Why should it take 15 months to reach the moon?

http://cnn.space.printthis.clickabil...partnerID=2018

Europe's first moon mission blasts off

KOUROU, French Guiana (Reuters) --Europe's first mission to the moon blasted
off late on Saturday aboard a European Ariane rocket, space officials said.

The Ariane-5 rocket carrying the SMART-1 moon exploration probe and two
commercial satellites blasted off at 8.14 p.m. (2314 GMT) from the European
Space Agency (ESA) launch center at Kourou, in French Guiana on the
northeast coast of South America.

Forty-one minutes after launch, the rocket released SMART-1 into space to
begin a 15-month journey to reach lunar orbit. The 370 kg (815 lb) probe
will scan the moon for up to 30 months.

SMART-1 will cover a distance of 100 million kilometers (62 million miles)
to reach the moon with only 60 liters of fuel," Giuseppe RACCA, ESA Project
Manager said before the launch.

"The main form of propulsion will be electric, charged by the satellite's
solar panels," he said.

The probe will provide data on the still uncertain origin of the moon and
has been described by ESA as an important instrument "to unraveling some of
the secrets of our neighboring world."

"Thirty-five years after Apollo and the Russian missions, there remains much
we don't know about the moon," David Southwood, ESA's Director of Scientific
Programs, told a news conference in Kourou.

"With SMART-1 we can test propulsion in deep-space orbit. The next step, I
hope, will be a Mars mission," he said.

ESA has hailed SMART-1 as an example of a 'faster, better, cheaper' mission
costing only 110 million euros ($126 million) -- about one-fifth of a major
ESA science mission. It is designed to operate in lunar orbit for up to 30
months.

The rocket also carries an INSAT 3-E satellite for the Indian Space Research
Organization and e-bird for the Paris-based satellite operator Eutelsat.

Originally scheduled for launch earlier in the year, the mission was
postponed due to technical problems aboard INSAT 3-E.




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___________________________
Bonnie Granat
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"Bonnie Granat" wrote in alt.astronomy:

snip

Check out info about the ion drive, how it works and accelerates.

http://www.space.com/news/smart1_preview_030926.html

quote
SMART-1 (Small Missions for Advanced Research and Technology) is also
billed as a technology testbed. It will use a futuristic ion-electric
engine that is highly efficient and requires less fuel, making the craft
lightweight. Ion engines use small amounts of xenon gas to generate slow
but steady acceleration, rather than the more powerful, rapid acceleration
created by conventional chemical rockets.

The trade-off for ion propulsion is time. It will take the spacecraft,
which is smaller than a kitchen table, 16 months to get to the Moon.
/quote


--
CeeBee


Uxbridge: "By God, sir, I've lost my leg!"
Wellington: "By God, sir, so you have!"


Google CeeBee @ www.geocities.com/ceebee_2

"Bonnie Granat" wrote in alt.astronomy:

snip

Check out info about the ion drive, how it works and accelerates.

http://www.space.com/news/smart1_preview_030926.html

quote
SMART-1 (Small Missions for Advanced Research and Technology) is also
billed as a technology testbed. It will use a futuristic ion-electric
engine that is highly efficient and requires less fuel, making the craft
lightweight. Ion engines use small amounts of xenon gas to generate slow
but steady acceleration, rather than the more powerful, rapid acceleration
created by conventional chemical rockets.

The trade-off for ion propulsion is time. It will take the spacecraft,
which is smaller than a kitchen table, 16 months to get to the Moon.
/quote


--
CeeBee


Uxbridge: "By God, sir, I've lost my leg!"
Wellington: "By God, sir, so you have!"


Google CeeBee @ www.geocities.com/ceebee_2

The ion engine used on the spacecraft is said to be 5-10 times more
efficient than an ordinary chemical booster. That is to say, it can provide
5-10 times more thrust than a regular engine, with the same amount of fuel.
The downside of the ion engine is that its thrust is _very_ gentle, so you
can't change your velocity very fast. While an ordinary booster can expend
all its fuel in a matter of seconds/minutes (which can be regarded as
instantaneous, compared to orbital periods in question here), an ion booster
can take months to spend its fuel and accomplish the desired velocity
change. So, in contrast to sending a spacecraft to the target via a standard
Hohmann transfer orbit (when you fire all your booster fuel at launch from
Earth parking orbit, aiming the apogee at the Moon's orbit), you have to
keep the ion engine running a long time and you basically end up with a very
long spiraling orbit to the Moon, which starts at Earth parking orbit and
ends at the Moon's orbit. That's pretty much the whole idea, though in
reality things get more complicated by the Moon's gravitational
perturbations...

--
The butler did it.

The ion engine used on the spacecraft is said to be 5-10 times more
efficient than an ordinary chemical booster. That is to say, it can provide
5-10 times more thrust than a regular engine, with the same amount of fuel.
The downside of the ion engine is that its thrust is _very_ gentle, so you
can't change your velocity very fast. While an ordinary booster can expend
all its fuel in a matter of seconds/minutes (which can be regarded as
instantaneous, compared to orbital periods in question here), an ion booster
can take months to spend its fuel and accomplish the desired velocity
change. So, in contrast to sending a spacecraft to the target via a standard
Hohmann transfer orbit (when you fire all your booster fuel at launch from
Earth parking orbit, aiming the apogee at the Moon's orbit), you have to
keep the ion engine running a long time and you basically end up with a very
long spiraling orbit to the Moon, which starts at Earth parking orbit and
ends at the Moon's orbit. That's pretty much the whole idea, though in
reality things get more complicated by the Moon's gravitational
perturbations...

