John Pazmino
 2006 September 19 
    I attended the conference 'New trends in astrodynamics' at 
Princeton University on 16-18 August 2006. I was  a delegate from both 
NYSkies Astronomy Inc and the New York City chapter of National Space 
    This is the third annual running of this conference, whence its 
short name 'Astrocon III'. The inaugural run was in 2004. While there 
were talks on new trends in astrodynamics at other astronomy and 
astronautics conventions, 'New trends in astrodynamics' is today the 
dedicated annual meeting for this subject. 
    All activity was in Peyton Hall of Princeton University or at 
Triumph, a nearby restaurant. All activities were a level walk from 
each other, the hotel, and the Princeton train station. 
    The conference ran from Wednesday, the 16th, morning, thru Friday, 
the 18th, evening. I went to Princeton on Tuesday afternoon and 
returned to the City on Saturday morning. That way I took in the 
entire event, even tho it meant two extra nights of lodging. 
    I was honored to present a talk 'Gravity behaves like that?'. This 
talk was assembled based on discussion with Dr Edward Belbruno, 
conference host, in May 2006. Belbruno is at Princeton University's 
Department of Astrophusical Sciences and at Innovative Orbital Design 
Inc. He also organized the first two astrcons. 
Train service 
    I rode a comet to this meeting! No kidding, I really did. The rail 
coach I sat in was one of the 'Comet' series of cars operated by New 
Jersey Transit. 
    From Penn Station, New York, trains leave for Princeton Junction 
about every half hour from dawn thru midnight or so. Both Amtrak and 
New Jersey Transit work Princeton Junction. While trains may skip 
certain stations along the way, just about every train stops at 
Princeton Junction. A similar situation applies for the trip from 
Princeton Junction back to Penn Station. 
    Princeton Junction is the station on the Northeast Corridor line 
of New Jersey Transit, running along the spine of New Jersey. To get 
to the Princeton University itself, you must transfer to a shuttle 
train, the 'dinghy', at Princeton Junction. The extra ride is only 
five or so minutes but it would be a three-kilometer round-about walk 
without it. 
    Be sure to have a ticket to 'Princeton' and NOT to 'Princeton 
Junction'. If you goof, the conductor on the dinghy collects the 
extra fare. Going back to Penn Station, ticket dispensers at the 
Princeton station collect the combined fare. 
    There is a caution about this transfer. You got FIVE MINUTES, at 
most!, to get your butt off of the one train and on to the other. 
Seasoned riders poise at the first train's doors, then gallop to the 
other train. Follow -- and keep pace with -- them. 
    If you miss the connection, take a seat, soak up the breeze. The 
next train comes along in no more than half an hour. 
Besides train 
    Princeton is served by NJT buses from all over New Jersey, Coach 
USA intercity bus, shuttle bus from Newark Airport, and campus 
minibus. I saw buses with other markings, so there could be services I 
    Air service is at Newark-Liberty airport, which in tu4n is tied to 
the NJT railine. Service is also at Philadelphia airport, with train 
or bus links to Princeton University. 
    Princeton is nestled among several major highways, including the 
New Jersey Turnpike (I95). Parking is included with the hotel room and 
is free at the conference hall. For other parking, there are metered 
spaces on and off street. 
    Princeton, New Jersey, developed out of the colonial English town 
and college in the center of the state. The town retains that flavor, 
mixed with some ersatz architecture on the campus. Streets have 
typical British-sounding names. Except for its 'southern' latitude, I 
could have been in the Hamptons of Long Island or in Cambridge, 
    Like other similar towns in the American northeast, the town and 
college grew into each other, with a weak stability boundary between 
the two. Streets and shops were filled with collegiate folk and off-
campus residents. I don't know if there is a 'town-&-gown' syndrome 
here, like in Greenwich Village and New York University or Morningside 
Heights and Columbia University. 
    The Europe delegates were awed at the overall beauty of Princeton, 
town and college. Universities in Europe are typicly unadorned by 
lawns, gardens, trees, paths. They are more like Hunter College or 
Manhattan Community College. There is no real campus. 
