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Indranil Roy Profile picture
Indranil Roy
@Indrani1_Roy
Physics. Philosophy. People. Poetry.
5 subscribers
May 16 • 34 tweets • 13 min read
1. There are a few inaccuracies in this explanation.
2. What has been explained here is how most missiles work. It does not explain why Brahmos is a game changer.

Here's a little explainer thread. I will keep it super simple Let's first understand what's wrong in the explanation:
1. Increasing the speed of the air, does NOT increase it's pressure/temperature.

Bernoulli's principle states that the opposite is true. When speed increases, pressure falls. This is the reason why aircrafts can fly.
May 9 • 13 tweets • 5 min read
The reporting on military affairs in India is worse than a clown show. At least, a clown knows what they are talking about.

Most of our defense reporters would be poor actors for soap operas.

Here's are the basics in air defense. To cover enormous areas, any air defense system is layered.

Just like if you have to go to your neighbors house, you walk. To go further, you take a bicycle. Further still, you take a motorcycle or car. Further still, you take a train or an aircraft.

It is the same concept.
Jan 18 • 6 tweets • 3 min read
Every country self-dependent on its own jets. E.g. US did it during the beginning of WWII. Prime example of today is China. Upcoming ones: S. Korea,Turkey.

Countries which've gone for "better available" options are losing their self-dependence, e.g. Japan, Germany, UK. Let me give you a concrete example of today. USA was looking for its next advanced trainer.

"Available options" from around the world competed. Advanced Hawk from UK, Leonardo T-100 from Italy, T-50 from Korea.

Guess what they did? Image
Image
Image
Jan 16 • 15 tweets • 4 min read
They not how much the current IAF chief has fought and will continue to fight for Tejas.

They don't understand the German WWII production rate either.

The Germans used wood in their planes when steel fell short. They sent young boys with 70 hrs of flight time into war. These guys are talkers. They don't understand what it takes to build hard-tech. Hard-tech that is built on industry. Industries that need to be fostered for at least a generation.

Such talkers have always laughed at doers.

Ignore such talkers. They are worthless like their talk
Dec 26, 2024 • 25 tweets • 8 min read
Shocked? Was this not evident over the past few years?

But panic and despair is what we should not.

1. I don't know what is 6th-gen in this?
2. Time to bite the bullet was yesterday. Do it at least today: Importing a handful is a band-aid that does not work Let's look at my first point. A lot of commentators are calling this 6th-gen. What is 6th gen in this? It's a tailless flying delta bomber. If this is 6th gen, then what gen was the B-2 bomber that flew in 1987? Image
Dec 24, 2024 • 13 tweets • 3 min read
Today there are a lot of commentators on everything underneath the sun. Very few have the depth in any field.

@Archit_Ch is not one of them. These guesses are reasonable, and most likely correct. @Archit_Ch DRDO's missile program is absolutely world class. It has three major classical advantages:
1. They have the design know-how, know-why and the data.
2. It has the requisite test facilities and
3. It has reliable production partners from prototypes to serial production
Dec 8, 2024 • 6 tweets • 2 min read
1. Drones are here to stay. More and more men are going to be removed from the cockpit
2. But, removing the man from the loop is very very hard.
3. The term AI-enabled is more abused than used. I don't say this with pride, but I can easily fool about what AI-enabled is 4. Most decision makers don't understand what AI is incredibly powerful but don't understand what AI can and cannot do. It sells for everybody from fund-raising and marketing of makers, to decision-makers, to govt.

We have used AI for bla-bla-bla makes you sound intelligent.
Nov 24, 2024 • 6 tweets • 2 min read
This swarm of drones is good for shows, not for warfighting.

For a show, one defines a 3D point-cloud and places a drone at each of the points. The trick is to find how these clouds may be morph throughout the show given the capability of the drones. But, this is an algorithmic challenge against static requirements. May I add that this is also an artistic challenge as well.

But, this is not what warfighting drones have to deal with. In a battlefield almost all aspects are evolving.
Nov 18, 2024 • 21 tweets • 7 min read
India did not enter the "hypersonic missile" group with this missile.

And that thing on the nose is an anomaly, not a feature.

Here's a quick and dirty thread on where this missile lies on the technology spectrum and what it means to India's security. Image The easy thing first. That disc at the top is just the cover of the canister. It's supposed to rupture at launch, but it did not. It got lodged in the nose and was broken only due to aerodynamic forces as the missile achieved speed.

Undesirable, but solvable.
Oct 29, 2024 • 11 tweets • 3 min read
So, the 36 Rafale purchase was an "emergency purchase" and a new "multi-vendor tender to acquire these aircraft under Make in India procedure" is non controversial way to proceed now.

What the hell was MRCA program then?

aninews.in/news/national/… At that point, bypassing the entire process was called a "masterstroke", "solving an Gordian knot", etc. Now, we are returning to the same process which was unsolvable (because the chosen vendor went back on price and ToT obligations) after the election!

Kya maaya hai!
Mar 29, 2024 • 11 tweets • 2 min read
#TejasMk2: Thoughts are boiling over.

Many things have changed since 2005, when the first 5th generation fighter F-22 was operationalized. Today's 4.5 generation fighters are technically superior to F22 in every aspect but stealth and thrust to weight ratio. There so I am not going to use the term 4th generation and 5th generation. I am going to say stealth and non-stealth aircraft.

