NASA's Breakthrough Propulsion Physics Program
Source:NASA Glenn Research Center
Millis, M. G., NASA Propulsion Physics Program, NASA
TM-1998-208400, 1998.
In Missions to the Outer Solar System and Beyond, Second
IAA Symposium on Realistic Near-Term Advanced Scientific Space
Mission, Aosta Italy, June 29 - July 1, 1998, International Academy of
Astronautics, Genta, G., ed., pp. 103-110.
August 20, 1999
Note: Figures did not transcribe correctly from original
report.
Abstract - In 1996, NASA established the Breakthrough
Propulsion Physics program to seek the ultimate breakthroughs in space
transportation: propulsion that requires no propellant mass,
propulsion that attains the maximum transit speeds physically
possible, and breakthrough methods of energy production to power such
devices. Topics of interest include experiments and theories regarding
the coupling of gravity and electromagnetism, vacuum fluctuation
energy, warp drives and wormholes, and superluminal quantum effects.
Because these propulsion goals are presumably far from fruition, a
special emphasis is to identify affordable, near-term, and credible
research that could make measurable progress toward these propulsion
goals. The methods of the program and the results of the 1997 workshop
are presented. This Breakthrough Propulsion Physics program, managed
by Glenn Research Center, is one part of a comprehensive, long range
Advanced Space Transportation Plan managed by Marshall Space Flight
Center.
1 INTRODUCTION
New theories and phenomena have emerged in recent
scientific literature that have reawakened consideration that
propulsion breakthroughs may be achievable - the kind of breakthroughs
that could make human voyages to other star systems possible. This
includes literature about warp drives, wormholes, quantum tunneling,
vacuum fluctuation energy, and the coupling of gravity and
electromagnetism. This emerging science, combined with the realization
that rockets are fundamentally inadequate for interstellar
exploration, led NASA to establish the "Breakthrough Propulsion
Physics" program in 1996.
This paper introduces this program and several of the
candidate research approaches that have already been identified. In
particular, this paper explains the methods used by this program to
conduct such visionary work as a lesson for other institutions who may
also wish to begin similar programs. Also, to give an indication of
some of the possible next research steps, the results of the 1997
workshop are presented.
2 BACKGROUND
Prior to 1996 the implications of emerging science to
the challenges of space propulsion were only sporadically studied, and
then mostly by individual researchers who did so on their own time.
Occasionally research and workshops were formally supported [1-11],
but progress was generally slow.
In 1996, the NASA Marshall Space Flight Center (MSFC)
was tasked to formulate a comprehensive strategy for advancing
propulsion for the next 25 years and they were requested to make this
strategy more visionary than previous plans. This strategy, called the
"Advanced Space Transportation Program (ASTP)," spans the nearer-term
technology improvements all the way through seeking the breakthroughs
that could revolutionize space travel and enable interstellar voyages
[12].
To address the most visionary end of this scale, MSFC
sought out the work of the NASA Glenn Research Center. Individuals at
Glenn had already been working on these topics [9, 10, 13-15] and
Glenn had experience working with far-future ideas through their
"Vision-21" exercises [5, 7, 16]. By applying the lessons learned from
Vision-21 and by forging collaborations amongst the individuals across
the country who were already working on these topics, Glenn
established the "Breakthrough Propulsion Physics" program to advance
science to address the goals of breakthrough space flight.
3 PROGRAM FOUNDATIONS
As the name implies, this program is specifically
looking for propulsion breakthroughs from physics. It is not looking
for further technological refinements of existing methods. Such
refinements are being explored in other programs under the ASTP.
Instead, this program looks beyond the known methods, searching for
further advances in science from which genuinely new technology can
emerge - technology to surpass the limits of existing methods.
