The Great Escape
The Martian Festival
Or, A Pretty Realistic & Informative Look Focused On Olympic
I wrote the following over a decade ago to post in the USENET newsgroup
I had hoped to start all sorts of discussion and whatnot, but all that
happened was that one reply came back to me. Sigh. As is Well Known, the
best way to inspire a net.discussion is either to say something that is
obviously wrong (and get flamed) or state a belief that disagrees with
other people's (and get flamed). I tried again a couple years later, and
got one reply, but it was from someone else. At least they said my posting
MacDonald Observatory produced a radio spot called Star Date, and for
a while they also posted the script to sci.astro. That had stopped a little
while before I wrote this, so I thought I'd follow their pattern. I guess
you'd have to call it a parody, but I thought of as a salute too. The scripts
ran something like this:
The Martian Festival is held each vernal equinox. More about the
events on Deimos -- after this.
March 32, 2187: The Great Escape
What good is a moon that's 15 km long - on it's longest axis? About
the only use found so far is athletics. For several Earth decades now,
Martian immigrants have been finding fascinating ways to take advantage
of Deimos' low gravity. On each Martian vernal equinox, the whole solar
system turns it attention to the Great Escape.
This year's Escape has several events:
The officials in charge of the Great Escape report that they have selected
a new company to provide rescue beacons to the participants. Along with
several more recovery vehicles, they are confident that last year's debacle
will not be repeated.
The original jump-off-the-moon event. Deimos' escape velocity is too
high for all but a few athletes to jump off without a running start. The
winner is the person to attain the highest terminal velocity.
The Precision Jump
Several targets have been set up on Deimos for this event. Entrants
choose two targets and jump from one to the other. Deimos's odd shape has
made this one of the favorite events. Points are awarded on accuracy and
landing style, and are multiplied by a difficulty factor for their jump.
Three jumps are made with the sum being the final score.
The Long Jump
Here the goal is to jump the highest - and return. The winner is the
person who stays off Deimos the longest time. Entrants who reach escape
velocity are disqualified.
The Low Jump
You can't jump directly into orbit because your trajectory will bring
you back to your starting point on the surface. In this event, entrants
take a running start and jump into a shallow climb. Somewhere along the
trajectory they throw a pair of hand-held weights to gain a little more
speed and inject themselves into a low orbit. The winner is the entrant
whose orbit has the shortest period. Entrants are disqualified if they
touch Deimos after their jump or if they throw their orbit injection weights
into orbit (hard to do, but you really don't want to free fall into one!)
Since the winning orbits are around Deimos' longest axis, officials require
everyone to jump in the same direction.
This is the only team event. The object is to move a "baton" around
Deimos faster than orbital dynamics of free fall would allow. Contestants
put themselves into highly elliptical orbits in the same plane, but shifted
by a large angle. They're timed so that a contestant heading out meets
a teammate heading in. The baton has a guidance computer that controls
a small thruster. The outbound contestants throw the baton to the next
person and the baton rendevous with him. Therefore, the baton passes between
people moving at speeds well above the circular orbit velocity. Each year
race officials further limit the amount of propellant, thereby increasing
the importance of accurate orbits and good passes. Despite the annual outcry
from contestants, a new record has been set each Escape.
Script by Ric Werme, content by Werme and Dave Spain. (c) 2187 McAuliffe
Observatory, Olympus Mons, Mars
Vital statistics of Deimos:
Dimensions: 10 x 12 x 15 km
Density: 5.521 g/cm^3 (Most recent measurement)
[Deimos' odd shape helps make the Great Escape the favorite part of
the Martian Festival. However, it plays havoc with computing the gravitational
field. Therefore, the following calculations have been done for a sphere
12 km in diameter.]
Escape velocity: 10.5 m/sec
Low altitude orbital velocity: 10.5/sqrt(2) m/sec
Period of above orbit: Easy, do-it-yourself calculation
As I noted at the top, I had hoped to inspire a lot of discussion about
this, but no one worked through some of the math. It was a pity, as I uncovered
an interesting relationship I never knew about before. When I wrote this,
I couldn't find the density of Deimos, so I substituted a better known
density, one known to four places, Earth's. When I discovered the period
of a low orbit arond Deimos was about 90 minutes, I went off and discovered that
density determines the orbital period. Radius cancels out! I have since seen
a value for Deimos' density, I assume derived from the passage of a Viking
orbiter. Not surprisingly, it's less than the 5.521 above, but I've never
thought through the implications to my story. As is, the 90 minute orbit is
really too long to make the Great Escape an exciting event.
Contact Ric Werme or
return to his home page.
Last updated 1999 August 6.