Analysis blog

The Future of Indian Orbital Rockets

As India moves to be a leading economic & military power, the nation’s premier space agency, together with Private-sector enterprise, gear up to provide ever-greater and ever-more affordable means of access to space – which in the 21st century is as much a building block of prosperity as roads & railways were in times past.

As a continuation to “A Brief History of Indian Orbital Rockets“, this piece delves into what is yet to come.

NOTE: As with the preceding article, I will only be mentioning those programs that aim to develop a full-fledged orbital launch capability as their primary goal; as such programs like the Nano Satellite Launch Vehicle (NSLV) which in the opinion of this author are primarily aimed at a Sub-orbital launch capability, have been excluded.

Small Satellite Launch Vehicle (SSLV)

Diagrams from official SSLV Brochures

While ISRO’s focus has rightfully been on increasing the size & payload capacity of its rockets, it hasn’t forgotten the commercial & strategic implications of a small, launch-on-demand rocket system that can greatly reduce both the cost & lead team it generally takes to put a satellite into orbit – and neither has the Government of India forgotten the strategic implications of the same technology. In 2018 the agency completed preliminary design on its SSLV platform that aimed to fulfill this emerging requirement.

In the opinion of this author, the SSLV was formulated to support two sectors, an explicitly stated civilian use centered around the rocket’s reduced cost, and a so-far ambiguous military/strategic role centered around the rocket’s record quick assembly time & use of solid-fuel motors for all 3 of its stages (unlike similar sized small vehicles like RocketLab’s Electron which still use liquid engines).

Various Satellite mounting options that the SSLV’s onboard Payload Adaptor can be configured for

Starting off with the civilian use-case; As the primary driving force behind the civilian launch market continues to be the cost factor, ISRO sought to reduce cost by maximizing technology commonality with the already proven PSLV & GSLV systems, considerably reducing the R&D cost for the new LV and allowing for a smaller margin to achieve profitability. Fine-tuning & streamlining the Private-sector production of components also enables the construction of affordable expendable stages. Adding to that, the reduction in infrastructure & human resources cost thanks to the strategic imperatives of this design (which we’ll go over in the next paragraph) also contributed to a planned sticker price per rocket of $4.2 million compared to $7.5 million for RocketLab’s Electron.

The largely ambiguous strategic use-case, rarely if ever talked about by either ISRO or Department of Space but inferred by this author to be the most pivotal role & effect of this launch vehicle, is one of supposition – a result of studying its design & configuration. The SSLV is designed to be highly modular, allowing for a full rocket to be assembled & readied for launch on just a 72-hour notice – down from the usual 60 days of notice it requires to assemble a large rocket like the PSLV (or the 16 days notice it takes to get a liquid-fueled small vehicle like the Electron ready for launch) – additionally, the Command & Control of the launch is designed to be managed by lightweight software from a single PC workstation. Whereas the PSLV took a workforce of 600 staff in the Vehicle Assembly Building (VAB) to put the rocket together, the small modular SSLV is designed to require only 6 people to complete its assembly, plus as per statements of the Chairman of ISRO, development of mobile launch solutions for the SSLV is also underway (offshore platform development confirmed, eventual use of land-mobile Transporter Erector Launcher (TEL) type vehicle for SSLV or some future version of it again inferred by the author). Similar in scope to the Chinese Long March-11 (offshore) & Kuaizhou-11 (road-mobile) rockets.

Assembly by a skeleton crew on short notice using modular components thanks to exclusion of liquid-fueled stages, C&C designed to accommodate field use without necessarily having access to extensive control facilities, or the ability to launch from austere conditions away from established launch pads all point toward a military-strategic nature of the system, very likely a requirement meant to be fulfilled by the newly formed Defence Space Agency (DSA), geared toward quickly re-establishing a limited satellite-based capability set on a short notice (to include navigation, earth observation, radar & infra-red reconnaissance, ELINT/SIGINT among other tactical uses) – in the event of existing long-term space assets being knocked out by an adversary’s ASAT weapons in a first-strike scenario.

The SSLV is currently undergoing static tests on its various stages & solid rocket motors, the first launch is expected sometime this year – it will be carrying the Microsat-2A payload (renamed to EOS-02 under the new broad-based ISRO naming scheme for satellites) on its first Demo flight.

