Ralph D. Lorenz Home Page

Updated November 2019

current address

Johns Hopkins University Applied Physics Lab

11100 Johns Hopkins Road, Laurel,

Maryland 20723-6099, USA

tel. 443-778-2903 fax. 443-778-8939

Apollo Splashdown Tests at North American Aviation. Side View (200 MB) Top View (440 MB) Underwater View! (900 MB)

Review Article on the history and applications of dust devil studies.


Planetary Climate before the Space Age
Createspace, June 2017
Cassini-Huygens Owners Workshop Manual
Haynes, April 2017
Dune Worlds
R. Lorenz and J. Zimbelman
Springer, May 2014

R. Lorenz and J. Mitton
Titan Unveiled
Princeton University Press, April 2008
Buy from Amazon.com
Harland and Lorenz
Space Systems Failures
Praxis/Springer,May 2005 Buy from Amazon.com
Ralph Lorenz
Spinning Flight: Dynamics of Frisbees, Boomerangs, Samaras and Skipping Stones
Springer/Copernicus,Summer 2006 Buy from Amazon.com

R. Lorenz and J. Mitton Lifting Titan's Veil
Cambridge May 2002 Buy from Amazon.com
Kleidon and Lorenz
NonEquilibrium Thermodynamics and the Production of Entropy
December 2004 Buy from Amazon.com
Ball, Garry, Lorenz and Kerzhanovich
Planetary Landers and Atmospheric Entry Probes
Cambridge, March 2007 Buy from Amazon.com

TV Appearances

Ralph has appeared extensively on TV in connection with his scientific work, and can consult on possible planetary analog locations for shoots.

Paper on the composition of Titan's seas - why Ligeia Mare is 'fresh' (methane-rich), flushed with rainfall, while Kraken Mare has a higher 'salinity' (ethane,propane etc.), rather like the Black Sea/Mediterranean. My APL web page has a somewhat up-to-date publications list.

Pictures and near-IR video of active volcanos on Vanuatu.

Papers and Data on dust devil field research. Includes pressure time series and some hundreds of vortex detections.

Paper and Datafile on a radar map of Titan seas, analytic bathymetry and tidal flows through the Throat of Kraken.

Pictures from trip to Namibia.

My first paper on Tatooine !

Paper accepted for publication in the journal Geomomorphology on the movement of barchan dunes at the Star Wars film set in Tunisia.

Global Topographic Map of Titan Images, Data and Paper

Researches on Moving Rocks at Racetrack Playa, Death Valley : A paper describing meteorological conditions at the playa. A paper showing that the principal role of ice in facilitating movement is by providing buoyancy that lifts a rock off the lake bed ('rafting'), not the augmentation of wind drag area ('sailing'). A paper examining the record of changes, suggesting climate change has caused the frequency of track formation to decrease by a factor of 4 since the 1970s. Finally, in winter 2013/2014 Lorenz and Jim and Dick Norris observed and documented rock movement, in a paper published in PLoS One and a companion paper submitted to Earth Surface Dynamics . Pictures and Videos are at www.racetrackplaya.org

Kite camera picture at White Sands National Monument.

Pictures from trip to the United Arab Emirates.

Pictures from trip to frozen methane seeps in Barrow, Arctic Alaska.

Pictures from trip to the Lawn Hill impact structure, Australia.

Pictures from Planetary Dunes trip to Flagstaff and Meteor Crater.

Pictures from Trip to see Annular Solar Eclipse at Bryce Canyon, UT.

120MB! Timelapse Movie [(c) Ralph Lorenz, 2011] of combined sand and snow movement at GSDNPP in February 2011.

Pictures from Trip to Ethiopia - the Rift Valley, the Danikil Depression including Dallol and the Erta Ale lava lake!

Timelapse Movie (m2v) [(c) Ralph Lorenz, 2011] of wind ripple movement over several days at Great Sand Dunes National Park, Colorado.

