Indian Space Program: News & Discussion

[a_bharat]

AgniKul Cosmos
@AgnikulCosmos
Humbled to share that we successfully test fired 3 semi-cryogenic rocket engines simultaneously, as a cluster. All the 3 engines are 3d printed as single pieces of hardware - designed and manufactured in-house at AgniKul Cosmos Rocket Factory - 1. As with all our propulsion systems, these 3 engines are also powered by electric motor driven pumps.

This test involved calibrating 6 pumps, 6 motors and tuning 6 speed control algorithms to work together in perfect sync to achieve uniform startup, steady state and shutdown performance across the entire system.

To the best of our knowledge, this is the first time such a test has been performed in India with semi cryogenic engines. We are extremely grateful to have the opportunity to be building world class, original space technology from India, for the world with the support of
@isro and @INSPACeIND

[uddu]

Dhawan-III | Static Test Fire | Skyroot Aerospace
National Science Day marks the discovery of the Raman Effect, encouraging young people across the country to continue pursuing their passions in STEM. Today feels like the right moment to share what we've been building to fuel further innovation at Skyroot.

Dhawan-III, our upgraded cryogenic rocket engine, just completed a 145-second endurance test on an indigenous mobile test stand built in-house.

This engine has been developed under the Aatmanirbhar Bharat ARISE-ANIC initiative with a focus on reusability and greener propulsion.

Happy National Science Day.

[sanjaykumar]

What do those shock diamond thingees signify?

[drnayar]

What do those shock diamond thingees signify?

Rocket engine exhaust often contains a distinctive pattern known as shock diamonds or Mach diamonds. These are a series of shock waves and expansion fans that increase and decrease, respectively, the supersonic exhaust gases’ pressure until it equalizes with atmospheric pressure. The bright glowing spots visible to the naked eye are caused by excess fuel in the exhaust igniting. As awesome as shock diamonds look, they’re actually an indication of inefficiencies in the rocket: first, because the exhaust is over- or underexpanded, and second, because combustion inside the engine is incomplete. Both factors reduce a rocket engine’s efficiency (and both are, to some extent, inescapable).

https://fyfluiddynamics.com/2015/10/roc ... stinctive/

[sanjaykumar]

Thanks. Often wondered.

[drnayar]

and they have use in assessing calibration of rocket engines and assessing performance

Pressure Matching: They appear when the exhaust pressure doesn't match the surrounding air. If an engine is designed for high altitude, it will show these diamonds at sea level because it is over-expanded.

Flow Verification: Engineers use high-speed schlieren photography to see these waves, confirming the exhaust is supersonic.

Performance Tuning: The angle and length of the diamonds allow engineers to calculate the exhaust Mach number and pressure ratios.

Combustion Efficiency: If diamonds are visible to the naked eye, it often means unburned fuel is reigniting in the shock waves, signaling incomplete combustion.

how they form :

Imbalance: Exhaust leaves the nozzle at a different pressure than the atmosphere.
Compression: The outside air "squeezes" the exhaust, creating a shock wave.
Expansion: The gas bounces back, expanding past the ideal point.
Repetition: This "bouncing" repeats, forming the diamond chain until the pressures eventually equalize

How nozzle shapes affect shaping [ or not]

Nozzle shape fundamentally changes how exhaust interacts with the atmosphere, which determines if and how shock diamonds appear. While traditional bells create fixed patterns, advanced shapes like aerospikes are designed to "self-correct" and minimize them.

1. Traditional Bell Nozzles (Static Patterns)
Bell nozzles are optimized for a single altitude. At any other altitude, the pressure mismatch creates visible shock diamonds.
Over-expanded (Low Altitude): The nozzle is "too big" for the high air pressure at sea level. The air "pinches" the exhaust inward as it leaves the nozzle, creating a series of inward-pointing shock waves that form the first diamond.
Under-expanded (High Altitude): The exhaust leaves at a higher pressure than the thin air and "billows" outward. It then snaps back inward due to expansion fans, creating diamonds that appear larger and further downstream.

2. Aerospike Nozzles (Minimal/Dynamic Patterns)
An aerospike engine is essentially a bell nozzle turned inside out.

Altitude Compensation: Instead of a fixed metal wall, it uses the ambient air pressure as one "wall" of the nozzle.
Diamond Suppression: Because the exhaust is always exposed to the atmosphere, it constantly adjusts its expansion to match the outside pressure. This means the exhaust is almost always "perfectly expanded," which theoretically eliminates or significantly reduces the pressure imbalances that cause shock diamonds.
Visual Difference: If diamonds do appear in an aerospike (such as in linear variants), they are often less distinct or only visible when viewed from specific angles (e.g., from the end of a linear spike).

3. Dual-Bell and E/D Nozzles
These are "hybrid" shapes designed to have two optimal points.

Dual-Bell: These have a "kink" in the nozzle wall. At low altitudes, the flow separates at this kink, creating a smaller effective nozzle and smaller, sharper shock diamonds. As the rocket climbs, the flow "attaches" to the full bell, and the diamonds shift to a larger pattern.