Status: Static Stage Testing

Liftoff mass: 120 tons | Height: 34m | Payload to LEO: 500kg | Payload to SSO: 300kg

Intended Objectives

Affordable access to space for smaller & lighter payloads, supported by more frequent launches | Possible strategic use as a means of re-establishing critical space-based services in the event of hostile Anti-Satellite action

Advanced Mission & Recovery Experiments (ADMIRE)

From a presentation by Dr. S. Somanath of Vikram Sarabhai Space Centre (VSSC), detailing various technologies being developed to support the reusable stage program

While its chief R&D activities continue to be on the front of next-gen propulsion systems for both rockets & hypersonic spaceplanes, as it should considering the fact it remains a state-run enterprise, ISRO isn’t blind to the advantages of re-usable vertical takeoff & vertical landing (VTVL) rockets à la SpaceX Falcon 9 and the value they bring to the commercial launch market – and the need to develop similar technologies for Indian launchers. The ADMIRE program aims to do just that: Development, demonstration & eventual commercialization of a liquid-fueled booster stage that can take off vertically like a normal rocket, and after separation, autonomously guide itself back to a designated LZ and land under its own power.

ADMIRE booster with its landing legs deployed

While the initial ADMIRE boosters themselves will be small, the focus will be on the software end, on developing the guidance & sensor package that will allow creation of a VTVL booster. The technology will then be scaled up and potentially applied to all liquid-fueled ISRO rockets performing commercial launch operations – incurring further cost reductions that way.

Status: Advanced Design & Back-end Development Stage

Intended Objectives

Developing technologies to support increased affordability of repeated space launches by recovering & re-using the boost stages

Private-sector Launchers 2022

Artist render of Skyroot Aerospace’s Vikram-I Launch Vehicle

Since around 2015, several private-sector start-ups have sought a piece of the multi-billion space industry pie by focusing on various niche technology fields such as in-space satellite propulsion, satellite-based services, and more recently following liberalization of the laws & regulations surrounding the space sector in 2019, privately-developed launch vehicles.

For the purposes of this article, I’m going to be focusing on three of the more prominent private companies currently engaged in some form of launch vehicle or related technology development. Namely Skyroot Aerospace, Agnikul Cosmos & Bellatrix Aerospace.

Skyroot, founded by a group of ex-ISRO scientists & funded to the tune of $15 million by several Indian & foreign investors and with the support of several top ISRO personnel in advisory positions is currently the best-placed organization to develop a private-sector launch capability in the form of their Vikram-series of small satellite launchers.

Skyroot Aerospace 3D-printed Dhawan-1 cryogenic engine

Vikram-I, the first in line to be developed is intended to have a payload capacity of 315kg to LEO & 225kg to SSPO – in the same overall payload class as the RocketLab Electron. But with all-solid propulsion, 3D-printed components & modular design, Skyroot is aiming for a 24-hour assembly period (making it a potential pitch for the DSA as well). This will be followed by the Vikram-II with a Cryogenic Methalox upper stage boosting the payload capacity to 520kg LEO/410kg SSPO, and finally the Vikram-III with the same Cryo engine supported by additional solid rocket boosters in the first stage, taking payloads to 720kg LEO/580kg SSPO.

Agnikul’s Agnilet 3D-printed liquid engine

Skyroot test-fired their Raman liquid-fueled Orbital Adjustment Module (for velocity-trimming of the payload section) in August 2020, followed by the Kalam-5 solid rocket motor in December 2020, and the LNG/LoX-fueled Dhawan-1 cryogenic engine was also unveiled that same year. The cryo stage intended for Vikram-II & III will allow for multi-orbit placement of satellite payloads. Skyroot expects the first launch of Vikram-I sometime in 2022.

Agnibaan by Agnikul Cosmos

Agnikul Cosmos, a startup incubated at the IIT-Madras university’s NCCRD (National Centre for Combustion Research & Development) and backed by $11 million in Series-A funding is focusing on smaller liquid-fueled rockets. Their 2/3-stage (depending on configuration) Agnibaan rocket is designed to have a LEO payload capacity of 100kg. In February 2021, their Kerolox-fueled Agnilet semi-cryogenic 2nd stage motor was test fired. This will be followed by tests of the Agnite first-stage motor sometime this year. The Agnibaan’s first stage will comprise of 7 clustered Agnite engines each producing 25kN of thrust. Angikul is also aiming for full road-mobility of the rocket’s carrier vehicle. First launch of this system is also expected in 2022.

