Space Power is about the generation of power from space.

The space around Earth is filled with intense sunlight, undiffused by atmosphere, continuously. It represents an inexhausible supply of energy that can be converted to electricity using semiconductors - that is without the use of any moving parts.

A small fraction of this energy could supply a large part of the world's future energy requirements for the foreseeable future. In addition, it could do it without the need for any kind of fuel, and without producing any waste product.

All that's needed is large-area collectors - and that means large, thousands of square kilometers - and a way to transmit the collected power down to Earth. Several different methods are possible, but the one that has received the most effort so far is the use of microwave beams or wireless power transmission.
29 July 2012
Added "Space Debris and Its Mitigation" to the archive.
16 July 2012
Space Future has been on something of a hiatus of late. With the concept of Space Tourism steadily increasing in acceptance, and the advances of commercial space, much of our purpose could be said to be achieved. But this industry is still nascent, and there's much to do. this space.
9 December 2010
Updated "What the Growth of a Space Tourism Industry Could Contribute to Employment, Economic Growth, Environmental Protection, Education, Culture and World Peace" to the 2009 revision.
7 December 2008
"What the Growth of a Space Tourism Industry Could Contribute to Employment, Economic Growth, Environmental Protection, Education, Culture and World Peace" is now the top entry on Space Future's Key Documents list.
30 November 2008
Added Lynx to the Vehicle Designs page.
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Equatorial Times No.4
The Newsletter of the SPS 2000 Community Around the World

Editor: Dr Patrick Collins

Some of the many islands in the Maldives chain of atolls
Welcome to this Issue

In this 4th issue of "Equatorial Times" we report on our recent visit to Maldives (described at greater length in a separate report) where we visited government officials in the capital of Male, and then traveled to the southern-most part of the country, Addu Atoll, just south of the equator, as another promising SPS 2000 rectenna site.

More and more countries are achieving rapid rates of economic growth. However efficiently they use energy, they will need more and more electricity. Consequently, during coming decades the human race will need large-scale new supplies of energy - for which SPS is very well suited. But research is currently held back by institutional problems, as discussed in our Editorial.

We had hoped that a meeting on SPS 2000 would be held at the World Radio Conference (WRC) of the International Telecommunications Union (ITU) this autumn, but unfortunately preparations have not advanced far enough. On page 2 we outline some of the issues that need to be discussed - at the following WRC, we hope.

Plus SPS News from around the world.

The SPS 2000 microwave beam and international agreement

We had hoped that SPS 2000 would be one item to be discussed at the World Radio Conference (WRC) organised by the International Telecommunications Union (ITU) this autumn, but for a number of reasons it has not been possible to arrange such a meeting this time. However, when SPS 2000 does reach the agenda, it will generate discussion on a wide range of issues involving many different countries. The following is a preview of some of these. SPS 2000 is much smaller than the futuristic systems delivering gigawatts of power that will be needed next century if SPS is to be a significant energy source for Earth. However, its microwave beam will still be much more powerful than the beams transmitted by other satellites, and so it will raise a number of new issues.

As currently planned, the SPS 2000 transmitting antenna will transmit about 10 MW of microwave power at 2.45 GHz from an antenna 130 meters square with a uniform power distribution. The beam will spread to a diameter of 2 km where it reaches the Earth's surface. Thus the energy density of the beam as it leaves the antenna at 1100 km altitude will be about 600 W/sqm, falling to an average intensity of about 3 W/sqm at the Earth. At an altitude of 800 km.

where Earth observing and communications satellites operate the average intensity will have dropped to about 40 W/sqm, with a maximum of 1100 about 100 W/sqm in the center of the beam. Satellites travelling at orbital speeds of about 8 km/sec will pass through the beam in about 1/8 of a second. Nevertheless, some satellites contain very 800 sensitive systems which may need to be protected from interference, and they will generally be owned by companies based in countries far from the equator.

