Given the understandable negative content of the posts recently regarding the AMSAT HEO satellite debate, perhaps it's time to return to basics and ask some fundamental questions about the way we design satellites and fund their launch.
The problem: AMSAT High Earth Orbiting satellites have historically had a mass between 150kg for P3 and 650kg+ for AO-40 and at 30,000 Euros per kg, we do not have the resources to self finance the launch costs of 4.5 million (30k x 150) to 15 million Euros to launch. However, AO-40 was probably a 1-off and will never be repeated. So let's say 4 - 5 million.
The way forward? 1) Raising the funds for the standard launch cost of the typical AMSAT HEO is beyond us. So other external funding solutions are needed either by providing a service which is paid for. - An example of exploring this route is the AMSAT NA proposed Advanced Communications Project via Intelsat. A second approach, is to include commercial payloads within the AMSAT spacecraft, or perhaps including AMSAT 'functionality' within other commercially or educationally funded spacecraft. Again, there are examples of this approach for LEOs. Delfi C3 is one success story. Also, and had it worked for more than a few orbits the ESA Education department / SSETI Express XO-53 was another. But at HEO the opportunites are very rare indeed, the only project currently being persued is the ESA ESEO educational mission with AMSAT UK providing a U/S transponder as part of a redundant communications system for the spacecraft. As we have been reminded in the past few days, self funding never worked before and it wont work in the future. I feel some sympathy for the AMSAT NA board who have an apparently impossible task to fulfil, but their enthusiasm to elicit support has let expectations exceed funding ability. - The response ha s been vocal. But at least they are trying. Finally on the funding issue, what have we done in the last 8 years? We've had the Eagle fund. We've had the successful AO-51 fund raising campaign, but really, since the launch of AO-40 in November 2000 we haven't saved for this 'HEO' eventuality. If we are ever going to replace spacecraft in the future, fund raising needs to be more sustained and less impulse led. We have little to show for the last 8 years.
2) There is however another option which may be self financing. A fundamental spacecraft redesign to reduce the mass to a figure we can afford to launch. Over the last 25 years, the mass of a P3 spacecraft has remained fairly constant. About 90kg of structure and payload with an additional 60kg of bi-propellent fuel. There are probably ways of trimming this back substantially. In LEO sat design we have seen a reduction in size from 400kg to the SSTL microsat of about 120kg in the 1980's. These days the SSTL 'microsat' has evolved down to 3 - 5kg. with projects like the NASA Nanosail design. But no such revolution has taken place in HEO satellites So, a few possibilities. You can probably think of more......
a) The 60kg of fuel has been needed to raise perigee and increase inclination from a typical geostationary transfer orbit. But there have been orbital change manoeuvres that have not gone to plan e.g. AO-10 and AO-40, but those satellites have still given us usable communications. Do we need all 60kg? How about raising the perigee to give a long life and a slight increase in inclination to get us out of the GTO belt around from around 7 degrees to 15 degrees? I wonder what the saving is there, 400 Newton motor down to 50 Newton motor. Fuel from 60kg down to 15kg? Saving = 45 + 5kg = 1.5 million Euros? OK the figures are guesswork, but there must be savings.
b) Spacecraft design. During our time with P3 spacecraft, we have seen transponder power change dramatically. I recall the first few days of AO-40 when I heard the 2m beacon stronger than many local FM stations. But then it used a 300 Watt BLF278 type device and was designed to give a huge signal. Equally, I also recall receiving a worked all continents satellite award for QSOs I made on the experimental AO-13 mode S transponder. That was 1 Watt (max) into a 5 turn helix on 2400. So, in the future, do we need 45 or 50 Watts of power in a 100kHz wide transponder? After all, if there are fewer amateurs, we can use less bandwidth saving power and mass in the process. 8 Watts and 50kHz? A consequence of such a design change would require a groundstation with more than a patch antenna to pick up the signal. But is that unreasonable, dishes are cheaper than launches.
c) Two final thoughts. Firstly, isn't the world moving away from metal structures to carbon and ceramic composites. Mass saving perhaps. Secondly, I don't think AMSAT with it's limited resources can afford to put spacecraft into orbit that will fail the moment the batteries die. Let's not dwell on the excellent Delfi example, but instead look at the Intelsat spacecraft. Is it not the case that they have a 10 year lifespan which is limited by stationkeeping fuel? While they operate 24/7 the power comes from the solar cells. The batteries are used only in eclipse. With our P3 designs, as I understand them, the spacecraft can not function on solar cells alone. Unfortunately, the advantage of our chosen HEO orbits also mean that the batteries on a P3 satellite go through a couple of eclipses a day. As battery life is proportional (or worse) to depth of discharge of the batteries, it's not surprising that most AMSAT spacecraft suffer battery failure. But with limited funds we really need to design in a mode so that 5 years on, the batteries can be switched out of circuit and a sensible geometry of solar panels can continue to provide some daylight only functionality.
Conclusion: Funding campaigns need to run over several years within a rolling plan to supply launch funding. Designs need to evolve to include new technologies. Mass reduction = lower launch cost should be near the top of the list. With fewer amateurs, and modern digital modes we need less bandwidth. It is not unreasonable for an AMSAT member to need a moderate size of antenna to work an HEO. So, lower power in space. Lifespan needs to be increased and with HEO that means battery failure should be anticipated and mitigated in the design. A daylight operating spacecraft is better than no spacecraft at all.
Thanks..........a quiet day here!
David
Could we do HEO within a 50kg budget? = 1.5million Euros spread over a 10 year lifespan?