There is a historical pattern to technological
revolutions, where new methods surpass the fundamental limits of their
predecessors [17]. Steam ships surpassed sailing ships, aircraft
surpassed ground transportation, rockets surpassed aircraft, and now
the search has begun for new methods to surpass rockets. This
evolutionary pattern is summarized in Figure 1. To sustain
technological preeminence, new methods must be sought when the
existing method is reaching the limits of its underlying physical
principles (the upper right asymptote of the S-curve in Figure 1), and
when new clues are emerging for alternative methods that might surpass
these limits [17].
In the case of spaceflight, rocket technology is
reaching the performance limits of its underlying physical principles
and new clues are emerging from science that might lead to new
propulsion principles.
There have been several recent advances in science that
have reawakened consideration that new propulsion mechanisms may lie
in wait of discovery. Recent experiments and Quantum theory have
revealed that space may contain enormous levels of vacuum
electromagnetic energy [18, 19]. This has led to questioning if this
vacuum energy can be used as an energy source [20, 21, 11] or a
propulsive reaction mass for space travel [22]. Next, new theories
suggest that gravity and inertia are electromagnetic effects related
to this vacuum energy [23, 24]. It is known from observed phenomena
and from the established physics of General Relativity that gravity,
electromagnetism, and spacetime are inter-related phenomena [25].
These ideas have led to questioning if gravitational or inertial
forces can be created or modified using electromagnetism [22]. Also,
theories have emerged from General Relativity about the nature of
spacetime that suggest that the light-speed barrier, described by
Special Relativity, might be circumvented by altering spacetime
itself. These "wormhole" [26, 27] and "warp drive" theories [28, 29]
have reawakened consideration that the light-speed limit of space
travel may be circumvented. Today, it is still unknown whether these
emerging theories are correct and, even if they are correct, if they
can become viable candidates for creating propulsion breakthroughs.
Although these emerging possibilities are of keen
interest to space technologists, the general scientific community is
more concerned with answering questions of the origin of the universe,
missing matter, black holes, and high-energy particle interactions. To
advance physics to solve the challenges of space travel a focused
effort is required. It should also be pointed out that such an
application-oriented program also provides new opportunities for
science itself. In the first step of the scientific method, where one
clearly formulates the problem to guide the search for knowledge, this
NASA program has a unique problem: space flight. This program is
specifically interested in the physics of how to propel a space
vehicle as far and as fast as possible with the least amount of
effort. Such a focus will present different lines of inquiry than the
more general physics inquiries. By asking different questions and
looking along a different path, this program provides an opportunity
for physicists to search for discoveries that may otherwise be
overlooked or delayed.
Since such work is more visionary than usual aerospace
endeavors, this program faces special programmatic challenges in
addition to the technical challenges of discovering the desired
breakthroughs. Fortunately, much has been written about the historical
lessons from technological revolutions [17], scientific revolutions
[30], and the human creative process [31]. Many of these lessons were
incorporated into the NASA Glenn "Vision-21" activities [16], and have
been incorporated into the Breakthrough Propulsion Physics program. In
the descriptions of the program's goals, objective, methods, and
research priorities that follow, these lessons are presented.
3.1 Program Goals
The first step toward solving a problem is to define the
problem. To determine the specific technical goals of the program, the
"Horizon Mission Methodology" [32] was used. This method forces
paradigm shifts beyond extrapolations of existing technologies by
using impossible hypothetical mission goals to solicit new solutions.
By setting impossible goals, the common practice of limiting visions
to extrapolations of existing solutions is prevented. The "impossible"
goal used in this exercise was practical interstellar travel. From
conducting this exercise, the three major barriers to practical
interstellar travel were identified and then set as the program's
technical goals. These are the breakthroughs required to revolutionize
space travel and enable interstellar voyages:
(1) MASS: Discover new propulsion methods that eliminate
or dramatically reduce the need for propellant. This implies
discovering fundamentally new ways to create motion, presumably by
manipulating inertia, gravity, or by any other interactions between
matter, fields, and spacetime.