Changing "footprint" of SPS 2000 microwave beam at different altitudes

At about 500 km, the altitude at which crewed spacecraft such as the Mir space station operate, the 500 SPS 2000 microwave beam will have spread to more than 1 km in diameter, and the average power density will have fallen to about 10 W/sqm, with a maximum of about 30 W/sqm in the center of the beam. As discussed in Equatorial Times 3, p2, biological systems are less sensitive to microwave 10 radiation than many telecommunication systems. Exposure to 20 w/sqm for a fraction of a second is not dangerous to health; it would have an unmeasurably small heating effect. Furthermore, astronauts and cosmonauts work inside spacecraft with metal walls which absorb microwave energy. Much lower still, at about 10 km altitude where airliners typically fly, the beam will have spread to more-or-less the size it will have on the ground - nearly 2 km in diameter with a maximum density of 10 W/sqm in the centre of the beam, and an average density of about 3 W/sqm. This is within international safety standards, in addition to which passengers will be protected by the walls of the aircraft. However, aircraft's electronic and communications systems may need to be protected from interference, and they are owned by companies in may different countries. By current international law, the "Industrial, Scientific and Medical (ISM) band" of 2.4 - 2.5 GHz may be used freely for industrial purposes, including SPS 2000. But, as we can see even from this simple discussion, it will impose certain constraints on other users of orbits and of the electromagnetic spectrum. And in order for SPS 2000 to be a popular project, we must ensure that the international negotiations through which the system design is accepted achieve as wide consensus as possible.

The technical conditions under which SPS 2000 operates will be of interest not only to countries which decide to be rectenna users, or are affected as above, but also to all other countries within 3 degrees of the equator, which will be swept by the microwave beam from SPS 2000; to near-equatorial countries close to 3 degrees latitude which will engage in cooperative research; to other potential users of future SPS systems, for which the successful realization of the SPS 2000 project will be of great interest; and to other potential participants, including suppliers of parts for the SPS 2000 satellite and/or rectennas.

Whenever they happen, discussions on SPS 2000 at the ITU will be particularly significant, because although SPS 2000 is a relatively small-scale system designed to operate within existing regulations, it represents the start of a path that should lead all the way to large-scale commercial SPS systems operating in geo-stationary orbit and above. Future SPS transmitting antennas may have beam intensities of as much as several kW/sqm over an antenna area of as much as 1 square km. This microwave intensity is similar to high-powered radar transmitters used at airports or on ships today, and is intense enough to melt thin wire placed in the beam! This will mean that other satellites will have to avoid passing through the beam near the transmitting antenna. The beam intensity on the ground will be several hundred W/sqm, high enough that safety systems will be needed to prevent it reaching populated areas. They will also need appropriate changes in law, as legal experts started to discuss about SPS in the 1 970s. Since that is the long-term target, decisions taken at the WRC about SPS 2000 will have an important influence on future developments. So it will surely be an interesting meeting. We look forward to meeting and exchanging views with readers on these matters in future.

Field Research Around the Equator (6)

Using a grant awarded by the Japanese Ministry of Education, Science and Culture ("Mon-bu-shoh" in Japanese), field research to study the feasibility of siting SPS 2000 rectennas in equatorial countries has been under way since 1994. The objectives of this research are to make contact with colleagues in candidate countries; to have initial discussions with government representatives and other interested parties in those countries; to identify candidate rectenna sites; to develop preliminary ideas about appropriate rectenna designs for each site; and to consider how each rectenna might best be utilised.

In March 1997, Dr. Hideo Matsuoka and Dr. Patrick Collins visited Maldives, a chain of more than 1100 islands south and west of India and Sri Lanka, which run from 6 degrees north of the equator to just south of the equator.

As in earlier field visits to Tanzania, Papua New Guinea, Brazil, Indonesia and Ecuador, there was considerable interest among officials in the Maldives government in participating in the SPS 2000 project by providing a site for a rectenna, and using the electricity which it would supply in a district where supplies are currently inadequate.

Maldives is the smallest country visited to date, having a population of only 250,000 and a land area of only a few square kilometers. However, the land is spread over some 30,000 square kilometers of atolls - roughly circular coral rings up to 50 km in diameter.

A significant proportion of the atolls' area is covered with water only 1 meter deep. Consequently there is large potential for land reclamation, and the government has plans for this.

The south-western part of Addu Atoll. The pale blue area is shallow water over the reef. The darker water to the left is within the atoll and reaches 30-40 meters; the water to the right is outside the atoll and very much deeper.

In addition, a large proportion of the land area of Maldives is only a few meters above mean sea level, and so there is continual danger from floods which occur periodically.

As in many other equatorial countries, Maldivians who live far from the main population centres lack electricity supplies, and there are many places where the power supply from an SPS 2000 rectenna would be very welcome.

As a possible candidate site, Professor Matsuoka and Dr. Collins visited the southern-most part of Maldives, Addu Atoll, which is a little south of the equator. Although one of the smaller atolls, Addu has an airport and a relatively large land area, since many of the islands are quite wide, and several have been connected with a road.