    Luminous graffiti abounds in the sky of Princeton, with a curious 
mix of sky-friendly and sky-hostile outdoor lighting. On the whole, 
street and area lighting is pretty miserable, with glare and spray of 
light into the sky. Stores and other small properties, on the other 
hand, generally have sound outdoor lighting. Their lamps are shielded 
or aimed at their target. 
    You better enjoy walking. Most New Yorkers don't mind long walks, 
but some of us in car-country may quail. The walk is entirely on level 
ground with only gentle slopes. Most streets have sidewalks and ADA 
curb cuts. Traffic control points often have pedestrian-priority 
    Cars travel at modest speed, allowing for casual jaywalking. 
However, at many corners cars enjoy, and pedestrians suffer, right-
turn-on-red. Keep alert! 
    Street signs are sometimes hidden or missing. Bone up on 
orienteering with a street map and the Sun. Recall that Princeton is 
both a town and a campus. You'll come across, in seeking directions, 
people who know the town but not the campus, and vice versa. 
    From the train station to the hotel or downtown Princeton is about 
a kilometer. From the hotel to the conference in Peyton Hall is also a 
kilometer. With the mild, sunny, breezy weather, my walking was 
    The conference hotel was Nassau Inn, in the center of Princeton 
and a walk from just about anyplace in town and on campus. This hotel 
keeps the English coziness with lots of rugs, wood furniture, soft 
chairs, mellow lighting. Its appointments are thoroly modern and 
expertly provided. In general for any visit to Princeton this is the 
place to lodge at. Other hotels are beyond walking distance from 
campus and downtown. 
    My room was in an annex, of modern motif harmonizing with the old 
structure, reached by skywalk. The room was entirely comfortable, 
acclimatized, and furnished with all the usual hotel amenities. A copy 
of USA Today was delivered each morning; more on this a bit later. 
    For meals at the hotel, the restaurant on the first floor offered 
good selections at pleasant prices. I took supper there on Tuesday 
night and breakfast on Saturday morning. 
Poster board
    One characteristic of mine when on travels is to use the room door 
as a poster board. Until 2002 I composed a hometown poster with scenes 
of New York City. These I collected from tourist books and ones I took 
myself. I pasted them in collage on a flipchart sheet, which I hung to 
the room door with low-tack masking tape. 
    The hometown poster served two purposes. First it generated 
interest in the City, sparking conversation among the delegates. 
Second, it made it easy to find my room in a corridor of similar-
looking room doors. 
    Alas, my hometown poster was confiscated at the AAVSO convention 
in hawaii in July 2002. That's a whole other story involving World 
Trade Center and National Park police. I didn't yet build a 
    For meetings since that episode, I use the room door to display my 
talk. I print out the slides, arrange them in order, tack them up. At 
these meetings, delegates in my section of the hotel love it! It may 
induce them to put up their presentations on hotel doors at other 
    At 'New trends in astrodynamics' one delegate told me he showed 
the slides on my door to his colleagues! He explained thru them 
several astrodynamical features, which in fact was the whole pwah of 
my talk!! 
    The conference fee included a banquet dinner on Thursday night and 
refreshments for the breaks. The latter consisted of cookies, coffee, 
rolls, sodas, and bottled water. These were replenished so only at the 
end of each day did they run out. I did my duty to rescue lonely 
sweets for a late night snack at the hotel. 
    The banquet was a glatt Italian eat-'em-up at Triumph in downtown 
Princeton. After entering what looked like a small pizzeria, a gentle 
down slope brought the delegates to a cavernous consumptorium of a 
couple hundred seats on three floors! The place was filled with 
college folk and their chatter. 
    We had a party room upstairs for ourselfs. Drink and food were 
plentiful, all Italian-style, no schlock-a-roni. Beers included 
several local blends, which I found quite hearty. 
    Lunch was taken at a college cafeteria a ha'K from Peyton Hall. 