(2) SPEED: Discover how to attain the ultimate
achievable transit speeds to dramatically reduce travel times. This
implies discovering a means to move a vehicle at or near the actual
maximum speed limit for motion through space or through the motion of
spacetime itself (if possible, this means circumventing the light
speed limit).
(3) ENERGY: Discover fundamentally new modes of onboard
energy generation to power these propulsion devices. This third goal
is included since the first two breakthroughs could require
breakthroughs in energy generation, and since the physics underlying
the propulsion goals is closely linked to energy physics.
3.2 Program Objective
The objective of the NASA Breakthrough Propulsion
Physics Program is to produce near-term, credible, and measurable
progress toward conquering these three goals. The underlined terms are
some of the programmatic features needed to conduct such visionary
work in formal institutions such as NASA.
The emphasis on "near-term progress" is because the
program's goals are presumably far from fruition while the support for
the program is sought in the near-term. It is therefore essential that
the long-range goals be broken down into smaller, near-term steps.
This is reflected in the Research Priorities discussed later.
Closely related to the need for near-term progress, is
the need to measure this progress. The program's sponsors want to see
progress within the funding cycles. The Research Priority criteria,
discussed later, include means to quantify progress.
The emphasis on "credible" is because such long range
ambitions are often tainted by non-credible work, or even
"pathological science" [33, 34], and since genuine progress can only
be made with credible work. The challenge to balance credibility
(necessary to make genuine progress) with vision (necessary to search
beyond known methods) is also addressed in the Research Priorities
discussed later. Another aspect of credibility is that this program
does not promise to deliver the breakthroughs, but does promise to
deliver progress toward achieving the breakthroughs. This position is
because it is too soon to know if the desired breakthroughs are indeed
achievable.
3.3 Collaborative Networking
Historically, pioneering new ideas has often been the
jurisdiction of exceptional individuals who not only possessed the
vision to realize their creations, but also the determination to
weather the setbacks, the skills to translate their ideas into
credible proofs-of-concepts, and the ability to make others comprehend
their creations. Individuals who posses all these skills at once are
rare, but this skill mix often exists in a group of individuals. By
providing a means for these individuals to collaborate and share their
skill mix to achieve a common goal, pioneering work can proceed
without having to wait for the next Goddard or Einstein.
This program was born out of the collaborative
networking of individual researchers who explored such topics out of
their own interests. This program will continue such collaborative
networking. This networking is open to all the NASA centers,
government labs, universities, and industries, and credible
individuals. Also, this program has recently opened up this
collaboration to the international community. Collaborative networking
has the following advantages:
. A diverse, multidisciplinary team provides a well
rounded and more objective program.
. Expertise and talent are scattered across the world,
and are not centralized at a single lab.
. Collaboration boosts credibility.
. Collaboration opens the way for collateral support
(where researchers seek support from their host organizations while
retaining open information exchange).
. Collaboration allows phased peer reviews, first with
the constructive team, then with external reviewers.
The internet is envisioned as the primary mechanism to
enable this degree of collaboration and to pool the collective
intellect across the world. Two internet sites have already been set
up, and a third is envisioned. One site, the "Warp Drive, When?" site
(http://www.GRC.nasa.gov/WWW/PAO/warp.htm), is for public education.
It describes the difficulties and emerging possibilities of
interstellar travel. The second site, the Breakthrough Propulsion
Physics Program site (http://www.GRC.nasa.gov/WWW/bpp/), lists the
details of this program and its status. The third site is envisioned
to be a limited access site. It will contain works in progress, more
in-depth annotated bibliographies, and allow on-line discussions.
Access will be limited to a "Contributor Network" of researchers
selected by the program's government member steering group. This
limited access site has not yet been completed, nor has the process
for nominating and selecting Contributor Network members been
specified.
Another means to allow collaborative networking is
through conferences and workshops. The following is a list of the
sessions and workshops held and planned that are related to this
topic:
. Feb. 97, Brainstorming Meeting, Austin TX.