Expansion-Deflection (E/D): Uses a center pintle to push exhaust outward. This creates a hollow exhaust plume where shock diamonds might form in a ring or complex internal structure rather than a solid center chain.

[Zynda]

^^This is great post. Thanks

[Amber G.]

The loss of the IRNSS-1F atomic clock reduces the number of working navigation satellites below the minimum required for full NavIC service, exposing long-standing reliability issues in the system’s atomic clocks and creating pressure for India to launch replacement satellites.. ..

India's NavIC satellite system faces challenge as IRNSS-1F failed after atomic clock malfunction: what we know

India's NavIC GPS alternative faces challenges after satellite IRNSS-1F failed, reducing operational satellites to three. A minimum of four is needed for complete coverage. The Union government last year stated that only four of the 11 satellites deployed for the NavIC system were fully operational.

[Ashokk]

IRNSS-1F successfully completed its mission life of 10 years

IRNSS-1F satellite launched in March 2016 has completed its design mission life of 10 years on 10th March 2026.

On 13th March 2026, procured on-board Atomic clock stopped functioning. However, the satellite will continue to function in-orbit for various societal applications to provide one way broadcast messaging services.

[Ashokk]

ISRO conducts sea level test of cryogenic engine at 22 tonne thrust level with full area nozzle

ISRO successfully conducted a sea level hot test of its Cryogenic engine (CE20) at 22 tonne thrust using nozzle protection system and multi-element igniter, on March 10, 2026 at ISRO Propulsion Complex, Mahendragiri. Earlier, the sea level tests utilizing nozzle protection system was being carried out at 19 tonne thrust level.

The CE20 cryogenic engine powers the upper cryogenic stage of LVM3 launch vehicle. In order to enhance the payload capability of the LVM3 vehicle, future missions of LVM3 are planned to be operated with an uprated C32 stage with 22 tonne thrust for the CE20 engine. In view of this, the flight acceptance test of the CE20 engine also needs to be conducted at 22 tonne thrust level. Therefore, the present test qualified the sea level testing of the engine with a test duration of 165 seconds at 22t thrust level using the Nozzle Protection System (NPS). The performance of the engine as well as the test facility was as expected during the entire test duration.

Testing the CE20 engine at sea-level possess considerable challenges primarily due to high area ratio nozzle, which has an exit pressure of ~50 mbar. Main concern during testing at sea-level include flow separation inside the nozzle, which leads to severe vibrations & thermal problems at the flow separation plane leading to possible mechanical damage of the nozzle.

The Cryogenic engine utilized for this test has undergone a record maximum number of hot tests (20 No.s) successfully, that has enabled the demonstration of several key technologies using a single engine such as engine ignition using multi element igniter, ignition margin demonstration for Gaganyaan over a wide range of propellants tank pressure and pre-ignition chamber pressure, engine qualification for Gaganyaan at 20 tonne thrust level, demonstration & qualification of 22tonne thrust level operation, boot-strap mode starting of CE20 engine without start-up system for enabling re-start in flight, indigenous turbopumps bearings qualification, indigenous sensor qualification and Nozzle Protection System qualification for high area ratio nozzle hot test at sea level.

[Amber G.]

IRNSS-1F successfully completed its mission life of 10 years

IRNSS-1F satellite launched in March 2016 has completed its design mission life of 10 years on 10th March 2026.

On 13th March 2026, procured on-board Atomic clock stopped functioning. However, the satellite will continue to function in-orbit for various societal applications to provide one way broadcast messaging services.

Thanks. There is a post by me and many newspapers are carrying this news. Few comments, background and updates:

- The loss of the IRNSS-1F atomic clock reduces the number of working navigation satellites below the minimum required for full NavIC service, exposing long-standing reliability issues in the system’s atomic clocks and creating pressure for India to launch replacement satellites.

• India’s regional satellite navigation system NavIC has suffered a setback after the satellite IRNSS‑1F lost its final functioning atomic clock on 13 March 2026.
  The satellite had three rubidium atomic clocks, and two had already failed earlier. When the last one stopped working, the satellite could no longer provide navigation services.
  
  With this failure, only three NavIC satellites remain capable of providing positioning, navigation, and timing (PNT) services, while at least four are required to maintain full regional navigation coverage.
  
  Although the navigation function has stopped, the satellite will continue operating in orbit for limited services, such as one-way broadcast messaging.The failure also highlights a broader reliability problem in the NavIC constellation:
  
  Out of 11 satellites launched since 2013, several have suffered failures, mostly due to malfunctions of imported rubidium atomic clocks.
  
  As a result, the constellation has become critically depleted, making it harder for NavIC to provide continuous navigation coverage.

