Bharat Rakshak

sudarshan

A question: Do we know the spacing of the 500N engines on the lander? I am assuming they are mounted in a square configuration. Also whats the rotational moment of inertia of the lander along its principal axes? I want to calculate how much the engine has to over perform in order to tumble the land...

sudarshan

https://live.staticflickr.com/65535/48740654077_155c38c50f_b.jpg From the below link: https://theicct.org/blog/staff/zero-emission-buses-are-worth-reaching-for Brazilian P-7 is apparently equivalent to EU-5, and P-8 to EU-6. The above link makes a case for fast-tracking adoption of EU-6 equivalent,...

sudarshan

This will become OT here (even if it is about the UK and not the USA), but just to mention - the numbers for the USA (the reported numbers, not including prison rapes) are estimated to be about 1/6th of the real figure. So overall - USA has about 16X the (reported) rate of sexual abuse/ rape as Indi...

sudarshan

The math is not right. It would be about 30 times (not 5 times) relative to the population. Yep, something wrong in those numbers. The numbers as reported above, show that the UK has more rapes per year than India (wouldn't surprise me, but seems unlikely). In terms of raw numbers, the undisputed r...

sudarshan

wow! so, the increase in velocity, then followed by loss of signal, and then thud! the saffron line looks like it made a screeching halt like a jet w/ landing gears down. No no, the saffron line (I presume you mean at the very end) isn't a "screeching halt," it means the lander is at rest...

sudarshan

So, if the initial segment was simple 'coasting', the glitch seems to be 'downward push' rather than a free fall. Of course it maybe because the initial vector was at a shallower angle. That's how I'm reading it too. So how about this scenario: One rocket overperforms. So thrust is higher, meaning ...

sudarshan

1. The x-axis in the plot by Amber.G is min:sec. If you look at the leftmost point, it is 19:55. At the next gradation, it becomes 20:00; and the next is 20:05. The only way this is possible with all the gradations on the x-axis being equally wide is if the xy in 19:xy is in seconds. (Added later: ...

sudarshan

I assumed its sec:hundredths of second. Usually telemetry is in millisecs that is reported as Secs: xxx So here they are reporting as secs: 0.xx0 Eg. 19 Secs 550 millisecs, 20.000, 20 secs 050 millisecs They probably have better data but the graph divisions are like that Hours minutes is very slow....

sudarshan

To my eye it looks like Delta V= 360m/sec- 220m/sec = 140 m/sec Delta T = 20.19=20.18 = 0.01 sec X2dot = 140/0.1 = 1400 m/sec^2 That's quite a bit of sustained shock. In Gs= 1400/(9.81*1/6) ~ 850 gs in moon environment? Numbers seem all over the place (no offense sir). 20:19-20:18 is 1 second, not ...

sudarshan

OK I'm out for now.

sudarshan

Woo hoo! -118 dB. Who's going to be first with the screenshot?

sudarshan

Per this tweet (not sure how genuine it it is, it claims to be a bot that monitors NASA's DSN site): That tweet might be genuine, it seems to be around the same time that suryag said to go check the site. I've been monitoring the site so far, but now I have to knock it off and go attend to somethin...

sudarshan

It was briefly at -115 dB (around the time of suryag's post saying to "go check on the website"). At that time I was so excited about the dB value, that I didn't notice the data rate or whether the downlink signal was just the carrier or actual data. Didn't get a screengrab either. Kicking...

sudarshan

No data rate (the data rate was "-"). It seemed like just the carrier signal on the downlink. I guess the lander won't send data to any old donkey who asks for it?

sudarshan

Erratic - down to -143 dB now. Dies occasionally and then comes back.

sudarshan

Quickly goto dsn, goldstone is able to get DL signal from CH2L :) earlier it was Madrid station I see it, seems like two-way communication. Moon must be visible from California now. In Madrid it would be close to setting or already set. Is there any significance to the shape of the wave form? Seems...

sudarshan

Hmm, scratch what I said above about near and far side, I might be guilty of spreading disinformatsiya. It seems, looking at crater maps, that the moon's south pole is on the far side as seen from earth? Will check and get back. But then, like UB said, I fail to see how a radio telescope from earth ...

sudarshan

The landing spot was on the near side of the moon. Yesterday was ashtami (shukla paksha - waxing phase), so one half of the near side of the moon was visible from the earth. Meaning, the other half of the near side was just starting its lunar day, and would continue to have sunlight for fourteen day...

sudarshan

No ji, earlier in the day, I swear, the Madrid CH2L thingy on the site said "Chandrayan 2 Lander." Maybe they switched it to the x-ray observatory now. It seems right now the Goldstone SOHO thingy is trying Chandrayan 2 Lander. Could be that the moon has set in Madrid, maybe?

sudarshan

^ Yeah, you think that's bad? Beat this!