The food was tasty, filling, cheap. On my first lunch, under mistaken 
instructions, I missed this cafeteria. I was told to go to a certain 
corner and look for a huge building I couldn't miss. 
     I did see a huge building, about 15 stories tall. I didn't miss 
it. And I didn't get in it! This tower was circumvallated by 
construction barriers. I ended up going back to downtown and getting a 
bite at one of the many shops there. 
    Corrected directions worked on Thursday and Friday. I had to cross 
the corner first and then spot the proper, other, huge building. 
Peyton Hall
    Peyton Hall is the home of the Department of Astrophysical 
Sciences. It is situated next to the football stadium! There was no 
game during the conference. in fall of 2004 I with other NSSers went 
to Peyton Hall to hear Dr Richard Gott speak on space and the survival 
of humankind. Cheering and narration from a game running then filtered 
into the hall. 
    'New trends in astrodynamics' convened in the first floor theater. 
Breaks were taken in the main lobby, with refreshments, handouts, and 
book display. Restrooms were on this same floor. 
    It was easiest to enter and leave thru the 'back' entrance, 
fronting Ivy Lane, than thru the front. Construction adjacent to 
Peyton Hall, for a new science hall, blocked roads on that side. More 
over, the back entry has a car park across the street. 
    A side room was available for Internet link via terminals. The 
delegates carried out email  and web searches. 
    Most delegates, of the 100ish in all, came from various astronomy 
and space institutes in the United States and overseas. Countries 
represented were Denmark, France, Germany, Israel, Italy, Netherlands, 
Russia, Scotland[!], Spain, Sweden. 
    Everyone spoke and understood English with good grammar and 
vocabulary. All the presentations were in English. I had trouble at 
first with the thick accents of some speakers, but their underlying 
English did come thru after a while. 
    All delegates were thoroly versed in aerospace or astronomy, but 
not always in both. Part of the purpose of this convention was to 
bring the two 'camps' together to learn about the opposite discipline. 
    I was the one home-based delegate! While National Space Society is 
a national advocate for space exploration with professional staff in 
its Washington DC headquarters, I represented the New York chapter. 
This is made of mostly home-based spacefarers. For NYSkies, a newer 
service in New York, lata mente supports home-based astronomy. 
    My off-campus background was no obstacle in general commingling 
with the other delegates. They conversed with me as easily as they did 
with campus delegates. 
NYSkies and NSS
    Delegates noted my affiliation with National Space Society and 
NYSkies Astronomy Inc. Unless they were aware of astronomy in New York 
City, they didn't hear about NYSkies. An other cause is that NYSkies 
is only a year and half old, quite new among astronomy services. 
    I was floored by the occasional query about Allies in Space! 
Neither NSS nor NYSkies started to advertise this event. It takes 
place on November 4th on Manhattan. 
    It seems that word-of-mouth is spreading thru the spacafaring 
community. Because I did not have in hand a signed rental agreement 
for the Allies in Space venue, I was careful not to mention it. I sent 
inquiries to the website '' for latest news. 
    As for National Space Society, I caught what could be a disturbing 
situation. Many of the older delegates know NSS. Many were in NSS 
chapters at one time or other, A couple were members of the L5 Society 
that preceded NSS! Because my badge noted only 'National Space 
Society' I reminded that I represent only the NYC Chapter, not the 
head office. 
    Among the young folk, almost NO ONE heard of NSS! If they hazarded 
a guess, to start a convo, it was wildly wrong. NSS is a laboratory?, 
aerospace firm?, institute?, publisher?, and so on. Even after I gave 
a quick explanation, they still offered that they never heard of it. 
    I pointed the delegates to the NSS and NYSkies handouts I left on 
the litterature table in the lobby. By the close of the meeting on 
Friday there were only scattered copies left. These I discarded. 
    Pluto would have been a routine topic at this conference, being 
the target of the New Horizons probe that employs many astrodynamical 
principles in its trajectory. Recall that USA Today was left at the 
room door in Nassau Inn? On Wednesday, the first day of the meeting, I 
picked it up when setting off for Peyton Hall. I tossed it on my bed. 
to read it when I get back that night. 
