An artist's conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion.
Project Orion was a study of a
spacecraft intended to be directly propelled by a series of explosions of
atomic bombs behind the craft (
nuclear pulse propulsion). Early versions of this vehicle were proposed to have taken off from the ground with significant associated
nuclear fallout; later versions were presented for use only in space.
A 1955
Los Alamos Laboratory document states (without offering references) that general proposals were first made by
Stanislaw Ulam in 1946, and that preliminary calculations were made by
F. Reines and Ulam in a Los Alamos memorandum dated 1947.
[1] The actual project, initiated in 1958, was led by
Ted Taylor at
General Atomics and physicist
Freeman Dyson, who at Taylor's request took a year away from the
Institute for Advanced Study in
Princeton, US to work on the project.
The Orion concept offered high thrust and high
specific impulse,
or propellant efficiency, at the same time. The unprecedented extreme
power requirements for doing so would be met by nuclear explosions, of
such power relative to the vehicle's mass as to be survived only by
using external detonations without attempting to contain them in
internal structures. As a qualitative comparison, traditional chemical
rockets—such as the
Saturn V that took the
Apollo program to the Moon—produce high thrust with low specific impulse, whereas electric
ion engines
produce a small amount of thrust very efficiently. Orion would have
offered performance greater than the most advanced conventional or
nuclear rocket engines then under consideration. Supporters of Project
Orion felt that it had potential for cheap
interplanetary travel, but it lost political approval over concerns with fallout from its propulsion.
[2]
The
Partial Test Ban Treaty of 1963 is generally acknowledged to have ended the project. However, from
Project Longshot to
Project Daedalus,
Mini-Mag Orion,
and other proposals which reach engineering analysis at the level of
considering thermal power dissipation, the principle of external
nuclear pulse propulsion
to maximize survivable power has remained common among serious concepts
for interstellar flight without external power beaming and for very
high-performance interplanetary flight. Such later proposals have tended
to modify the basic principle by envisioning equipment driving
detonation of much smaller fission or fusion pellets, although in
contrast Project Orion's larger nuclear pulse units (nuclear bombs) were
based on less speculative technology.
Basic principles
The Orion Spacecraft – key components.
[3]
A design for a pulse unit.
The Orion nuclear pulse drive combines a very high exhaust velocity,
from 12 to 19 mi/s (19 to 31 km/s) in typical interplanetary designs,
with
meganewtons of thrust.
[4]
Many spacecraft propulsion drives can achieve one of these or the
other, but nuclear pulse rockets are the only proposed technology that
could potentially meet the extreme power requirements to deliver both at
once (see
spacecraft propulsion for more speculative systems).
Specific impulse
(Isp) measures how much thrust can be derived from a given mass of
fuel, and is a standard figure of merit for rocketry. For any rocket
propulsion, since the
kinetic energy of exhaust goes up with velocity squared (
kinetic energy = ½ mv
2), whereas the
momentum and thrust goes up with velocity linearly (
momentum = mv), obtaining a particular level of thrust (as in a number of
g acceleration) requires far more power each time that exhaust velocity and
specific impulse (Isp) is much increased in a design goal. (For instance,
the most fundamental reason that current and proposed
electric propulsion
systems of high Isp tend to be low thrust is due to their limits on
available power. Their thrust is actually inversely proportional to Isp
if power going into exhaust is constant or at its limit from heat
dissipation needs or other engineering constraints).
[5]
The Orion concept detonates nuclear explosions externally at a rate of
power release which is beyond what nuclear reactors could survive
internally with known materials and design.
Since weight is no limitation, an Orion craft can be extremely
robust. An unmanned craft could tolerate very large accelerations,
perhaps 100
g.
A human-crewed Orion, however, must use some sort of damping system
behind the pusher plate to smooth the instantaneous acceleration to a
level that humans can comfortably withstand – typically about 2 to 4
g.
The high performance depends on the high exhaust velocity, in order
to maximize the rocket's force for a given mass of propellant. The
velocity of the plasma debris is proportional to the square root of the
change in the temperature (
Tc) of the nuclear
fireball. Since fireballs routinely achieve ten million degrees Celsius
or more in less than a millisecond, they create very high velocities.
