View source for Bathyscaphe

{{short description|Free-diving self-propelled deep-sea submersible}}
{{distinguish|Bathysphere}}
[[File:Bathyscaphe Trieste with USS Lewis (DE-535) over the Marianas Trench, 23 January 1960 (NH 96797).jpg|thumb|Bathyscaphe ''[[Trieste (bathyscaphe)|Trieste]]'' before its only dive into the [[Mariana Trench]]]]
[[File:Bathyscaphe Trieste.jpg|thumb|The ''Trieste'' in 1958]]

A '''bathyscaphe''' ({{IPAc-en|ˈ|b|æ|θ|ᵻ|ˌ|s|k|eɪ|f|,_|-|ˌ|s|k|æ|f}}) is a [[free-diving]], self-propelled [[deep sea|deep-sea]] [[submersible]], consisting of a crew cabin similar to a [[bathysphere]], but suspended below a float rather than from a surface cable, as in the classic bathysphere design.<ref name=brand>{{cite journal |author=Brand, V |title=Submersibles – Manned and Unmanned. |journal=South Pacific Underwater Medicine Society Journal |volume=7 |issue=3 |year=1977 |issn=0813-1988 |oclc=16986801 |url=http://archive.rubicon-foundation.org/6154 |access-date=2008-07-10 |archive-url=https://web.archive.org/web/20080801135138/http://archive.rubicon-foundation.org/6154 |archive-date=1 August 2008 |url-status=usurped }}</ref>

The float is filled with [[gasoline]] because it is readily available, buoyant, and, for all practical purposes, incompressible. The incompressibility of the gasoline means the tanks can be very lightly constructed, since the pressure inside and outside the tanks equalizes, eliminating any differential.  By contrast, the crew cabin must withstand a huge pressure differential and is massively built. [[Buoyancy]] at the surface can be trimmed easily by replacing gasoline in the tanks with water, because water has a greater density.

[[Auguste Piccard]], inventor of the first bathyscaphe, coined the name ''bathyscaphe'' using the [[Ancient Greek]] words {{wikt-lang|grc|βαθύς}} ({{translit|grc|bathús}}), meaning 'deep', and {{wikt-lang|grc|σκάφος}} ({{translit|grc|skáphos}}), meaning 'vessel, ship'.

== Mode of operation==
[[Image:Trieste nh96807.svg|upright=1.75|thumb|Internal arrangement of ''Trieste''.]]
To descend, a bathyscaphe floods air tanks with sea water, but unlike a [[submarine]] the water in the flooded tanks cannot be displaced with compressed air to ascend, because the water pressures at the depths for which the craft was designed to operate are too great.  For example, the pressure at the bottom of the [[Challenger Deep]] is more than seven times that in a standard "H-type" compressed [[gas cylinder]]. Instead, ballast in the form of [[iron]] shot is released to ascend, the shot being lost to the ocean floor.  The iron shot containers are in the form of one or more hoppers which are open at the bottom throughout the dive, the iron shot being held in place by an electromagnet at the neck.  This is a [[fail-safe]] device as it requires no power to ascend; in fact, in the event of a power failure, shot runs out by gravity and ascent is automatic.

==History of development==

The first bathyscaphe was dubbed ''[[FNRS-2]]'', named after the [[NFWO|Fonds National de la Recherche Scientifique]], and built in [[Belgium]] from 1946 to 1948 by [[Auguste Piccard]]. (''FNRS-1'' had been the balloon used for Piccard's ascent into the stratosphere in 1938). Propulsion was provided by [[Battery (electricity)|battery]]-driven [[electric motor]]s.<ref name=brand/> The float held {{convert|37850|L|||}} of aviation gasoline. There was no access tunnel; the sphere had to be loaded and unloaded while on deck. The first journeys were detailed in the [[Jacques Cousteau]] book [[The Silent World (book)|''The Silent World'']]. As described in the book, "the vessel had serenely endured the pressure of the depths, but had been destroyed in a minor squall". ''[[FNRS-3]]'' was a new submersible, using the crew sphere from the damaged ''FNRS-2'', and a new larger {{convert|75700|L|||}} float.

