The Nation's space programs are in a horrible mess and appear to be locked in a downward spiral. Almost all defense and civil government space programs suffer from similar symptoms:
As a result of these symptoms, the following conditions are now the norm:
Although these symptoms and conditions have been deliberately overstated for emphasis, they are more true than not. The question is then: Is there any way out of this morass? After all, countless committees have grappled with this situation and proposed courses of action, but apparently to not very much effect. In fact, the problem really has no solution as long as the U.S. Government remains the principal customer for space systems for several reasons: the government suffers from chronic risk aversion, it avoids new technologies and concepts, it has deep pockets of tax money and protests otherwise, there are few real incentives to save major amounts of money, new space systems are overloaded with requirements that guarantee that they overrun budgets and timelines and underperform, and the requirements process is broken so that even if requirements initially are contained, they inexorably will rise during a program and lead to major cost and schedule growth.
The only escape from this situation is to use market forces to bring costs down and spur innovation. This typically is how commercial systems live. However, a large market requires that products and services be relevant to large numbers of people. It requires risk-taking and a willingness to fail often. It requires many actors in competition, which means commercial approaches to space products and services.
The government's role must be to take most of the risk out of new technologies, which the private sector cannot now afford to do. Furthermore, the government must avoid competing with the private sector (we should imitate Japan, where the government and industry are partners in fostering national growth, whereas in the United States they are more adversaries than partners). In short, the Nation's space programs must mimic how commercial systems in general have always worked and how commercial space systems in particular must work.
New Technologies as Drivers
In the next few decades, an explosion of new technologies will transform space systems, including commercial ones, in every way. While it is impossible to forecast what technologies and systems will appear, there are a number of currently identified, though not yet fully developed, technologies that will enable a great number of advances to be made in the space field. Some purveyors of current techniques and systems view many of these technologies with suspicion because they have seen past technology development efforts take longer and be much more difficult than anticipated, and they then project these real-life experiences, rightly or wrongly, onto all future technology proposals. Others are heavily invested in current technologies and are threatened by the promises of newer ones, consciously or unconsciously. And other purveyors are skeptical of the new technologies because they lack the proper science grounding or fail to understand the technologies' principles of operation.
Many people will label the technologies discussed in this chapter, and therefore the space capabilities that they will enable, as somewhere between too optimistic and bordering on science fiction. I would like to offer two perspectives as defense against these criticisms. The first is from Arthur C. Clarke: "Any sufficiently advanced technology is indistinguishable from magic." The second perspective is from Niccolo Machiavelli's The Prince: "Those who advocate a new order of things have a very difficult journey, for they have as enemies those who would lose by the introduction of the new, and yet only lukewarm supporters in those who would gain thereby."
The only credible way to make the case that the technologies that will be presented are not too risky or optimistic is to examine the capabilities and technologies that existed 50 years ago and compare them with today's technologies that are accepted as commonplace (see figure 9–1).
Figure 9–1. 50-year Technological Perspective
A projection 50 or even 25 years into the future will fall short because we may underestimate the pace of exponentiating technological development and we cannot forecast new inventions. As a result, it is proposed that the technologies about to be discussed are a reasonable set to expect to see developed in the future, possibly much sooner than 50 years because of the accelerating pace of technology. Rather than offering too optimistic a vision of the future, these technologies probably present, if anything, too conservative and myopic a view. Some thoughts on the likely steps, time, and effort that will be required to bring these technologies to maturity, with the understanding that such an effort is fraught with uncertainty, are offered later in the chapter.
Some of the technologies with maximum leverage, presented in random order, include:
These and other new technologies will revolutionize space system applications. These applications will transform defense and civil space programs but will also enable commercial programs in the process. The result will be a space future that is very different from today's practices and will include:
While each of the above and other technologies will have a major effect, the carbon nanotubes or buckytubes will have the greatest effect and will result in access to space at costs so low as to seem free relative to today's launch costs of about $20,000 per kilogram.
