Share this page!

Enter URL or ID to Unroll

You can paste full URL like: https://x.com/threadreaderapp/status/1644127596119195649
or just the ID like: 1644127596119195649

How to get URL link on X (Twitter) App

  1. On the Twitter thread, click on or icon on the bottom
  2. Click again on or Share Via icon
  3. Click on Copy Link to Tweet
  4. Paste it above and click "Unroll Thread"!
  5. More info at Twitter Help
Indranil Roy Profile picture
Indranil Roy
@Indrani1_Roy
Physics. Philosophy. People. Poetry.
4 subscribers
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
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.
Oct 31, 2022 • 12 tweets • 6 min read
@Spectre66108666, this is not against you. This is an often-repeated misconception. So, please allow me to first dispel this misconception.

And then criticize the program properly 😅 @Spectre66108666 1. Look at the noses of transonic jetliners and cruise missiles. The bulbous nose is more aerodynamically efficient for subsonic and low transonic speeds. ImageImageImageImage
Oct 17, 2022 • 37 tweets • 8 min read
I came across this wonderfully prescriptive article by our very own RKS Bhadauria sir. I am quite pleasantly surprised on how strongly my own thoughts are aligned with his on this subject. Please allow me to add a few more of my thoughts.
iadb.in/2022/10/15/oct… Image 1. In my humble opinion we don’t have the capacity for a private vs public sector showdown. We are trying to play catch-up (with enemy at the doors) and intend to emerge as a leader in 1-2 decades. Wishful thinking, a complete restart and unorganized execution can’t get us there.
Sep 17, 2022 • 19 tweets • 11 min read
@prody24445539 On Monday. No links. But a proper technical rebuttal based on peer reviewed published papers.

I can tell you that you have taken a concern and led to the belief that the concern must have manifested. Not true. @prody24445539 I just wanted to dispel some of the concerns of buzz in Mk2. Obviously, nothing is proven until the aircraft is ultimately built and flown. But the design has undergone a lot of studies and cleared every review possible before the config was finalized.
Sep 1, 2022 • 11 tweets • 2 min read
Many have expressed some surprise and confusion on the 6,500 crores allotted for building Tejas, testing and certifying Mk2 prototypes.

Some find it high! Actually, it is very cheap. We paid over twice that amount (~13,500 crores) for "India Specific Enhancements" on the Rafale 5 years back. These enhancements were only related to avionics and new weapons.
Sep 1, 2022 • 8 tweets • 3 min read
What a beautiful design by Prof Das!
@prody24445539

This is the bane of or R&D setup of India. That ideas like this NEVER see light of day. And in 2015 we imported nearly 200 light trainers!

Why? Why? Why? @Rajeev_GoI, I know your love for aviation and look up to you as an enabler. Can we as a country continue to waste such capabilities and opportunities? Can a cell and associated funds be set up to foster such private enterprises?
Aug 30, 2022 • 34 tweets • 7 min read
I am going to reply to this tweet. @bheemmz please don’t be offended. Nothing against you. Here “you/yours” refers to a 3rd person. This tweet just contains some often-repeated misconceptions which need to be clarified. My discussion today is going to be limited to fixed wings. @bheemmz 1. This tweet conflates design and manufacturing expertise and where these expertise lie within the Indian aerospace ecosystem. Also the idea that canards on fighter are some super-duper technology needs some debunking.
Jul 26, 2022 • 5 tweets • 2 min read
Rohit is the best civilian observer of indigenous equipment (related to armour). I have read his writings for over 15 years now.

Caution: Olive green runs in his blood and he will take you the dogs if you utter a word against IA. I also want to say that IR capability that was developed for Nag has even more offshoots than what Rohit outlined. The seeker of KV of the Indian ASAT is an offshoot. The seeker of the upcoming VSHORADS and Astra-IR are also offshoots.