Issues arising

Due to the very limited land area in Maldives, it seems desirable that an SPS 2000 rectenna should be constructed over the sea. Since there is a large area of shallow waters protected within the coral walls of the atolls, this will be easier than building over the open sea. Although it will be more expensive than building a rectenna over land, it will give experience of "marinization" of a rectenna - that is, designing and building it to operate even when wet with sea water. This experience will be particularly valuable since many countries, including both Japan and Europe, will need to build rectennas over the sea due to their limited area and shortage of unused land.

Looking west over the lagoon of Addu Atoll

Another issue that was discussed was the environment. The government of Maldives is a vigorous representative of low-lying island nations at international conferences on global environmental problems, since they have a particular interest in preventing a rise in average sea levels due to "global warming" causing a partial melting of the antarctic ice-fields. Other equatorial countries participating in SPS 2000 such as Papua New Guinea, and some Pacific islands which are to be visited in future, are in very similar situations, and there could be benefits from collaboration in connection with their participation in SPS 2000.

However, a rising sea level is not a problem only for island nations like Maldives. Many capital cities are built by the sea or at sea level, and many countries have large populations and major cities at low level on the coast. It has been estimated, for example, that Japan would have to incur costs of many tens of trillions of Yen (hundreds of US $billions) to protect its major cities from flooding if the sea rose even a few meters above its current mean level.

Looking east over the lagoon of Addu Atoll

In this context SPS is potentially of great value as a counter-measure to "global warming", since it would produce very little C02 per kWh of electricity generated (see report on ISAS Space Energy Symposium on PS). Consequently, by playing an important role in the development of SPS 2000, equatorial islands have the potential also to influence the development of SPS, and hence help to solve this very important problem.

Copies of the full report on our Maldives visit are available on request. The next visit is being planned for Malaysia during autumn 1997.

Language corner

As we travel to countries around the equator, there are clearly many occasions when it would be interesting - and useful - to be gifted linguists. Unfortunately we're not. Nevertheless, even we notice some interesting words. For example, in Tanzania the word "Bahari" means ocean. Later, visiting Indonesia, it came up in conversation that the same word is used in central Java, nearly 10,000 km away!

Apparently, several hundred years ago, traders from central Java in Indonesia sailed as far west as the east coast of Africa. We also heard that the same word is used in Arabic - and it's known that Arabic traders reached as far west as East Africa and as far east as Indonesia.

So words have been spreading around the equator like this for a long time. It would be interesting to do some more research on this. Are some words used in Ecuador also used in the western Pacific? Or are some words that are used in West Africa also perhaps used on the east coast of South America?

Launch Vehicle News

As discussed in Equatorial Times 3, the cost of launch is one of the most important issues for determining the feasibility of SPS as a major new energy source for the Earth. Recently, the topic of reducing launch costs substantially has received increasing attention, both within government space agencies, and among launch vehicle makers.

For example, on July 21-22 there is to be a conference on Cheap Access To Space (CATS) in Washington DC organized by the Space Frontier Foundation and sponsored by NASA, at which policy makers, engineers, NASA staff and independent business-people will meet to discuss this topic. The author Tom Clancy (author of political thrillers including The Hunt for Red October) will also speak about his own investment in the new company, Rotary Rocket, which is developing a low-cost launch vehicle. With a few more adventurous millionaires like Tom Clancy, "CATS" shouldn't take long.

The present configuration of the Reusable Launch Vehicle (RLV) being studied at the National Space Development Agency of Japan, (NASDA). With a payload to low Earth orbit of 10 tons, and a target launch cost of $10 million/launch this could be just right for launching the modules of the SPS 2000 satellite. However, it's not due to start operation until 2010 - and SPS 2000 may not be able to wait that long.

SPS News
16th ISAS Space Energy Symposium

Of the 30 papers presented at the 16th ISAS Space Energy Symposium in February, about half concerned SPS, of which 3 specifically concerned SPS 2000. One reported on research on the effect of radiation on SPS 2000 solar cells; one reported on the electrical design of a functional model of SPS 2000; and one reported on the 1996 field research visits to Indonesia and Ecuador.

In addition, there was a special afternoon session on SPS and the Global Environment, including 7 presentations, of which 5 concerned the analysis of the C02 that would be produced if SPS became a major energy source, performed by researchers at the laboratories of Professor Hideo Matsuoka at RCAST and Professor Kanji Yoshioka at Keio University. They concluded that SPS would produce much less C02 than other forms of electricity generation - making it a very attractive means of combating "global warming". It is encouraging that this work, which is to be published as a book, was carried out by researchers not involved in space research. SPS is too often considered to be a "space project", and therefore of little economic importance (see next item).

