Chandrayaan 3: Launch and Discussions

[nitzter]

https://twitter.com/isro/status/1694713817916473530

Lander Imager camera video from ISRO

The wait is finally overrrrr!!! Thanks Ashok ji.

PS - They could have shown a few more seconds of video after touchdown - the dust settling part.

[Amber G.]

I love listening to the current ISRO Chairman S Somanath talk, and really have high confidence in his character and abilities:

Many of us do. I talked about him in positive terms years ago in BRF, and as I said then I was particularly happy in the choice when he became ISRO chairman. IMO he has respect from scientists and aam janata. True also outside India... good reputation in NASA and US admin too.

Here is a post I posted (in US-India thread) months ago:

Another important milestone for NISAR (NASA-ISRO Synthetic Aperture Radar) - US India partnership -- Scientific heart of this NASAEarth satellite to head to southern India ahead of its planned 2024 launch in style from JPL...

NASA-ISRO Earth Science Instruments Get Send-Off Before Moving to India:



And ... ne news of Modi/Biden state visit just became ooficial/ public .."

Wow!... (After NSA Meet)
Per news reports: US President Joe Biden Invites Prime Minister Narendra Modi ji for First State Visit. This is the highest honor in terms of protocol. (generally reserved for close friends)..Addressing the congress.. sate dinner etc..

[Amber G.]

A short note for appreciationto @ashokk' (and similar posters ).
(One of the reason I visit BRF (and also post ) is that this is still a place where you are not likely to miss important news items.. Thanks Ashok ).

[SSSalvi]

didn't take these termites very long to come crawling out of the woodwork

The @isro dreamt of by Pandit Nehru, nurtured by Indira Gandhi ji, and taken to great heights by Rajiv Gandhi ji and Dr. Manmohan Singh ji achieves a new milestone!

A proud moment for all, as we excitedly watch the #Chandrayan3 take off to conquer the moon!

Jai Hind pic.twitter.com/xXkMWwLKwG

— K C Venugopal (@kcvenugopalmp) July 14, 2023

India's voyage to the moon and beyond is a tale of pride, determination & vision.

It was independent India’s first Prime Minister, Jawaharlal Nehru, whose scientific outlook and vision laid the foundation of Indian space research.

Today, the success of Chandrayaan-III is a… pic.twitter.com/Uc1PiIIesl

— Congress (@INCIndia) August 23, 2023

And to counter here is one fact:
Mangalyaan was launched during Mauni Baba but it could not reach Mangal.
It could do so only because of the guidance by Our Beloved Narendra Modiji after he became the Prime Minister!!!!!!!

[juvva]

Gold mine interview with Somnath (even though title says Sivan but Somnath interview in the second half). No redundancies were required or used by VIKRAM, Landing was handled by the inertial unit. The LXXXX cameras were not used is what I understood which is a bit odd because VIKRAM did re-target.

i believe the lander entered a re target mode , to assess if re targeting was required, it did not find the need to re target, and so continued to move vertically downwards as was shown in the live animation and completed the landing nominally.

[Ashokk]

A short note for appreciationto @ashokk' (and similar posters ).
(One of the reason I visit BRF (and also post ) is that this is still a place where you are not likely to miss important news items.. Thanks Ashok ).

Thank you Amber G. ji for the kind words. Really enjoy your posts on the technical & theoritical aspects of space travel. I have learnt a lot from BRF over the years and I try to contribute whatever little that I can.

[Amber G.]

Q. Will a satellite in a large elliptical orbit around the earth be within line of sight of the far side of the moon (even a partial amount of the far side) or is the Langrange point the only spot that can provide line of sight to both the earth and moon?

Thanks. Appreciate your knowledge sharing across various posts.

Earthbound orbits are possible upto 1.5 million kilometres apogee. ( That is Lagrange1 point distance ... beyond it Sun will gobble the craft as its orbit slave )

You find whether this is beyond moon or not

To add:
- I had chance to look at S^3's blog about basic orbits (see link provided by him many posts ago)..nice stuff, nicely explained especially perturbations from ideal elliptical orbits -- complex items. Orbits in more than two bodies are complex and short of non-stable over a longer time-span.

- Partial amount of the far side can be viewed from Earth - (About 59% is visible due to liberation). And sats employed (in various orbits) could help but providing 100% coverage with 100% of the time window over a long period becomes quite complex... orbits will require constant corrections...

