1970s proposal for a large fusion powered unmanned interstellar probe
Daedalus spacecraft concept
Project Daedalus
(named after
Daedalus
, the
Greek mythological
designer who crafted wings for human flight) was a study conducted between 1973 and 1978 by the
British Interplanetary Society
to design a plausible
uncrewed
interstellar probe
.
[1]
Intended mainly as a scientific probe, the design criteria specified that the spacecraft had to use existing or near-future technology and had to be able to reach its destination within a human lifetime.
Alan Bond
led a team of scientists and engineers who proposed using a
fusion rocket
to reach
Barnard's Star
5.9
light years
away. The trip was estimated to take 50 years, but the design was required to be flexible enough that it could be sent to any other target star.
All the papers produced by the study are available in a BIS book,
Project Daedalus: Demonstrating the Engineering Feasibility of Interstellar Travel
.
[2]
Concept
[
edit
]
Daedalus would be constructed in Earth orbit and have an initial mass of 54,000
tonnes
including 50,000 tonnes of fuel and 500 tonnes of scientific payload. Daedalus was to be a two-stage spacecraft. The first stage would operate for two years, taking the spacecraft to 7.1% of
light speed
(0.071
c
), and then after it was jettisoned, the second stage would fire for 1.8 years, taking the spacecraft up to about 12% of light speed (0.12
c
), before being shut down for a 46-year cruise period. Due to the extreme temperature range of operation required, from near
absolute zero
to 1600 K, the
engine bells
and support structure would be made of
molybdenum
alloyed with
titanium
,
zirconium
, and
carbon
, which retains strength even at
cryogenic temperatures
. A major stimulus for the project was
Friedwardt Winterberg
's
inertial confinement fusion
drive concept,
[1]
[3]
for which he received the Hermann Oberth gold medal award.
[4]
This velocity is well beyond the capabilities of
chemical rockets
or even the type of
nuclear pulse propulsion
studied during
Project Orion
. According to Dr.
Tony Martin
, controlled-fusion engine and the
nuclear?electric systems
have very low
thrust
, equipment to convert nuclear energy into electrical has a large mass, which results in small
acceleration
, which would take a century to achieve the desired speed; thermodynamic nuclear engines of the
NERVA
type require a great quantity of fuel,
photon rockets
have to generate power at a rate of 3
×
10
9
W per kg of vehicle mass and require mirrors with
absorptivity
of less than 1 part in 10
6
,
interstellar ramjet
's problems are tenuous interstellar medium with a density of about 1 atom/cm
3
, a large diameter funnel, and high power required for its electric field. Thus the only suitable propulsion method for the project was
thermonuclear pulse propulsion
.
[5]
[6]
[7]
Daedalus would be propelled by a
fusion rocket
using pellets of a
deuterium
/
helium-3
mix that would be ignited in the reaction chamber by
inertial confinement
using
electron beams
. The electron beam system would be powered by a set of
induction coils
trapping energy from the
plasma
exhaust stream. 250 pellets would be detonated per second, and the resulting plasma would be directed by a
magnetic nozzle
. The computed burn-up fraction for the fusion fuels was 0.175 and 0.133 producing exhaust velocities of 10,600 km/s and 9,210 km/s respectively. Due to scarcity of helium-3 on Earth, it was to be mined from the atmosphere of
Jupiter
by large
hot-air balloon
supported robotic factories over a 20-year period, or from a less distant source, such as the
Moon
.
[8]
The second stage would have two 5-metre
optical telescopes
and two 20-metre
radio telescopes
. About 25 years after launch these telescopes would begin examining the area around Barnard's Star to learn more about any accompanying planets. This information would be sent back to Earth, using the 40-metre diameter second stage
engine bell
as a communications dish, and targets of interest would be selected. Since the spacecraft would not decelerate, upon reaching Barnard's Star, Daedalus would carry 18 autonomous sub-probes that would be launched between 7.2 and 1.8 years before the main craft entered the target system. These sub-probes would be propelled by
nuclear-powered
ion drives
and would carry cameras,
spectrometers
, and other sensory equipment. The sub-probes would fly past their targets, still travelling at 12% of the speed of light, and transmit their findings back to the Daedalus' second stage, mothership, for relay back to Earth.
