evolved into a kerosene-fueled first-stage and a hydrogen-fueled second stage. Liquid oxygen was the oxidizer in all cases. They examined a wide spectrum of insurance, maintenance, and vehicle costs and published their analysis in Aviation Week and Space Technology in June 1998. This is shown in Figure 3.1 as the light grey area curve. Their analysis merges into the three previously discussed analyses. At the fly rate of a commercial airline fleet the kerosene-fueled TSTO payload costs are in the 1 to 10 $US per payload pound. NASA Administrator O'Keefe's data presented in Space News International is shown as a solid line. This most recent Shuttle data is the greatest payload cost data set. As a point of interest, Dr Charley Lindley, then a young California Institute of Technology PhD graduate, worked for The Marquardt Company on Scramjet propulsion for the first Aero Space Plane. The bottom line is, as stated by Penn and Lindley, "It is not the technology, it is the fly rate that determines payload costs.''

Thus, one way to improve the launch cost issue is to schedule the Shuttle to operate more frequently, or purchase surplus Energia launchers. Given the stated NASA goals of $US 1,000 and $US l00 per pound of payload delivered to LEO by 2020, the solution is launch rate, not specifically or exclusively advanced technology. It is not specifically a technology issue because operational life and number of flights are design specifications: it is they that govern durability, not necessarily technology. Translating the Penn and Lindley data into a single-stage-to-orbit launcher with all hydrogen fuel engines, results are in Figure 3.2. Six categories of cost were adjusted for a SSTO launcher from the Penn and Lindley data: namely Propellant, Infrastructure, Insurance, Maintenance, Production and RDT&E (Research, Development, Technology and Engineering). The costs of hydrogen fuel and oxygen oxidizer are essentially constant with flight rate, as they are new (recurring) for each flight. The one cost that changes the most is the amortized infrastructure cost. However, this cost and the other four costs (Insurance, Maintenance, Production and RDT&E) do not become minimal until high commercial aircraft fleet fly rates are achieved. The corollary is that propellant (in this case hydrogen, not

100,0001

1,000 n

UPropellant V- Infrastruct QInsurance C Maintain Production RDT&E

1,000 n

UPropellant V- Infrastruct QInsurance C Maintain Production RDT&E

Figure 3.2. Payload costs per pound based on fleet flight rate, after Penn and Lindley.

100 1,000 10,000 100,000 1,000,000

Fleet flight rate (flights/year)

Figure 3.2. Payload costs per pound based on fleet flight rate, after Penn and Lindley.

kerosene) does not become the primary cost until fleet flight rates in excess of 10,000 flights per year are achieved. This and larger fleet flight rates are achieved by commercial airlines, but are probably impractical in the foreseeable future for space operations. From the MOL requirements given in Chapter 1, near-future fleet flight rates will be in the hundreds per year, not hundreds of thousands. NASA goals of US$1,000 per pound can be met if the fleet launch rate is about 130 per year, or 2.5 launchers per week. For a fleet of seven operational aircraft, that amounts to about 21 launches per year per launcher, assuming an availability rate of 88%. That is about one flight every two weeks for an individual aircraft. At this point the five non-propellant costs are about 30 times greater than the propellant costs. For the NASA goal of US$l00 per pound to LEO requires about a 3,000 fleet flight rate and a larger fleet. Given 52 weeks and a fleet of 33 launchers with an 88% availability rate, the weekly flight rate is 58 launches per week, yielding a fleet flight rate of 3,016 flights per year. Such a fly rate demands an average of 8.3 flights per day! At this point the five non-propellant costs are about three times greater than the propellant costs. That is in the realm of the projected space infrastructure shown in Figure 2.23. Commercial aircraft exceed 1 million flights per year for the aircraft fleet, and that is why the cost for commercial aircraft passengers is primarily determined by fuel cost, not by individual aircraft cost. So, whatever the future launcher system, for the space infrastructure envisioned by Dr William Gaubatz in Figure 2.23 to ever exist, the payload cost to LEO must be low enough and the launch rate high enough to permit that infrastructure to be built.

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