The Indian Space Programme
Page 29
At the outset, PSLV had sufficient thrust to place a 1 tonne satellites into polar orbit. Since then, through a series of enhancements, ISRO has extended this capability to 1.8 tonnes. Even before the PSLV became operational, the Indian government had approved the second series of INSAT in 1987. INSAT-2 weighing around 2.5 tonnes was larger and heavier than the IRS satellites. Getting the INSAT class communication satellites to the higher geosynchronous orbit was beyond the capability of the enhanced PSLV. To get INSAT-2 to orbit, ISRO had to commercially engage foreign launch service providers, predominantly ESA's Ariane 5. In the process, undermining one of its key objectives. Self-sufficiency. Almost a decade and a half before the INSAT-2 was approved, the Geosynchronous Satellite Launch Vehicle (GSLV) had been proposed in November 1972 with the modest goal of placing an 800-kg spacecraft in GTO.[561] The design incorporated solid, liquid and cryogenic stages, and the intention was to have the first GSLV launch by 1981.
Cryogenic engines rely on LOX and LH2. In their liquid form, oxygen and hydrogen are very cold and a formidable challenge for engineers. Though the GSLV at 50 m is not much larger than the PSLV at 44.5 m, it incorporates the next evolutionary step, cryogenic technology, which provides the most efficient thrust a launch vehicle can generate. For ISRO, “it was clear that the last stage of the GSLV had to be a cryogenic stage.”[562] This third stage was to provide half of the total 9.7 km/s velocity necessary to attain GTO.
Most countries that developed the cryogenic engine technology (LOX + LH2) had also developed semi-cryogenic engines (LOX + kerosene). Although ISRO had proposed developing a 7.5-tonne semi-cryogenic engine in the early 1970s during the PSLV design phase that never happened. The story of the development of cryogenic engine has been one of ISRO’s most complex challenges involving economic sanctions, political intrigue, cost overruns and a series of delays. It started with the acquisition of the liquid-engine technology from France, which “created a culture in the liquid propulsion group which favoured import of technology”. This fateful decision, according to investigative journalist Gopal Raj, demanded “a heavy price” that ISRO paid when the time came for designing the GSLV.[563] Although it shares some characteristics with the PSLV and is not much bigger, the three-stage GSLV is a more powerful launch vehicle than the four-stage PSLV. The first stage is composed of a solid core with four liquid engine strap-ons. The second is uses a liquid propellant. The innovation lies in the third stage with a cryogenic engine using LOX as oxidant and LH2 as fuel.
GSLV Mk1
GSLV Mk2
LVM-3/GSLV-Mk3
Operational During
2001– 2010
2010- mid-2017
2014- mid-2017
Number of Flights
6
5
1 sub-orbital flight in 2014. 1 to GEO in May 2017
Payload to GTO (tonne)
1.82
1.95 – 2.35
4 – 4.5
Lift-off Mass (tonne)
414
414
600+
Max Height × Width (m)
49.13 × 2.8
49.13 × 2.8
43.5 × 4
Table 10‑8 Overview of GSLV Configurations and Launch History
To accommodate the GSLV, an additional launch pad, the SLP, using a new approach in integrating the launch vehicle was proposed in 1988. Rather than transporting individual components and assembling the launch vehicle at the launch pad using the Mobile Service Tower, the launch vehicle would be assembled in a VAB, and transported to the launch pad complete requiring only the propellant. Since the initial design, the GSLV has evolved into a variety of configurations and sub-configurations. GSLV Mk1, which is no longer in service, came in three variants, Mk1, Mk1+ and Mk1 (F06). All Mk1 variants, including the last Mk1 to be flown in 2010, used cryogenic engines purchased from the USSR/Russia.
By 2010, ISRO had developed its own cryogenic engine, which is the distinguishing feature of Mk2. By 2010 11 GSLV had been launched - 6 Mk1 (2 failed, 2 succeeded and 2 partially failed), 5 Mk2 (4 successful and 1 failure). Of the two heavy-lift attempts, LVM-Mk3 suborbital flight in 2014 and 1 GSLV-Mk3 in 2017 were successful. GSLV variants come in a number of specifications. The launch profile between the Mk1 and Mk2 is similar. The Mk1 used the 3rd stage cryogenic engine from the USSR and the Mk2 used one developed by ISRO in India. The following sequence describes the GSLV Mk2 GSAT-14 mission launched on 22 February 2014. At launch, the strap-ons of GSLV Mk2 ignited first at T-4.8 seconds. Collectively, the four strap-ons, each using a Vikas 2 engine, lack sufficient thrust for the vehicle to take-off. If for any reason all four do not ignite and provide the designed consistent thrust, the onboard computer controlling the launch sequence has time to switch them off and abort the launch.