Piccard's second bathyscaphe was actually a third vessel [[Bathyscaphe Trieste|''Trieste'']], which was purchased by the [[United States Navy]] from [[Italy]] in 1957.<ref name=brand/> It had two water ballast tanks and eleven buoyancy tanks holding {{convert|120000|L|||}} of gasoline.<ref>{{cite web
|url=http://www.wetpaper.com.au/errata/pdfs/PP's_287-298.pdf
|title=Chapter 11
|publisher=Wet Paper
|access-date=2008-09-25
|archive-date=2008-09-11
|archive-url=https://web.archive.org/web/20080911071135/http://www.wetpaper.com.au/errata/pdfs/PP's_287-298.pdf
|url-status=dead
}}</ref>

==Accomplishments==

In 1960 ''Trieste'', carrying Piccard's son [[Jacques Piccard]] and [[Don Walsh]], reached the deepest known point on the Earth's surface, the [[Challenger Deep]], in the [[Mariana Trench]] in the Pacific Ocean.<ref name=brand/>

The onboard systems indicated a depth of 37,800&nbsp;ft (11,521&nbsp;m) but this was later corrected to 35,813&nbsp;ft (10,916 m) by taking into account variations arising from salinity and temperature. Later and more accurate measurements made in 1995 have found the Challenger Deep to be slightly shallower at 35,798&nbsp;ft (10,911&nbsp;m).

The crew of the ''Trieste'', which was equipped with a powerful light, noted that the seafloor consisted of [[diatom]]aceous ooze and reported observing "some type of flatfish, resembling a [[Sole (fish)|sole]], about 1 foot long and 6 inches across" (30 by 15&nbsp;cm) lying on the seabed.<ref>[http://www.americanheritage.com/articles/magazine/it/1992/1/1992_1_28.shtml "To the bottom of the sea"] {{webarchive|url=https://web.archive.org/web/20081203173230/http://www.americanheritage.com/articles/magazine/it/1992/1/1992_1_28.shtml |date=2008-12-03 }}, T. A. Heppenheimer, AmericanHeritage.com</ref> This put to rest the question of whether or not there was life at such a depth in the complete absence of light.

== See also ==
{{commonscat}}
* 1948 {{annotated link|FNRS-2|''FNRS-2''}}
* 1953 {{annotated link|FNRS-3|''FNRS-3''}}
* 1953 {{annotated link|Bathyscaphe Trieste|''Trieste''}}
* 1961 {{annotated link|Archimède|''Archimède''}}
* 1964 {{annotated link|Bathyscaphe Trieste II|''Trieste II''}}
* 1964 {{annotated link|DSV Alvin|''Alvin''}}
* 1964 {{annotated link|Aluminaut|''Aluminaut''}}
* 1970 {{annotated link|DSV Shinkai|DSV ''Shinkai''}}
* 1987 {{annotated link|Mir (submersible)|''MIR''}}
* 2012 ''[[Deepsea Challenger]]''
* 2018 [[DSV Limiting Factor|DSV ''Limiting Factor'']]
* {{annotated link|Deep-sea exploration}}
* {{annotated link|Diving chamber}}
* {{annotated link|Sea Pole-class bathyscaphe}}
* {{annotated link|Submersible}}
* {{annotated link|Timeline of diving technology}}

== References ==
{{Reflist}}

== External links ==
*{{cite journal |author=Barham EG |title=Siphonophores and the Deep Scattering Layer |journal=Science |volume=140 |issue=3568 |pages=826–828 |date=May 1963 |pmid=17746436 |doi=10.1126/science.140.3568.826 |bibcode=1963Sci...140..826B |s2cid=43485719 }}
*[https://web.archive.org/web/20010303233816/http://www.history.navy.mil/photos/sh-usn/usnsh-t/trste-b.htm The US Navy account of the dive, with photographs]
*{{cite web|last=Brewington|first=Krystal|year=2003|title=Depth of the Deepest Dive in a Bathyscaphe|url=http://hypertextbook.com/facts/2003/KrystalBrewington.shtml|work=The Physics Factbook}}
*[http://www.bathyscaphtrieste.com/ History of the Bathyscape Trieste]
* [http://college.hmco.com/history/readerscomp/ships/html/sh_034900_fnrs2.htm FNRS-2]
*[https://books.google.com/books?id=oN0DAAAAMBAJ&dq=1954+Popular+Mechanics+January&pg=PA110 "13,000 Feet Under the Sea in the French Bathyscaphe] ''Popular Mechanics'', May 1954, pp.&nbsp;110–111.
*[https://web.archive.org/web/20140625050833/http://deepseachallenge.com/ Deepsea Challenger – Mariana Trench Dive (03/25/2012).]

{{Underwater diving|other}}
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[[Category:Ship types]]
[[Category:Bathyscaphes| ]]
[[Category:Crewed submersibles]]
[[Category:Deep-submergence vehicles]]
[[Category:Swiss inventions]]