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NSRC 2020

 
Sea Launch
A system of floating launch platforms on the Equator, analogous to Sea Launch’s system, coupled with a reusable launchers, could support dozens of launches a day. (credit: Sea Launch)

Launching 64 times per day


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Current Earth-to-Orbit (ETO) launch systems, such as Proton and Soyuz, launch at most a dozen times per year. Concepts for replacement ETO launch systems are often evaluated at similar yearly flight rates; a typical evaluation regime constitutes 12 flights per year for 30 years. This essay considers an entirely different and much higher assumption as to flight rate: 64 times per day, three orders of magnitude higher than current flight rate, and evaluates its impact. Although in general it is well known that higher flight rates imply lower average costs, this essay will focus specifically on an extremely high flight rate system to a particular low Earth orbit.

Consider an ETO launch system comprising a sizable fleet of fully-reusable vertical take-off/vertical landing three-stage-to-orbit vehicles operating from four equatorial floating launch platforms, analogous to the one used today by Sea Launch, situated 90 degrees apart in longitude (that is, 10,019 km or 6,225 mi. apart), two in the Pacific Ocean and one each in the Atlantic and Indian Oceans.

The average costs are $78 per kilogram ($36 per pound) or $713,000 NPV per launch, or less than 1% of the current value.

Each flight delivers a 9,000-kilogram (20,000-pound) payload to a circular equatorial orbit where the payload is transferred by orbital transfer vehicle (OTV) or some other mechanism to a space station. The space station is in a circular equatorial orbit, allowing 16 launch windows per day from each of the four launch platforms, thus resulting in 64 launch windows per day en toto for the ensemble of launch platforms. In an average year, this system launches 23,376 times, delivering 212,509 metric tons (233,760 English tons) of payload or personnel to orbit, more in one year than has been launched since the dawn of the space age in 1957.

The exact design of the launch system is left largely unspecified here, but we can anticipate the following characteristics. The first stage launches vertically from the launch platform to an appropriate staging point, separates, and then returns to the same launch platform, landing vertically. The second stage fires and, after some time, eventually separates from the orbiter; after doing so, it lands vertically at the launch platform 90 degrees east from the one from which the stack originally launched. The orbiter performs a direct injection to a circular orbit, quickly releases the payload, deorbits after staying in space less than one orbit, and lands vertically on one of the launch platforms, though not necessarily the same platform from which it launched. The system is designed for high vehicle utilization and each of the three stages returns to a launch platform within an hour or two of launch, ready to begin post-flight maintenance activities and preparation for subsequent launches.

Payloads are retrieved by OTVs and transferred to the space station and the OTVs are regularly maintained there. The space station could be a multi-use facility, serving as hotel, conference center, sports facility, manufacturing and orbital assembly facility, and transshipment node for transfer to geosynchronous orbit, other high-Earth orbits, and all points beyond.

The required launcher fleet size for each stage is a function of the average turnaround time between flights. Assuming that a particular stage has an average turnaround time of three days, Little’s Law implies that the fleet required for a 64-launches-per-day pace is 192 vehicles. Different stages might have different average turnaround times and therefore different required fleet sizes. Similar calculations govern the required fleet size for the orbital transfer vehicles.

The amount of payload delivered to the space station by the launch system would be so huge that it is fair to say that this single system alone would transform mankind into a spacefaring civilization and change forever the way we live.

To establish this system, the launch vehicles and orbital transfer vehicles must be designed, developed, tested, evaluated and so forth; manufacturing plants established; fleets manufactured; floating launch platforms constructed; the initial space station established; and a variety of other details resolved. We do not anticipate that the establishment of this system would require “unobtanium” or the development of other wholly new technologies. Though it is certainly the case that the vehicle must be carefully designed, especially the second stage, the launch system itself has three stages and would therefore be more technically achievable with existing technologies than more challenging single- or two-stage-to-orbit alternatives that potentially could be considered and are often considered in advanced space concept studies. The floating launch platforms would use construction technology derived from deep-water oil drilling platforms, albeit on a larger scale. Suppose that the initial investment could be covered by $300 billion in net present value (NPV). Suppose further that operations costs, ongoing facilities costs, vehicle replacement costs, costs of failure, and other costs for the thirty years of operations equate to $200 billion of NPV.

Thus, assumed initial investment plus operations costs for thirty years total $500 billion NPV. The payloads launched during this thirty-year period sum to 6,375,273 metric tons (7,012,800 English tons). The average costs equate to $78 per kilogram ($36 per pound) or $713,000 NPV per launch. Assuming that current launch costs are $5,000 per pound, this system would reduce launch costs to less than 1% of the current value.

Depending upon the design of the system, the total thirty-year investment might be more or less than $500 billion. Different assumptions yield different costs per launch and per pound of payload, but it is seems reasonable to assume that a variety of assumptions would yield roughly the same result, namely, total investment or campaign cost over thirty years on the order of $1 million per flight or less NPV.

Many studies of ETO systems start with a vehicle design and then derive the cost and operational characteristics associated with it. By contrast, we specify an investment constraint—less than $500 billion campaign cost over 30 years—and we leave unspecified the technical details.

The amount of payload delivered to the space station by the launch system would be so huge that it is fair to say that this single system alone would transform mankind into a spacefaring civilization and change forever the way we live. If we assume that a person plus supporting equipment (e.g., life support) equates to 225 kilograms (500 pounds), then the average cost is less than $18,000 in NPV, and though prices charged would undoubtedly be higher, this cost level would bring space travel within the financial capability of thousands or millions of people. With so many people visiting the space station, an entire revenue-generating space economy would likely arise, with people visiting the station for pleasure, business conferences, permanent habitation and other purposes.

The anticipated $500-billion total thirty-year investment required to achieve this, though not small, is by comparison much lower than the federal defense budget for a single year and approximately 13% of the federal budget for a single year.

Many studies of ETO systems involve the analysis of a particular vehicle point design or minor variations around a particular point design; that is, these studies start with a vehicle design and then derive the cost and operational characteristics associated with it. By contrast, we specify an investment constraint—less than $500 billion campaign cost over 30 years—and we leave unspecified the number and types of engines and propellants on the various stages; we leave unspecified whether the first stage executes a rocketback or some other type of maneuver in order to return to base; we leave unspecified whether or not any of the stages are airbreathing; we notionally specify that the three stages land vertically, but without commitment were it to be shown that some other configuration would be more advantageous; we notionally specify four floating launch platforms, but if it were to be shown that three or some other number were better, that would be acceptable (though the analysis and vehicle would have to change correspondingly).

We leave most of the vehicle and system characteristics open for the designer. We issue a challenge to design a vehicle and system that does not require any fanciful new technologies but which can launch payloads to equatorial orbit extremely frequently and launch a total of a six million metric tons of cargo and passengers in thirty years operation for a combined initial investment and thirty-year operations costs of approximately $500 billion NPV, less than $500 billion if possible, or at least not wildly greater than that.

If the challenge can be met with great confidence and the result popularized, then efforts could be made to detail the proposal, decide upon appropriate project phasing and secure the required initial investment. Appropriate project phasing might involve one or more smaller projects of smaller investment that demonstrate early the basic concepts of the large system while allowing a progressive return on investment.


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