Editing Breakthrough Propulsion Physics Program

The '''Breakthrough Propulsion Physics Project''' ('''BPP''') was a [[research project]] funded by [[NASA]] from 1996 to 2002 to study various proposals for [[Revolutionary technology|revolutionary]] methods of [[spacecraft propulsion]] that would require breakthroughs in physics before they could be realized.<ref name="millis2005">{{cite journal|last1=Millis|first1=Mark G.|title= Assessing Potential Propulsion Breakthroughs|journal= Annals of the New York Academy of Sciences|volume=1065|pages=441–461|date=Dec 1, 2005|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060000022.pdf|access-date=8 February 2018|bibcode=2005NYASA1065..441M|doi=10.1196/annals.1370.023|pmid=16510425|hdl=2060/20060000022|s2cid=41358855|hdl-access=free}}</ref><ref name="frontierschapter3">{{cite book|last1=Davis|first1=Eric W.|last2=Gilster|first2=Paul A.|editor-first1=Marc G.|editor-last1=Millis|title=Frontiers of propulsion science|chapter=Recent History of Breakthrough Propulsion Studies|date=2009|publisher=American Institute of Aeronautics and Astronautics|location=Reston, Va.|isbn=9781615830770}}</ref> The project ended in 2002, when the Advanced Space Transportation Program was reorganized and all speculative research (less than [[Technology readiness level]] 3) was cancelled.<ref name="frontierschapter3"/>
During its six years of operational funding, this program received a total investment of $1.2 million.  

The Breakthrough Propulsion Physics project addressed a selection of "incremental and affordable" research questions towards the overall goal of propellantless propulsion, hyperfast travel, and breakthrough propulsion methods.<ref name="millis20042" /> It selected and funded five external projects, two in-house tasks and one
minor grant.<ref name="frontierschapter3"/>
At the end of the project, conclusions into fourteen topics, including these funded projects, were summarized by program manager Marc G. Millis.<ref name="millis2005" /> Of these, six research avenues were found to be nonviable, four were identified as opportunities for continued research, and four remain unresolved.<ref name="millis2005" /><ref name="millis20042">{{cite journal|last1=Millis|first1=Mark G.|date=2004|title=Prospects for Breakthrough Propulsion From Physics|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040070788.pdf|access-date=8 February 2018}}</ref>

==Non-viable approaches==
One in-house experiment tested the Schlicher thruster antenna, claimed by Schlicher<ref>{{cite journal|last1=Schlicher|first1=R|last2=Biggs|first2=A|last3=Tedeschi|first3=W|title=Mechanical propulsion from unsymmetrical magnetic induction fields|journal=31st Joint Propulsion Conference and Exhibit|page=2643|doi=10.2514/6.1995-2643|year=1995}}</ref> to generate thrust.  No thrust was observed.<ref name="frontierschapter3" /><ref>{{cite journal|last1=Fralick|first1=Gustave|last2=Niedra|first2=Janis|title=Experimental results of Schlicher's thrusting antenna|journal=37th Joint Propulsion Conference and Exhibit|date=Nov 1, 2001|doi=10.2514/6.2001-3657|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020009088.pdf|hdl=2060/20020009088|hdl-access=free}}</ref>

Another experiment examined a gravity shielding mechanism claimed by Podkletnov and Nieminen.<ref name="frontierschapter3" /><ref>{{cite journal|last1=Podkletnov|first1=E.|last2=Nieminen|first2=R.|title=A possibility of gravitational force shielding by bulk YBa2Cu3O7−x superconductor|journal=Physica C: Superconductivity|date=December 1992|volume=203|issue=3–4|pages=441–444|doi=10.1016/0921-4534(92)90055-H|bibcode=1992PhyC..203..441P}}</ref>  Experimental investigation on the BPPP<ref>{{cite journal|last1=Robertson|first1=Tony|last2=Lichford|first2=Ron|last3=Peters|first3=Randall|last4=Thompson|first4=Byran|last5=Rogers|first5=Stephen L.|title=Exploration of Anomalous Gravity Effects by rf-Pumped Magnetized High-T(c) Superconducting Oxides|journal=AIAA Joint Propulsion Conference; 8-11 Jul. 2001; Salt Lake City, UT; United States|date=Jan 1, 2001|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020016600.pdf}}</ref> and other experiments<ref>{{cite journal|last1=Hathaway|first1=G|last2=Cleveland|first2=B|last3=Bao|first3=Y|title=Gravity modification experiment using a rotating superconducting disk and radio frequency fields|journal=Physica C: Superconductivity|date=April 2003|volume=385|issue=4|pages=488–500|doi=10.1016/S0921-4534(02)02284-0|bibcode=2003PhyC..385..488H}}</ref> found no evidence of the effect.<ref name="millis2005" />

