ISRO's Mars Orbiter Mission

[Technical Ben]

Dang If we keep this up, Mars will start developing its own Kessler Syndrome Cool news nonetheless.

There seems to be a lot of gold going that way!

[Tech Support]

lol at tech support SN.

How are people responding to the launch there? Any public interest past nationalism?

quite interested actually, the papers are covering it well, the more 'nationalistic' channels do more harm than good by comparing it with MAVEN and not really understanding how all this works. the general public ? they know this a significant achievement for India, beyond that; little interest. however college students and in particular the prestigious IIT are all abuzz with excitement and actual debate on the significance of Methane.

Ps. my Screen name ? haha, I thought it would be funny. especially since I am getting into the software Industry.

Edited November 8, 2013 by Tech Support

[Tech Support]

Thanks guys, I just realised this explanation myself when AFK. A faster, shorter burst would probably be more efficient, but the vehicle is not capable of such a thing. It also does not take into account the bigger engine needed, as the comparison is usually made between low and high intensity burns of the same engine and setup.

I understood that it also has to do with the failure or incompletion of the proposed big launcher. If what is needed will not work, you will need to make what's available work.

are you referring to the GSLV ? if so, yes that particular rocket has long been a headache for ISRO ( seven launches, three failures), you would be interested to know that there is a GSLV launch scheduled for December 15, (which itself is a delay after they aborted a launch in august after a fuel leak); with an indigenous cryogenic engine (we usually use Russian)

Edited November 8, 2013 by Tech Support

[Tech Support]

this page provides updates on the mission status http://www.isro.org/mars/updates.aspx

so far, two orbit raising burns have been completed.

[Camacha]

are you referring to the GSLV ? if so, yes that particular rocket has long been a headache for ISRO ( seven launches, three failures), you would be interested to know that there is a GSLV launch scheduled for December 15, (which itself is a delay after they aborted a launch in august after a fuel leak); with an indigenous cryogenic engine (we usually use Russian)

Yes, the GSLV should be it. According to Wikipedia 4 launches failed and 1 failed partially, but Wikipedia is of course not infallible. I think it is a brave decision to try it again with home grown engines, as the Russian engines generally are realiable as anything.

On the other hand, I love the spirit. Failing is not necessarily bad, as rocket science is supposed to be hard. It would not be as much fun if everything worked on the first try, now would it?

And I do love the somewhat cheesy music and website styling.

Edited November 8, 2013 by Camacha

[Tech Support]

I got my data from the ISRO site here, and I totally agree with you ! failures are the stepping stones to success they say. and its great to see them trying again and again till they get it right. most of the satellites we used to send were failures, but we have learned from mistakes and now have a remarkable success rate.

[Tech Support]

from ISRO's press release.... simply put, they tried something new, it didn't work and now they will make up for it with another burn.

In the fourth orbit-raising operation conducted this morning (Nov 11, 2013), the apogee (farthest point to Earth) of Mars Orbiter Spacecraft was raised from 71,623 km to 78,276 km by imparting an incremental velocity of 35 metres/second (as against 130 metres/second originally planned to raise apogee to about 100,000 [1 lakh] km). The spacecraft is in normal health. A supplementary orbit-raising operation is planned tomorrow (November 12, 2013) at 0500 hrs IST to raise the apogee to nearly 1 lakh km.

During the orbit-raising operations conducted since November 7, 2013, ISRO has been testing and exercising the autonomy functions progressively, that are essential for Trans-Mars Injection (TMI) and Mars Orbit Insertion (MOI).

During the first three orbit-raising operations, the prime and redundant chains of gyros, accelerometers, 22 Newton attitude control thrusters, attitude and orbit control electronics as well as the associated logics for their fault detection isolation, and reconfiguration have been exercised successfully. The prime and redundant star sensors have been functioning satisfactorily. The primary coil of the solenoid flow control valve was used successfully for the first three orbit-raising operations.