. Aug. 97, Breakthrough Propulsion Physics Workshop,
Cleveland OH [35].
. Jan. 98, STAIF, 2 sessions, Albuquerque, NM.
. Jun. 98, IAA Symposium, Aosta ITALY.
. Jul. 11, 98, AIAA Joint Propulsion Conference, 1
session, Cleveland, OH.
. Jan. 99, STAIF, 3 sessions, Albuquerque, NM.
. Spring 99, Breakthrough Propulsion Physics Workshop #
2 (in planning).
. Jul. 99, AIAA Joint Propulsion Conference, 1 session,
Los Angeles, CA.
3.3 Supporting Research
Presently, this program has only received enough funds
to conduct the kick-off workshop and establish the web sites. Efforts
are underway to secure funding to formally solicit and support
research tasks. In the interim, and for international researchers that
are not eligible for US funding, researchers are encouraged to seek
funding through their own host organizations. With the precedent of
this NASA program, and by using this program's Research Priorities as
a guide, it may now be easier for other researchers to secure funding
for such visionary work.
Recently the NASA "Small Business Innovative Research
(SBIR)" and "Space Technology Transfer Research (STTR)" funding
mechanisms have had breakthrough propulsion added to their
solicitation topics (http://sbir.gsfc.nasa.gov/). Researchers are
encouraged to investigate these alternative funding mechanisms.
Once funded, this program plans to use an annual "NASA
Research Announcement" (NRA) to solicit and support research tasks.
This solicitation will be open to academia, industry, government labs,
and NASA centers. Selection will be via a peer review process using
the Research Prioritization Criteria to provide an initial ranking.
Because it is too early to focus on a given approach, it is
anticipated that multiple, different approaches will be supported from
the top ranking candidates. Proposed tasks should be of relatively
short duration (1-3yrs), modest cost ($50 to $150K), and traceable to
at least one of the three program goals.
4 RESEARCH PRIORITIES
To simultaneously focus emerging sciences toward
answering the needs of space travel and to provide a programmatic tool
for measuring the relative value and progress of research, this
program has established the prioritization criteria listed below. This
evaluation system has already gone through three iterations including
two trial runs. A derivative of this system is planned as the scoring
system for the program's NRA solicitation. The features of the system
that are discussed in this report include: (1) near-term focus on long
range goals, (2) metrics of progress, and (3) credibility criteria
with vision.
4.1 Research Prioritization Criteria List:
This list shows those factors that would be scored to
measure the relative value and progress of research. Each of the
lettered criteria below would receive a numeric score which would then
be combined to arrive at a total score for a given research approach.
. Relevance To Program:
A. Directness (must seek advances in physics that are
relevant to propulsion or power).
B. Magnitude of potential gains for goal #1 (mass) +
goal #2 (speed) + goal #3 (energy).
. Readiness:
C. Level of progress achieved to date (measured using
the scientific method levels).
D. Testability (ease of empirical testing).
[Note: experiments are considered closer than theory to
becoming technology].
. Credibility: [Note: these are designed to insure
credibility while still being open to visionary ideas]
E. Fits credible data (references must be cited).
F. More advantageous to program goals than current
approaches (references of competing approaches must be cited).
G. Discriminating test suggested.
. Research Task Factors:
H. Level of progress to be achieved upon completion of
task (measured using the scientific method levels).
I. Breadth of work (experiment, theory, and/or
comparative study).
J. Triage (will it be done anyway or must this program
support it?).
K. Lineage (will it lead to further relevant
advancements?).
L. Time required to complete task (reciprocal scoring
factor).
M. Funding required (reciprocal scoring factor).
N. Probability of successful task completion (based on
credentials and realism of proposal).