OTOH Advantages of L2:

Stable Orbit: L2 is an ideal location for a relay satellite because it provides a stable orbital position relative to both the Earth and the Moon. This stability reduces the need for frequent adjustments to maintain communication coverage.

No Eclipse Periods: Unlike satellites in Earth orbit, a satellite at L2 experiences very few or no eclipse periods when it is blocked by the Earth or Moon. This ensures consistent power generation from solar panels, which is essential for maintaining satellite operations.

Reduced Atmospheric Interference: Being far from Earth's atmosphere, L2 experiences minimal atmospheric interference, resulting in clearer and stronger communication signals.

Reduced Orbital Maintenance: The stable position at L2 reduces the need for frequent orbital adjustments, which can save fuel and extend the satellite's operational lifespan.

>>>> Queqiao's positioning at the Earth-Moon L2 point provided a critical solution to the communication challenges posed by the Moon's far side. It ensured continuous and reliable communication between lunar missions and mission control on Earth, enabling successful operations and data transmission from this previously inaccessible region of the Moon.

[Amber G.]

And to counter here is one fact:
Mangalyaan was launched during Mauni Baba but it could not reach Mangal.
It could do so only because of the guidance by Our Beloved Narendra Modiji after he became the Prime Minister!!!!!!!

There is a "Jahawar point/ Jawahar sthal" at the point of Impact impact of probe from CY1 ( The impact happened on Nov, 14 - Nehru's birthday)...some big-shot was bragging about this..

Pointed out that there is large "Modi crater" on the "moon" and the conversation became somewhat heated. ( This moon is not our moon but one of the moon of Jupiter (Callisto), and '' Modi" is not named after PM... (old name, I believe named after some Japanese person/ folklore).. but that is besides the point ...)

[SSSalvi]

i believe the lander entered a re target mode , to assess if re targeting was required, it did not find the need to re target, and so continued to move vertically downwards as was shown in the live animation and completed the landing nominally.

If you observe the set of images ( while PM sir seen watching keenly on half the screen ), you can see two different locations being targeted a few hundred meters apart .. first image shows a few uneven patches while the second location is really a flat surface.
Also the commentary says that with retargeting our algorithms have been proven ( or some similar thing ).

Also last 10 seconds of Landing Camera video https://twitter.com/isro/status/1694713817916473530 you can see that Lander stopped over a place and then moved sodeways before the dust blocks view.

[juvva]

let us enjoy the heart burn of the british ( sorry if you feel i misspellt the last word):

https://youtu.be/lcS8afETDr8?feature=shared

[SivaR]

Now ISRO can do magic

3. How easy it would be to launch rocket from moon to outer space compared to launching from earth, with moons low gravity advantage, provided we can generate rocket fuel from moon's water/gas/elements.b][/b]

We will still need delta-V of about 30 Km/sec to, say go to Mars (unless, we do gravity assist with Moon or Earth etc) .. but from earth we need around 8 km/sec just to get to a space -station.. so savings are tremendous... besides since there is no air on moon, it is possible to have ground based shooting guns type launch to provide more efficiency than rockets. (On earth, you can not shoot with high velocity as the friction from air there ... so you need 2 or 3 stages...))
[/quote]

Thanks for explaining Amber Ji.
Dr. Abdul Kalam/ Dr. Sivan are from my alma matter (Madras Institute of Technology/ Aeronautical Dept.) . It feels very proud to see their work is Yielding huge dividends . I still remember its just a batch of 10 in a class and most of them entering to ISRO/DRDO, due to other commitments, I moved to corporate job. Still remember the labs run using fell over world war 2 planes. We need to build something similar to Jet Propulsion Lab (JPL, California, USA) in India to move to next level, this is the future(at-least $100Bn industry in few years) and the ROI will be huge.

[RCase]

Earthbound orbits are possible upto 1.5 million kilometres apogee. ( That is Lagrange1 point distance ... beyond it Sun will gobble the craft as its orbit slave )

You find whether this is beyond moon or not

To add:
- I had chance to look at S^3's blog about basic orbits (see link provided by him many posts ago)..nice stuff, nicely explained especially perturbations from ideal elliptical orbits -- complex items. Orbits in more than two bodies are complex and short of non-stable over a longer time-span.

- Partial amount of the far side can be viewed from Earth - (About 59% is visible due to liberation). And sats employed (in various orbits) could help but providing 100% coverage with 100% of the time window over a long period becomes quite complex... orbits will require constant corrections...

