SPS 2000 is a study project started by the SPS Working Group in Japan to demonstrate energy delivery from space to Earth soon; to put it on the table as a real option for development into a major new source of electric power for Earth. The electricity industry consider SPS as just a "paper idea", and it also suffers from the "space industry problem" that launch costs are still unbelievably high, and so most outsiders don't understand that it's possible for them to be much, much lower.

SPS is of course an energy project, an electricity project - not a "space project". And fundamentally there are lots of funds for energy research. For example, in Japan nuclear energy research receives several $billion per year. The "Monju" fast-breeder reactor which recently suffered an extremely expensive accident has already cost many tens of $billions - and the budgeted cost of the plutonium re-processing plant to supply it has recently doubled to $15 billion, although the capacity has been cut in half. In addition, the electricity companies of Japan alone invest several $10s of billions per year in electricity generation and transmission equipment.

Why do governments do this nuclear research, even though it's extremely expensive - and unpopular? Because they see no alternative. They foresee fossil fuels running out in a few decades, and no other potentially large-scale sources of electricity.

So why don't they do similar research on SPS? Because SPS doesn't have enough credibility - because no one will say what an SPS is, other than a kind of dream for 50 years from now. And when they say "Well, if you can't tell us what an SPS is, can you tell us what you want to do to research it?" people describe experiments of a few KW using satellites costing $hundreds of millions - so the energy people understandably lose interest. Such small-scale, expensive experiments have nothing to do with electricity supply.

However, if there was a realistic plan to build and test an SPS, which would deliver useful solar-generated electricity from space to Earth, within a reasonable budget and a reasonable time-scale, there must be a good chance that it would be funded. But there is no such plan. In nearly 30 years the " SPS community" has never produced such a plan! There are visions of enormous systems far in the future, and plans for little bits of research here and there, but nothing in between. (Please remember: a vague proposal isn't a plan. In order for a project to be implemented it's necessary to produce a detailed engineering plan.)

The "SPS 2000" system is being designed to fill this gap. A number of details of this project are still open to dicussion and may be changed, but the basic idea seems to be unarguable. If we want to build an SPS we have to do something like this:

• We need to deliver at least Megawatts of power from space to Earth. 10 Megawatts would be fine; even a few MW will be okay. But kilowatts, or even hundreds of kW, are too little to be of serious interest to electricity organisations that handle tens of thousands of Megawatts. In addition the power has to come to Earth because here on Earth is where taxpayers live, and where the demand for power is.

• We also have to design it now, so we have to use what exists. We can't plan to use technology that may be developed sometime in the future.

• It also has to be in low Earth orbit, in order to be low-cost. Remember, if it was in GEO (that is, 35,800 kilometers from Earth) then the transmitting antenna would have to be 40 times larger than a LEO one - or else the receiving antenna would have to be 40 times larger. Consequently the satellite has to orbit above the equator in order to have frequent transmission opportunities. And so it has to be done in partnership with the equatorial countries.

• Now, of course such a system is a compromise. Above all, the power delivery is only intermittent, so we need storage at the rectennas, which will add to the cost, and the continuous output for users will be only hundreds of KW. But this is unavoidable for a LEO demonstration system. And fortunately both the power beam itself and the rectennas will still be multi-megawatt scale, so they'll be large enough to be interesting for electricity engineers. And of course the rectennas will be available for reception of power from any number of satellites - not just the SPS 2000 satellite.

• Another requirement is that the power has got to be used, in order for SPS to be able to be assessed as a real electricity system. As it happens, there are many people living near the equator with no electricity. Living in cities it's easy not to realise that 100 KW is enough for 1000 homes, and will be very significant for people with no electricity power.

  So far, each of the five equatorial countries visited is keen to participate in SPS and provide a site for a rectenna. So although low Earth orbit may not be ideal, if we accept the fact that it's inevitable, we can enjoy the fact that the project will be helpful and popular with developing countries round the equator. Aren't rich countries always making speeches about the need to help poorer countries? Well, here's a good chance to work together on a path-breaking new technological development.