4.2 Near-Term Focus to Long-Range Goals
The program's goals are presumably far from fruition
while the support for the program is sought in the near-term. To
address this paradox it is essential that the long-range goals be
broken down into smaller, affordable, near-term steps. Proposals are
therefore required to suggest only an incremental task related to the
ultimate goals, and are graded inversely to their duration and cost
(criteria L and M). Also, from this point of view, "success" is
defined as learning more about reaching the breakthrough, rather than
actually achieving the breakthrough. Negative test results are still
results, indicating progress.
4.3 Metrics of Progress
Closely related to the focus on near-term steps, is the
need to measure progress. To demonstrate to the program sponsors that
progress is being made in the short time-frame of funding cycles,
these Prioritization Criteria can be used to quantify progress. By
simply taking the difference in score before and after a task is
completed, a numerical value of "progress" can be calculated. Since
there is no precedent for such a system, these values will only have
meaning when comparing the progress of different tasks over different
years.
One crucial feature inherent in this system is to have a
scale to gauge the status of an approach. Patterned after the
"Technology Readiness Scale" used to compare engineering status, the
Scientific Method has been adapted to address the science that
precedes technology. This scale, listed below in order of increasing
maturity, are used in criteria C and H. For scoring, a numeric value
would be assigned to each level based roughly on an estimate of the
relative quantity of work to achieve that level.
. Sci. Method Step Ø: Pre Science - recognizing an
opportunity.
. Sci. Method Step 1: Problem Formulated.
. Sci. Method Step 2: Data Collected.
. Sci. Method Step 3: Hypothesis Proposed.
. Sci. Method Step 4: Hypothesis Tested & Results
Reported.
. Tech Readiness Level 1: Basic Principles Observed &
Reported, same as Sci. Step 4.
. Tech Readiness Level 2: Applications Conceptual Design
Formulated.
4.4 Balancing Credibility With Vision
Another challenge of seeking breakthroughs is ensuring
credibility without sacrificing openness to new perspectives. This is
particularly challenging since genuinely new ideas often extend beyond
the established knowledge base, or worse, can appear to contradict
this base. In other words, a genuinely new, credible idea is very
likely to appear non-credible. Also, it is common when soliciting new
ideas to receive a large number of "fringe" submissions that are
certainly non-credible. To address this challenge, it is recommended
to:
(1) concentrate on credible empirical data (how nature
is observed to work) rather than depending on current theories or
paradigms (how nature is interpreted to work),
(2) compare the new idea's value to existing approaches,
(3) ensure that the new idea can be put to a test, and
(4) look for the characteristic signs of non-credible
science [34]. It should be noted that these credibility criteria do
not check if an idea is correct, but rather check to see if the idea
is credibly constructed and is leading to a correctness test.
Some of the characteristics of non-credible work is that
references are not explicitly cited, and that conclusions are made
without substantiating the work with supporting evidence. This can be
easily checked by requiring that submissions cite credible, peer
reviewed, references. References are required for supporting evidence
(criteria E), and for comparisons to existing theories (criteria F).
Fringe or pathological researchers often do not do this homework.
These credibility checks still leave plenty of room for
unconventional, visionary ideas.
Empiricism is emphasized over theory as a credibility
check since theory is an interpretation to explain observations of
nature - our current best perspective. Theories evolve over time as we
gain more understanding about nature, but the empirical observations,
the raw data, do not change. For example, the data of the motions of
the planets are the same, regardless if one uses the Copernicus theory
or the Earth-centered theory to describe the data. When seeking new
ideas, it is crucial that they are consistent with credible data, but
they may entertain new interpretations of that data. This emphasis of
empiricism over theory is the primary technique to allow credible
vision.
To ensure that the idea is oriented toward the goals of
the program, and to ensure that the author has done their homework, it
is required that the proposal articulate how the new idea compares to
existing approaches (criteria F). This not only checks for relevance
and to insure reference citations, as mentioned before, but positions
the idea to address the next critical criteria; a discriminating test.
A discriminating test (criteria G) is required to focus
the work toward the make-or-break issues, and to provide the basis for
a credible "correctness" test.