Bellatrix Garuda

Which brings us to Bellatrix – a startup primarily focused on in-space satellite propulsion with their May 2021 test of India’s first privately-developed Hall-effect thruster, and which also deserves a mention in this list. Although they do have plans for launch vehicles of their own – namely the 12-ton 150kg SSO Chetak and 43-ton 1,000kg SSO Garuda, their focus for the immediate future remains development of the Bellatrix Aerospace Orbital Transportation Vehicle (OTV) – now named Pushpak, a ‘space taxi’ similar in profile to the American Momentus Vigoride. The OTV is powered by 4 x 200W Hall thrusters and allows for even smaller launch vehicles to send payloads into Geostationary orbits by providing continuous propulsion in space long after the rocket itself is spent. The OTV has been contracted by Skyroot Aerospace to be used on their Vikram-series launchers.

CGI of Bellatrix Aerospace OTV (Orbital Transportation Vehicle) made by Youtuber Gareeb Scientist

Both Skyroot & Agnikul are currently targeting the small launch vehicle sector as that’s the area with the most clear-cut way to profitability at this stage and with their current levels of investment.


Liftoff mass & Height unknown | Payload to LEO: 315-720kg | Payload to SSO/SSPO: 225-580kg


Liftoff mass: 14 tons | Height: 18m | Payload to LEO: 100kg

Status of both: Stages Under Development

Intended Objectives

Low-cost access to space for micro & small satellite payloads | Development of end-to-end Private sector aerospace ecosystem

Human-rated GSLV Mk-III

GSLV Mk-3 with Gaganyaan capsule by Harshal Pal

A human-rated (HR) variant of the Mk-3 GSLV is envisaged for the Gaganyaan missions. The core stage, cryogenic stage & solid boosters of the HR Mk-3 are essentially the same as the regular version, but with certain design changes introduced to increase its slated reliability, and with every component, nut & bolt tested & qualified to a much higher standard considering the fact that the astronauts’ lives depend on it.

The chief difference will of course be the large Orbital Module (comprised of the Crew Module that carries 3 astronauts & the Service Module) and the large rocket-boosted CES (Crew Escape System; validated in a Pad Abort Test in 2018) that sit on top of the Cryogenic stage in place of the regular payload fairing.

Configuration of Orbital Module & CES on the Mk-3 GSLV

The process of human-rating the Mk-3 GSLV officially began in November 2020.

The first developmental launch of the Mk-3HR, Gaganyaan-1 mission, was expected in late 2021 but has apparently slipped into 2022, it will be followed by a 2nd developmental flight in the same year, and finally culminating in the crewed Gaganyaan-3 mission currently scheduled for sometime in 2023.

Until the MLV family of launchers (next in line in this article) are perfected, the Mk-3HR will continue to be the go-to human transportation system for Indian astronauts in all following missions.

Status: In Process of Human-rating

Liftoff mass: 640 tons (est.) | Height: 45m (est.) | Payload to LEO: 10,000kg

Intended Objectives

First human spaceflight-capable Indian rocket | Sustaining manned access to space

Modular Launch Vehicle (MLV) 2025-2030

Indian Space Transportation System Roadmap (underwent several iterations since this slide was released)

The MLV is the successor program for ISRO’s plan for a Unified Launch Vehicle (ULV) project which existed in one way or the other on the drawing board since before 2013. Much like how the PSLV hinged on the Vikas liquid engine and the GSLVs hinged on India’s development of an indigenous cryogenic engine, the MLV program hinges on the development of the SCE-200 – a large staged-combustion semi-cryogenic engine producing upwards of a massive 2,000kN of thrust. To put it in perspective, that’s more than twice the thrust produced by SpaceX’s Merlin 1D engine that powers the Falcon 9 & Falcon Heavy.

The SCE-200’s design is heavily based on the RD-810 of Ukraine’s Yuzhnoye Design Bureau which had a hand in Soviet rocket engine development pre-1991. However, even though they sold the design, considering Yuzhnoye never actually built any engines based on this design before, much of the engineering models had to be developed, tested & perfected by ISRO & private subcontractor Godrej Aerospace themselves, throwing a spanner into any hope for a short development time. The RD-810 traces its lineage back to the original Soviet RD-120 engine family – of which the Chinese YF-100 & YF-115 that power some of China’s biggest rockets, are also members – but none are as big or powerful as the SCE-200.


ISRO is currently in the process of building new static test sites for performing sea-level test-fires of the engine – indicating maturity of the design & development process to a satisfactory level.