However, a practical design must also limit the destructive radius of
the fireball. The diameter of the nuclear fireball is proportional to
the square root of the bomb's explosive yield.
The shape of the bomb's reaction mass is critical to efficiency. The
original project designed bombs with a reaction mass made of
tungsten. The bomb's geometry and materials focused the
X-rays and plasma from the core of nuclear explosive to hit the reaction mass. In effect each bomb would be a nuclear
shaped charge.
A bomb with a cylinder of reaction mass expands into a flat,
disk-shaped wave of plasma when it explodes. A bomb with a disk-shaped
reaction mass expands into a far more efficient cigar-shaped wave of
plasma debris. The cigar shape focuses much of the plasma to impinge
onto the pusher-plate.
The maximum effective specific impulse,
Isp, of an Orion nuclear pulse drive generally is equal to:
where
C0 is the collimation factor (what fraction
of the explosion plasma debris will actually hit the impulse absorber
plate when a pulse unit explodes),
Ve is the nuclear pulse unit plasma debris velocity, and
gn is the standard acceleration of gravity (9.81 m/s
2; this factor is not necessary if
Isp
is measured in N·s/kg or m/s). A collimation factor of nearly 0.5 can
be achieved by matching the diameter of the pusher plate to the diameter
of the nuclear fireball created by the explosion of a nuclear pulse
unit.
The smaller the bomb, the smaller each impulse will be, so the higher
the rate of impulses and more than will be needed to achieve orbit.
Smaller impulses also mean less
g shock on the pusher plate and less need for damping to smooth out the acceleration.
The optimal Orion drive bomblet yield (for the human crewed 4,000 ton
reference design) was calculated to be in the region of 0.15 kt, with
approx 800 bombs needed to orbit and a bomb rate of approx 1 per second.
[citation needed]
Sizes of Orion vehicles
The following can be found in
George Dyson's book
[6] pg. 55 published in 2002. The figures for the comparison with Saturn V are taken from
this section and converted from metric (kg) to US
short tons (abbreviated "t" here).
|
Orbital
test |
Interplanetary |
Advanced
interplanetary |
Saturn V |
| Ship mass |
880 t |
4,000 t |
10,000 t |
3,350 t |
| Ship diameter |
25 m |
40 m |
56 m |
10 m |
| Ship height |
36 m |
60 m |
85 m |
110 m |
Bomb yield
(sea level) |
0.03 kt |
0.14 kt |
0.35 kt |
n/a |
Bombs
(to 300 mi Low Earth Orbit) |
800 |
800 |
800 |
n/a |
Payload
(to 300 mi LEO) |
300 t |
1,600 t |
6,100 t |
130 t |
Payload
(to Moon soft landing) |
170 t |
1,200 t |
5,700 t |
2 t |
Payload
(Mars orbit return) |
80 t |
800 t |
5,300 t |
– |
Payload
(3yr Saturn return) |
– |
– |
1,300 t |
– |
In late 1958 to early 1959, it was realized that the smallest
practical vehicle would be determined by the smallest achievable bomb
yield. The use of 0.03 kt (sea-level yield) bombs would give vehicle
mass of 880 tons. However, this was regarded as too small for anything
other than an orbital test vehicle and the team soon focused on a 4,000
ton "base design".
At that time, the details of small bomb designs were shrouded in
secrecy. Many Orion design reports had all details of bombs removed
before release. Contrast the above details with the 1959 report by
General Atomics,
[7] which explored the parameters of three different sizes of
hypothetical Orion spacecraft:
|
"Satellite"
Orion |
"Midrange"
Orion |
"Super"
Orion |
| Ship diameter |
17–20 m |
40 m |
400 m |
| Ship mass |
300 t |
1000–2000 t |
8,000,000 t |
| Number of bombs |
540 |
1080 |
1080 |
| Individual bomb mass |
0.22 t |
0.37–0.75 t |
3000 t |
The biggest design above is the "super" Orion design; at 8 million tonnes, it could easily be a city.
[8] In interviews, the designers contemplated the large ship as a possible
interstellar ark.
This extreme design could be built with materials and techniques that
could be obtained in 1958 or were anticipated to be available shortly
after. The practical upper limit is likely to be higher with modern
materials.