    At Peyton Hall I strolled into a gaggle of delegates munching 
sweets and sipping coffee. One word floated above all: Pluto. 
    One delegate showed me the USA Today. On the front page was an 
article, with a cartoon chart!, about the IAU treatment of Pluto. The 
IAU meeting was running in mid August in Prague, Czech Republic. One 
of its principal topics was the definition of a planet and what to do 
with Pluto. IAU posted a committee to offer proposals for a full vote. 
    So is Ceres, Charon, and 2003-UB313! IAU has to consider expanding 
the solar system to TWELVE planets, up from today's nine. Pluto was 
NEVER deplanetized, altho IAU tried to in 1997. 
    The IAU committee proposed that a planet be a Sun-orbiting body 
that's large enough to round itself thru self-gravity. Ceres certainly 
fits this definition. Several other large asteroids are rounded by 
self-gravity, but they were not mentioned as becoming planets. 
    Charon is now a moon of Pluto. The loophole is that the center of 
mass of the Pluto-Charon system is between the two bodies. Each does 
'orbit the Sun', swerving from one side to the other of the path for 
this center of mass. 
    Pluto would be the first true binary planet. For decades, Earth 
and Moon were treated as a double planet, on account of the large 
fraction of mass in the Moon. However, the center of mass of the two 
is inside the Earth. The Moon 'orbits the earth', not the Sun. This is 
in spite of the concave path the Moon pursues around the Sun. 
    2003-UB313 poses a problem. We know too little about it to say it 
is round. The thing could be a jagged lump, too weak to smooth out 
into a ball. It could be a loosely-bound aggregate of city-size 
boulders. Its size is still only estimated based on photometry and 
    We all debated the pros and cons of the proposal. One thing was 
forte mente stated by every one. No one will accept an IAU-declared 
deplanetization of Pluto. Several balked at taking in the far outer 
new icy blobs as planets. Let us first learn more about them first 
before assuming they fit the new definition. We can later enroll them 
as planets if they qualify. 
    We bantered about a corollary question: What's a satellite? 
    This sounds trivial. A satellite is a body that orbits a planet. 
End of story. The wrinkle is that the body has to be individually 
identified and tracked. The stones making up Saturn's rings are not 
satellites as such. 
    Now for the killer. This whole convention concerns such issues as 
temporary satellite capture by, typicly, Jupiter! Jupiter snares up 
comets, makes them orbit him for some years, then releases them into 
new solar orbits. 
    Shoemaker-Levy-9 was discovered as a comet while in Jupiter orbit. 
If we found it several years earlier and it was dormant at the time, 
we would likely have listed and named it as a satellite. A chaotic 
one, like the other outer moons of Jupiter, but a moon it would be. 
Then, bingo!, it breaks open from the tides of its deep swingby of 
    Suppose we found comet Helin-Roman-Crockett while it was orbiting 
Jupiter. We book, name, and follow it as a new moon of Jupiter. It, 
too, would be a chaotic outer moon. Then it leaves Jupiter and 
migrates into its own heliocentric orbit! We lost a satellite and 
gained a comet? 
    The speakers delivered their papers by digital projection or 
overhead, or viewgraph, transparencies. I at first planned to cut a 
CD, like I do for AAVSO, but then learned that each speaker must bring 
his own computer with the show loaded into it. With no desire to 
scrounge up and lug along a laptop, I stamped out the transparencies 
from my digital images. 
    It was lucky that I went with overheads. I reviewed my talk on 
Thursday night and found I had too many slides for my 25-minute time 
slot. I pulled out a few extras. At the conference on Friday, before I 
was called to the podium, I yanked out more extra slides. With a 
digital show I would have frittered time in the talk to manually skip 
over these slides, they being embedded on the CD. 
    This actually works out best for my repeat presentations for NSS 
and NYSkies. I would need a computer for them, also, to use their 
digital projectors. I can now use their overhead projectors. 