The MLV family which will use this engine in both single & clustered configurations, comprises of medium to heavy & super-heavy (by NASA standards) launchers built around the same engines, same stages, and maximum commonality between rockets in both hardware & software aspects to reduce cost and streamline production. As shown in the slide above, the smallest member of the family could have a modest capacity of 11 tons to LEO and 5 tons to GTO (not much different from the current Mk-3 GSLV) and scales up to a Heavy-class that uses clustered core & clustered boosters to lift 16 tons to GTO and a cool 41 tons to LEO (estimates increased to 52 tons in more recent official graphics depicting SHLV) – larger than Europe’s biggest planned launcher Ariane 64 and approaching Falcon Heavy.

SCE-200 in Single & Clustered Configuration

The MLV family will form the core of ISRO’s future commercial & human spaceflight missions and contribute toward a sustained Indian human presence in space, plans for a space station, and more. The first static test-firing of the engine is expected this year or the next, with the first launches of rockets powered by actual SCE-200 stages expected toward the middle of this decade, and operationalization of the full MLV family by around 2030.

The long-term future of ISRO & India’s space ambitions ride on the SCE-200 family, future variants of the Cryogenic engine family (C32 and so on), and the MLV program – the building blocks for a robust space access system.

Status: Under Development

Liftoff mass: 300-1,000 tons (est.) | Height: ~45-75m (est.) | Payload to LEO: 11,000-52,000kg | Payload to GTO: 5,000-16,000kg

Intended Objectives

Streamlined design & production across medium & heavy launch vehicles with maximum systems commonality | Expanding scope of payloads to include large crew modules for advanced space exploration & robotic interplanetary missions | Sustaining Indian manned & unmanned access to space in the decades to come

Two-Stage To Orbit (TSTO) Program

The TSTO-TD is not unlike some NASA-AFRL studies (pictured) into Reusable Two-Stage To Orbit Hypersonic spaceflight

The RLV-TD mentioned in Part-1 is one among many technology-demonstration efforts that feed into ISRO’s overarching program to develop Two-Stage To Orbit (TSTO) reusable flight capability that leverages a combination of air-breathing Scramjets & rocket engines.

The first step began with the August 2016 test of the Scramjet-TD which launched on a sounding rocket and achieved speeds of Mach 6 before splashing down in the sea. The RLV-TD testing program which also began the same year was focused on validating the various airframes & gathering aerodynamic data required for the project to progress. ISRO remains at work to further develop the Scramjet demonstrators, a new design meant to achieve speeds of Mach 7 was revealed in 2019 and several programs came to light since then.

CAD model of HAVA demonstrator

Notably the Hypersonic Air-breathing Vehicle Airframe-integrated structure (HAVA), designed for Mach 6-7 envelop meant to launch on top of a rocket was unveiled and is expected to be tested in the coming years. These developmental programs would culminate in the planned TSTO-TD HOTOL (horizontal take-off & landing) vehicle (pictured below) powered by a combination of Turbo-Ramjets, Scramjets & Rockets to achieve a full flight envelop ranging from Mach 0 to Mach 12 and capable of throwing a 2,000-kg payload into LEO.

Diagram of TSTO-TD with intended flight trajectory & specifications, shared by Dr. S. Somanath of VSSC

While the ultimate, larger production vehicle that would likely emerge from these programs is as of yet unknown, hazarding an educated guess gives us a cross between the Space Shuttle and the Reaction Engines’ Skylon concept.

While the civilian aspects of these programs are all well and good, we cannot forget the strategic implications and cross-pollination of these technologies which have applications in everything from Hypersonic Glide Vehicles (HGVs) mounted on rocket boosters to X-37B-esque spaceplanes that can snatch-and-grab foreign satellites and bring them home to study.

Status: Technology Demonstration & Proof-of-Concept Testing

Intended Objectives

Maximizing re-usability & cost-effectiveness by eliminating the need to have expendable stages | Enabling sub-conventional (covert/clandestine) options for dealing with hostile space assets

To sign off…

Moonshot Rockets

“The Way Forward to 2050” – A roadmap of the long-term goals of ISRO shared by official sources

Since long, there has been talk of a Super-Heavy (by Soviet standards) class of launch vehicle from ISRO (with LEO payloads exceeding 100,000-150,000kg and ~50,000kg to Trans-Lunar Injection), aimed at a Moonshot capability for interplanetary space exploration & potential colonization, at the same level as the erstwhile Saturn V or China’s upcoming Long March 9.

As of now, this remains speculation and while its true that ISRO holds long-term plans for all that & more, at present it cannot be said that a Moonshot rocket is on the immediate wish-list for India.

But its definitely something to aim for.

By Parthu Potluri

Student, Defence & Space Enthusiast