Congress leader Udit Raj: "If only ISRO scientists believed in science instead of breaking coconuts...."

https://www.newsnation.in/india/news/co ... 36918.html

sudarshan

Gagan ji, the stream of Neil Armstrong was black and white. Seeing the doppler shifted data radio spectrum, told the story of wobbling last seconds of flight. The minute oscillation in observed doppler shift corresonding to net delta velocity component (radial to radio receiver); the spatial non-omn...

sudarshan

UB ji, the craft need not have impacted on its head. It could have rolled that way later. We'll see, there's still hope.

sudarshan

Ashokk wrote:On the DSN website right now one of the antennas in Madrid is sending data to the Chandrayaan-2 lander (CH2L) at 11kW

Sending data? You mean it's working?

sudarshan

Sudharshan'ji craft was definitely *not* tumbling during the rough descent phase. That went flawless. I think the cutover from rough descent to smooth landing was not even. What could be the reasons? We need to break down into sequences the smooth landing phase and maybe given public information tr...

sudarshan

Well then now is the chance, right? The "Ghastly Trolls" should now dig up old footage of the Bagla's antics and put it up for all to see how much he has "done for ISRO." That Doppler curve shows steady deceleration during the rough braking phase. If the craft were tumbling then,...

sudarshan

Currently drowning my sorrows (over Vikram succumbing to Vetal) by drinking cold water (hic

) since I don't drink alcohol. Will be back to this thread in a bit.

sudarshan

5. Sudarshan: If you look at the embedded video, the craft dropped rapidly at around 3:00 but look at the altitude drop from 3:06 to 3:13. The 7-second update of altitude showed that it had recoved its poise. The altitude drop is around 150 m to 200m (eyeballed it).So its velocity just before loss ...

sudarshan

I guess the Chinese were under pressure to get it right, if they didn't want to be breaking rocks in Heilongjiang or Inner Mongolia

. Contrast with how Modi treated ISRO with consummate respect even with what happened.

sudarshan

So if I understand right, the first stage of the descent was with four retro-rockets, then it was supposed to go down to two? What is the reason for that? Why not keep the four rockets, and manipulate their thrust? Four rockets is like a quadcopter drone. Easier to manage the turning moments. With t...

sudarshan

^^^ Fair enough. ^^^^ Well if the video is real-time, then the craft was at ~1.8 km height around 2:57, then by 3:06, it was down to ~0.6 km (just by eye-balling). So 1.2 km drop in 9 secs :eek:. 130 m/sec? So the rockets were accelerating it down instead of decelerating - must have turned upside do...

sudarshan

Even assuming that the last communication was at 300m (based on the last point on graph), the concern we have is that the rate of descent from 2.1km to 300m was too fast for the craft to survive. As per ISRO's plan from 500m altitude the decent has to be 1m/sec. Leaving aside the path between 2.1km...

sudarshan

Are you saying it didn't have that much fuel?. How does it waste it when its purpose was getting over in few more minutes? Touch down at 10m/sec?. Are you crazy? Doesn't matter what the gravity is. When we say 10m/sec, we mean 10m/sec. That would be hard crash. Last 10 meters, the actual plan was t...

sudarshan

Used to have a copy of that bassbort abblicashun somewhere. So many good things on Bakistan, so little time. Maybe it can still be downloaded from Baki embassy? Search on google for "passport form pakistan online pdf" and pick the first link. Or alternatively, just click below: http://pak...

sudarshan

Thank you for that article, definitely a more sophisticated view. I think it's pretty irresponsible of people, especially celebrities, to post pictures from years ago (as much as 20 to 30 years ago!) or from a different place and setting altogether, and add on the tag of "Amazon rain-forest is ...

sudarshan

Mort ji, like I said, if the energy density of the battery by weight is one-third of petrol, that might add an additional 3 to 4% to the overall vehicle weight due to the battery alone. There might be savings on the drive train, especially with independently controlled wheels (one motor per wheel) w...

sudarshan

No, conventional battery chemistries aren't there yet. 1Kg of petrol is about 10 KWhr. Aluminum-air is at best 1/3 of that. We're both saying the same thing here. I said on a "volumetric basis," aluminium-air was slightly ahead of petrol. Petrol is around 0.75 g/cc, aluminium is about 2.7...

sudarshan

I don't think time and effort should be wasted on conventional battery chemistries. The energy-to-weight ratio simply isn't there. It would be better to focus on plug-in hybrids and fuel cell technologies. ISRO could be the lead for fuel cell technologies, they've proven their worth in many areas a...

sudarshan

You know they meant 1 gwh (gigawatt hour). That would be about 25,000 batteries per year capacity (40 kwh battery for a range of about 250 kms -- Nissan Leaf). The alternative chemistry to Li-ion they are talking about is probably Aluminum-Air which is several times more energy dense compared to Li...

sudarshan

Indian Oil to build a 1 GW electric vehicle battery plant. What exactly is a "1 GW battery plant"? Is there some DDMitis somewhere here? Do they mean that they will produce enough batteries every second, to store 1 GJ of energy? Or is the plant going to consume 1 GW of power to make the b...

sudarshan

https://www.ndtv.com/world-news/in-viral-video-imran-khan-says-germany-japan-share-a-border-2027149 Imran says Germany and Japan are neighbors. Delegates puzzled. Nothing to be puzzled about. Please read the full context of the speech, it is about how "Germany and Japan were both killing millio...

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