Most of the three thousand tonnes of each of the "super" Orion's propulsion units would be inert material such as
polyethylene, or
boron
salts, used to transmit the force of the propulsion units detonation to
the Orion's pusher plate, and absorb neutrons to minimize fallout. One
design proposed by Freeman Dyson for the "Super Orion" called for the
pusher plate to be composed primarily of uranium or a
transuranic element so that upon reaching a nearby star system the plate could be converted to nuclear fuel.
Interplanetary applications
The Orion nuclear pulse rocket design has extremely high performance.
Orion nuclear pulse rockets using nuclear fission type pulse units were
originally intended for use on interplanetary space flights.
Missions that were designed for an Orion vehicle in the original
project included single stage (i.e., directly from Earth's surface) to
Mars and back, and a trip to one of the moons of Saturn.
[8]
One possible modern mission for this near-term technology would be to
deflect an asteroid that could collide with Earth. The extremely high
performance would permit even a late launch to succeed, and the vehicle
could effectively transfer a large amount of kinetic energy to the
asteroid by simple impact. Also, such an unmanned mission would
eliminate the need for shock absorbers, the most problematic issue of
the design.
Nuclear fission pulse unit powered Orions could provide fast and
economical interplanetary transportation with useful human crewed
payloads of several thousand tonnes.
Interstellar missions
Freeman Dyson performed the first analysis of what kinds of Orion missions were possible to reach
Alpha Centauri, the nearest star system to the
Sun.
[9] His 1968 paper "Interstellar Transport"
[10]
(Physics Today, October 1968, p. 41–45) retained the concept of large
nuclear explosions but Dyson moved away from the use of fission bombs
and considered the use of one megaton
deuterium
fusion explosions instead. His conclusions were simple: the debris
velocity of fusion explosions was probably in the 3000–30,000 km/s range
and the reflecting geometry of Orion's hemispherical pusher plate would
reduce that range to 750–15,000 km/s.
[11]
To estimate the upper and lower limits of what could be done using
contemporary technology (in 1968), Dyson considered two starship
designs. The more conservative
energy limited pusher plate design simply had to absorb all the thermal energy of each impinging explosion (4×10
15
joules, half of which would be absorbed by the pusher plate) without
melting. Dyson estimated that if the exposed surface consisted of
copper
with a thickness of 1 mm, then the diameter and mass of the
hemispherical pusher plate would have to be 20 kilometers and 5 million
metric tons, respectively. 100 seconds would be required to allow the
copper to radiatively cool before the next explosion. It would then take
on the order of 1000 years for the energy-limited
heat sink Orion design to reach Alpha Centauri.
In order to improve on this performance while reducing size and cost, Dyson also considered an alternative
momentum limited
pusher plate design where an ablation coating of the exposed surface is
substituted to get rid of the excess heat. The limitation is then set
by the capacity of shock absorbers to transfer momentum from the
impulsively accelerated pusher plate to the smoothly accelerated
vehicle. Dyson calculated that the properties of available materials
limited the velocity transferred by each explosion to ~30 meters per
second independent of the size and nature of the explosion. If the
vehicle is to be accelerated at 1 Earth gravity (9.81 m/s
2) with this velocity transfer, then the pulse rate is one explosion every three seconds.
[12] The dimensions and performance of Dyson's vehicles are given in the table below
|
"Energy Limited"
Orion |
"Momentum Limited"
Orion |
| Ship diameter (meters) |
20,000 m |
100 m |
| Mass of empty ship (metric tons) |
10,000,000 t (incl.5,000,000 t copper hemisphere) |
100,000 t (incl. 50,000 t structure+payload) |
| +Number of bombs = total bomb mass (each 1 Mt bomb weighs 1 metric ton) |
30,000,000 |
300,000 |
| =Departure mass (metric tons) |
40,000,000 t |
400,000 t |
| Maximum velocity (kilometers per second) |
1000 km/s (=0.33% of the speed of light) |
10,000 km/s (=3.3% of the speed of light) |
| Mean acceleration (Earth gravities) |
0.00003 g (accelerate for 100 years) |
1 g (accelerate for 10 days) |
| Time to Alpha Centauri (one way, no slow down) |
1330 years |
133 years |
| Estimated cost |
1 year of U.S. GNP (1968), $3.67 Trillion |
0.1 year of U.S. GNP $0.367 Trillion |
Later studies indicate that the top cruise velocity that can
theoretically be achieved by a thermonuclear Orion starship, assuming no
fuel is saved for slowing back down, is about 8% to 10% of the
speed of light (0.08-0.1c).