During the fourth orbit-raising operations held today (November 11, 2013), the redundancies built-in for the propulsion system were exercised, namely, (a) energising the primary and redundant coils of the solenoid flow control valve of 440 Newton Liquid Engine and ( logic for thrust augmentation by the attitude control thrusters, when needed. However, when both primary and redundant coils were energised together, as one of the planned modes, the flow to the Liquid Engine stopped. The thrust level augmentation logic, as expected, came in and the operation continued using the attitude control thrusters. This sequence resulted in reduction of the incremental velocity.

While this parallel mode of operating the two coils is not possible for subsequent operations, they could be operated independently in sequence.

[Tech Support]

the supplemental orbital correction was completed at 5.30 PM (IST) and the orbiter is now at an orbit of 118,642 km appo. and 250 km pre.

[Meithan]

Awesome. I'm glad it's all going well. Keep us posted.

[Tech Support]

The fifth orbit raising manoeuvre of Mars Orbiter Spacecraft, starting at 01:27 hrs(IST) on Nov 16, 2013, with a burn Time of 243.5 seconds has been successfully completed.The observed change in Apogee is from 118642km to 192874km.

[Tommygun]

How high are they aiming for before they try and burn for Mars?

[Tech Support]

How high are they aiming for before they try and burn for Mars?

This was the last orbit raising manoeuvre, from now on the payloads will be tested till the transfer burn is done on Dec 1.

Edited November 16, 2013 by Tech Support

[Meithan]

Nice graphic. Assuming the perigee's still around 250 km altitude, that's a ~91 hour orbit, with an apogee about halfway to the Moon.

I'm confident that the Dec 1 burn will be successful and then MOM will race MAVEN (assuming it launches successfully too -- only two days to go!) to Mars .

[Tech Support]

I totally ripped it off the FB page, but I am sure they don't mind . you should check it out, they are posting some really interesting photos of the probe under testing and construction, they are also explaining basic space science.

[FanaticalFighter]

That image looks suspiciously like it was taken in GMAT

Anyway, another Indian here. Unfortunately, I live in New Delhi, so I haven't seen any rocket launches with my own eyes. Still, MOM is a pretty damn awesome spaceprobe. I remember on launch day absolutely EVERYBODY asking me what a hohmann transfer orbit was .

@Tech Support: Nice of you to make this thread

[Meithan]

I totally ripped it off the FB page, but I am sure they don't mind . you should check it out, they are posting some really interesting photos of the probe under testing and construction, they are also explaining basic space science.

I just had a look and I have to say that's a great PR site! I loved the diagrams and explanations.

[Psycix]

The most impressive fact is that this mission cost only about $69 million. (US dollars) That includes satellite, launch vehicle, and ground stations.

In comparison, the upcoming MAVEN mission has a pricetag of $671 million.

[Meithan]

The most impressive fact is that this mission cost only about $69 million. (US dollars) That includes satellite, launch vehicle, and ground stations.

In comparison, the upcoming MAVEN mission has a pricetag of $671 million.

And to think MAVEN doesn't carry a methane detector nor a color camera! (But to be fair, it carries a much more complex suite of instruments -- and it's also quite heavier, about 2.5 tons vs. MOM's 1.3 tons.)

[Meithan]

I looked up MOM's and MAVEN's specifications and calculated their ÃŽâ€v, just for fun:

Mars Orbiter Mission

Full mass: 1337 kg

Dry mass: 485 kg

Main Engine: 440N LAM

Engine Isp: 310 s

ÃŽâ€v: 3084 m/s

MAVEN

Full mass: 2559 kg

Dry mass: 903 kg

Main Engine: 6 x 170N MR-107

Engine Isp: 230 s

ÃŽâ€v: 2236 m/s

MAVEN cheats because it's injected into a Mars transfer trajectory by the Centaur upper stage of the Atlas V rocket.

Does anyone know the ÃŽâ€v that MOM has applied so far during the orbit raising maneuvers? I wonder how much of its ÃŽâ€v budget will be spent leaving Earth.