Thanks S^3 and Amber. I understand from a communications and equilibrium point of view that it is more practical to place a relay station/satellite at the Langrange point. More of a curiosity question that it should have been possible to 'see' more than the 59% (not necessarily 100%) with earth orbiting satellites to get a hint of what is there. The tidal locking concept of why we only see one side of the moon always was something I stumbled upon only a few years ago and thanks to Youtube, there were videos to demonstrate this concept. I would wager that most high school Physics teachers (and probably a good number of college level Physics staff) in India were probably clueless about this phenomenon.

[Y I Patel]

Congratulations to all concerned for this watershed moment!

Also, heartfelt thanks to all who made this the best thread to visit for any information on this topic.

[Amber G.]

^^^ (WRT to far site of the moon)

The tidal locking concept of why we only see one side of the moon always was something I stumbled upon only a few years ago and thanks to Youtube, there were videos to demonstrate this concept.

I remember it extremely well .. when for the *first* time humanity got a glimpse of the far side of the Moon -- during the Soviet Luna 3 mission. It captured and transmitted photographs of the lunar far side in October 1959. This achievement was a significant milestone in space exploration and a major news event during that era.

Luna 3, was an automatic spacecraft equipped with cameras and other scientific instruments. It performed a flyby of the Moon and transmitted photographs of about 70% of the far side back to Earth. These images provided the first-ever views of the side of the Moon that is never visible from Earth. The news was met with international attention and excitement. It marked a technological achievement and a breakthrough in space exploration. The images captured by Luna 3 were grainy and lacked the detail we are familiar with today but it was *very* exciting.. top news in all the newspapers..

(For aam janta - and reporters - they got to understand the 'far' side for the first time.... and after Apollo 11 landing, it also became a common knowledge that 'earth' from moon does not rise or set (like all heavenly bodies do) , but just remains at a stationary place..)

I would wager that most high school Physics teachers (and probably a good number of college level Physics staff) in India were probably clueless about this phenomenon...

I would like to think that most high school physics teacher ought to know that...anyway ,,, here is what I would do .. (or think most people ought to know that):
this phenomena of tidal locking is not true for moon only,,, It is quite common in our solar (and other solar systems too)...
For example apart from our moon:

Mercury is also tidally locked to the Sun. This means that it rotates on its axis exactly three times for every two orbits it completes around the Sun. As a result, its day is longer than its year, and it exhibits a unique rotation pattern.

Venus: Venus is almost tidally locked to the Sun. It rotates very slowly and in the opposite direction of its orbit, so its rotation period is longer than its orbital period. While it's not fully tidally locked, it exhibits a similar phenomenon known as "resonant rotation."

Pluto and Charon: The dwarf planet Pluto and its largest moon, Charon, are tidally locked to each other. They both always show the same face to each other as they orbit around a common center of mass.

Some Exoplanets: Tidal locking is common among exoplanets (planets outside our solar system) that orbit close to their host stars. Many of these exoplanets are expected to be tidally locked due to their proximity to their stars and the gravitational interactions between them.

And for moons of other planets in our solar system:
Io, Europa, Ganymede, and Callisto (Jupiter's Moons) Io, one of Jupiter's largest moons, is not tidally locked to Jupiter, but it is in a state of synchronous rotation. This means that Io's rotation period is the same as its orbital period around Jupiter. However, unlike most tidally locked bodies, Io's rotation is not locked to its parent planet's gravitational pull alone. The strong tidal interactions between Io, Jupiter, and the other Galilean moons create complex interactions that result in Io's synchronous rotation.

Other three large moons of Jupiter, collectively known as the Galilean moons, are tidally locked to Jupiter. This means that they always show the same face to Jupiter as they orbit the planet. The gravitational interactions between these moons and Jupiter have caused them to become tidally locked over long periods of time.

Triton (Neptune's Moon): Triton, Neptune's largest moon, is tidally locked to Neptune.
(Wish we had more astronomy in our schools for such interesting facts.. )

[VickyAvinash]

^^^ (WRT to far site of the moon)

The tidal locking concept of why we only see one side of the moon always was something I stumbled upon only a few years ago and thanks to Youtube, there were videos to demonstrate this concept.

(Neptune's Moon): Triton, Neptune's largest moon, is tidally locked to Neptune.
(Wish we had more astronomy in our schools for such interesting facts.. )

Very informative post Amber G. ji. BRF never stops to surprise.