Research on quantum tunneling was sponsored by the BPPP.  It was concluded that this is not a mechanism for faster-than-light travel.<ref name="millis2005" /><ref name="frontierschapter3" />

Other approaches categorized as non-viable are oscillation thrusters and gyroscopic antigravity, Hooper antigravity coils, and coronal blowers.<ref name="millis2005" />

==Unresolved approaches==
A theoretical examination of additional atomic [[energy levels]] (deep Dirac levels) was carried out.  Some states were ruled out, but the problem remains unsolved.<ref name="frontierschapter3" />

Experiments tested [[James F. Woodward|Woodward]]’s [[Woodward effect|theory]]<ref>{{cite journal|last1=Woodward|first1=James F.|title=A new experimental approach to Mach's principle and relativistic graviation|journal=Foundations of Physics Letters|date=October 1990|volume=3|issue=5|pages=497–506|doi=10.1007/BF00665932|bibcode=1990FoPhL...3..497W|s2cid=120603211}}</ref><ref>{{cite journal|last1=Woodward|first1=James F.|title=Measurements of a Machian transient mass fluctuation|journal=Foundations of Physics Letters|date=October 1991|volume=4|issue=5|pages=407–423|doi=10.1007/BF00691187|bibcode=1991FoPhL...4..407W|s2cid=121750654}}</ref> of inducing transient inertia by electromagnetic fields.  The small effect could not be confirmed.  Woodward continued refining the experiments and theory.  Independent experiments<ref>{{cite journal|last1=Cramer|first1=John|last2=Cassisi|first2=Damon|last3=Fey|first3=Curran|title=Tests of Mach's Principle with a mechanical oscillator|journal=37th Joint Propulsion Conference and Exhibit|date=Oct 1, 2004|doi=10.2514/6.2001-3908|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050080680.pdf|hdl=2060/20050080680|s2cid=55948442 |hdl-access=free}}</ref> also remained inconclusive.<ref name="millis2005" /><ref name="frontierschapter3" />

A possible torsion-like effect in the coupling between electromagnetism and spacetime,<ref>{{cite journal|last1=Ringermacher|first1=Harry I.|title=An electrodynamic connection|journal=Classical and Quantum Gravity|date=1994|volume=11|issue=9|pages=2383–2394|doi=10.1088/0264-9381/11/9/018|language=en|issn=0264-9381|bibcode=1994CQGra..11.2383R|s2cid=250763583 }}</ref> which may ultimately be useful for propulsion, was sought in experiments. The experiments were insufficient to resolve the question.<ref name="frontierschapter3" />

Other theories listed in Millis's final assessment as unresolved are [[Abraham-Minkowski controversy|Abraham–Minkowski]] electromagnetic momentum, interpreting inertia and gravity quantum vacuum effects, and the Podkletnov force beam.<ref name="millis2005" />

== Space drives ==
One of the eight tasks funded by the BPP program was to define a strategy towards space drives.<ref name="frontierschapter3" />  

As a motivation, seven examples of hypothetical space drives were described at the onset of the project.<ref name="millis2005" />  These included the gravity-based pitch drive, bias drive, disjunction drive and diametric drive; the [[Alcubierre drive]]; and the vacuum energy based differential sail.<ref name="millis1997" />