- Launching a Second-Generation NavIC Constellation (NVS series)

ISRO is replacing the early IRNSS satellites with next-generation satellites called the NVS series.

• Planned satellites: NVS-01, NVS-02, NVS-03, NVS-04, NVS-05
  These satellites have longer lifetimes (~12 years) and improved navigation payloads.
  The first one, NVS-01, was already launched in 2023.

[/list]
- Switching to Indigenous Atomic Clocks

• The biggest technical fix is replacing imported clocks with Indian-built rubidium atomic clocks.
  
  Early NavIC satellites used imported SpectraTime clocks, and many of them failed in orbit.
  To fix this, ISRO’s Space Applications Centre (Ahmedabad) developed the Indian Rubidium Atomic Frequency Standard (IRAFS).
  First flown on NVS-01.Designed specifically to avoid the reliability issues seen in the original satellites.
  This is probably the most important engineering change in the system.

- Rebuilding the Minimum Constellation

• For navigation, you need at least four working satellites to solve for position and time.
  After the failure of IRNSS-1F, only three satellites currently provide full navigation signals, which affects service reliability.

ISRO’s strategy

• Launch additional NVS satellites
  Replace aging IRNSS spacecraft
  Restore at least 4–7 operational satellites
  The original NavIC architecture was 7 satellites (3 GEO + 4 inclined geosynchronous).

- Expanding Signals for Civil Devices

• The new satellites also add a new L1 band signal (similar to GPS L1).
  
  This is important because it allows mass-market chipsets (phones, wearables, IoT) to support NavIC more easily.
  
  Earlier NavIC signals were mainly L5 and S-band, which limited adoption.

ISRO’s response is essentially a generation replacement strategy:

Replace aging IRNSS satellites
Use indigenous rubidium atomic clocks
Launch NVS-series satellites with longer lifetimes and additional signals
Restore the minimum navigation constellation

Time Line (My take/hope):
Phase 1 — Start of Second-Generation Satellites
2023 — NVS-01 launched, First second-generation NavIC satellite.

Launched 29 May 2023 using GSLV-F12, Indian-made rubidium atomic clock and new L1 civilian signal.

Phase 2 — Early Replacement Attempts

2025 — NVS-02 launched, Second satellite in the replacement series.
However it did not reach its intended operational orbit, limiting its usefulness for navigation.

So effectively, only NVS-01 is fully contributing so far.

Phase 3 — Main Replacement Wave

ISRO plans to launch three more satellites:

NVS-03, NVS-04, NVS-05

These are intended to restore the constellation strength and replace aging IRNSS spacecraft.

Expected timeframe:
launches through 2025–2026 (some may slip slightly depending on launch cadence).
2023 - NVS-01 - operational
2025 NVS-02 launched (limited/failed due to orbit issue)
2026 NVS-03 launch
2026 NVS-04 launch
2026+ NVS-05 launch

----
For those who are more interested in Physics/technical part:

Implication

- Even with the recent atomic-clock failure in IRNSS-1F, the constellation should recover because:
- 3–4 new satellites are in the pipeline
- The new satellites have better clocks and more redundancy
- Additional atomic clocks per satellite are planned for reliability.

Realistically, NavIC should regain a stable constellation around ~2026–2027 once several NVS satellites are in place.

Technical aside (interesting GNSS detail):

NavIC satellites are GEO + inclined geosynchronous, so each satellite covers a large part of the Indian region. That means only ~7 satellites are required, unlike ~24 for Global Positioning System or ~30 for Galileo.

Amber G.

[uddu]

ISRO tests CE-20 engine at 22-tonne thrust

[Prem Kumar]

IRNSS-1F successfully completed its mission life of 10 years

What's galling is the pathetic attempt at spin-doctoring by ISRO

Yes, IRNSS-F completed 10 years. But that's not the story. The story is that we are without a working IRNSS system, our so-called answer to GPS/GLONASS

Absolute crapshow by ISRO, Minister for Space & ultimately the buck stops with Modi

And there is the sabotage angle too, which our Govt has belatedly woken up to. Many of us here have been screaming about it for years now, though some posters in this very forum tried to pooh-pooh it as some conspiracy theory

[S_Madhukar]

And decade later we are still happy only with regional navigation? So we will wait for 12 years to be sure the new atomic clocks work as expected and then we might think of a global navigation network. For all you know spoofers for the enemy and sabotage at our end must have happened in parallel

[Prem Kumar]

As someone wise said: "It takes the same amount of energy to dream big as it does to dream small"

With the corollary that the former is hugely motivating, while the latter feels limiting

We are happy dreaming small, not ruffling feathers & playing it safe. Be it "Light" combat aircraft, which must strictly be followed only by "Medium" combat aircraft. Or Agni-5's successor being only 6000 Km Agni-6 with range carefully represented as avoiding Europe. Or our homegrown LLM be specific to Indian languages/content only

We will never become a superpower because the mental shift hasn't happened yet