Position Paper SSPS10062009
Updated from a position paper released January
30, 2009
Space Solar Power Satellite technology, Versus
Ground Based Power Sources Feasibility Study
By George Howard
National Space Society
Heart of America Chapter
Kcnssh18@aol.com
September 06, 2009
Kansas City, MO
It is currently in vogue by the National Space
Society and the Space Frontier Foundation to promote Space Solar Power
Satellite technology as a means of freeing our nation from foreign
oil and other foreign energy sources. I applaud all those who have
taken up this challenge but in the same breath I encourage each of
you to look at the cost benefit ratio of SSPS technology in
comparison to ground based power production technology. There are
hidden costs to the SSPS that can be calculated and most of the
costs for ground based power technology are known. So we can make a
comparison that is valid for most observers.
After looking into the mass requirements, launch
capacity requirements and environmental impact of this technology I
am brought to the conclusion that this is what many call “gee whiz
technology”. The requirements of this technology are approximately
100 to 200 times the annual launch capacity of all Space faring
nations combined. There is no realistic chance of a Space Solar
Power Satellite being put into operation in this era of time. The
ability to do so does not exist.
Launch requirements:
According to The Illustrated Encyclopedia of
Space Technology, copyright 1981; the total mass to be placed in
space would be 88,000 to 110,000 US tons for SSPS that could produce
a commercially viable amount of power. Using this information we can
determine that if boosters capable of placing 100 tons into orbit
were used it would require 880 to 1100 such launches. A Saturn 5
booster of the Apollo program could launch about 140 tons into
orbit. This is about the size needed for a booster to accomplish the
task to launch one booster per day for about 3 years. One hundred
tons for cargo and 40 tons for a crew module.
110000 tons of equipment
_________________ = 1100 days to launch
completion or 3.01 years.
100 tons launched per day
Each
carrier vehicle with a 100 ton payload would be about the size of an
Apollo Saturn 5 rocket, the Apollo program required 15 to 18 Saturn
5 boosters to be built. The SSPS program would require over 1000 of
this size booster to be built. This is a tall order to say the
least.
Environmental impact:
There is no real world comparison to launch one
Saturn 5 sized rocket everyday for three years. However it is known
what happens when one Saturn 5 rocket is launched or a Space Shuttle
or Energia booster. The launch results in an approximately 150 mile
wide disruption of the ozone layer for several days. If you launch
one rocket this size each day it would result in a persistent
disruption that would extend over several thousand miles. If as an
example the ozone hole persisted for 15 days before ozone completely
recovered you may end up with the following result. A rough
calculation would be 150 miles multiplied by 15 equaling a 2250-mile
long disruption area. If you do this for three years it may result
in a wider disruption area. The affected area will vary based on the
fuels and oxidizers used.
Astronaut Health Impact:
A
Space Solar Power Satellite is required to be in geo-synchronous
orbit and this would require astronauts to travel through and work
in and near the Earth’s radiation belts. This would result in
increased radiation exposure to astronauts, limiting their stay in
orbit. Instead of 90-day missions as is done with the International
Space Station (ISS), it would more likely be 1-week GEO missions to
facilitate the limited radiation exposure. If you had a 4-mission
schedule for astronauts you would arrive at a staffing estimate of
approximately 275 astronauts rotated over the three-year
construction time. The construction space station the astronauts
would live in would require enhanced radiation protection, because
it would operate in high orbit near and in the Earth’s radiation
belts. Space station facilities of this type do not yet exist. In
addition to building a SSPS it would be needed to establish this GEO
orbit space habitat infrastructure as well. There are a number of
unknown factors that would need greater study regarding health
impact on astronauts in GEO orbit. The Earth's Van Allen Radiation
belts are the big issue. The Inner Van Allen Belt produces
approximately 2000 REM of radiation and would be fatal to an
astronaut in a fairly short period of time. An SSPS would operate
within the area of the Inner Van Allen Belt. The Outer Van Allen
Belt has a lower radiation level but is still dangerous.
Launch safety and reliability
Manned rated launch vehicles require very high
reliability 98% to 99% success. The space shuttle transport system
(STS) has flown over 100 missions and suffered two catastrophic
failures. The STS is an example of 98% reliability. If a SSPS Space program were
implemented with a 98% reliability using 1100 launch vehicles, the
number of catastrophic failures can be calculated. It is the number
of launches multiplied by the 2% failure expected, (1100 x .02 = 22
catastrophic failures.) If you have 5 astronauts for crew rotation
on each flight, there would be 5 x 22 = 110 astronauts lost. With
110 astronauts lost out of 275 we can project an attrition rate,
(110/275 = 0.40 or 40%.) I don’t think any astronaut would find this
acceptable. To implement a Space Solar Power Satellite program
launch safety and reliability should be increased to be comparable
to commercial airline safety (99.999% reliability).
Energy conversion and transmission, Space versus
ground.