The project then considered the mechanisms behind these drives.  At the end of the project, three mechanisms were identified as areas for future research.  One considers the possibility of a reaction mass in seemingly empty space, for example in [[dark matter]], [[dark energy]], or [[zero-point energy]].  Another approach is to reconsider [[Mach's principle]] and [[Euclidean space]].  A third research avenue that might ultimately prove useful for spacecraft propulsion is the [[Coupling (physics)|coupling of fundamental forces]] on sub-atomic scales.<ref name="millis2005" />

== Quantum vacuum energy experiments == 

One topic of investigations was the use of the [[zero-point energy]] field. As the [[Werner Heisenberg|Heisenberg]] [[uncertainty principle]] implies that there is no such thing as an exact amount of energy in an exact location, [[quantum fluctuation|vacuum fluctuation]]s are known to lead to discernible effects such as the [[Casimir effect]]. The differential sail is a speculative drive, based on the possibility of inducing differences in the pressure of vacuum fluctuations on either side of a sail-like structure — with the pressure being somehow reduced on the forward surface of the sail, but pushing as normal on the aft surface — and thus propel a vehicle forward.<ref name="frontierschapter3" /><ref name="millis1997">{{cite journal|last1=Millis|first1=Marc G.|title=Challenge to Create the Space Drive|journal=Journal of Propulsion and Power|date=September 1997|volume=13|issue=5|pages=577–582|doi=10.2514/2.5215|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990023236.pdf|access-date=8 February 2018|hdl=2060/19980021277|s2cid=3088306 |hdl-access=free}}</ref><ref name="Popular Science">{{cite magazine |url=https://books.google.com/books?id=kP6ESrt1xLUC&q=disjunction+drive&pg=PA50|magazine=Popular Science |title=Space at Warp Speed: Disjunction Drive |page=50 |first=Mariette |last=DiChristina |date=May 2001 |access-date=2012-01-25}}</ref>

The Casimir effect was investigated experimentally and analytically under the Breakthrough Propulsion Physics project.  This included the construction of MicroElectroMechanical
(MEM) rectangular Casimir cavities.<ref name="millis20042" /><ref>{{cite journal|last1=Maclay|first1=G. Jordan|title=Analysis of zero-point electromagnetic energy and Casimir forces in conducting rectangular cavities|journal=Physical Review A|date=17 April 2000|volume=61|issue=5|pages=052110|doi=10.1103/PhysRevA.61.052110|bibcode=2000PhRvA..61e2110M}}</ref> Theoretical work showed that the effect could be used to create net forces, although the forces would be extremely small.<ref name="millis2005" /><ref name="millis20042" /><ref>{{cite journal|last1=Maclay|first1=G. Jordan|last2=Forward|first2=Robert L.|title=A Gedanken Spacecraft that Operates Using the Quantum Vacuum (Dynamic Casimir Effect)|journal=Foundations of Physics|date=March 2004|volume=34|issue=3|pages=477–500|doi=10.1023/B:FOOP.0000019624.51662.50|bibcode=2004FoPh...34..477M|arxiv=physics/0303108|s2cid=118922542}}</ref> At the conclusion of the project, the Casimir effect was categorized as an avenue for future research.<ref name="millis2005" />

==Tau Zero Foundation==

After funding ended, program manager Marc G. Millis was supported by NASA to complete documentation of results. The book ''Frontiers of Propulsion Science'' was published by the [[AIAA]] in February 2009,<ref> M. Millis and E. Davis, ''Frontiers of Propulsion Science'', AIAA, Progress in Astronautics & Aeronautics Vol 227, 2009. {{ISBN|978-1563479564}}
{{ISBN|1563479567}} </ref> providing a deeper explanation of several propulsion methods.

Following program cancellation in 2002, Millis and others founded the Tau Zero Foundation.

==See also==
* [[Field propulsion]]
* [[United States gravity control propulsion research]]
* [[Wormhole]]

==References==
{{reflist}}

[[Category:Interstellar travel]]
[[Category:Spacecraft propulsion]]
[[Category:Scientific speculation]]
[[Category:Warp drive theory]]