    The digital presentations caused substantial deadtime between 
speakers. Because each had his own computer, the previous computer had 
to be unhooked from the projector and the new one attached. This chore 
ate up a couple minutes. Then there were niggling glitches in the 
computers. A conference technician jumped in to get things working. 
    The presentations were grouped by broad topic for each morning and 
afternoon session. There were two phyla: spaceflight and celestial 
dynamics. I do not try to summarize many papers here, due to their 
complexity and number. I picked out just two, one in spaceflight and 
one is astrodynamics. Others I comment on as a group. 
    Abstracts and roster of speakers are on the convention website 
''. You may also visit the website of 
each speaker at his institution. The conference procedings will be 
issued around yearend 2006. 
    There was a keynote speaker on Wednesday night, Dr Richard Gott, 
Princeton University. He gave a shorter version of his 2004 space and 
human survival talk. This may be his theme at 'Allies in space'. 
    Wednesday night also featured the cinema 'Day the Earth stood 
still'. As corny as it is, it is a wonderful harmless sci-fi film. The 
younger American delegates recall it from reruns or remakes; us olders 
saw it in the flesh in the 1950s. 
    Some of the overseas delegates were a bit wowed at the theme. In 
their home countries, there are very few 'flying saucer' cinemas for 
public entertainment. When I explained that in an other cinema 'War of 
the worlds' the Martians landed in Grover's Mill, a town only ten or 
so kilometers from the convention, they were thoroly amused. 
Greg Olsen 
    Greg Olsen recounted his experience as a space tourist on 
International Space Station in 2005. He was a rider, not a crew 
member. There was little he did in running the station during his 8-
day visit. Never the less, he gained a deeper appreciation for the 
dangers of outer space and bravery of the people who travel thru it. 
    Olsen's tour is well known to spacefaring fans. I offer here just 
a few extra tidbits. The Soyuz capsule was originally built as the 
housing for 50-megaton H-bombs on Soviet ICBMs! It was cobbled into a 
human capsule in the 1960s and since has changed very little. Olsen's 
vessel, while newly minted, is a copy of a 40-year-old design. like 
riding a newly built 1965 Ford. 
    The launch, rendezvous, docking were totally automated with no 
action by the capsule crew. Olsen rode up with two Russian cosmonauts. 
There wasn't much for the crew to do because they were crammed into a 
2-meter ball with no room to move around. 
    One feature of a Russian launch freaked Olsen out. People were 
allowed to wander around the rocket while it's on the pad and 
preparing for liftoff. Only during the countdown is the area cleared. 
He was treated, for example, to a bon-voyage party with civilian VIPs 
and family at the base of the rocket. 
    Because the ride to ISS can take much of a full day, and the crew 
is sitting tightly together with no way to answer a nature call, 
everyone wears diapers.  On ISS men use a suction tube for urine; 
women wear a sponge that's discarded when wetted. Both genders use a 
chemical toilet for bowel movements. Olsen noted that the food diet 
and changes in metabolism kept him from bowel movement for SIX DAYS. 
    He was in space for too short a time to develop any space effects 
of health. The worse to happen is that a tourist may aggravate a 
existing health problem that wasn't caught in the training and testing 
before the flight. 
    Two common situations, still bedevilling Russia and America, are 
sea-sickness and claustrophobia. Phobiacs wash out in training because 
they have to simulate the Soyuz and ISS ride several times. Sea 
sickness is handled by lots of bark bags. They must be cupped tightly 
around the mouth to catch every thing, then quickly sealed shut. 
Neither country yet found a way to tell before flight if a crew member 
may get sea-sick. 
    He had to stay within the Russian part of ISS, never venturing 
into the US section. He wore only Russian spacesuits and spoke Russian 
during his stay. When tourist spacewalks start in 2008, the tourist 
must leave and enter only thru the Russian hatch and be accompanied 
only by Russian cosmonauts. The US so far wants nothing to do with 
space tourism. 
    The spacesuit was custom made for his contours. Since no one else 
can wear it, it was given to him after the flight as a souvenir. Other 
cosmonauts keep their suits, too. If a cosmonaut goes back up in a 
later flight, a new suit is cut for him.