The ship's payload bay containing its sub-probes, telescopes, and other equipment would be protected from the
interstellar medium
during transit by a
beryllium
disc, up to 7 mm thick, weighing up to 50 tonnes. This erosion shield would be made from beryllium due to its lightness and high latent heat of vaporisation. Larger obstacles that might be encountered while passing through the target system would be dispersed by an artificially generated cloud of particles, ejected by support vehicles called dust bugs about 200 km ahead of the vehicle. The spacecraft would carry a number of
robot
wardens capable of autonomously repairing damage or malfunctions.
Specifications
[
edit
]
Overall length: 190 metres
Payload mass: 450 tonnes
|
First stage:
|
Second stage:
|
Empty mass:
|
1,690 tonnes (at staging)
|
980 tonnes (at cruise speed)
|
Propellant mass:
|
46,000 tonnes
|
4,000 tonnes
|
Engine burn time:
|
2.05 years
|
1.76 years
|
Thrust:
|
7,540,000
newtons
|
663,000 newtons
|
Engine exhaust velocity:
|
10,600,000 m/s
|
9,210,000 m/s
|
Delta-V
|
35,000,000 m/s (0.117c)
|
13,000,000 m/s (0.0432c)
|
Variants
[
edit
]
A quantitative engineering analysis of a
self-replicating
variation on Project Daedalus was published in 1980 by
Robert Freitas
.
[9]
The non-replicating design was modified to include all subsystems necessary for self-replication. Use the probe to deliver a seed factory, with a mass of about 443 metric tons, to a distant site. Have the seed factory replicate many copies of itself on-site, to increase its total manufacturing capacity, then use the resulting automated industrial complex to construct probes, with a seed factory on board, over a 1,000-year period. Each REPRO would weigh over 10 million tons due to the extra fuel needed to decelerate from 12% of
lightspeed
.
Another possibility is to equip the Daedalus with a
magnetic sail
similar to the magnetic scoop on a
Bussard ramjet
to use the destination star
heliosphere
as a brake, making carrying deceleration fuel unnecessary, allowing a much more in-depth study of the star system chosen.
See also
[
edit
]
Further reading
[
edit
]
References
[
edit
]
- ^
a
b
Project Daedalus Study Group: A. Bond et al.,
Project Daedalus ? The Final Report on the BIS Starship Study
, JBIS Interstellar Studies, Supplement 1978
- ^
A. Bond et al.,
Project Daedalus: Demonstrating the Engineering Feasibility of Interstellar Travel
- ^
F. Winterberg, "Rocket propulsion by thermonuclear microbombs ignited with intense relativistic electron beams", Raumfahrtforschung 15, 208-217 (1971).
- ^
Winterberg is
Hermann Oberth
Gold Medalist,
Physics Today, December 1979
- ^
Project Daedalus: The Propulsion System Part 1; Theoretical considerations and calculations. 2. Review of Advanced Propulsion Systems
Archived
2013-06-28 at the
Wayback Machine
- ^
Title: Project Daedalus. Authors: Bond, A.; Martin, A. R. Publication: Journal of the British Interplanetary Society Supplement, p. S5?S7 Publication Date: 00/1978 Origin: ARI ARI Keywords: Miscellanea, Philosophical Aspects, Extraterrestrial Life Comment: A&AA ID. AAA021.015.025 Bibliographic Code: 1978JBIS...31S...5B
- ^
Project Daedalus ? Origins
- ^
Helium-3#Extraterrestrial abundance
- ^
Freitas, Robert A. Jr. (July 1980).
"A Self-Reproducing Interstellar Probe"
.
J. Br. Interplanet. Soc
.
33
: 251?264.
Bibcode
:
1980JBIS...33..251F
.
External links
[
edit
]
|
---|
Spacecraft
| |
---|
Sea vessels
| |
---|
Aircraft
| |
---|
Ground
| |
---|
|