Carbon nanotubes are a new form of matter discovered just over a decade ago. They are perfect molecular structures of carbon atoms, forming carbon-carbon atomic bonds into hollow cylinders; they are true carbon polymers. This material is the strongest and stiffest one possible in this universe, as the carbon-carbon double valent bond is the strongest known. Carbon nanotubes have a strength-to-weight ratio 600 times greater than high-strength steel or aluminum alloys. The material is very flexible and tough; it can elongate 20 to 30 percent and yet rebound with no damage. Likewise, it is tolerant of buckling on compression and can recover with no damage. It conducts heat three times better than pure diamond, has an electrical conductivity like copper, and can be grown to be a metal or a semiconductor. It is the most thermally stable of all polymers, has the highest possible accessible surface area of any material, and will not rust or corrode to over 900° F. The phenomenal strength-to-weight ratio and toughness of carbon nanotubes is illustrated in figure 9–2.
Figure 9–2. Ultimate Toughness of Spacecraft Materials
These materials will revolutionize spacecraft (as well as practically all ground and air uses), but as in most things, change will come incrementally—with initial forms being composites whose matrix is laced with carbon nanotubes, spun textiles of carbon nanotubes in randomized orientations—and only eventually reaching the holy grail: the growing of net-shaped, pure, single-wall carbon nanotubes with wall-wall tube contact and with all tubes in a parallel or desired orientation (see figure 9–3).
Figure 9–3. Likely Development of Carbon Nanotube Material
While recognizing that progress will be incremental, we will focus on the ultimate impact of the pure grown single-wall carbon nanotubes. Typically, people focus on spacecraft structures and conclude that carbon nanotubes will at most reduce the weight of a spacecraft by 15 percent, the fraction of an average spacecraft that the structure represents. But this is in error, since in the timeframe of interest, practically all components and devices of spacecraft will be able to be grown with carbon nanotubes. This includes tankage, plumbing, engines, electronics, solar arrays, actuators, batteries, momentum wheels, antennas, sensors and their apertures, and on and on. It is therefore likely that practically all of the components of a spacecraft can be made of carbon nanotubes. The actual weight reduction of a component upon substituting carbon nanotubes for today's materials depends on how the component is loaded. Materials experiencing mostly tension will see a weight reduction of a factor of 600 compared to steel or aluminum alloys, while those in bending or compression will see the square root of 600, or 25. However, if we consider the actual fraction of a typical spacecraft that is employed by each subsystem and the weight reduction potential in that use, the typical entire spacecraft will see about a factor of 20 weight reduction.
Similarly, if all the components as well as all structure elements of a typical launch vehicle were made from carbon nanotubes, its dry weight would be reduced by a factor of over 50, but its effect on the lift capability of the launch vehicle would be a factor of 7 (see figure 9–4).
Figure 9–4. Impact of Carbon Nanotubes on Spacecraft and Launch Vehicles
The implications are clear from the figure: the net effect of reducing spacecraft weight by a factor of 20 without sacrifice of function, and the increase of launch vehicle capability by a factor of 7 for the same size, together result in a factor of up to 140 in reduction of the costs of fielding a space system, solely due to the introduction of pure oriented carbon nanotubes. While it remains to be proven in practice, this weight reduction for the same capability—or, conversely, the capability increase for the same weight—should translate directly into a factor of up to 140 in cost for the same capability.
Amazingly, it does not stop there. The technology of launch vehicles will result in roughly one order of magnitude decrease of launch costs every decade or so independent of the introduction of carbon nanotubes (see figure 9–5). This is not a pipe dream but rather is based on many studies performed over the years by the National Aeronautics and Space Administration (NASA) that have shown such price reductions; however, the time period in which these steps are likely to be attained is based only on what could be done if the will and budgets existed. The early steps are likely to occur later; however, when carbon nanotubes are introduced, it is likely that the later steps will occur sooner and prompt even more dramatic cost reductions than shown in the figure. The last step shown in figure 9–5 is the widely publicized space elevator, a concept long postulated that could be made feasible by carbon nanotube materials but that would be totally impractical because every satellite currently in orbit or that will ever be launched into orbit would eventually collide with it and destroy it. No reasonable, effective countermeasures have yet been identified, so the space elevator is unlikely to materialize.
Figure 9–5. Potential Future of Launch into Space
The net result of the foregoing is that the costs of access to space a few decades from now will be comparable to those of airborne systems and will be so low that, compared to the costs of current vehicles, launch into space will be relatively inexpensive. This will bring the costs of space programs into an attainable range for a large number of commercial entities, which will begin to develop and field their own space systems to offer products and services in the marketplace. The entry of commercial enterprises will be the key to breaking the downward spiral of the Nation's space program. In fact, it will enable a second industrial revolution, but this time in space.