    He wanted to take pictures of the descent, there being very few 
good ones of this phase of a Soyuz flight. He lost his camera on ISS, 
a disgustingly easy occurrence in zero-G. Unless an item is positively 
restrained, it will eventually drift away into some out-of-reach 
cranny of ISS. With no camera, he contented himself with the view out 
of the window on the way down to Earth. The camera was found later and 
its pictures were sent back to Olsen via downlink. 
    The descent capsule is the middle of the Soyuz ensemble. The 
retrorocket is jettisoned to burn up in the air. The round ball is 
filled with rubbish and other discards. Then it's jettisoned to decay. 
The middle section holds the crew to touch down on land. 
    This middle module is steered by spinning and tumbling it! The air 
stream presses against its shifting surfaces to manoeuver the craft. 
As a result, the ride felt like being in a barrel rolling down a bumpy 
hill. This technique was the topic of one aeronautics talk in the 
    The Soyuz is packed with survival supplies and equipment for both 
the up and down trip. Overwhelmingly Olsen's training was on survival 
tactics in space, on the ride up and down, and on the ground. It can 
take days for a retrieval team to reach the craft after touch down in 
a far away desert spot.
    There's no restriction on repeat flights, specially now with the 
extra-cost spacewalk on ISS. Olsen isn't planning an other trip, but 
if he does, it's a new $20 million fare ($35 million with a spacewalk 
and extended stay). There are only two seats per year for tourists. 
Edward Belbruno 
    Belbruno presented an innovative idea about pansermia, the 
dispersion of life-carrying material from star to star. In his idea, a 
particle is diverted from an interior orbit to an exterior orbit. This  
occurs when the particle passes thru the weak stability boundary of 
the planet. The new orbit sends the particle out of the star's planet 
    To reach an other star, the stars should be close and have low 
velocity relative to each other. Latent life would perish is the trip 
between stars is too long, mainly from destruction by biocidal 
    He studied open clusters for having many close stars with low 
relative velocities. Altho open clusters evaporate after several tens 
to hundreds of millions of years. In his modeling of star clusters, 
the ejection speed of the material from one star is fast enough to 
reach a neighbor star within a few million years. This is well within 
the life of the cluster and the safe transit thru radiation. 
    At the other star, the particle, in an approach path, is diverted 
by an outer planets via a pass thru its Belbruno region. The particle 
is shifted to an interior orbit where other planets may intercept it 
and let it deposit its life cargo. 
    The chances of a one particle to precisely leave one star and be 
captured at the next is minuscule. However, the transferred material 
will likely be a mist, cloud, spray of particles in uncountable 
numbers. The chances rise into the realm of plausibility. 
    Outside of his talk, during breaks, Belbruno noted a fascinating 
phaenomenon he's working on. It seems that it's easy for a comet to 
shift from one resonant orbit to an other via interaction with 
Jupiter's weak stability boundary. The transition from a 3/2 orbit 
exterior to Jupiter to a 2/3 interior orbit, or the reverse, seems the 
most common among comets. 
    The resonance ratio of an orbit is cited in the litterature as 
that of the periods of the two bodies or the number or laps. Thus 2/3 
could mean the comet has a period 2/3 that of Jupiter (about 8 years) 
or it runs 2 laps around the Sun to Jupiter's 3. In the latter case, 
the period is 18 years. The author must specify what the ratio means 
for his article. 
    Is there some rigorous demonstration that such transfers are  a 
general property of chaotic astrodynamics? Is there some deeper 
feature of gravity that favors 2/3 -> 3/2 or 2/3 -> 3/2 orbit shifts 
near Jupiter? Belbruno discussed such a mechanism and offered an 
outline for proving it in 1997. 