[2] An atomic (fission) Orion can achieve perhaps 3%-5% of the speed of light. A nuclear pulse drive starship powered by matter-
antimatter pulse units would be theoretically capable of obtaining a velocity between 50% to 80% of the
speed of light. In each case saving fuel for slowing down halves the max. speed.
At 0.1
c, Orion thermonuclear starships would require a flight
time of at least 44 years to reach Alpha Centauri, not counting time
needed to reach that speed (about 36 days at constant acceleration of 1
g or 9.8 m/s
2). At 0.1
c, an Orion starship would require 100 years to travel 10 light years. The astronomer
Carl Sagan suggested that this would be an excellent use for current stockpiles of nuclear weapons.
[13]
Later developments
A concept similar to Orion was designed by the
British Interplanetary Society (B.I.S.) in the years 1973–1974.
Project Daedalus was to be a robotic interstellar probe to
Barnard's Star that would travel at 12% of the speed of light. In 1989, a similar concept was studied by the U.S. Navy and NASA in
Project Longshot.
Both of these concepts require significant advances in fusion
technology, and therefore cannot be built at present, unlike Orion.
From 1998 to the present, the nuclear engineering department at
Pennsylvania State University has been developing two improved versions
of the Daedalus design known as
Project Ican and
Project Aimstar.
[14]
Economics
The expense of the fissionable materials required was thought high,
until the physicist Ted Taylor showed that with the right designs for
explosives, the amount of fissionables used on launch was close to
constant for every size of Orion from 2,000 tons to 8,000,000 tons. The
larger bombs used more explosives to super-compress the fissionables,
reducing fallout. The extra debris from the explosives also serves as
additional propulsion mass.
The bulk of costs for historical nuclear defense programs have been
for delivery and support systems, rather than for production cost of the
bombs directly (with warheads being 7% of the U.S. 1946-1996 expense
total according to one study).
[15]
After initial infrastructure development and investment, the marginal
cost each of additional nuclear bombs in mass production can be
relatively low. In the 1980s, some U.S. thermonuclear warheads had $1.1
million estimated cost each ($630 million for 560).
[16]
For the perhaps simpler fission pulse units to be used by one Orion
design, a 1964 source estimated a cost of $40000 or less each in mass
production, which would be up to approximately $0.3 million each in
modern-day dollars adjusted for inflation.
[16][17]
Project Daedalus later proposed fusion explosives (
deuterium or tritium pellets) detonated by electron beam inertial confinement. This is the same principle behind
inertial confinement fusion. However, theoretically, it might be scaled down to far smaller explosions, and require small shock absorbers.
Vehicle architecture
A design for the Orion propulsion module
From 1957 until 1964 this information was used to design a spacecraft
propulsion system called "Orion", in which nuclear explosives would be
thrown behind a pusher-plate mounted on the bottom of a spacecraft and
exploded. The shock wave and radiation from the detonation would impact
against the underside of the pusher plate, giving it a powerful "kick".
The pusher plate would be mounted on large two-stage
shock absorbers that would smoothly transmit acceleration to the rest of the spacecraft.
During take-off, there were concerns of danger from fluidic shrapnel
being reflected from the ground. One proposed solution was to use a flat
plate of conventional explosives spread over the pusher plate, and
detonate this to lift the ship from the ground before going nuclear.
This would lift the ship far enough into the air that the first focused
nuclear blast would not create debris capable of harming the ship.
A preliminary design for the explosives was produced. It used a
shaped-charge fusion-boosted fission explosive. The explosive was
wrapped in a
beryllium oxide "channel filler", which was surrounded by a
uranium radiation mirror. The mirror and channel filler were open ended, and in this open end a flat plate of
tungsten
propellant was placed. The whole thing was built into a can with a
diameter no larger than 6 inches (15 cm) and weighed just over 300
pounds (140 kg) so it could be handled by machinery scaled-up from a
soft-drink vending machine (indeed, Coca-Cola was consulted on the
design).