The Space Industrial Revolution
The revolution that will be enabled by finally bringing space fielding and operations costs in line with all other operations costs in the air or on the ground will unleash a plethora of services that have been studied and discussed over the years but that have not been taken seriously due to high costs of doing business in space.
Some of the commercial space programs that could take off include evolution of conventional services, including communications, navigation, tracking and location, and remote sensing. However, a host of new products and services will emerge, some robotic and others manned. The robotic services will include:
The manned services will include:
Potential Commercial Space Programs
A few of the most likely commercial space programs that could emerge in the 2010 to 2040 time period will be described here.
Public space travel (space tourism). Public space travel has been on the forefront of the commercial drive into space for decades, only awaiting reliable and less expensive space transportation to materialize.
Suborbital space travel—that is, climbing to an altitude of at least 100 kilometers—officially qualifies the traveler as an astronaut by international agreement. The drive into suborbital space was greatly aided by the X-prize competition, won in 2004 by Burt Rutan's SpaceShipOne and his pilot. Other candidates are still trying to get off their flights, including other air-launched first stage configurations. There is a healthy but relatively small market forecast for suborbital flights, since they entail at most a few minutes of weightlessness, even though they are much less risky than orbital flights. Nonetheless, Virgin Galactic, the company formed to commercialize the SpaceShipOne concept, has several hundred reservations.
Surveys done in the last decade suggest that orbital flights are needed for a large market to develop. The surveys predict that 100,000 people annually would like to go into space at a $100,000 ticket price, and 1,000,000 would go annually at a $10,000–$20,000 ticket price. Public space travel (space tourism) has already started with a few wealthy tourists going to the International Space Station (ISS). While suborbital travel has yet to occur, commercial suborbital flights are planned (Rutan/Virgin Galactic). Initially, tourists will stay in the transportation vehicles, as they must for suborbital travel, but they will also do so in the initial orbital trips. If public space travel is to develop as hoped for, orbital hotels will be needed. This would represent a new business for the travel industry with a forecast market well over $30 billion annually. Hilton, Sheraton, and others are beginning to consider such ventures; however, entrepreneur Robert Bigelow has funded and flown, at his own expense, a test inflatable habitat (Genesis) and fully intends to develop and orbit space hotels.
Once demonstrated to be safe, the necessary inexpensive orbital vehicles will inevitably follow, starting with initially expendable vehicles adapted from evolved expendable launch vehicles (EELVs), and eventually transforming into fully reusable vehicles (Kistler two-stage-to-orbit, single-stage-to-orbit [SSTO]), which will offer greatly reduced launch costs and increased reliabilities.
These small steps are very encouraging and promise to make real the large business potential in public space travel. By the end of the 2030s, there could well be dozens of space hotels serviced by routine flights to them for tourist stays of a week or more. While the hoped-for cruise-ship–like space resorts will eventually become real, they will probably take longer to materialize. However, excursions around the Moon are also planned by Bigelow, and extravehicular activities are already being planned.
Space business parks. The advent of cheap and reliable space transportation, in addition to heralding ubiquitous public space travel, will also enable privately developed and operated space business parks—mixed-use facilities in orbit dedicated to supporting a number of different businesses with common infrastructure.
These business parks will be privately developed, owned, and operated. They will comprise leasable facilities for long- or short-term occupancy by a variety of business tenants, which could include laboratories for pharmaceutical research or production and real estate for sports, movies, and other business activities. These tenants will be supplied by common supporting infrastructure by the park operator, including:
An artist's concept of such a facility is illustrated in figure 9–6.
Figure 9–6. Space Business Park Concept
Power delivery to International Space Station. Support to the ISS could well be an early commercial service. Indeed, current NASA programs are competing commercial provision of logistics to the ISS from the ground, though no commitment has been made yet for their use.
The ISS has a number of characteristics that may make it a good candidate for commercial support. One such is the provision of power to the science and other users aboard the ISS, which is very limited. The ISS itself has little dedicated experimentation space, is very expensive to operate (costing about $1 million per person per day), is very sensitive to vibration (to support microgravity processing), and has no spare habitation space.