Quicktime (5MB) [(c) Ralph Lorenz, 2011]

Some Notes on the setup. A paper describing the ripple movement over 70 days, and its relationship to wind conditions, has been published in Geomorphology.

Pictures from Trip to Egypt.

Timelapse movies [(c) Ralph Lorenz, 2010] of Simple aeolian ripple motion over an hour or so and Compound ripples on a linear (seif) dune at Quattani, Egypt. (NB better versions will be forthcoming as soon as I get some video-editing software. My raw movie data is higher resolution and longer than shown here, contact me for details.) A

paper on flight power requirements for airships, airplanes and helicopters on Titan.

paper has been published in Aeolian Research.

Video of lecture on Titan at SETI Institute, August 2010

Pictures from Trip to Xian and Jaiyuguan, China

Pictures from BBC film shoot in Alaska

Pictures from field trip to Australian outback

Pictures from field trip to Tunisian desert

Pictures from trip to Waqf as Suwwan impact structure, Wadi Rum, Dead Sea and Petra, Jordan

Titan Bumblebee concept for a 1kg vertical take-off UAV drone to explore around a lander EPSC08/ IPPW6 presentation . A paper with full details was published in JBIS in 2008.

Titan's rotation reveals that it has an internal water ocean paper published in Science Magazine 21 March 2008.

Preprint of B. Stiles et al., Astronomical Journal, 2008 paper on measuring the rotation state of Titan from radar images. pdf

Dunes on Titan.! See paper published in Science Magazine 5 May 2006. Cassini RADAR image below

bigger version file. Large segment of T8 radar swath showing long dunes image A picture of me in the Pinacates dunefield in Mexico. I have processed some SIR-C Shuttle Imaging Radar data of Namibian dunes, perhaps the best terrestrial analogue jpg These same dunes are seen nicely in this Optical image taken by space shuttle astronaut with digital camera (see eol.jsc.nasa.gov)

Ralph with Huygens Probe at the European Space Operations Centre in Darmstadt, Germany for the Huygens descent to Titan (This is the SM2 test article, used in parachute trials from a balloon in Sweden in 1995)

Huygens lands on Titan!!


A short video showing how the multipath interference pattern observed in the Huygens radio signal strength post-landing can be demonstrated with $10 of electronics using ultrasound. 2MB MPEG file. 0.5MB WMV file.

The sound of Huygens' dynamic descent.

A sound file made by encoding (specifically modulating the frequency of the tone with the strength of the radio signal) the strength of Huygen's signal as received by Cassini as a tone - the dynamic sound reveals the spin and swinging of the probe during its descent. 4MB WAV sound file. press release gives background info - see also UA News and ESA For trajectory reconstruction of a different kind, see paper on paper on frisbee dynamics

Ralph built the Huygens penetrometer (with help!!) in 1994. The penetrometer is part of the Huygens Surface Science Package (SSP) - John Zarnecki at PSSRI - The Open University in Milton Keynes, UK is the Principal Investigator. 10 years later, at -180 degrees C and nearly a billion miles from Earth, the penetrometer worked first time, recording the impact force over about 1/20 of a second as Huygens hit Titan at about 5 m/s at 13.45 CET on 14th January 2005. For further details and the preliminary interpretation ('creme brulee') see Datasheet on Huygens Penetrometer and Titan Result. and paper on the penetrometer detailed design.
Methane Rain on Titan.
Titan may have a hydrological cycle like Earth's, as evidenced by observations of changing clouds and river valley networks on Titan, but with methane as a working fluid. In Titan's low gravity, thick atmosphere environment, raindrops could be up to 9.5mm across and would fall at only about 1.5 m/s - about as fast as large snowflakes fall on Earth. For details see paper. (Plan. Space Sci, 1993). Note, that the tiny amount of sunlight reaching Titan's surface is not enough to drive a vigorous cycle - only on average 1cm per Earth year of rainfall - see Weather on Titan in Science Magazine (20 October 2000) However, since Titan's atmosphere can hold large amounts of methane, this low average rainfall may be manifested as massive once-in-a-century downpours.....(this paradigm also fits with the relatively small cloud cover percentage on Titan, which can be predicted by a heat engine theory, see paper. published in GRL just prior to the Huygens encounter). i