• The project also has to be within a "reasonable" budget. Well, that certainly means it can't cost $50 billion, like the international space station! Of course, ideally it should cost the same as other energy plants on Earth. But for a "pilot plant" it's okay if it costs rather more - but not 10 times more! Currently the target is that the SPS 2000 satellite should cost about the same as a solar energy plant or a dam on Earth - about $100 million for about 10 MW. In fact it currently looks as though it will probably cost 3 times more, which should be acceptable. Trying to get the cost down like this drives the design - for example getting rid of a rotating joint between the solar array and the transmitting antenna, and doing without active attitude-control. If the cost isn't brought down like this, it can be concluded that the space industry will never be able to deliver cheap electricity to Earth, and the electricity industry will continue to ignore SPS.

  That leaves the launch costs. Unfortunately most existing launch vehicles are out of the question, as they're far too expensive. But using the cheapest rockets, such as the Russian Proton, from Brazil's equatorial launch site, the whole project could probably cost less than $1 billion. Better still, if one of the reusable launch vehicles now being planned in various countries is developed, we could use some of their test-flights. Then we'd really be in business! Designing for launch by expendable rockets and for automatic assembly is also a compromise that will not apply to future commercial SPS. But it may be unavoidable if SPS is to be demonstrated in the near future.

• A pilot plant should also be designed to be extended progressively. Basically speaking, once there's a system of rectennas around the equator, which are used only about 3% of the time by the initial satellite, their operators will be keen to receive power from other satellites as well - and they'll be prepared to pay for deliveries of power. This will create a real terrestrial market for microwave power from space - the first. And creating a market opens the doors to progressive development of larger and better power-satellites.

Commercial satellite-makers planning satellites for delivering power to the same system of equatorial rectennas will need to use the same frequency of 2.45 GHz, and to meet agreed specifications for the rectennas. Apart from these constraints on the microwave power beam, satellite designers will have considerable freedom. We're still far from knowing the best configuration for SPS, and the more experience is developed with different satellite designs the better. It's a nice picture to imagine solar power satellites of several different shapes and sizes delivering power to the rectennas in sequence from different orbits. And it would make for good competition between them!

If SPS 2000 can start things moving, in view of current commercial plans for constellations of communication satellites, we can envisage constellations of satellites being designed to deliver power to the SPS 2000 rectennas. It might even turn out that, with the development of low-cost reusable launchers, power satellites will grow progressively larger, rectennas will get built in more and more countries, and it will lead on to fully commercial systems. But in order for this scenario to happen, we have to start. Henry Ford didn't wait to invent the V-8 engine before he started making cars. And if he and other manufacturers had waited, then the car industry would never have started.

It's also important that the rectenna operators in the equatorial countries will have a major role to play at the start in determining the specifications for acceptable microwave power supplies, and in giving commercial contracts to microwave energy suppliers. "The customer is right" is the basis of business, and so once there are customers for power from space the situation will be radically different from today.

From the point of view of public support, energy, and particularly environmentally clean energy, is a subject of great popular concern in many countries, and so is capable of receiving large-scale funding. Consequently it should be possible to raise a budget for an SPS demonstration project - if there's a good, credible plan, supported by researchers around the world. But in order to produce such a plan, more work is still required.

Of course some people say that a 10 MW demonstration SPS is too difficult. To which the best reply is the saying "You don't know what you can do until you try". Until we do something like this, it's difficult to imagine how the energy industry will ever get interested in SPS. But if we succeed, it's difficult to imagine that they will not be interested. And once they're interested they have plenty of money to develop SPS on a larger commercial scale.

The above isn't intended as a criticism of other approaches - working with utilities on ground-based WPT, fundamental antenna design, sounding-rocket experiments, environmental research, extra-terrestrial resource utilization, and many others. But the best way to put SPS on the electricity industry's agenda has to be to design and then build a substantial demonstration SPS. SPS has to earn credibility with the electricity industry, and it has to do that by doing what interests the electricity industry - generating electricity on Earth at prices that are within striking distance of terrestrial systems.

It's also almost certain that, as SPS gets better known as a realistic project, it will become popular with the general public, because it offers a much more attractive future than the massive expansion of nuclear power that governments continually try to promote in spite of public distrust. And once the electricity industry gets to see that SPS is popular with the general public around the world, they'll learn that even they can be loved instead of distrusted!