Indian probe begins journey to Mars (BBC)

[eppur_se_muova]

India's mission to Mars has embarked on its 300-day journey to the Red Planet.

Early on Sunday the spacecraft fired its main engine for more than 20 minutes, giving it the correct velocity to leave Earth's orbit.

It will now cruise for 680m km (422m miles), setting up an encounter with its target on 24 September 2014.

The Mars Orbiter Mission (MOM), also known as Mangalyaan, is designed to demonstrate the technological capability to reach Mars orbit.

But the $72m (£45m) probe will also carry out experiments, including a search for methane gas in the planet's atmosphere.
***
more: http://www.bbc.co.uk/news/science-environment-25163113

[longship]

1. I love this shit.

MOM is a very cool probe. Kudos to India for doing this right. Bon chance to Mangalyaan!

And an R&K for the OP.

[Ghost Dog]

2. What an interesting use of the verb 'to embark'

Origin: mid 16th century: from French embarquer, from em- 'in' + barque 'bark, ship'

Good work; recovered from the earlier glitch.

[muriel_volestrangler]

3. A rather badly written ending to the article

India's PSLV rocket - the second choice for the mission after a beefier launcher failed - was not powerful enough to send the MOM on a direct flight to Mars.

So engineers opted for a method of travel called a Hohmann Transfer Orbit to propel the spacecraft from Earth to Mars with the least amount of fuel possible.

Hohmann transfer orbits are pretty normal for Mars missions. NASA's MAVEN, launched in November, is using one too:

After their Earth departures, MAVEN on November 18 and MOM planned for November 30, their interplanetary trajectory will be the well-known, minimum propellant, Hohmann Transfer, in which they coast "up" away from the Sun, slowing all the way to Mars. Upon arrival, each spacecraft will again fire its rocket engine to be captured by Mars's gravity and enter orbit around the planet.

http://www.planetary.org/blogs/emily-lakdawalla/2013/11220947-maven-mom-trajectory-explainer.html

It is 'direct' in the sense that you fire the engine once to go from Earth's (roughly circular) orbit round the Sun to an elliptical one with Earth's distance as the minimum from the Sun, and Mars' as the maximum; when you get there, you fire it again to make it circular at Mars. Earth and Mars are at the right stages in their orbits every 25 months or so, which is why missions to Mars tend to happen in groups - like these 2 together.

What MOM did that was unusual, because they had a less powerful rocket, was to build up some speed in Earth orbit first, by firing the rocket repeatedly at the low point of an increasingly elliptical orbit round Earth. This is more efficient (it's called the Oberth effect), but means orbiting Earth repeatedly to do it. As the Palentary blog says:

MOM chooses to do things differently. Having less massive a spacecraft than MAVEN, ISRO is depending on its proven Polar Satellite Launch Vehicle, and a reliable propulsion system that is built into the spacecraft: a 440-newton bi-propellant fed rocket engine (Cassini has biprop 440 N engines too!), and instead of one very powerful Centaur burn (about 99,000 newtons), ISRO would use its much smaller engine repeatedly. It has to be repeated burns, rather than one long burn, because in order to raise the spacecraft's apoapsis - the high point in its orbit - it has to fire when it is speeding past its closest point to Earth, at periapsis. (For more details on this, look for "The Key to Space Flight" here.)

So with repeated burns while going through periapses, the MOM spacecraft is working its way to a high enough energy to get on a trajectory that will be hyperbolic with respect to Earth; it will have the ability to inject onto its interplanetary cruise, orbiting the Sun instead of Earth. MAVEN did this all at once with a powerful rocket; MOM is doing it in steps using its smaller rocket, but the energy required (per unit of spacecraft mass) is about the same.