5 AUGUST 1997 WORKSHOP
One of the first major milestones of the program was to
convene a workshop with established physicists, government researchers
and select innovators to jointly examine the new theories and
phenomena in the context of seeking propulsion breakthroughs. This
workshop was held on August 12-14, 1997, in Cleveland Ohio [35].
The purpose of the workshop was to understand the
fundamental issues and opportunities for new propulsion physics and to
foster collaborations amongst researchers. A key deliverable was to
assemble a list of candidate research tasks. To achieve this purpose,
this workshop featured a plenary sequence of 14 invited presentations
about emerging physics with both optimistic and pessimistic
viewpoints, 30 poster papers for provoking thought, and 6 parallel
breakout sessions for the participants to generate a list of next-step
research tasks.
Since this workshop dealt with seeking breakthroughs in
science, it asked participants to be visionary. Admittedly, these
breakthroughs may turn out to be impossible, but progress is not made
by conceding defeat. For the sake of promoting progress, participants
were asked to entertain, for the duration of the workshop, the notion
that these breakthroughs are indeed achievable. Simultaneously,
however, this workshop looked for sound and tangible research
approaches. Therefore, participants were also asked to be credible --
credible progress toward incredible possibilities.
In total, 84 participants attended the workshop,
including 26 from industry, 18 from universities, 12 from six
government labs, 16 from five NASA centers, and 12 students.
5.1 Invited Presentations
The invited presentations, from established physicists,
covered many of the relevant areas of emerging physics. The intent of
these presentations was to provide credible overviews of where we
stand today in physics and introduce the unknowns and unresolved
issues. Below is a list of these presentations in the order that they
were presented. Where a related or equivalent work is available, a
reference is cited.
(1) L. Krauss (Case Western Reserve Univ.),
"Propellantless Propulsion: The Most Inefficient Way to Fly?" [36]
(2) H. Puthoff (Inst. for Advanced Studies at Austin),
"Can the Vacuum be Engineered for Spaceflight Applications?: Overview
of Theory and Experiments" [11, 21, 23, 24]
(3) R. Chiao (Univ. of California at Berkeley) & A.
Steinberg, "Quantum Optical Studies of Tunneling Times and
Superluminality" [37]
(4) J. Cramer (Univ. Washington), "Quantum Nonlocality
and Possible Superluminal Effects" [38]
(5) R. Koczor & D. Noever (MSFC), "Experiments on the
Possible Interaction of Rotating Type II YBCO Ceramic Superconductors
and the Local Gravity Field" [39, 40]
(6) R. Forward (Forward Unlimited), "Apparent Endless
Extraction of Energy from the Vacuum by Cyclic Manipulation of Casimir
Cavity Dimensions" [41, 20]
(7) B. Haisch (Lockheed) & A. Rueda, "The Zero-Point
Field and the NASA Challenge to Create the Space Drive" [24]
(8) A. Rueda (California State Univ.) & B. Haisch,
"Inertial Mass as Reaction of the Vacuum to Accelerated Motion" [24]
(9) D. Cole (IBM Microelectronics), "Calculations on
Electromagnetic Zero-Point Contributions to Mass and Perspectives"
[21].
(10) P. Milonni (Los Alamos), "Casimir Effect: Evidence
and Implications" [18]
(11) H. Yilmaz (Electro-Optics Tech. Ctr.), "The New
Theory of Gravitation and the Fifth Test" [42]
(12) A. Kheyfets (N. Carolina St. U.) & W. Miller,
"Hyper-Fast Interstellar Travel via Modification of Spacetime
Geometry" [26-29, 43].