[Amber G.]

Meanwhile:

#VikramLander --- its really on the Moon.

Here's the JPL Horizons vs Scot Tiley Doppler data from yesterday. It proves that Vikram is on the Moon.



The #VikramLander frequency residuals show a very low error. .... All appears norma

[Jayram]

incoming landing telemetry - Nothing official yet from ISRO though
https://twitter.com/debapratim_/status/ ... 3574158559
Saying #ISRO nailed the landing is a severe understatement!!

The Vikram Lander touched down with a vertical velocity of 0.983 m/s and a horizontal velocity of 0.053 m/s.

Faaar below the maximum 3 m/s which Vikram's landing legs were designed to withstand. #Chandrayaan3


The reddit post on this is has a clearer image at touchdown

[Jayram]

That image has confirmation also of retargeting that occurred at landing that started at 1095 secs and lasted 50 secs. Engines E2 and E4 firing with higher thrusts than the other two. Wonder if that was due to weight distribution imbalances in the Lander or real time angle corrections or both.
All in all an engineering triumph of a performance.

[Amber G.]

^^^

The Vikram Lander touched down with a vertical velocity of 0.983 m/s

To put in perspective, that is the velocity on an object falling from an height of about 5 cm (2 inches) on earth.

(Or an ant crawling, or slow jogging .... or a conveyor belt..where your luggage arrives in an airport)..

[Jayram]

Wow!! And since this is the moon we are talking about would it be accurate to say this is equivalent to dropping an object from a height of approx. 12 inches on the moon? (Due to moon gravity being 1/6 that of earth?)

[Ashokk]

https://twitter.com/Ramanean/status/1694752050545152489 (tweet is from the guy who found the CY2 crash location)

#Chandrayaan3's Final landing location: -69.37302, 32.32017 (in a 10x10m box) | Calculated from ISRO's video (1/5)

https://twitter.com/umapathyshiva/statu ... 7366274367

#Chandrayaan3 broucher released on 10-07-2023..It's very very closely accurate..

[disha]

I've few questions popped in my mind after this landing.
1. With lunar gravity very low, returning to earth should consume much less thrust. What would be the ratio , is it 1:100?
2. Entering back to earth, how much thrust ratio needed compared to escaping the earth's gravity, my understanding is huge thrust is used for escaping the earth's gravity.
3. How easy it would be to launch rocket from moon to outer space compared to launching from earth, with moons low gravity advantage, provided we can generate rocket fuel from moon's water/gas/elements.
4. In case we make moon habitable, does building international space station become redundant?

Sivab/Siva509'ji, I thought that you attended MIT and have a tech background to answer the same.

Anyway, without resorting to equations and mathematics and ratios, in my humble opinion, one must strive to answer those questions to

1. Spark imagination & further curiosity among equally intelligent persons
2. And de-mystify it and make it more accessible!

So here we go (for couple of your questions):

1. Lunar gravity is 1/6th the earth gravity, so anything that needs to escape moon requires 1/6th the velocity that is required for earth. So whatever thrust is required to achieve the velocity. You can give some thrust for a lot of time or lot of thrust in a short amount of time, but the end goal should be the velocity gain. To your question, the thrust to be used to launch an equivalent mass from moon thus follows to be 1/6th. Or to turn it around you can launch 6x more payload from moon than Earth.*

However returning to Earth, unless you take assistance from atmosphere, do aero-braking and glide down and or parachute down, you will require enormous amount of energy and thus fuel. That is why the spaceX 2nd stage rockets are discarded and only first stage/boosters are returned.

* As explained to a 5 year old again, sending humans to mars will be easier if we have a moon base. Since we can send 6x more payload to mars from moon, we can pack in extra supplies, extra fuel, more people etc etc. *Or send them faster for the same payload.* That led to discussion on setting up a moon base. **

** The five your old somehow took a liking to Mercury and wanted to be the first human to mercury. Until the teacher told the 5 yr old that mercury is a *dead* planet. The concept of "death"/"dead" is scary to a 5 year old and the dreams of being the first person to mercury is already crushed. Such a shame.

2. The thrust that is needed to escape Earth's gravity well is huge. One has to put in so much of fuel that the rocket is almost useless to carry any useable payload. That is why Rockets are multi-staged. This follows work by Russian scientist Tsiolkovsky. In nutshell, you shed unnecessary baggage. The lowest stage has pushed the upper stages *with* propellant to a certain velocity and then discarded. Since the propellant has been expended in the lower stage, why carry the tankage and the structure (the stage) around?