[18]
At 1 microsecond after ignition, the gamma bomb plasma and neutrons
would heat the channel filler, and be somewhat contained by the uranium
shell. At 2–3 microseconds, the channel filler would transmit some of
the energy to the propellant, which vaporized. The flat plate of
propellant formed a cigar-shaped explosion aimed at the pusher plate.
The plasma would cool to 14,000 °C, as it traversed the 25 m distance
to the pusher plate, and then reheat to 67,000 °C, as (at about
300 microseconds) it hit the pusher plate and recompressed. This
temperature emits ultraviolet, which is poorly transmitted through most
plasmas. This helps keep the pusher plate cool. The cigar shaped
distribution profile and low density of the plasma reduces the
instantaneous shock to the pusher plate.
The pusher plate's thickness would decrease by about a factor of 6
from the center to the edge, so that the net velocity of the inner and
outer parts of the plate are the same, even though the momentum
transferred by the plasma increases from the center outwards.
At low altitudes where the surrounding air is dense,
gamma scattering could potentially harm the crew and a radiation refuge would be necessary anyway on long missions to survive
solar flares. Radiation shielding effectiveness increases exponentially with shield thickness (see
gamma ray
for a discussion of shielding), so on ships with mass greater than a
thousand tons, the structural bulk of the ship, its stores, and the mass
of the bombs and propellant would provide more than adequate shielding
for the crew.
Stability was initially thought to be a problem due to inaccuracies
in the placement of the bombs, but it was later shown that the effects
would tend to cancel out.
[19][20]
Numerous model flight tests (using conventional explosives) were conducted at
Point Loma, San Diego in 1959. On November 14, the one-meter model, called "Hot Rod" (or "putt-putt"), first flew using
RDX
(chemical explosives) in a controlled flight for 23 seconds to a height
of 56 meters. Film of the tests has been transcribed to video
[21] shown on the BBC TV program "To Mars by A-Bomb" in 2003 with comments by Freeman Dyson and
Arthur C. Clarke. The model landed by parachute undamaged and is in the collection of the Smithsonian National Air and Space Museum.
The first proposed shock absorber was merely a ring-shaped airbag.
However, it was soon realized that, should an explosion fail, the 500 to
1000 ton pusher plate would tear away the airbag on the rebound. So a
two-stage, detuned spring/piston shock absorber design was developed. On
the reference design, the first stage mechanical absorber was tuned 4.5
times the pulse frequency whilst the second stage gas piston was tuned
to 1/2 times the pulse frequency. This permitted timing tolerances of 10
ms in each explosion.
The final design coped with bomb failure by overshooting and
rebounding into a 'center' position. Thus, following a failure (and on
initial ground launch) it would be necessary to start (or restart) the
sequence with a lower yield device. In the 1950s methods of
adjusting bomb yield
were in their infancy and considerable thought was given to providing a
means of 'swapping out' a standard yield bomb for a smaller yield one
in a 2 or 3 second time frame (or to provide an alternative means of
firing low yield bombs). Modern variable yield devices would allow a
single standardized explosive to be 'tuned down' (configured to a lower
yield) automatically.
The bombs had to be launched behind the pusher plate fast enough to
explode 20 to 30 m beyond it every 1.1 seconds or so. Numerous proposals
were investigated, from multiple guns poking over the edge of the
pusher plate to rocket propelled bombs launched from 'roller coaster'
tracks, however the final reference design used a simple gas gun to
shoot the devices through a hole in the center of the pusher plate.
Potential problems
Exposure to repeated nuclear blasts raises the problem of
ablation
(erosion) of the pusher plate. However, calculations and experiments
indicate that a steel pusher plate would ablate less than 1 mm if
unprotected. If sprayed with an oil, it need not ablate at all (this was
discovered by accident; a test plate had oily fingerprints on it, and
the fingerprints suffered no ablation). The absorption spectra of
carbon and
hydrogen minimize heating. The design temperature of the shockwave, 67,000 °C, emits
ultraviolet.
Most materials and elements are opaque to ultraviolet, especially at
the 340 MPa pressures the plate experiences. This prevents the plate
from melting or ablating.