    I hazarded that if such a proof can be found, it could have 
enormous significance in earthly applications. Start with a stable, 
well-behaved, predictable state of a system. It then is put thru a 
chaotic, random-like process. Yet it emerges into a new stable quiet 
    More over, information from the initial state, in this case the 
resonant ratio, is carried thru the transition and modified in a 
simple manner into other information. The original information can be 
recovered by simply reversing the modification, in this case by taking 
the reciprocal. Hence, there could exist certain types of 
randomizing processes that really don't destroy information!  
    An other extension of Belbruno's work, in a broader sense, is in 
electric and magnetic interference. If we treat these fields as 
produced by 'bodies, poles and charges, we have the mother of N-body 
problems! In all my own years in the electric power industry and 
relating to colleagues in radio-based communications, the 
intermingling of fields is among the most devastating problems of all. 
Drop ours, fadings, hum, static, crosstalk, whistle, echo, and other 
annoying and disruptive effects come from the mixing of these fields. 
    I just never heard of any strong attempt to solve the 
electromagnetic 'N-body problem' or to find a work around for the 
troubles it causes. Perhaps some exchange is called for between the 
astrodynamists and the electromagnetic engineers? 
John Pazmino
    My own talk related the use of home computers, like the laptops 
brought by the delegates, can effectively demonstrate and illustrate 
many of the new trends in astrodynamics. Such computers have the math 
and speed to do the calculations and display the graphical results as 
well as the large-scale computers of only a decade or so ago. The new 
machines are so cheap, a couple hundred dollars for the system box, 
that litterally any home astronomer and spacefarer can acquire one. 
    Paralleing the hardware availability is that offering of reliable 
realistic software for dynamic simulations. I used dance in my talk 
but SolSysIm and ORSA are also good choices. 
    Dance, short for Dance of the Planets, is a commercial product, 
still at sale despite its vintage from the early 1990s. ORSA and 
SolSyIm are free downloads. I did not attempt to compare, rank, 
evaluate the softwares. 
    To simplify the talk, I used events with comets and Jupiter. These 
were Lexell, Brooks-2, Helin-Roman-Crockett, Gehrels-3, Oterma, and 
Shoemaker-Levy-9. I finished with Earth meets of asteroid 2004-MN4, or 
Apophis, because of their newsiness in spring 2006. 
    I showed the concept of chaotic behavior with Lexell and Apophis, 
temporary capture with HRC, Geherls-3, and SL9, resonant transfer 
orbits with Oterma and Apophis. Brooks-2 showed a simple gravity 
resist via a deep hairpin spin around Jupiter. 
    In the Q&A I learned that the term 'capture' means any interaction 
within the Belbruno region of Jupiter. I used the word to mean a phase 
of motion around Jupiter during the interaction, like a satellite. In 
my preparation for the talk I found only three 'satellite' events 
among comets: HRC, Gehrels-3, SL9. All the others were passbys with 
greater or lesser deflection of trajectory within the weak stability 
    The views, all generated by Dance, were either a bird's eye view 
of the solar system out to Jupiter or a closeup of Jupiter within the 
realm of his satellites. The perspective was inertial relative to the 
stars, not the more usual corotating frame.
    The details I'll give at my repeat talk at the NYC chapter meeting 
on September 9th and at NYSkies on September 21st. At these meetings 
I'll elaborate on the dynamical concepts, showing how they are within 
reach of the home spacefarere and astronomer. 
Solar sails
    In the sessions on spacecraft propulsion, many papers related to 
solar sails. At first, in the mindset of orthodox rocketry, solar 
sails seem like a silly way to travel about the solar system. In fact, 
they could, if perfected, be a useful cheap, low mass/fuel means of 
getting from planet to planet. 
    The problem to hand is that for the foreseeable future, a 
spacecraft's ENTIRE provision to survive its flight must be taken on 
board the craft at launch from Earth. This burden includes rockets for 
manoeuvering in space, entering orbit at other planets, and 
transferring from one target to an other. Such rockets are large, 
heavy, complex. They are prone to failure or detonation. Their fuel 
must be compounded, stored, handled, with substantial safety risk. 