One potential commercial service could be beaming of power from a commercial co-orbiting free flyer to the ISS, which studies indicate could supply hundreds of kilowatts at a fraction of the costs were the ISS to grow its on-board power. A simple commitment by the government to buy a certain number of kilowatt hours per year from a commercial entity delivered to the ISS would suffice to obtain private funding. This service is typical of a number of services that could be provided by commercial ventures:
This would be a good way to begin commercial infrastructure in space, with the government being the anchor tenant. The power delivery concept is illustrated in figure 9–7.
Figure 9–7. Power Delivery to International Space Station
Fast global package delivery. A global reach rocket vehicle, whether just suborbital or orbital with deboost, could fly anywhere in the world, spaceport-to-spaceport, in under 2 hours. This could readily give rise to Global Federal Express–like mail and package markets, which studies have shown is a large unmet demand and market. The service would be provided by small but fully reusable unmanned vehicles, which a combination of SSTO technologies will make feasible, probably in the 2015 to 2020 time period.
This service could be one of the first commercial robotic transportation space applications. Studies have shown ready financial feasibility of such a fast global delivery service, which would cut the time to deliver a package or document by an order of magnitude from today's aircraft-based systems. It would be technically feasible once the government reduces the risk of the needed technologies.
Support to lunar base. Many studies have shown that a lunar base has high potential for science, exploration, and industrial research. Indeed, a lunar base is the centerpiece of NASA's human space exploration plans, which it is planning in the 2020 time frame. While it would be a government undertaking to establish the base itself, any such facility will need ongoing support in the form of oxygen, propellants, water, surface digging, processing plants, and transportation infrastructure.
Water may well exist as ice in a lunar South Pole crater. The base thus could supply its own needs plus those for exploration of other lunar areas. It could export liquid oxygen to Earth orbits for propulsion applications. It would begin as a simple outpost, with the crews living in the landers, but would soon be followed by a complete and permanent base, which would be used as a learning and staging base for forays to Mars and elsewhere in the solar system. A more complete facility would follow in the 2020–2030 time period. It would initially be a government-emplaced and -run facility but would transition to being commercially operated, building on the government's investment. This operation would be a commercial enterprise of unprecedented magnitude.
Movie studios in orbit. Creating the illusion of free fall (zero gravity) in space movies and adventure television series is difficult, expensive, and very limited. Studies have shown that habitation modules or converted shuttle external tanks can provide needed volume and be outfitted with studio equipment. Such orbital "sound stages" could be owned and operated by a film studio, or they could be owned by a consortium and leased to individual studios as needed. Studies have shown financial viability of space movie studios under the right circumstances. Such studios would be attached to space stations or business parks for housekeeping support.
LEO-GEO transfer infrastructure. A permanent low Earth orbit (LEO)-GEO transportation infrastructure that is made available to both government and commercial users on a fee basis is a distinct possibility in the time period of interest and is enabled by the technologies described earlier. While initial infrastructures would use chemical or electric propulsion, a particularly intriguing concept is one that uses momentum exchange tethers to sling payloads between heavy permanent platforms. The heavy platforms transfer energy and momentum to the payload, which is transferred from LEO to GEO without consuming any propellants. Each platform adds up to 2,000 meters per second to the payload's velocity since the tangential velocity of the spinning tethers adds to the orbital velocity when releasing the payload and subtracts from the orbital velocity at the catching end to make a zero relative velocity catch.
The payloads are thus placed into a 6-hour Hohmann transfer trajectory to near-GEO, and no propellants are expended in the transfer. Of course, the energy to do so must come from somewhere, and indeed it comes from slightly lowering the orbits of the heavy platforms, which they then make up with ion propulsion over a longer time at an Isp of 5,000. Thus, in effect, the payloads are transferred with an effective Isp of 5,000 per second, yet the transfer is completed in 6 hours. This is impossible to attain with any known propulsion technology. In fact, this tether "ladder" in space works equally well in reverse, lowering GEO payloads to LEO for servicing, upgrading, or disposal. Eventually, as such systems are emplaced, the GEO traffic will increase greatly, and if the "upmass" equals the "downmass" over time, the energy gained by lowering payloads from GEO to LEO can be used to boost the next payloads from LEO to GEO, and, except for some unavoidable losses, the system requires no energy to operate. Thus, a propellantless permanent transportation infrastructure would have been created. This infrastructure would be operated by the commercial sector for the Nation (see figure 9–8).