One issue that remained unresolved at the conclusion of the project
was whether or not the turbulence created by the combination of the
propellant and ablated pusher plate would dramatically increase the
total ablation of the pusher plate. According to Freeman Dyson, during
the 1960s they would have had to actually perform a test with a real
nuclear explosive to determine this; with modern simulation technology,
this could be determined fairly accurately without such empirical
investigation.
Another potential problem with the pusher plate is that of
spalling—shards
of metal—potentially flying off the top of the plate. The shockwave
from the impacting plasma on the bottom of the plate passes through the
plate and reaches the top surface. At that point spalling may occur,
damaging the pusher plate. For that reason, alternative substances
(e.g., plywood and fiberglass) were investigated for the surface layer
of the pusher plate, and thought to be acceptable.
If the conventional explosives in the nuclear bomb detonate, but a
nuclear explosion does not ignite (a dud), shrapnel could strike and
potentially critically damage the pusher plate.
True engineering tests of the vehicle systems were said to be
impossible because several thousand nuclear explosions could not be
performed in any one place. However, experiments were designed to test
pusher plates in nuclear fireballs. Long-term tests of pusher plates
could occur in space. Several of these tests almost flew.
[citation needed] The shock-absorber designs could be tested at full-scale on Earth using chemical explosives.
But the main unsolved problem for a launch from the surface of the Earth was thought to be
nuclear fallout.
Any explosions within the magnetosphere would carry fissionables back
to earth unless the spaceship were launched from a polar region such as a
barge in the higher regions of the Arctic, with the initial launching
explosion to be a large mass of conventional high explosive only to
significantly reduce fallout; subsequent detonations would be in the air
and therefore much cleaner.
Antarctica is not viable, as this would require enormous legal changes as the continent is presently an international wildlife preserve.
Freeman Dyson, group leader on the project, estimated back in the 1960s that with conventional
nuclear weapons
(a large fraction of yield from fission), each launch would cause
statistically on average between 0.1 and 1 fatal cancers from the
fallout.
[22] That estimate is based on
no threshold
model assumptions, a method often used in estimates of statistical
deaths from other major industrial activities, such as how modern-day
U.S. regulatory agencies frequently implement regulations on more
conventional pollution if one life or more is predicted saved per $6
million to $8 million of economic costs incurred.
[23]
Each few million dollars of efficiency indirectly gained or lost in the
world economy may statistically average lives saved or lost, in terms
of opportunity gains versus costs.
[24]
Indirect effects could matter for whether the overall influence of an
Orion-based space program on future human global mortality would be a
net increase or a net decrease, including if change in launch costs and
capabilities affected
space exploration,
space colonization, the odds of
long-term human species survival,
space-based solar power, or other hypotheticals.
Danger to human life was not a reason given for shelving the project –
those included lack of mission requirement (no-one in the US Government
could think of any reason to put thousands of tons of payload into
orbit), the decision to focus on rockets (for the Moon mission) and,
ultimately, the signing of the
Partial Test Ban Treaty in 1963. The danger to electronic systems on the ground (from
electromagnetic pulse)
was not considered to be significant from the sub-kiloton blasts
proposed since solid-state integrated circuits were not in general use
at the time.
Orion-style nuclear pulse rockets can be launched from above the
magnetosphere
so that charged ions of fallout in its exhaust plasma are not trapped
by the Earth's magnetic field and are not returned to Earth.
From many smaller detonations combined, the fallout for the entire launch of a 6,000
short ton (5,500
metric ton) Orion is equal to the detonation of a typical 10
megaton (40
petajoule)
nuclear weapon, if pessimistically assuming the use of nuclear
explosives with a high portion of total yield from fission. Historical
above-ground nuclear weapon tests included 189
megatons
of fission yield and caused average global radiation exposure per
person peaking at 0.11 mSv/a in 1963, with a 0.007 mSv/a residual in
modern times (superimposed upon other sources of exposure, primarily natural
background radiation which averages 2.4 mSv/a globally but varies greatly, such as 6 mSv/a in some high-altitude cities).
[25][26]
Any comparison would be influenced by how population dosage is affected
by detonation locations, with very remote sites preferred.
With special designs of the nuclear explosive, Ted Taylor estimated
that fission product fallout could be reduced tenfold, or even to zero
if a
pure fusion explosive
could be constructed instead. A 100% pure fusion explosive has yet to
be successfully developed according to declassified US government
documents, although relatively clean PNEs (
Peaceful nuclear explosions) were tested for canal excavation by the Soviet Union in the 1970s with 98% fusion yield when 15
kilotons total each (only 0.3
kilotons fission).