(13) F. Tipler, III (Tulane U.), "Ultrarelativistic
Rockets and the Ultimate Future of the Universe"
(14) G. Miley (U. of Illinois), "Possible Evidence of
Anomalous Energy Effects in H/D-Loaded Solids-- Low Energy Nuclear
Reactions"
5.2 Identifying Next-Step Research Tasks
To generate the list of next-step research tasks, the
participants were divided into six breakout groups. Each of the three
program goals were addressed by two of the six groups. A facilitator
led the group through a process designed to elicit a large number of
ideas and then to evolve these ideas into candidate next-step research
tasks - tasks that address the immediate questions raised by the
emerging physics and the program goals. To be programmatically
acceptable, it was desired that these research tasks be
short-duration, low-cost, and incremental steps toward the grand
goals. Based on the invited presentations, poster papers, and the
ideas generated during the breakout sessions, about 80 task ideas were
collected.
6 CANDIDATE NEXT-STEP RESEARCH
The following section highlights just some of the
approaches that have been suggested to begin the search for propulsion
breakthroughs. These are arranged according to the three program goals
and highlight the intriguing phenomena and theories, critical issues,
and candidate next-step approaches for each program goal. Some of the
48 ideas that were generated during the Austin Texas brainstorming
session, and some of the 80 ideas from the August workshop hare
covered here. Note that there are many redundancies amongst these 128
ideas, and that most of these have not yet been fully reviewed.
6.1 Toward Eliminating Propellant Mass
It is known that gravity, electromagnetism and spacetime
are coupled phenomena. Evidence includes the bending of light, the
red-shifting of light, and the slowing of time in a gravitational
field. This coupling is most prominently described by General
Relativity [25]. Given this coupling and our technological proficiency
for electromagnetics, it has been speculated that it may become
possible to use electromagnetic technology to manipulate inertia,
gravity, or spacetime to induce propulsive forces [22]. Another
phenomena of interest is the Casimir Effect, where closely spaced
plates are forced together, presumably by vacuum fluctuations [19].
One explanation is that this force is the net radiation pressure of
the virtual vacuum fluctuation photons, where the pressure is greater
outside the plates than within, since wavelengths larger than the
plate separation are excluded. The force is inversely proportional to
the 4th power of the distance. Even though this effect can be
explained by various theories [18], the idea that the vacuum might
create these forces leads to speculations that an asymmetric vacuum
effect, if possible, could lead to a propulsive effect [22]. There are
many unsolved issues regarding these speculations, including whether
these phenomena can lead to controllable net-force effects and whether
such effects can be created, even in principle, without violating
conservation of momentum and energy [22].
Although it is presently unknown if such propellantless
propulsion can be achieved, several theories have emerged that provide
additional research paths. It should be noted that all of these
theories are too new to have either been confirmed or discounted, but
their potential utility warrants consideration. This includes negative
mass propulsion [44], theories that suggest that inertia and gravity
are affected by vacuum fluctuations [23, 24] and numerous other
theories about the coupling between matter, electromagnetism, and
spacetime [4, 42, 45-50]. Another recent development, which has yet to
be credibly confirmed or discounted, is where anomalous weight changes
are observed over spinning superconductors [39].
Regarding candidate next steps, experiments have been
suggested to test most of the theories cited above, including the
theories linking inertia to vacuum fluctuations [11]. Furthermore,
Robert Forward suggested a search for negative mass based on recent
astronomical data [51]. Also, experiments at MSFC are continuing to
test the claims of weight changes over spinning superconductors [40].
6.2 Toward Achieving the Ultimate Transit Speed
Special Relativity states that the speed of light is an
upper limit for the motion of matter through spacetime. Recently,
however, theories using the formalism of General Relativity have
suggested that this limit can be circumvented by altering spacetime
itself. This includes "wormhole" and "warp drive" theories. A wormhole
is a shortcut created through spacetime [26, 27] where a region of
spacetime is warped to create a shorter path between two points. A
warp drive involves the expansion and contraction of spacetime to
propel a region of spacetime faster than light [28]. Figure 2
illustrates the Alcubierre warp drive, showing the opposing regions of
expanding and contracting spacetime that propel the center region.