[RCase]

^^^ (WRT to far site of the moon)

... 'earth' from moon does not rise or set (like all heavenly bodies do) , but just remains at a stationary place..)

Is this because of the size of the earth being bigger?

[RCase]

let us enjoy the heart burn of the british ( sorry if you feel i misspellt the last word):

https://youtu.be/lcS8afETDr8?feature=shared

Sour grapes Brits!

I guess those Brit colonialists need to be reminded that the sun has set on the British empire. UK is a third rate power today and a poodle of the US. They are talking about their measly 'aid' that they send to India, most probably to be used for subversive activities. India doesn't need their aid and they can shove it up their bottoms.

We need to remind themf that they actually owe reparations of over $45 T (which is way beyond their means). These descendants of thieves and crooks need to be reminded that they are a criminal country that has grown because of looting the wealth of various countries. Their Thief-in-Chief still is in possession of stolen properties like the Kohinoor.

[RCase]

Admission rules for 'Elitists' (especially Brits) - Must have a cow over non-elitist countries success in space!

[Amber G.]

^^^ (WRT to far site of the moon)

Is this because of the size of the earth being bigger?

The Moon is in synchronous rotation with Earth, which means that it takes roughly the same amount of time for the Moon to complete one rotation on its axis as it does to orbit around the Earth.(Both are ~27.3 days) As a result, one side of the Moon (the near side) is always facing Earth, while the other side (the far side) remains hidden from view.

Because the Moon is always showing the same face towards Earth, observers on the Moon's surface would see the Earth in a fixed position in the sky. It wouldn't appear to rise or set as we see the Moon do from Earth. The Earth would essentially stay in one spot, although there might be some slight variations due to the Moon's orbital and rotational factors... (Tilt of orbital axis is about 5 degrees so it may move slightly up-down ~ about 5 degrees)

This phenomenon is a consequence of the gravitational interactions between the Earth and the Moon over long periods of time - over billions of years, causing their rotational and orbital motions to become synchronized. (See tidal locking in previous posts)

[sajaym]

Lander specifications
Power : 738W (Winter solstice)
Does this mean that the power is enough to keep the lander in hibernation till the next lunar day? Is there any possibility that the lander will call the rover 'back inside' at the end of the first lunar day?

[madhu]

https://twitter.com/debapratim_/status/ ... jSKVw&s=09

Saying #ISRO nailed the landing is a severe understatement!!

The Vikram Lander touched down with a vertical velocity of 0.983 m/s and a horizontal velocity of 0.053 m/s.

Faaar below the maximum 3 m/s which Vikram's landing legs were designed to withstand. #Chandrayaan3

[SriKumar]

The reddit post on this is has a clearer image at touchdown

THe altitude in this screenshot reads 3.46m at landing. time is shown as 0.00. The entire lander is only 1.1m high and yet Altitude is 3.46 m and it has 'landed'? Measurement error (unlikely, a 3 meter error is too large) or something else? (If landed, then both horizontal and vertical velocities should be 0.0; so it probably has not landed yet even though time shows 0.0).

The Laser altimeter is about halfway up the Lander, so about 0.6m above the 'feet' or landing pads of Vikram. That leaves it still 3.46-0.6 = 2.86m above the surface with a velocity of -0.983 ms. If indeed that velocity is -0.983 m/s at 3.46 m altitude, then perhaps the engines cut off at this point but if they do, the free-fall would give it a touch-down velocity of sqrt( 0.983^2 + 2*(9.81/6)*2.86) = 3.21 m/s (going by v^2 = u^2 + 2 *g*s and taking lunar gravity into account). I recall hearing somewhere that the engines would cut off a meter or two above lunar surface.

[SSSalvi]

^^^ (WRT to far site of the moon)

Is this because of the size of the earth being bigger?

It is same why we see only one side of Moon.
This side will always face Earth, although it will see Earth in rotation and all equatorial surface will be seen over about 1 earth day.

Added later: After posting I found that AmberG had already explained it .. but as usual he adds his simple math/numeric masala making it more spicy.

[SSSalvi]

The Vikram Lander touched down with a vertical velocity of 0.983 m/s and a horizontal velocity of 0.053 m/s.