    In the initial applications of the Belbruno technique to 
spaceflight in the 1990s, the rocket failed in some way. The craft was 
left with only a minimum of manoeuvering. That was all the umph needed 
to ride the weak stability boundary and complete the original mission. 
    Inverting the situation, endowing the craft with a tiny thrust 
system, the mission must exploit the Belbruno trajectory. Solar sails 
receive unlimited energy from the Sun, but deliver only the barest 
minute power output as thrust. In this way, space missions can be 
vastly cheaper, smaller, lower mass/fuel, less complex, safer. In turn 
this means a cheaper, simpler, smaller launch vehicle from Earth. 
    The downside is that the trip takes forever.  An example is the 
SMART-1 craft, which took some 15 months to reach the Moon. (It used 
tiny jets, not solar sails.) The mission, once arrived at its target, 
procedes just like a conventional rocket-driven one. SMART-1 is now 
doing superb mapping of the Moon. 
    The talks were a mix of trajectory planning and engineering of the 
sails. Some cunning mechanisms were shown for packing the sail into 
the launch vehicle and then unfurling it in space into a sheet the 
size of an airport. One design was a vessel -- including the payload -
- that weighs 14 grams per square mater of sail. Ordinary photocopy 
paper weighs 75g/m2; thin typing paper, 40. 
    A similar theme was expressed in papers promoting assorted ion and 
radiation propulsions. The scenario is the same, fitting a ship with a 
low fuel, low thrust device and riding a Belbruno path.. 
    At the Thursday night banquet, Belbruno presented awards for two 
speakers, Dr David Dunham and Dr Pini Gurfil. 
    Dunham, Applied Physics Lab at Johns Hopkins University, provided 
substantial logistics and support for the conference. He also spoke at 
the convention about the Belbruno trajectory employed by the upcoming 
STEREO mission to monitor the Sun. 
    Home astronomers know Dunham for his decades-long study of grazing 
occultations of stars by the Moon. One of the purposes of this work 
is to improve te orbit theory of te Moon, which eventually 
incorporated elements of chaotic dynamics. 
    Gurfil, Department of Aerospace Engineering at Israel Institute of 
Technology, presented an intriguing perspective on chaotic 
astrodynamics thru gauge theory. This is a new and major advance of 
quantum gravity theory, which so far is applied to 'regular' gravity 
situations. There is as yet no complete integration of gravity into a 
quantum system, but any successful melding must explain the features 
of capture and chaos. 
    Deeper down, the application of a tool from quantum mechanics 
successfully in gravity mechanics could lead to a unification of the 
two disciplines. This was a hope of many scientists, including 
Einstein, for quite a full century. 
    This was a scholarly meeting, yet many talks were well within 
reach of the home spacefareer or astronomer. Other papers were, well, 
as high as the Moon, Mars, and beyond. 
    Many papers worked thru various aspects of the Belbruno theory, 
for trajectories near the Moon and Jupiter. Some used real natural 
examples, like I did in my paper; others, hypothetical particles. 
    The weak stability scheme is a stunning example of chaos in 
nature. The interaction of the gravity fields and the exquisite 
sensitivity of a trajectory thru them to its starting conditions, can 
generate wildly different paths. Which of the possible results 
actually occurs can not be predicted because it is impossible to know 
in advance or later replicate the exact starting state of the 
    Spacefarers and astronomers since the 1990s had to expand their 
litteracy, if not expertise, into chaos theory. This applies to home 
astronomers and spacefarers, not just those on campus. 
    My talk explained how home computers are quite capable ot 
demonstrating chaos in the interaction of comets with Jupiter and an 
asteroid with Earth. Hence, there is now in hand, or in a nearby bush, 
the tools for building this litteracy. 
    Unless you acquire some awareness of the new trends in 
astrodynamics, you'll be mired in the low Earth orbit of brute force 
space travel. 
    Was 'New trends in astrodynamics' worth it for me as a home 
astronomer? Yes!, for the cultural enrichment from the other 
delegates, new ideas to explore -- Ed and I chatted about them during 
the breaks -- and the overall holiday value of visiting Princeton.