The last session of the Symposium was a Round Table Discussion which considered a wide range of issues relating to SPS, including particularly the need for researchers from a wide range of disciplines to contribute to SPS research, in view of its potential importance for society.

New SPS Research Committee to be formed in Japan

At the meeting of the SPS Working Group following the Space Energy Symposium, it was suggested that ISAS has led SPS work in Japan about as far as it can - and that a new organisation is now needed that is not based at a space research center. Research on the space-based aspects will continue at ISAS and elsewhere, but, as discussed in our Editorial on p7, SPS faces a serious institutional problem. In truth it's an energy project, but it's very widely seen as a "space project". And unfortunately, because for decades space activities have been performed by non-commercial government organizations, they are perceived as being very costly and of little economic importance.

Consequently it has been decided to establish a new SPS Research Committee, to be based elsewhere than at a space research organization. Although this proposal is still tentative, and the best form for the organization has not yet been finalised, some 50 invited members have so far agreed to participate, and it is hoped that it will be a timely initiative, and effective in helping SPS to take its rightful place on the international energy agenda.

SPS 2000 presentation at conference in Thailand

A paper on studies toward siting an SPS 2000 rectenna in Indonesia is being presented at the 1997 Thailand-Japan Symposium on Antennas and Propagation (TJSAP'97) in Bangkok by Dr Yuliman Purwanto of Satya Wacana Christian University in Salatiga in Central Java. The paper is based on research by Dr Purwanto and his colleagues on Indonesia's possible participation in the SPS 2000 project, and this is the first time that a paper on this subject has been presented at a conference in South East Asia. It is very encouraging that this subject is being introduced to a new audience in this way. We will report on this paper in our next issue.

SPS 2000 rectenna planning computer program

Based on work performed at the Matsuoka Laboratory at RCAST, a computer program has been prepared for analyzing the energy output of the SPS 2000 rectennas that are being planned for a number of sites around the equator. This calculation is fundamental to planning a rectenna, since it enables the user to calculate the rectenna diameter they need in order to achieve the power output that they require, the scale of energy storage capacity that they need, and details of the distribution system for the power produced, and to plan the use and operation of the system. Performing these calculations requires a number of different factors to be taken into account, as described in "Estimating SPS 2000 rectenna energy output" (see Equatorial Times 2, p2).

The user of the computer program inputs values for factors such as the latitude of the rectenna site, the provisional diameter, and the ratio between the night-time demand and the day-time demand for the power produced by the rectenna. The computer program then calculates the amount of energy that will be received at the rectenna on each pass of the satellite, and the amount of electricity storage capacity that will be required.

This software is intended primarily for use by SPS 2000 researchers in countries participating in the project, and will be supplied on request free of charge. It is described in more detail in Matsuoka Laboratory Working Paper 9.

Hokkaido University research report

In March, Professor Kiyohiko Itoh of Hokkaido University produced the Final Report on the results of 3 years' research at his laboratory (see p8 photo of Equatorial Times 3) on microwave power transmission, which was funded by a research grant from the Japanese Ministry of Education. Totalling some $300,000-$400,000, this funding has been very fruitful in advancing the state-of-the-art of this technology which is of central importance for SPS 2000- including making and publicly demonstrating several working models of SPS satellite transmitting antenna modules. We hope that generous financial support for this pioneering team will continue, so that the goal of low-cost, high-efficiency, high-power, solid-state, silicon-based transmitting antenna modules can be reached.

SPS '97 conference

"SPS '97", the follow-up to the SPS '91 conference held in Paris, will be held in Montreal from August 24-28. Some 80 presentations are scheduled, covering the full range of topics relating to SPS, including design of the various satellite systems - solar power generation, microwave power transmission, large structure assembly - fundamental technology research, and related issues such as law and economics. Several papers from Japan will be presented, including one on the SPS 2000 project, one on a small SPS demonstrator project, one on ground-based wireless power transmission experiments, and one on the potential importance of current work on reusable launch vehicles for SPS.

Editorial - "Energy, Energy, Energy"

As more and more countries achieve rapid economic growth, the demand for energy, and particularly for electricity, increases. Even if the rich countries reduce their demand, global demand for electricity may grow by as much as 10 times over the coming century. So there is a clear need to develop new large-scale, clean sources of electricity.