Faaar below the maximum 3 m/s which Vikram's landing legs were designed to withstand. #Chandrayaan3

That also explains why the dust cloud at touchdown was far below the expected ( just a common sense quantum.. I don't know if any quantitative number is there ) pollution fog.

[Jayram]

The reddit post on this is has a clearer image at touchdown

THe altitude in this screenshot reads 3.46m at landing. time is shown as 0.00. The entire lander is only 1.1m high and yet Altitude is 3.46 m and it has 'landed'? Measurement error (unlikely, a 3 meter error is too large) or something else? (If landed, then both horizontal and vertical velocities should be 0.0; so it probably has not landed yet even though time shows 0.0).

The Laser altimeter is about halfway up the Lander, so about 0.6m above the 'feet' or landing pads of Vikram. That leaves it still 3.46-0.6 = 2.86m above the surface with a velocity of -0.983 ms. If indeed that velocity is -0.983 m/s at 3.46 m altitude, then perhaps the engines cut off at this point but if they do, the free-fall would give it a touch-down velocity of sqrt( 0.983^2 + 2*(9.81/6)*2.86) = 3.21 m/s (going by v^2 = u^2 + 2 *g*s and taking lunar gravity into account). I recall hearing somewhere that the engines would cut off a meter or two above lunar surface.

Not an expert but we may be overthinking this . two points - LDV (Laser Doppler velocimetry) reads 0.0 - no motion detected ie touch down and the this time is then frozen at 1193.573 -consistent over on the left and right side of the picture. So at that point all the rest of the sensor data is frozen and is what we see in the picture. After all if all the sensor data was reset at touch down the usefulness of that data at that point would be diminished and would not allow for any troubleshooting.
Engines cutoff a meter of two above the surface seems excessive in my opinion especially if there is a possibility of a bounce( in low lunar gravity) with uneven time of touchdown (due to uneven weight distribution of the LM) of the each of the four legs.

[SSSalvi]

^^^
1, Engine shutoff earlier ... to avoid large dust settling on solar panels??
2. Why ISRO in its official posting on Reddit use a Camera photo of screen instead of actual screen sharing? Very bad of ISRO PR.

[Amber G.]

That also explains why the dust cloud at touchdown was far below the expected ( just a common sense quantum.. I don't know if any quantitative number is there ) pollution fog.

As you know, there is lot of curiosity, (and lot of theoretical models) if 'dust' on the polar region is significantly different .. We would know in about a week or so... what some have been wondering for a *long* time..

[juvva]

The reddit post on this is has a clearer image at touchdown

THe altitude in this screenshot reads 3.46m at landing. time is shown as 0.00. The entire lander is only 1.1m high and yet Altitude is 3.46 m and it has 'landed'? Measurement error (unlikely, a 3 meter error is too large) or something else? (If landed, then both horizontal and vertical velocities should be 0.0; so it probably has not landed yet even though time shows 0.0).

The Laser altimeter is about halfway up the Lander, so about 0.6m above the 'feet' or landing pads of Vikram. That leaves it still 3.46-0.6 = 2.86m above the surface with a velocity of -0.983 ms. If indeed that velocity is -0.983 m/s at 3.46 m altitude, then perhaps the engines cut off at this point but if they do, the free-fall would give it a touch-down velocity of sqrt( 0.983^2 + 2*(9.81/6)*2.86) = 3.21 m/s (going by v^2 = u^2 + 2 *g*s and taking lunar gravity into account). I recall hearing somewhere that the engines would cut off a meter or two above lunar surface.

iirc the engines cut off only after the sensors in the pads of the legs , signal contact with the lunar surface.
there is no possibility of free fall.

[Amber G.]

Maybe I shouldn't provide input—so please disregard this unless there's a genuine desire and readiness to comprehend fundamental science. Understanding these concepts necessitates the use of simple mathematics.

<snip>
Sivab/Siva509'ji, I thought that you attended MIT and have a tech background to answer the same.

Anyway, without resorting to equations and mathematics ..
So here we go (for couple of your questions):

1. Lunar gravity is 1/6th the earth gravity, so anything that needs to escape moon requires 1/6th the velocity that is required for earth. So whatever thrust is required to achieve the velocity. You can give some thrust for a lot of time or lot of thrust in a short amount of time, but the end goal should be the velocity gain. To your question, the thrust to be used to launch an equivalent mass from moon thus follows to be 1/6th. Or to turn it around you can launch 6x more payload from moon than Earth.*...