For papers on Titan, see publications list below. For radar images of Titan, go here



New items

Revised publications list

See paintings by my sister Kirsty (we're twins)

Ralph's Frisbee Research

Tucson Observing Weather

BBQ Chicken recipe

Pictures (including curling), Scotland December 2003

Pictures from Japan, December 2003

Pictures from falconry trip in Scotland, August 2003

Artist's impressions of Titan

Article in Science Magazine The Glitter of Distant Seas" on the detection with the Arecibo radar of lakes/seas on Titan

Article in Science Magazine < Full Steam Ahead, Probably> on the Statistical Mechanics approach to Maximum Entropy Production in the climate system

Pictures from holiday in Scotland, Christmas/New Year 2002

Beyond Daisyworld workshop picture

LPL Fieldtrip to Mt St Helens, Channeled Scablands and Colmbia River Basalts Pictures (large)

Article in Astronomy.com on Titan's Tidal Winds

Article in Astronomy.com on December 2001 Titan Occultation

Article in Astronomy.com on Arecibo Radar Observations of Iapetus

IDL code for HST basemap on which to overlay Cassini observing plans

Pictures from trip Vannes (France) and Dollar (Scotland), April 2002

Pictures from holiday in Scotland, Christmas/New Year 2000

Year 2000 paper on post-Cassini exploration of Titan. First articulates the concept of a battery-powered rotorcraft (imagined at the time to be a helicopter, but could just as well be a Titan quadcopter) that recharges from a radioisotope power source while sitting on the ground. Notes that it takes 38 times less power to hover on Titan than on Earth.

Amateur Titan Spectroscopy/Photometry science rationale (pdf)

A survey of types of useful amateur observations of Titan (pdf)

Paper from Planetary and Space Science on amateur observations (pdf) ...

Article on Weather on Titan in Science Magazine (20 October 2000)

Roof Tests of Huygens SSP tilt sensors on DISR tilt/spin table

Cassini Earth Swingby Radar Observations of the Eastern Pacific and South America

Video Astrophotography Images

Datathief in IDL

Other stuff

Ralph's Spacecraft Impact Penetrometry Page

Current Activities

Pictures from a flight around Tucson

'Death of a Watery World' Article on Mars in New Scientist

Pictures of impact geology and wildlife from trip to South Africa

Digital Pictures from the LPL fieldtrip to Yellowstone National Park Geology and People

Digital Pictures from the fieldtrip at the recent Giant Meteorite Impact conference in Sudbury, Canada

Digital Pictures from the Paris Air Show and recent trip to Mount Saint Helens.

Other Stuff

Recent Projects

  • Modelling of lava flows and thermal emission on Io
  • Design Study of Deep Jupiter Probes (under JPL Contract)
  • Analysis of HST Images of Titan (with Peter Smith and Mark Lemmon )
  • Titan observed by HST at a variety of wavelengths: 336nm (UV), 439nm (Blue) 547nm (Green) 588nm (Orange) 673nm (Red) and 889nm (Near-IR methane band). The colours above aren't quite right (as you wouldn't be able to see the first and last image!) but help to make a mental connection between appearance and wavelength.
  • Image looks best with squared data numbers to enhance contrast. Also available, straight data numbers or cubed for extreme contrast. The variation of limb-darkening is apparent - in the UV the disk is flat, like our Moon, while at visible wavelengths it is more like a Lambertian scatterer. The North-South asymmetry (which varies with season) is strongest in the blue, but small in UV and red. The methane band has the asymmetry reversed.

    Previous Projects