BTW: I didn't realize 10 resonates with 8 until I read this last reply
]]>Niehoff VISIT 1 has a period of 1.25 years. This can rendesvous with earth every 4 periods or 5 years. 1.25/1.881 = .6646 which is very close to 2/3 of the Mars orbit. It can rendesvous with Mars every third period or 3.75 years. But since .6646 doesn't exactly equal 2/3, there is a drift, 2.2 degrees each rendesvous by my calculations.
Niehoff VISIT 2 has a period of 1.5 years. This can rendesvous with earth every 2 periods or 3 years. 1.5/1.881 = .7976 which is very close to 4/5 of the Mars orbit. It can rendesvous with Mars every fifth period or 7.5 years. But since .7976 doesn't exactly equal 4/5, there is a drift, 4.4 degrees each rendesvous.
Both the Niehoff orbits aren't very far from a Hohmann orbit (1.4174 year period) and the Delta vee isn't very much greater.
The Aldrin orbit is about 2.2 years and intersects earth's orbit in 2 places. After it leaves the descending earth crossing, it miss this crossing 2.2 years later but passes through near earth space at the ascending crossing at a time = 2.1354 years (Mars synodic period) after the first crossing. At that point it uses it's own delta vee plus an earth gravity assist to rotate it's line of apsides. The Aldrin cycler crosses Mars orbit at a substantial angle. Delta vee for Aldrin to Mars shuttles are about 12 km/s. I guess this is considered acceptable because the tiny shuttles would be only a fraction of the cycler's mass.
I thought I had sent a message earlier. Apologies if something like this shows twice.
]]>What about the ffrequency? The cyclers have to resonate with both Earth and Mars. Because this is not strictly obtaineble, you have to put one resonance and to correct ffor the alteraations off the position. I cam by a very useful design by using a 8:15 reesonance, Mars would orbit about 8 times the sun while Earth does this 15 times. The total period of this systeem will be 15 years minus some days. The route of the cycler will turn slightly to the west.
When 7 cyclers are used, every launch-window is taken. When you let them cycle with a period of 1.5 year, the Earth-Mars transfer is about 8 months, the traansffer back will be about 28 months, because the cycler´reaches it´s perihelium (at the same distaant as Earth) when Earth is in conjunction.
For every fruitful flight, the orbits 4 times fruitless. It passes Earth every 3 year and by an Earth-flyby (about 2 million km) it will alter it´s orbit.
Maybe it´s an idea to use some asteroid for this purpose.
]]>What do you think?
]]>-- RobS
]]>Near as I can tell, there is no such thing as a zero energy orbit between planets, only between lagrange points in the same system (in our case, the Earth/sun/moon system). But That's neither here nor there.
What are the useful orbits? I think I recall seeing an orbit that some commits take from Juperter L1 to L4 to L5 back to L1. So if we took a similar trajectory from mars, would we come anywhere near earth? And if we did how fast would we be going, what direction would we be going by earth at and how might the gravity of earth affect these Martian orbits?
]]>I like Buzz’s idea of these cycler ships being luxurious hotels.
I like this idea also. Very much because a large cycler can offer facilities that reduces the dangers of interplanetary travel.
= = =
RobS is accurate as usual, and that is why I tend to see cyclers as starting points for actual cities rather than primarily as a means for transportation. A luxury hotel is a good starting point for a village, which can grow and eventually afford massive radiation shields, such as feet of polyethylene or water rather than inches.
]]>I don’t know if a cycler ship would be practical to get people to the Moon and then back to Earth. I am reminded of the luxury transatlantic liners of the early 1900’s.
People could travel in style, like in a nice hotel. So why don’t we have those today? Because an airplane can get you across the Atlantic in less than a day. People prefer speed over luxury.
If we can get a ship to the Moon in a day, people will not want to ride in a luxery hotel that takes a couple of days.
]]>Transportation between the Earth and Mars is shaped by several points worth considering:
1. Are the vehicles heading for Mars sufficiently reliable that we can be sure we can launch them at a precise second on a certain day. Since cyclers don't slow down and wait for you, you MUST launch a taxi to them at a certain time. If our Earth departure vehicles are like the current space shuttle, whose launch must be delayed because of safety concerns again and again for weeks at a time, then cyclers are not practical. I see cyclers as a mature technology; something used not for the first missions to Mars, but for later missions involving settlement of the place.
2. Are the vehicles heading for Mars made out of materials the settlers will need on the surface of the planet. If so, you may not need a cycler because the entire trans-Mars vehicle may be heading for the surface of the planet in pieces. In my Mars novel, for example, I postulate the eventual development of inflatable habitats about ten meters in diameter and ten meters (four stories) high. Each habitat has a heat shield, an outer anti-micrometeoroid shell, and three inner air-tight shells (for redundancy). Each transports 12 people under snug conditions (25 square meters per person). The habs fly in pairs so they can counterbalance each other for artificial gravity, and pairs fly together in pairs as well so that if there is an emergency, there are three habs into which the inhabitants of the fourth can be evacuated. After arriving in Mars orbit by aerobraking and docking to a station there, the residents remove all furniture, life support equipment, and solid objects from the habs, then deflate the inner shell and add air pressure to the next shell out, thereby squeezing the inner shell into minimum volume ("shrink-wrapping" it). It is removed through an airlock and stored in the cargo hold of a reusable shuttle that has flown up from the surface. Then the second and third shells are similarly compressed to minimum size and removed, leaving the kevlar micrometeoroid shell and heat shield. Any cargo returning to the earth is placed inside and strapped down, and then the shell is sent back to Earth using a stage fueled from Phobosian propellant. Several shuttle flights transport the people, furniture, life support equipment, and the three pressure membranes to the surface, where the latter are set up separately inside a dome to provide 75 square meters of living and working space per arrival.
Under these circumstances a cycler might not be needed, except to provide roomier transport between planets, and possibly to provide heavy radiation shielding.
3. How many people are returning from Mars? If the number equals those going to Mars, a cycler is more useful. If not, a cycler may be empty most of the time.
4. Orbits chosen and propulsion systems used. These effect the maintenance costs of the cyclers immensely. For example, a cycler on a 26-month orbit betwen the planets will take six months to go to Mars and twenty months to return to Earth. No one will want to use it for the return trip, obviously, so you will need a second cycler on a complementary orbit (six months to Earth, twenty back to Mars). Will someone have to crew the cyclers when there are no passengers on board? How will you maintain the systems when it is empty? How will you make money on your investment when it is occupied only a quarter of the time? What do you do if the propulsion system malfunctions when the ship is passing Mars? Mars's gravity is not strong enough to send the cycler back to Earth; you need some sort of propulsion system to supplement the gravity slingshot, preferrably when the cycler is deep in Mars's gravity well. But that's the very point when the Mars-bound passengers have already left and the Earth-bound passengers have not yet arrived. An ion engine may be the alternative.
So there are concerns with cyclers that have to be addressed.
-- RobS
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