klaes@advax.enet.dec.com (Larry Klaes) (11/13/90)
Henry Thomas (hthomas@irisa.fr) writes: >> A similar(?) problem occurred on Venus, where the probes Venera >> 11-14 lasted only a few hours. The first ones didn't reached the >> ground because theirs parachutes where destroyed by the acid >> atmosphere. Not really. The first Soviet attempts to land on Venus failed either because of prior mechanical difficulties or due to being crushed by the high atmospheric pressure towards the surface. The landers of the VENERA 4, 5, and 6 missions (1967-1969) were designed to withstand only twenty Earth atmospheres (20 bars), the best esti- mate of air pressure on Venus' surface at the time. Even the temper- atures were thought to be several hundred degrees cooler than now known. Yes, MARINER 2 did indicate an overall surface temperature of 425 degrees Celsius (797 degrees Fahrenheit) back in 1962, but the Soviets were still holding out for a relatively cool and low air pressure Venus even in the late 1960s. For example, the VENERA 4 lander was designed to float in case it came down in a Venerean ocean! In addition, the sulfuric acid which pervades Venus' thick atmosphere was unknown at the time of the early VENERA missions. Its existence was postulated in 1973 and generally confirmed by the Soviet and American Venus missions of 1978. While not designed against acid, the descent parachutes on the early VENERA landers were very tough, plus the drop through Venus' air lasted no more than one hour. It was the intense air pressure which destroyed these vehicles. Not until the successful landing of VENERA 7 in December of 1970 was it finally confirmed that Venus has a surface pressure equivalent to being 990 meters (3,300 feet) beneath an Earth ocean, followed by temperatures one hundred degrees hotter than recorded by MARINER 2. Larry Klaes klaes@advax.enet.dec.com or ...!decwrl!advax.enet.dec.com!klaes or klaes%advax.dec@decwrl.enet.dec.com or klaes%advax.enet.dec.com@uunet.uu.net "All the Universe, or nothing!" - H. G. Wells