[22][27]
The vehicle and its test program would violate the
Partial Test Ban Treaty
of 1963 as currently written, which prohibited all nuclear detonations
except those conducted underground, both as an attempt to slow the arms
race and to limit the amount of radiation in the atmosphere caused by
nuclear detonations. There was an effort by the US government to put an
exception into the 1963 treaty to allow for the use of nuclear
propulsion for spaceflight, but Soviet fears about military applications
kept the exception out of the treaty. This limitation would affect only
the US, Russia, and the United Kingdom. It would also violate the
Comprehensive Nuclear-Test-Ban Treaty
which has been signed by the United States and China, as well as the
de-facto moratorium on nuclear testing that the declared nuclear powers
have imposed since the 1990s. Project Orion however would not violate
the
Outer Space Treaty which bans nuclear weapons in space, but not peaceful uses of nuclear explosions.
It has been suggested that the restrictions of the Treaty would not
apply to the Project Daedalus fusion microexplosion rocket. Daedalus
class systems use pellets of one gram or less ignited by particle or
laser beams to produce very small fusion explosions with a maximum
explosive yield of only 10–20 tons of TNT equivalent.
The launch of such an Orion nuclear bomb rocket from the ground or from
low Earth orbit would generate an
electromagnetic pulse that could cause significant damage to
computers and
satellites, as well as flooding the
van Allen belts
with high-energy radiation. This problem might be solved by launching
from very remote areas, because the EMP footprint would be only a few
hundred miles wide. The Earth is well shielded by the Van Allen belts.
In addition, a few relatively small space-based
electrodynamic tethers could be deployed to quickly eject the energetic particles from the capture angles of the Van Allen belts.
An Orion spacecraft could be boosted by non-nuclear means to a safer
distance, only activating its drive well away from Earth and its
attendant satellites. The Lofstrom
launch loop or a
space elevator hypothetically provide excellent solutions, although in the case of the space elevator existing
carbon nanotubes composites do not yet have sufficient
tensile strength.
All chemical rocket designs are extremely inefficient (and expensive)
when launching mass into orbit, but could be employed if the result were
viewed as worth the cost.
Operation Plumbbob
A test similar to the test of a pusher plate occurred as an
accidental side effect of a nuclear containment test called "Pascal B"
conducted on 27 August 1957.
[28]
The test's experimental designer Dr. Brownlee performed a highly
approximate calculation that suggested that the low-yield nuclear
explosive would accelerate the massive (900 kg) steel capping plate to
six times
escape velocity.
[29]
The plate was never found, but Dr. Brownlee believes that the plate
never left the atmosphere (for example it could have been vaporized by
compression heating of the atmosphere due to its high speed). The
calculated velocity was sufficiently interesting that the crew trained a
high-speed camera on the plate, which unfortunately only appeared in
one frame, but this nevertheless gave a very high lower bound for the
speed.
Appearances in fiction
See also
References
- ^ Everett,
C.J.; Ulam S.M. On a Method of Propulsion of Projectiles by Means of
External Nuclear Explosions. Part I. University of California, Los
Alamos Scientific Laboratory, August 1955. See p. 5 [1] Archived
- ^ a b Cosmos by Carl Sagan
- ^ Nuclear Pulse Space Vehicle Study Vol IV – Conceptual Vehicle Designs and Operational Systems, Fig 2.1, pp 4., NASA
- ^ Ross, F.W. – Propulsive System Specific Impulse. General Atomics GAMD-1293 8 Feb. 1960
- ^ Dr. Anthony Zuppero, Idaho National Engineering and Environmental Laboratory. "Physics of Rocket Systems" retrieved 2012-04-24
- ^ Dyson, George. Project Orion – The Atomic Spaceship 1957-1965. Penguin. ISBN 0-14-027732-3
- ^ Dunne; Dyson and Treshow (1959). Dimensional Study of Orion Type Spaceships. General Atomics. GAMD-784.
- ^ a b Dyson, George (2002). Project Orion: The True Story of the Atomic Spaceship. New York, N.Y.: Henry Holt and Co. ISBN 0-8050-7284-5.