There is no bigger exponent of stealth aircraft than USA. and they have been very clear about their lessons.
Feb 7, 2024 • 23 tweets • 10 min read
Many of you want to know more about this locomotive.

This loco is completely designed and built by Chittaranjan Locomotives Works (CLW). This engine is an incremental development of the WAG9 engines which has been a workhorse for Indian Railways for the past two decades.
Image This is their 500th locomotive for the fiscal year. Their target is to produce 540 locos for this fiscal year.

If they manage do that, they will break their own world record of 436 that they reached last year. Year on year, this is a 24% jump in production rate. Image
Jan 29, 2024 • 35 tweets • 14 min read
For me, NGLV is the most exciting developments from ISRO. Enough info has trickled out to make some educational guesses.

Thank you @TitaniumSV5 for capturing the slide Dr. V. Narayanan, Director, LPSC.I had some first-order questions which are now answered.

Beware, long thread. @TitaniumSV5 In this thread I will answer 3 basic questions:
1. Why does the first LM470 use 9 liquid methane-oxygen (methalox) engines?
2. Why develop new methalox engines, when ISRO is already developing semi-cryo kerosene-oxygen (keralox) engines for LVM 3?
3. Why 3 stages?
Dec 19, 2023 • 7 tweets • 2 min read
1. Tejas Mk2 is happening
2. No major technical challenges
3. The rollout of Mk2 will predate AMCA/TEDBF
4. I wish the MRFA jamboree continues till Mk2 rollout because justifying it after Mk2 rollout and first flight will be very difficult. I will just add my two cents about the questions being asked here.

This outrage/meltdown is good. This delay is a making of the decision makers, not engineers. So let them hear it.

Will they hear it? Does it matter? That's a different question altogether.
Aug 28, 2023 • 14 tweets • 3 min read
This is an incredible footage of what is called a "hesitation roll". The aircraft flies nearly straight and level, rolling 90 degrees at a time and then 'hesitating' before rolling the next 90 degrees. The pass is completed with 4 such 90-degree rolls. Although, this looks fairly simple, there is an enormous amount detail that is visible only in a video of this quality (thank you @Praneethfrank).

Notice carefully how the nose moves around to initiate each 90-degree roll and then settle to different AoA at every hesitation.
Apr 6, 2023 • 30 tweets • 10 min read
Here's a thread on ALH/LCH and LUH main gear box. The MGB is the magic around which the engineering is done. It is the primary reason behind ALH/LCH's phenomenal high-altitude performance.

@AnilBhambhani11, @unnipillai18,@realkaypius, @BahadurManmohan: please correct any errors. First let's have a look at the ALH's main gear box (MGB) and rotor head in the first row.

The second row is that of AW139, a fabulous helicopter of roughly the same size and power

Notice how much more compact and clean ALH's MGB and main rotor head are? ImageImageImageImage
Apr 4, 2023 • 19 tweets • 6 min read
The Ferrari of utility helicopters. I want to explain a few things to heli-newbies. H160 is a fantastic helicopter! But it won't meet Indian requirements. It's service ceiling (IGE) is 2835 mtrs. Dhruvs is twice of that! And not just that ...
Apr 3, 2023 • 6 tweets • 1 min read
*** ANNOUNCEMENT ***
From now on I am adapting a Copy-left policy. If you like a thread of mine and want to publish it, go right ahead.
1. No need for my permission.
2. Giving credit is welcome. It's fine otherwise too.
4. Any moratoriums will be donated. Please PM me. I right mostly on aviation and computation, because I love physics and math. I hate the way technology is taught and reported. Sorry. But, I stand by this.

It is NOT DIFFICULT. We squeeze the fun out of it. Make it look difficult, because we don't understand it.
Apr 2, 2023 • 6 tweets • 2 min read
My wife & I were returning from a fishing trip. We had fished through the dusk & early twilight. It was now dark and we were enjoying the drive back home which hugs the river that was now glistening in the moonlight. There was nobody else on that stretch if the road when We negotiated a turn & saw what looked like a child sitting in the middle of the road about 200 yards ahead with its back towards us. By the time the car came to a halt we must be about 50 yards from it.
Feb 7, 2023 • 24 tweets • 8 min read
I love the education that I received on the following tweet.

I love it when people told me that the scientist, engineers and pilots built, flew and certified a thing, they should know a thing or two more than the critics.

Badi mehnat se yahaan pahuche hai, isse chorna nahi. 1. Let me tell you a bit about this beautiful bird. Murmurs abt this bird started taking shape around 2007. At that time it was called the LO(Observation)H.

The idea was simple: half a Dhruv, i.e. single engine with half the payload, a modern Cheetah/Chetak substitute.
Dec 27, 2022 • 26 tweets • 7 min read
India is almost self-sufficient in missile technology. Sophisticated state-of-the-art missiles are going from design-board to first-launch in less than 3 years, getting tested dozens of times in the next 3 & getting inducted. This success story must be studied and internalized. 1. The story starts 5 decades ago with Project Valiant and Devil. There was nothing to bank on. No existing designs or designers or data. No industry, no testing facilities. Only a handful of men and women who dreamt of self-dependence And a govt. which supported them.