Figure 9–8. Propellantless, Reversible LEO–GEO Transportation
Passive power distribution via GEO relay. Large passive radio frequency (RF) reflectors in orbit can be used to relay RF energy generated by powerplants in an energy-rich part of the globe to other areas that may be energy-poor, where it would be received and converted to electricity used to augment the local powergrid. This system would also be suitable for rugged or underdeveloped areas where population centers are far apart and for countries with no oil, such as Japan. Studies have shown that this means of distributing electrical energy is cheaper than wire transmission lines for distances greater than about 2,000 kilometers.
The system uses simple meshes or membranes to reflect the RF power, and the spacecraft is much lighter and less expensive than those that generate the power in space. A single spacecraft would contain several independently steered reflectors so that energy could be supplied to a number of destinations. Studies show that a $6-billion investment could result in a 35 percent internal rate of return and would be a financially rewarding project that could readily find commercial financing (see figure 9–9).
Figure 9–9. Power Relay Using Space Reflectors
Solar power from space. Solar power satellites were conceived by Peter Glaser in 1958. The concept of converting abundant, clean, and inexhaustible solar energy into microwaves and beaming them to rectennas at receiving facilities connected to the powergrid is simple. However, the concept initially used huge structures assembled by hundreds of astronauts and was an enormous space program whose technology did not exist and whose sizeable investment could not be recouped by the large, noncompetitive energy prices that could be charged to customers.
More recent studies were made with modern technology including adaptive membrane reflectors, modular robotic assembly, highly efficient solar arrays, medium/low Earth orbit constellations, formation flown elements, gravity gradient stabilized configurations, efficient solar arrays, microwave or laser beam power delivery, and a whole host of modern electronic approaches to the antennas and transmitters. These studies have shown that power could be delivered at a price competitive with fossil or nuclear power and that a totally renewable and clean energy source could be implemented with little if any significant environmental impact, which could solve the world's power and pollution problems at the same time.
Such space solar power systems could be available in the 2030 time period if governments lower the technology risk, which is beyond the capability of privately financed technological institutions. Such programs represent a huge commercial market for entrepreneurial private industry. Power utilities and commercial providers would likely team to develop, field, and operate these systems. The very large mass to be orbited would be a huge market for development of low-cost launchers, which would be needed if the delivered cost of electricity is to be competitive with other options. Thus, although this is a long-term proposition and a very large undertaking, it is no larger than many other commercial energy plant activities. One LEO concept is illustrated in figure 9–10.
Figure 9–10. Solar Power Delivery from Space
The several concepts described in the last section could each represent a major commercial space program. In the aggregate, they represent a potentially enormous collection of space programs that represents the future of the commercial space sector. This potential was assessed by constructing a reasonable but not definitive development and operation roadmap plan for each of the programs described above and the annual number of launches and the mass launched into space derived for each. Figures 9–11 and 9–12 illustrate, respectively, the mass in orbit and the number of launches per year resulting from these commercial space programs as a function of time through 2080.
Figure 9–11. Potential Annual Launched Mass
Figure 9–12. Potential Number of Annual World Launches
Inspection of these figures indicates that if these programs develop as postulated, the total mass into orbit of these commercial programs will grow rapidly within a decade of their introduction and by 2030 will equal the total mass launched into space by all current and projected defense and civil space programs. The mass will then grow even more rapidly, driven by the space solar power delivery systems and public space travel, becoming two orders of magnitude larger than the government programs by 2040 and three orders of magnitude larger by 2050 and beyond.
Likewise, an examination of the second figure shows that the annual number of launches of large, EELV-class launch vehicles will increase by an order of magnitude by 2035–2040 and by two orders of magnitude by 2050 and beyond. While it is true that these figures were developed for assumed scenarios of development of the individual component programs, and it is impossible to predict whether the particular programs will be developed, the trends in the figures are inevitable and inescapable.
The prior sections have laid out a series of potential commercial programs that could materialize in about the next 30 years and a potential roadmap for their appearance. It must be realized that both the programs themselves and especially their development and employment schedules and activity levels are based on the author's educated estimates, as there are no hard and fast commitments or schedules for any such applications by any entities save for the first public space travel venture by Virgin Galactic and Scaled Composites, Inc. Thus, while the programs described are believed to be reasonable estimates, their actual appearance is dependent on many commercial, business, and technology activities and decisions whose undertaking, let alone outcome, is not possible to predict.
