Ralph D. Lorenz Home Page
Updated November 2019
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
| 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 |
Princeton University Press, April 2008
| Harland and Lorenz |
Space Systems Failures
| Ralph Lorenz |
Spinning Flight: Dynamics of Frisbees, Boomerangs, Samaras and Skipping
| R. Lorenz and J. Mitton
Lifting Titan's Veil |
Cambridge May 2002
| Kleidon and Lorenz |
NonEquilibrium Thermodynamics and the Production of Entropy
| Ball, Garry, Lorenz and Kerzhanovich|
Planetary Landers and Atmospheric Entry Probes
Cambridge, March 2007
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
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
Researches on Moving Rocks at Racetrack Playa, Death Valley :
describing meteorological conditions at the playa.
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').
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
Earth Surface Dynamics .
Pictures and Videos are at
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
Pictures from trip to the Lawn Hill impact structure,
Pictures from Planetary Dunes trip to Flagstaff and Meteor
Pictures from Trip to see Annular Solar Eclipse at Bryce Canyon,
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
on flight power requirements for airships, airplanes and helicopters on
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
with full details was published in JBIS in 2008.
Titan's rotation reveals that it has an internal water ocean
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.
Dunes on Titan.! See
published in Science Magazine
5 May 2006. Cassini RADAR image below
bigger version file.
Large segment of T8 radar swath showing long dunes
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
These same dunes are seen nicely in this
Optical image taken by space shuttle astronaut with digital camera
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
Huygens lands on Titan!!
FOR CHARM TELECON. 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
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
gives background info - see also UA
News and ESA
For trajectory reconstruction of a different kind, see paper on
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
Huygens Penetrometer and Titan Result. and
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
(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
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
published in GRL just prior to the Huygens encounter).
For papers on Titan, see publications list below. For radar images of Titan,
by my sister Kirsty (we're twins)
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
Beyond Daisyworld workshop picture
LPL Fieldtrip to Mt St Helens, Channeled Scablands and Colmbia River Basalts
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
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
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
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