--
The butler did it.

There's a lot of work being done just now on continuous low-thrust
interplanetary trajectory mechanics. I've read some of it, written by
Tadashi Sakai at Georgia Tech. But I prefer transfer orbits that use
"instantaneous" pulse delta-vees. The math is prettier, even with a course
correction or two.

http://sdebug.org/posts/transca.html
http://sdebug.org/posts/trans3.html

But I guess if you don't MIND waiting more than a year to get to where you
might have gone in less than a week, then it doesn't MATTER.

Not only do the more common high-thrust rockets use the instantaneous pulse
transfer orbit math, so do "mass drivers" which shoot metal jacketed loads
from magnetic induction catapults. Aside from science missions that must
sacrifice time because of extremely tight budgetary requirements, I think
that the "billiards" style of celestial mechanics will dominate the "race
car" style for a very long time yet.

Jerry Abbott


"Ugo" wrote in message
...
The ion engine used on the spacecraft is said to be 5-10 times more
efficient than an ordinary chemical booster. That is to say, it can
provide
5-10 times more thrust than a regular engine, with the same amount of
fuel.
The downside of the ion engine is that its thrust is _very_ gentle, so you
can't change your velocity very fast. While an ordinary booster can expend
all its fuel in a matter of seconds/minutes (which can be regarded as
instantaneous, compared to orbital periods in question here), an ion
booster
can take months to spend its fuel and accomplish the desired velocity
change. So, in contrast to sending a spacecraft to the target via a
standard
Hohmann transfer orbit (when you fire all your booster fuel at launch from
Earth parking orbit, aiming the apogee at the Moon's orbit), you have to
keep the ion engine running a long time and you basically end up with a
very
long spiraling orbit to the Moon, which starts at Earth parking orbit and
ends at the Moon's orbit. That's pretty much the whole idea, though in
reality things get more complicated by the Moon's gravitational
perturbations...

--
The butler did it.

There's a lot of work being done just now on continuous low-thrust
interplanetary trajectory mechanics. I've read some of it, written by
Tadashi Sakai at Georgia Tech. But I prefer transfer orbits that use
"instantaneous" pulse delta-vees. The math is prettier, even with a course
correction or two.

http://sdebug.org/posts/transca.html
http://sdebug.org/posts/trans3.html

But I guess if you don't MIND waiting more than a year to get to where you
might have gone in less than a week, then it doesn't MATTER.

Not only do the more common high-thrust rockets use the instantaneous pulse
transfer orbit math, so do "mass drivers" which shoot metal jacketed loads
from magnetic induction catapults. Aside from science missions that must
sacrifice time because of extremely tight budgetary requirements, I think
that the "billiards" style of celestial mechanics will dominate the "race
car" style for a very long time yet.

Jerry Abbott


"Ugo" wrote in message
...
The ion engine used on the spacecraft is said to be 5-10 times more
efficient than an ordinary chemical booster. That is to say, it can
provide
5-10 times more thrust than a regular engine, with the same amount of
fuel.
The downside of the ion engine is that its thrust is _very_ gentle, so you
can't change your velocity very fast. While an ordinary booster can expend
all its fuel in a matter of seconds/minutes (which can be regarded as
instantaneous, compared to orbital periods in question here), an ion
booster
can take months to spend its fuel and accomplish the desired velocity
change. So, in contrast to sending a spacecraft to the target via a
standard
Hohmann transfer orbit (when you fire all your booster fuel at launch from
Earth parking orbit, aiming the apogee at the Moon's orbit), you have to
keep the ion engine running a long time and you basically end up with a
very
long spiraling orbit to the Moon, which starts at Earth parking orbit and
ends at the Moon's orbit. That's pretty much the whole idea, though in
reality things get more complicated by the Moon's gravitational
perturbations...

--
The butler did it.

"Jerry Abbott" wrote in message
...
There's a lot of work being done just now on continuous low-thrust
interplanetary trajectory mechanics. I've read some of it, written by
Tadashi Sakai at Georgia Tech. But I prefer transfer orbits that use
"instantaneous" pulse delta-vees. The math is prettier, even with a
course
correction or two.

http://sdebug.org/posts/transca.html
http://sdebug.org/posts/trans3.html


"This website is intended to teach celestial mechanics to White people of
average intelligence having a proper high school education."

Does this mean non-white folks aren't supposed to read through your
materials? :-/

"Jerry Abbott" wrote in message
...
There's a lot of work being done just now on continuous low-thrust
interplanetary trajectory mechanics. I've read some of it, written by
Tadashi Sakai at Georgia Tech. But I prefer transfer orbits that use
"instantaneous" pulse delta-vees. The math is prettier, even with a
course
correction or two.

http://sdebug.org/posts/transca.html
http://sdebug.org/posts/trans3.html


"This website is intended to teach celestial mechanics to White people of
average intelligence having a proper high school education."

Does this mean non-white folks aren't supposed to read through your
materials? :-/

http://sdebug.org/posts/transca.html
http://sdebug.org/posts/trans3.html


"This website is intended to teach celestial mechanics to White people of
average intelligence having a proper high school education."

Does this mean non-white folks aren't supposed to read through your
materials? :-/

I mean that White people are my targeted audience, the ones for whom I am
pleased to work. Naturally, since my work is posted online, it is free to
anyone with a modem, a computer, and an ISP to examine.

Jerry Abbott