[Tech Support]

could you calculate it based the amount of time the engine has been burned so far ? if yes, then that value is 2240.9s

[FanaticalFighter]

Nope, delta V doesn't depend on time of engine burn, seeing as we don't know the rate of consumption of fuel. It'd be better to use energy conservation equations to see the difference in energies of MOM's initial and final orbits.

Oh, and as for the pricing, MOM is actually cheaper than even that. I read somewhere that a considerable percentage of that budget spent on MOM was for stuff like tracking stations, infrastructure etc that can be used again.

Edited November 17, 2013 by FanaticalFighter

[Meithan]

Nope, delta V doesn't depend on time of engine burn, seeing as we don't know the rate of consumption of fuel.

Actually, mass flow rate of the engine is simply related to the specific impulse and the thrust, , and we know those numbers. If we assume constant Isp, and consider it's been burning for 2240.9s total, then it has burned through 324 kg of propellant so far. Since its initial mass was 1337 kg, that translates into a spent delta-v of 844.60 m/s, out of 3084 m/s total

Another way to compute the delta-v, perhaps more precisely, is to compare the initial and final orbits after each maneuver. Since the burns occur near perigee, one can deduce the delta-v applied by looking at how much the apogee changed.

[PakledHostage]

Another way to compute the delta-v, perhaps more precisely, is to compare the initial and final orbits after each maneuver. Since the burns occur near perigee, one can deduce the delta-v applied by looking at how much the apogee changed.

I think your estimate is pretty close. Out of curiosity, I just plugged the numbers into my spreadsheet. The difference in orbital speed at periapsis between the initial 250 km x 23563 km orbit and the current 250 km x 192874 km orbit is about 870 m/s.

[Meithan]

It's nice to see things work out

I computed a few more numbers that might be interesting. The escape speed at 250 km altitude is very close to the usually quoted 11 km/s. After launch, MOM's perigee speed was 9.9 km/s, so it needed an extra about 1.1 km/s at perigee to reach Earth escape speed. After the orbit raising burns, its current perigee velocity is now 10.8 km/s. It now just needs a small kick of around 180 m/s to escape Earth's gravity. Of course, it'll need to apply more in order to leave on a Mars interception course.

Notice that we're achieving escape speed from perigee. Now consider this. As I said, escape velocity at 250 km/s is about 11 km/s. At the initial apogee altitude of 23,563 km, escape velocity is about 5.2 km/s -- considerably lower. Isn't it easier to escape at apogee? Why don't we burn at apogee instead?

The reason is that while escape velocity is indeed lower at apogee, the spacecraft's velocity is also considerably smaller. It turns out that the difference between the escape speed and the craft's orbital speed is in fact greater at apogee than at perigee. Let me show it with numbers:

Departing from initial 250 km x 23,563 km orbit:

Escape speed at perigee: 11.0 km/s

Orbital speed at perigee: 9.9 km/s

Delta-v to escape at perigee: 1.1 km/s

Escape speed at apogee: 5.2 km/s

Orbital speed at apogee: 2.2 km/s

Delta-v to escape at apogee: 3.0 km/s

The required delta-v for escape is almost three times larger at apogee! So it's much more efficient to burn for escape at perigee, where we're moving fast. And what does that remind us of? Yup, our friend the good ol' Oberth effect.

The mechanical energy of the spacecraft is the same at any point of its orbit, and the energy for escape is also a unique value (namely, zero). That means that escaping Earth from a given initial orbit requires a fixed amount of extra energy, regardless of where we do the burn. But the Oberth effect says that we get more kinetic energy out of every kg of spent fuel when we're moving faster. So we don't need to spend as much fuel to gain that extra energy if we burn at perigee. And that's equivalent to a lower delta-v requirement.

[Tech Support]

wow, I am way out of my depth here with Math ! Meithan, those are some very interesting calculations, kudos !