The gravitational acceleration on the Moon (1.62 m/s²) is indeed one-sixth of that on Earth, but the escape velocity (2.4 km/s) is about two ninth of Earth's (11.2 km/s). The relationship between escape velocity and gravitational acceleration is relatively simple, Hint: it's not a direct ratio. ( One can find the formula in any textbook.or <here>)

As I'll explain in simpler terms, having a moon base is crucial for making human travel to Mars more feasible. This is because we can send payloads from the moon to Mars that are six times larger compared to sending them directly from Earth. This enables us to carry additional supplies, more fuel, a greater number of people, and so on. Alternatively, we can achieve faster travel with the same payload. This idea prompted discussions about establishing a moon base.

As Pauli once remarked, "This is not even wrong." .. It doesn't work that way!

Mass differs from weight; a 100 kg mass on Earth remains a 100 kg mass on the Moon. (Hint: In orbit, everything is weightless, but that doesn't mean you can carry an unlimited payload.) Newton's laws deal with mass, and for a given change in velocity (delta-V), the energy (fuel) required depends hardly on whether you're on the Moon or not (assuming you're beyond the gravitational "potential well" of local body ).

You have to do work against Sun's gravity to go to Mars..

Whether you're near the Moon or Earth, the delta-V needed to reach Mars (or other outer planets) is approximately 42 km/s. Since Earth (or the Moon) is already moving at around 30 km/s, you might opt to wait for the right orbital alignment. This way, you'd only need about 12 km/s at the optimal time. (For this, you might need to wait for a year or a few, aligning Earth's or the Moon's trajectory with that of Mars.)

Moon's g is 1/6th of earth etc doesn't significantly alter flight time .. Forget about getting faster/slower due to this-- the flight time is mainly dictated by Newton's laws. (assuming you have limited fuel).

While gravity assists, mechanics, and planetary alignments can conserve fuel, apart from the fuel needed to escape Earth's (or the Moon's gravity well - where it has some advantage), the "one-sixth factor" doesn't hold much significance.

Hope this is useful.

(One of the main advantage of having base at moon is apart from low gravity there is vacuum - so one can give high initial velocity (without worrying about air resistance (as o Earth)) right around the surface..)

[Cain Marko]

Even though I can't understand half of Dishaji and AmberGs posts on math, space and medicine, I propose....

Can we just appoint AmberG as BRs Bill Nye, the Science Guy ( or should it be, gal?).

AmberG, is BR's Scienceji. There. That's proper desi and even rhymes. Screw Bill Nye.

[SSridhar]

Lander specifications
Power : 738W (Winter solstice)
Does this mean that the power is enough to keep the lander in hibernation till the next lunar day? Is there any possibility that the lander will call the rover 'back inside' at the end of the first lunar day?

Winter solstice power means the maximum power generated when night is longest and day is shortest on Earth. It is the intensity of light (photons) that fall on the panel that matters. So, in winter solstice, solar panels will still work. But, not in dark nights. During a lunar night, there could be some 'earthshine' on the moon but the intensity of light should be negligible. Besides, the surface temperature during a lunar night plummets drastically which would also affect the panel and electronics. In short, winter solstice performance is not a useful parameter to have hopes on surviving the lunar night. But, as Somnath said, let’s hope for the best. If that happens, it would be phenomenal to say the least. This launch has already made significant achievements. That would be one more if it happens.

[Deans]

Sour grapes Brits!

I guess those Brit colonialists need to be reminded that the sun has set on the British empire. UK is a third rate power today and a poodle of the US. They are talking about their measly 'aid' that they send to India, most probably to be used for subversive activities. India doesn't need their aid and they can shove it up their bottoms.

We need to remind themf that they actually owe reparations of over $45 T (which is way beyond their means). These descendants of thieves and crooks need to be reminded that they are a criminal country that has grown because of looting the wealth of various countries. Their Thief-in-Chief still is in possession of stolen properties like the Kohinoor.

I have reminded a Brit of the following:
1. They don't give us any Govt aid and haven't done so since 2015
2. Our overseas Aid is more than UKs (though UK is officially higher, it is either contribution to IMF/WB or does not leave the UK)
3. Our GDP in PPP terms is $ 10.2 trillion, they are $3.3 trillion (we are 3 times higher).
4. We have a far more advanced space program.

[SSSalvi]

Curiously ,ISRO Tweeted but withdrew this

Image of CH3 Lander by CH2 Orbiter camera