It has also been suggested that the light speed limit
may be exceeded if velocities could take on imaginary values [52]. In
addition, there are theories for "nonlocality" from Quantum Physics
that suggest potentially superluminal effects [38]. These theories not
only present challenging physics problems, but are intriguing from the
point of view of future space travel. Do these theories represent
genuinely possible physical effects, or are they merely mathematical
curiosities?
Wormholes, if they exist, may be observable through
astronomical searches. The characteristic signature of a negative mass
wormhole (possibly a traverseable type) has been specified to aid this
search [53]. Regarding possible experiments, it has been suggested to
use the strong magnetic fields that are momentarily generated by
chemical and nuclear explosions and lasers to test the space-warping
effect of magnetic fields [54].
Regarding other faster-than-light possibilities, there
have also been some intriguing experimental effects. Photons have been
measured to tunnel across a photonic band-gap barrier at 1.7 times the
speed of light [37]. Even though the author concludes that information
did not travel faster than light, the results are intriguing. It has
been suggested to conduct similar experiments using matter rather than
photons to unambiguously test the information transfer rate. In
addition, recent experiments of the rest mass of the electron
antineutrino have measured an imaginary value [55]. Even though this
result is attributed to possible errors, an imaginary mass value could
be a signature characteristic of a tachyon (hypothetical
faster-than-light particles). It has been suggested to revisit this
and other similar data to determine if this can be credibly
interpreted as evidence of tachyons. It was also pointed out that
other experiments have been suggested to search for evidence of
tachyons [56].
The notion of faster-than-light travel evokes many
critical issues. Issues include causality violations, the requirement
for negative energy, and the requirement for enormous energy densities
to create the superluminal effects. Theoretical approaches have been
suggested to address these issues, including the use of quantum
gravity.
6.3 Toward New Modes of Energy Production
Since the first two breakthroughs could require
breakthroughs in energy generation, and since the physics underlying
the propulsion goals is closely linked to energy physics, it is also
of interest to discover fundamentally new modes of energy generation.
The principle phenomena of interest for this category is, again, the
vacuum fluctuations. It has been theorized that this energy can be
extracted without violating conservation of energy or any
thermodynamic laws [20, 21]. It is still unknown if this vacuum energy
exists as predicted, how much energy might be available to extract,
and what the secondary consequences would be of extracting vacuum
energy.
It has been suggested to continue experimental work to
study the Casimir effect, not only to address these energy questions,
but to explore the more general physics of geometry and temperature
effects on the Casimir effect. Techniques have been suggested for
using micromechanical technology to study Casimir effects [57]. Not
only are micromechanical structures an emerging technology, but the
dimensions of such structures are similar to the dimensions required
for Casimir effects. Also, should any viable device be engineered,
these methods might be adaptable for high-volume manufacturing. On
another vein, it has been suggested to continue the study of the
sonoluminescence effect and its relation to vacuum fluctuation energy
[58].
On a more conventional vein, ideas were raised at the
workshop by Tipler and LaPointe for seeking alternative methods of
antimatter production.
7 CONCLUSIONS
New theories and laboratory-scale effects have emerged
in the scientific literature which provide new approaches to seeking
major propulsion breakthroughs. NASA has established a program to
begin exploring these possibilities. Since the propulsion goals are
presumably far from fruition, a special emphasis of the program is to
identify affordable, near-term, and credible research that could make
measurable progress toward these propulsion goals. To kick-off the
program, collaborative networking, internet communication, and
workshops are being used. During a recent workshop, many of these new
approaches were reviewed, and several research task ideas were
generated for taking the next steps toward propulsion breakthroughs. A
NASA Research Announcement has been chosen as the mechanism to solicit
and support research, once sufficient funds become available. A peer
review system has been drafted to rank these and other future
proposals. In the interim, other funding opportunities such as the
SBIR and STTR are available.
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by Marc G. Millis
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