These activities will be undertaken principally by the private sector. However, as in many advanced technology commercial activities, they could well be preceded by some government activities to reduce the risk of those technologies that could have beneficial dual use for government activities as well. This could run the range of simple technology investment to cooperative government-industry partnerships resulting in demonstrations useful to both parties. Indeed, such government investment could be substantial and may be key in the start of some commercial activities that would otherwise be unable to raise private financing. In addition, inducements could be offered by the government in the form of tax incentives, grants of licenses, and other benefits to spur some activities perceived to be either dual use or of substantial benefit to the Nation's economy.
Indeed, the government is already investing in fundamental technology developments such as research in carbon nanotubes and other advanced technologies that will be necessary to fully realize the potential of some of these applications. This investment is sponsored by the Defense Advanced Research Projects Agency, the Air Force, the National Science Foundation, and others. Practically every technologically advanced nation is doing likewise due to the extreme promise of carbon nanotubes in a host of commercial and military application areas. In addition, many electronics, power, and thermal applications of carbon nanotubes are being researched and will probably be the first to make it into the commercial electronics marketplace.
The potential for a delay in when some commercial applications might materialize exists if the government's financial support of research in this and other science and technology areas is reduced substantially—an eventuality that, while not anticipated, cannot be ruled out and could have considerable negative effect. However, since there is intense international activity in carbon nanotube science and technology, major reductions would place the United States behind other nations and therefore are not very likely to occur. This is particularly true considering that so many commercial products will benefit from inclusion or adoption of carbon nanotube technologies. These include consumer electronics of every description; structures for cars, trains, airplanes, boats, and ships; medical equipment and diagnostic techniques; sporting goods; and many other products whose use underpins the economic well being of our country.
This raises the question of what happens to the commercial space applications identified should carbon nanotube development fall short of the described progress. In a very real sense, none of the commercial programs described in this chapter depend on carbon nanotubes. They could just as well be developed and operated with conventional materials, though they would be heavier and costlier than if they used carbon nanotubes and other advanced technologies. Nonetheless, even if that came to pass, the business model and financial feasibility of these programs would still be positive for the most part, though their introduction might be delayed to allow demand to compensate for the increased price these services would thus feature.
Being able to develop some thoughts on a technology investment strategy to facilitate commercial undertakings such as those described herein would seem attractive. Unfortunately, even if it would be possible to develop such a strategy, it would have questionable utility because it would have to assume myriad critical activities and factors that underpin all commercial entrepreneurial ventures and that can only be considered by the parties themselves. In addition, the undertaking of any such strategy, even if its limitations were to be accepted, would be completely beyond the scope of this chapter. Thus, the development of a more specific technology investment strategy and development roadmap than the one discussed in the previous section is not possible.
Based on commercial activity already beginning in public space travel (both suborbital and later orbital), it seems evident that these programs, if economically successful, will spur technology investment to create the next application. This effect will begin to create the momentum for the realization of the second industrial revolution in space that is central to this vision for the future of commercial space.
This chapter has shown that technological advances in the 2010–2020 time period, spurred by private capital and some government seed technology investment, will enable new commercial products and services, in addition to new government programs. These technologies will result in orders-of-magnitude reduction in the costs to develop, orbit, and operate space systems for both government and commercial space programs. The principal driver will be orders-of-magnitude reduction of launch costs, which will unleash explosive growth in new, nontraditional commercial space programs in addition to growth in more traditional communications, navigation, location, and sensing commercial programs.
By 2030 or beyond, the magnitude of these commercial programs will, in the aggregate, exceed all government space programs in the total investment in space systems, in the number of annual launches, in the total mass in orbit, and in the infrastructure in orbit. The future commercial space program as a whole will represent a second industrial revolution—but this time, in space.
These commercial space programs and their ground and space infrastructure will rapidly become a vital portion of the Nation's economy, providing energy, information, and goods and services on which many people and entities will be dependent. In addition, they will be used by defense and intelligence agencies for routine as well as some strategic and tactical support of those agencies' objectives. In addition, new commercial programs and new uses for programs not even imagined will arise. For all these reasons, future commercial programs will become an inseparable aspect of national security and will have to be protected against attack, much as airports, planes, trains, and critical infrastructure need protection. Any spacepower theory must take this into account.