Strap-on
Stage 1
Stage 2
Stage 3
Mk. 1. Three variants a, b and c. Total flights=6.
Now Retired
4 x L-40H
S125
L39.3
CE-7.5
UH25 and N2O4
HTPB
UH25 and N2O4
LOX + H2
Mk2 Total. Flights=3
4 x L-40H
S139
L39.3
CE-12.5
UH25 and N2O4
HTPB
UH25 and N2O4
LOX + H2
Table 10‑9 Typical GSLV Mk1 & Mk2 Specification.
As the strap-ons performance was nominal, the core stage was ignited at T=0, and the launch was committed since the solid core stage once ignited cannot be stopped. GSLV’s first-stage directional control is provided by EGC on the four-liquid strap-ons. The four nozzles are controlled dynamically by the computer to maintain a predefined course stored in its memory. The strap-ones EGC is so effective that directional control for the core stage is not required. High-speed winds in the Earth’s atmosphere, especially between 10 and 30 km, and the potential inconsistent thrust from the solid core stage are potentially the most unpredictable forces that IGS has to manage.
The core stage exhausted its 138 tonnes of solid propellant at T+1 minute and 47 seconds, but the strap-ons continued for another 40 seconds. Since the strap-ons were strapped to the first stage, they carried the dead weight of the now spent core stage. At T+2 minutes and 29 seconds, at an altitude of 70 km, the strap-ons also used up their propellant and shut down. The second-stage engine was ignited about 2 seconds prior to the separation of the first. The flexible linear shaped charge was used for stage separation, and exhaust from the second-stage engine helped push away the spent first stage with the attached strap-ons.
The second-stage Vikas 4 engine was optimised for the vacuum environment of space. Stage two also used EGC for directional control. By the time the second stage kicked in, the launch vehicle was in space and no longer vulnerable to the strong, unpredictable external forces present in the upper atmosphere. At T+3 minutes and 46 seconds, while travelling at just over 3 km/s at an altitude of 115 km, the payload fairing that protected GSAT-14 against the Earth’s atmosphere became superfluous in the vacuum of space and was ejected, preparing the satellite for deployment. At 4.9 km/s, which is around half the velocity necessary for orbit, the second-stage Vikas 4 engine shut down at T+4 minutes and 49 seconds and separated from the third stage three seconds later with a pyro-actuated cullet release mechanism. The launch vehicle, then just 10 m long, was a quarter of that at launch.
The final stage using LH2 and LOX fired at T+4 minutes 53 seconds and burned for over 12 minutes, longer than both of the previous stages combined. In the absence of the Earth’s atmosphere and building on the momentum provided by the previous stages, the third stage achieved the required orbital velocity of 9.7 km/s before exhausting its 12.5 tonnes of propellant and shutting down. The third cryogenic-stage directional control was provided by two small swivelable vernier engines powered by LH2 and LOX. Seconds after the third-stage shutdown, the payload GSAT-14
was pushed out by spring thrusters mounted at the separation interface into a GTO of 80-km perigee with an apogee of 35,975 km. This highly elliptical GTO orbit was circularised over next several days to the 35,975-km orbit by ISRO’s MCF in Hassan. Once it arrived in its operational slot, GSAT-14 started providing its service as a communication satellite.
Launch Vehicle Mark 3 (LVM3)
On 18 December 2014, ISRO conducted the Crew Module Atmospheric Re-entry Experiment (LVM3-X/CARE), an experimental sub-orbital flight powered only by the first and second stages. The LVM3-X/CARE payload consisted of a 3.7-tonne mock-up of a crew module as the payload. It was launched using only the boosters and the core stage into a sub-orbital flight to an altitude of 126 km.