In Space there is reportedly about 1300 watts per
square meter of solar energy. On the ground due to atmospheric
absorption there is only 1000 watts per square meter. If photo
voltaic panels have 15% efficiency they produce 195 watts m2 in
Space and 150 watts m2 on the ground peak power. The power output is
dependent on the angle of incidence of light hitting the panel. If
the panel is pointed directly at the Sun it provides peak power and
if it not then it provides less power. Ground based Solar panels are
usually fixed in one position resulting in variable light angle of
incidence and a power curve average of about 75 watts. So at face
value Space based solar power looks like it has a dramatic advantage
over ground based. After looking at where the power loses are, the
two methods end up being power competitive.
Space based SSPS producing 195 watts m2 this is
15% efficiency conversion and, has a reported 50% lose in microwave
conversion resulting in 97.5 watts m2 actual power transmitted;
this is 7.5% efficiency. These are estimates because no SSPS systems
are in place. Some estimates of microwave rectenna efficiency
over very long distances 22,500 miles in GEO orbit with beam
expansion and microwave absorption due to water vapor in the Earth's
atmosphere could be as low as 15%. The actual power received on
the ground would be 15% of the 97.5 watts per m2 or 97.5 x .15 =
14.62 watts per m2. The end use efficiency sent to the utility lines
is calculated to be 14.62 watts divided by 1300 watts per square
meter available in Space, 14.62 / 1300 = .0112 or 1.12% end use
efficiency. This is not a cost effective power production method. It
is inspired but not practical.
Ground based Solar power can be made more
efficient by designing the photo voltaic panels to be mounted on Sun
tracking pivots resulting in a power curve closer to their peak
power of 150 watts m2. So you can actually obtain as much if not
slightly more power from ground based solar power at a lower cost
than Space based SSPS. Conventional power utility companies produce
power on a use it or lose it basis. Power plants generate
electricity and sent it directly to the power lines without storing
it. Ground based solar power systems produce power and distribute it
directly to the user with a portion of the electricity stored in
batteries for night time use. So you get 24 hour power. The
efficiency of ground based solar power is close to the efficiency of
the photo voltaic panels used. The efficiency of the ground based
system would be about 15%. Ground based solar does not have as many
steps in the process and ends up producing more usable
power.
Conclusion:
Space solar power satellite technology is vastly
more expensive than ground based power and produces a power
output after power loses are taken into account equal to or lesser
than ground based power systems. There is currently little advantage
for SSPS. It is a great idea, it is just far beyond what
we can do today. It is something for far in the future. This gives a
strong impression that the scientists that introduced this concept
intended it to be a technology to inspire space enthusiasts and
provide a future vision but not as an immediate application to be
used today.
This should be obvious to aerospace professionals
that support this technology and it leaves me wondering what the
motivations of such Space Interest leaders are. Support of such
things raises a "red flag" and questions, so it is counter
productive for you to support this. It really makes me want to
check my facts. The SSPS technology has numerous characteristics
that make it vastly impractical and aerospace professionals should
see that. It gives a distinct impression that you are pulling the
Space enthusiast's leg. If you do this for a short time, you are
making a valid point to check facts and not follow blindly, in the
form of a bad practical joke. If you do this for 30 to 40 years then
you are trying desperately to get someone to slap you. It just does
not go over well when you do this to people and then they realize
that they were misled. You end up with a whole lot of Space
enthusiasts that will not listen to a darn thing you have to say and
they still will not check their facts. You have to teach people how
to prove or disprove feasibility instead.
The SSPS has been promoted since about 1969,
this is longer than almost any one person has stayed in Space
Interest. When you pass on a message to a long line of people
often the original meaning and intent of the message is lost. You
must go back and examine what was originally intended and the
context of what was said. What I see is art work
using representative technology based on late 1960s and 1970s
era equipment. This is an example of what available technology could
do if it could be launched into Space. It would get the job done but
the drawbacks would be extensive. It is a vision of the future using
understandable technology but not practical technology.
There are two primary motivations for someone to
promote such a technology.
1. You may be presenting representative
visionary art work based on current technology to represent what
could be in the future. This is not realistic technology, simply
state to your listeners that this is the situation and they should
get the idea.
2. You may be trying to teach critical
thinking by presenting something that obviously would not be
practical, so you want your audience to point out the flaws. If your
Space enthusiast audience trusts you without question then they will
never see what you were trying to teach them and they are going to
believe everything you say and that is not what you wanted. You need
to tell your audience something to the effect that this is a game
and we are going the call it "What is wrong with this
picture", you then tell them the efficiencies of the processes
involved and ask them if this is a cost effective process. If need
be, bring them through the steps so they will get the right answer.
Amateur space enthusiasts tend to follow along
and support what aerospace professionals in space interest advocate.
This is a time when amateur space enthusiasts need to learn to
verify facts and confirm information. They need to see this project
is vastly beyond the capabilities of space agencies today. It is a
good idea in concept but something for far in the future. Space has
many other viable uses within our reach today. Take a position of
verifying concepts presented to you and determine whether or not
they are achievable or not. The SSPS concept seems to be more of a
practical joke on people who don't check their facts, than it is a
viable power concept.
The
position of the NSS Heart of America is to support ground based
renewable energy resources. We support the continued development of
synthetic fuels, solar energy farms; nuclear fusion power, wind
energy power networks and the ever-increasing assortment of
renewable power production technologies that will reduce carbon
emissions and free us from energy resources held by unstable
governments around the world.