- ^ "Nuclear Pulse Propulsion: A Historical Review" by Martin and Bond, Journal of the British Interplanetary Society, 1979 (p.301)
- ^ http://galileo.phys.virginia.edu/classes/109.jvn.spring00/nuc_rocket/Dyson.pdf
- ^ "The Starflight Handbook" by Mallove and Matloff, John Wiley & Sons, 1989, ISBN 0-471-61912-4 (page 66)
- ^ Bond & Martin, page 302
- ^ Cosmos series, Episode 8
- ^ "Antimatter Space Propulsion at Penn State University (LEPS)". Engr.psu.edu. 2001-02-27. Retrieved 2009-11-15.
- ^ Brookings Institution.[2] Incurred Costs of U.S. Nuclear Weapons Programs, 1940-1996] retrieved 2012-01-11
- ^ a b Encyclopedia Astronautica. Project Orion retrieved 2012-1-11
- ^ CPI Inflation Calculator retrieved 2012-01-11
- ^ Jacobsen, Annie (2012), Area 51: An Uncensored History of America's Top Secret Military Base, Back Bay Books, ISBN 0316202304, p.305
- ^ Teichmann, T. – The angular effects due to asymmetric placement of axial symmetric explosives: GAMD-5823, 26 Oct 1963
- ^ David, C. V. Stability study of Nuclear Pulse Propulsion (Orion) Engine System. GAMD-6213, 30 Apr 1965
- ^ August 6, 2007. "Project Orion". YouTube. Retrieved 2009-11-15.
- ^ a b Disturbing the Universe – Freeman Dyson
- ^ New York Times. "EPA Plans to Revisit a Touchy Topic -- the Value of Saved Lives" retrieved 2012-1-11
- ^ "Understanding Risk" retrieved 2012-1-11
- ^ UNSCEAR "Sources and Effects of Ionizing Radiation" retrieved 2012-1-11
- ^ "Radiation Risk" retrieved 2012-1-11
- ^ The Soviet Program for Peaceful Uses of Nuclear Explosions by Milo D. Nordyke. Science & Global Security, 1998, Volume 7, pp. 1-117
- ^ "Operation Plumbbob". July 2003. Retrieved 2006-07-31.
- ^ Brownlee, Robert R. (June 2002). "Learning to Contain Underground Nuclear Explosions". Retrieved 2006-07-31.
Further reading
- McPhee, John (1994). The Curve of Binding Energy. Farrar, Straus and Giroux. ISBN 978-0-374-51598-0.
- "Nuclear Pulse Propulsion (Project Orion) Technical Summary Report"
RTD-TDR-63-3006 (1963–1964); GA-4805 Vol. 1, Reference Vehicle Design
Study, Vol. 2, Interaction Effects, Vol. 3, Pulse Systems, Vol. 4,
Experimental Structural Response. (From the National Technical
Information Service, U.S.A.)
- "Nuclear Pulse Propulsion (Project Orion) Technical Summary Report" 1
July 1963–30 June 1964, WL-TDR-64-93; GA-5386 Vol. 1, Summary Report,
Vol. 2, Theoretical and Experimental Physics, Vol. 3, Engine Design,
Analysis and Development Techniques, Vol. 4, Engineering Experimental
Tests. (From the National Technical Information Service, U.S.A.)
- "Dynamic America; a history of General Dynamics Corporation and its
predecessor companies", John Niven, Courtlandt Canby, and Vernon Welsh
Designer, Erik Nitsche, 1960 Page Image
- General Atomics, Nuclear Pulse Space Vehicle Study, Volume I -- Summary, September 19, 1964
- General Atomics, Nuclear Pulse Space Vehicle Study, Volume III -- Conceptual Vehicle Designs And Operational Systems, September 19, 1964
- General Atomics, Nuclear Pulse Space Vehicle Study, Volume IV -- Mission Velocity Requirements And System Comparisons, February 28, 1966
- General Atomics, Nuclear Pulse Space Vehicle Study, Volume IV -- Mission Velocity Requirements And System Comparisons (Supplement), February 28, 1966
- NASA, Nuclear Pulse Vehicle Study Condensed Summary Report (General Dynamics Corp), January
