An international, cross-curricular exploration of Space Science, through on-line learning tools
International | Africa | Bangladesh | Chile | China | CzechMiranda | Japan | Macedonia | Mexico | MiraNet | MirandaNorth | Poland | Regional | Star | Taiwan | Thailand| UK-Japan Science | UK-China Links | USA
STAR | Presentation | Article | Integrated Web Sites | Online Discussions | Taiwan
An international, cross-curricular exploration of Space Science, through on-line learning tools
Text of Online Discussions between the scientists and the students
AS Level teaching materials
Online Science Discussion | Online English
Discussion | Online RE Discussion
| Online Discussion of 'Other Matters'
Background
The Holy Cross School is a Catholic High School, formerly called Holy Cross
Convent School. As part of the STAR Project, we were involved in discussions
with Joe Kolecki, NASA Pathfinder scientist, on many levels.
Dear Joe,
My new class, currently six boys and six girls, have read "A Once and Noble Race" and have also looked at some of the STAR web materials. Thanks for providing the literary stimulus, as well as the scientific information!
We have just had an interesting discussion about the question you set us: Why go to Europa? The need for mankind to explore the environment and set challenges (like mountaineers, explorers, and even sportsmen and women) figured large in the discussion. We need to find out more about what is enticing about Europa and Jupiter, and provide a scientific as well as a more general set of reasons. That will form part of today's lesson. I argued that planet-hopping to avoid an expanding sun was probably a rather premature reason, and by some time scale.... Nonetheless, they are starting to think about issues.
One student is studying AS Level Photography, and will, I hope, contribute some ideas on the space applications of this to the group. We plan to add ideas from their other subject interests (e.g. Food Technology, Modern Languages (for the multinational astronauts, perhaps, to create video-diaries in different languages), Mathematics (to calculate some of the distances, times of communication etc.), Psychology (for how to form a team that could work together reliably for years, and far from home). It could blossom: that is my hope.
I shall keep you posted about progress.
Warmest regards,
Lawrence
Michael then writes:
Dear Joe,
I am one of the students participating in the STAR project with Mr Williams. I have collected various data needed to calculate a time-scale for the journey to Europa. I am unsure, however, if the statistics I have gathered are correct and it would be a great asset if you could point me in the right direction with this investigation.
Fastest recorded space craft speed
NASA-German Helios 1+2 reached speeds of 252, 800 km/h
Relative distance from Earth to Europa = 800,000,000km
Fluctuation upon the orbits of Earth and Europa
Therefore 800,000,000 / 252,800 calculates at 3,165 hours from Earth to Europa.
Therefore it should at this speed take 132 days to reach Europa.
I am however slightly sceptical of this speed, and wondered if you could perhaps reply with more accurate data which would be needed for this investigation. Surely, it cannot take a shorter time to reach Europa than the time calculated by Holy Cross to reach Mars!
Yours sincerely,
Michael Nightingale (Mike)
Richard Challoner 6th Form Consortium
Joe replies:
Hi Mike,
I was involved in the Pathfinder mission to Mars. I know that the Pathfinder spacecraft left earth at about 120,000 km per hour and reached Mars at about 88,000 km per hour. The Pathfinder voyage required 7 months or 210 days, approximately. And, while the distance from earth to Mars would be about 64 million km when the spacecraft arrived, the actual travel distance was more like 496 million km. The orbit was not a straight line, you see; it made use of the sun's gravity so that the spacecraft made an essentially comet-like (elliptical) orbit around the sun and met up with Mars on the other side from which it had been launched. I will give more details of this scenario if you would like.
We would do something similar with a mission to Jupiter. To thrust the entire way would be prohibitively expensive. And, unless we were sending humans, thrusting would be unnecessary. So, we would use the sun and establish an elliptical orbit that would allow the spacecraft to coast from the earth to Jupiter. We might do some fancy manoeuvring in the inner solar system first, however, to use the gravity of Venus and Earth to gain more speed. But the final result would be a coast to Jupiter all the same.
You might want to check out the Galileo mission to Jupiter. Here is a website: http://www2.jpl.nasa.gov/galileo/ . Galileo took 14 years to get from earth to Jupiter. You might also want to check out the Cassini mission to Saturn. See http://saturn.jpl.nasa.gov/overview/mission.cfm . The Cassini mission, took only about 7 years to get to Saturn from earth. Perhaps this is the model for your story. Since Saturn is about twice as far from the sun as Jupiter, you might reasonably guess that it would take somewhere between 3 and 4 years (that is, 1100 - 1500 days) to get to Jupiter with late 20th century, "Cassini-type" technology. Obviously, there is variability in the numbers! Please read these sites carefully, as you will learn a great deal that will prove helpful to you.
Going on, once orbital insertion at Jupiter has been accomplished, additional orbital manoeuvring to get to Europa would follow. Each orbit-insert (the initial one around Jupiter and the second one around Europa) would require giving up spacecraft energy. This energy would have to be regained before the spacecraft could ever return home to earth. The energy would come, of course, from burning spacecraft fuel, whether that fuel were brought from earth (a very costly and inefficient proposition) or extracted from the raw gases of Jupiter's upper atmosphere (a much more effective scenario all the way around).
You must also remember that the outward-bound spacecraft, in travelling from the earth to Jupiter must be given an initial boost in total energy (done by on-orbit thrusting while still at earth) and, once on its way, would continuously loose energy as it climbed toward Jupiter. Just as a ball slows down when thrown upward, the spacecraft will also slow down since it is moving "upward" through the solar system (i.e., from Earth to Jupiter).
Your math is correct, considering that time is distance divided by speed. But the speed, in this case, is constantly diminishing. Your calculation assumes that it remains constant, which it could only do under conditions of continuous thrusting. And even then, your estimated time would be too short as it is doubtful that the spacecraft would travel in a straight line.
Hope this helps!
Best wishes on your STAR adventure!!!!!
Your friend and colleague at NASA,
Joe Kolecki
[Back]