In many of the more industrialized countries nuclear power now plays a significant role, and it receives the great majority of energy research funding. But as a candidate to become the major source of energy over the next century it is very unappealing. It is the source of the most toxic and long-lived pollution in the world, and the fact that it produces the material for nuclear weapons would be politically very destabilising.

By contrast, SPS, of which the potential contribution is unlimited, and which faces no pollution or political problems, receives almost no funding - not even as much as 1/1000 of the funding that nuclear power has received around the world. The reason for this is not because cost benefit analysis shows SPS to be unattractive. The major problem facing SPS is not technical, environmental, social or economic - but institutional.

That is, there are a number of technical issues which need more research, but in the opinion of many experienced engineers they are soluble - in various different ways.

There are no environmental problems, in the sense that the potential problems are well understood and SPS systems can be designed to avoid them. Furthermore, SPS has unique potential for solving the longer-term resource problems facing humans by leading to the use of non-terrestrial resources (as we will discuss in a later issue). There are no social problems, in the sense that there is no reason to expect popular resistance to SPS, as there is in many countries to nuclear power. Indeed, on the contrary, there is likely to be strong public support for SPS once it becomes better known.

The economic feasibility of SPS is very simple to understand, since it depends on a single factor - the cost of launch - and this is where the institutional problems arise. Launch costs today are about 100 times too high for SPS to be economically competitive with other sources of electricity. On learning this, many people conclude: "Well, in that case, even though SPS is interesting, it obviously isn't realistic for the next few decades." This reaction is understandable - but it's mistaken. But in order to understand why it's mistaken we must study some institutional history.

The launch industry has a very unusual history. Unlike any other form of transportation, transport to orbit has been controlled by government monopoly organisations for several decades. As is well known to anyone with business experience, this inevitably leads to high costs and inadequate innovation. As examples of this, launch costs today are higher than they were 30 years ago, and launchers designed 40 years ago are still in use. In this unusual situation it's understandable that electricity industry engineers do not appreciate the potential to reduce launch costs, and decide "When launch costs fall we'll have another look at SPS". But this is much too pessimistic, since prospects for reducing launch costs are finally improving (see Equatorial Times 3, pp 4-5). Work in many countries on reusable launch vehicles is gaining momentum, making the prospect of being able to launch SPS components and assemble them in orbit at acceptable cost better and better, and thereby justifying investment in SPS research today.

However, SPS advocates have a major task to explain why SPS can be economic, since it requires explaining the strange state of launch costs, and how they can be greatly reduced.

Even more difficult is the fact that responsibility for SPS is spread through many government departments. Clearly SPS is an energy project - but the main challenges concern the satellite, which is outside the expertise of energy experts, and outside the responsibility of energy departments. SPS would also be very beneficial for the environment, and so should be of interest to environment departments. Even more complex, according to current law SPS satellites are communications satellites, and so they lie within the responsibility of telecommunications departments!

Overcoming these institutional problems is going to be difficult. But it is necessary in order for SPS research to receive funding on a scale that matches its promise. There is currently much popular interest in the end of the century and millenium - a very rare event in the calendar - and the public are looking for a positive vision of the future. If these institutional problems can be overcome SPS can become the keystone of such a vision, since it offers an optimistic, open, unlimited future.

The Engineering Faculty of the University of Kobe, where a number of microwave power transmission experiments, including the MIILAX (MIcrowave Lifted Airplane eXperiment) have been carried out by the research group of Professor Nobuyuki Kaya, who is also currently Chairman of the Power Committee of the International Astronautical Federation (IAF).

Glossary of terms used
Cheap Access To Space
Carbon di-Oxide
International Astronautical Federation
Institute for Space & Astronautical Science
International Telecommunications Union
Industrial Scientific & Medical band (= 2.4 - 2.5 GHz)
MIcrowave Lifted Airplane eXperiment
NAtional Space Development Agency of Japan
Research Center for Advanced Science & Technology
Reusable Launch Vehicle
Rectifying Antenna
square meter
Thailand-Japan Symposium on Antennas and Propagation
World Radio Conference
Wireless Power Transmission

Next issue, December 1997:
  • Field research visit to Malaysia
  • Indonesian rectenna study
  • Report on SPS '97
  • SPS-related Internet web-sites

For correspondence, contributions or further information, please contact Patrick Collins at: Research Center for Advanced Science & Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153, Japan.
Fax no: (81) 3 3481 4587

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