LVM3-X
Strap-on X2
Booster Stage
Stage 3
Burn Time (s)
130
200
Not used
Propellant Type
HTPB
Liquid UDMH + N2O4
Simulated
L×W (m)
25 × 3.2
17 × 4
13.5 × 4
Propellant Mass (tonnes)
207
110
Simulated
Table 10‑10 Suborbital flight on 18/12/2014. LVM3-X/Care
The third stage cryogenic engine was not present for the flight with LOX and LH2 replaced by liquid and gaseous nitrogen of equivalent weight. The crew module splashed down near the Andaman and Nicobar Islands in the Bay of Bengal 20 minutes and 43 seconds after launch. The launch of
Figure 10‑7 LVM3-X/Crew Module Atmospheric Re-entry Experiment Flight Profile. Credit ISRO
LVM3-X/CARE concluded with a twin-parachute controlled splashdown in the Bay of Bengal. The module was recovered immediately after splashdown by the Indian coast guard. The primary objective of the LVM3-X/CARE was to test the large solid strap-ons used on ISRO’s latest launch vehicle.[564]
The scope of this test flight included assessing the flight dynamics, the core module subsystems, three-axis-control manoeuvres for re-entry, heat shield, parachute systems, splashdown and recovery. The other key objective was to test the strap-on boosters and the re-entry characteristics for a module which could potentially form a part of a future human spaceflight programme.
GSLV-Mk3
ISRO’s next generation launch vehicle initially called the Launch Vehicle Mark 3 or LVM-3, ISRO appears to have returned to the original naming convention and is now called the GSLV-Mk3 even though it has no evolutionary connection with GSLV Mk2. GSLV-Mk3 made its maiden flight on 5th June 2017 successfully placing GSAT-19 in GEO. GSLV-Mk3 is India’s heavy-lift launch vehicle albeit with a capacity to launch about 4.5 tonnes to GTO. Other heavy-lift vehicles (i.e. Ariane 5, Delta 4 Heavy and Long March 5) have about twice that capacity. GSLV-3 uses 2 solid strap-ons as the first stage, liquid propellants for the second stages and has a cryogenic third stage.
The extent to which ISRO can enhance GSLV/LVM3 is limited. The GSLV-Mk3 was designed over two decades ago. To catch-up with larger capacities of heavy-lift vehicles used by other nations, further technological developments are required. Incorporating semi-cryogenic fuel for the liquid stages and introducing some level of recovery and reuse of the boosters or stages are some of the potential options that ISRO is contemplating.[565] To master heavy launch capability, ISRO needs to develop larger cryogenic engines.
Stage 1
Stage 2
Stage
Burn Time (s)
140
263
643
Propellant(Tonnes)
S205 X 2
116
28
Propellant type
HTPB (solid)
UH25 and N2O4 (Liquid)
LOX + H2 (Cryogenic)
Length × Width (m)
26.2 × 3.2
21.39 X 4
13.5 × 4
Table 10‑11 GSLV-Mk3-D1/GSAT19 Specifications
Operationalising this heavy launch system will not only end ISRO's reliance on foreign launch services for its communication satellites but allow ISRO to consider new missions including the exploration of the solar system, human spaceflight, space station and provide greater access to the growing commercial space launch market.
Future Launch Vehicles
Most launch vehicles around the world still use the expendable single-use technology that initiated the Space Age more than half a century ago. The rocket technology that took Yuri Gagarin into space was not very different from that used to take astronauts to the ISS in the 21st century.[566] Engines for launch vehicles which operate at a higher efficiency are cryogenic and semi cryogenic engines. ISRO plans to replace the current launcher family, PSLV, LVM and the GSLV with a single modular design. At one stage referred to as the Unified Launch Vehicle (ULV) but may be renamed in the future. Using a combination of fuel types (solid, liquid, semi cryogenic and cryogenic) each ULV flight will be customised to meet the mission objectives.
Historically, when a new engine technology is introduced, ISRO initially engages in an international agreement before becoming self-sufficient. France was involved with the solid and liquid engine development and the USSR, at least briefly, with the cryogenic engine technology. To engage with the semi-cryogenic technology, in 2006 ISRO signed a framework agreement with the Ukrainian manufacturer Yuzhnoye on a joint project called Jasmine.[567] In this agreement, ISRO would develop the Yuzhnoye RD-810 engine as the SCE-200 (semi-cryogenic engine with a thrust of 200 tonnes) for future launch vehicles. GSLV-Mk3 that placed GSAT-19 in orbit on 5 June 2017 used ISRO's CE-25 cryogenic engine as the third stage. The CE-25 uses an ‘Open Cycle' design that uses a small amount of fuel to in a separate combustion chamber sometimes known as a pre-burner chamber.
Figure 10‑8 Future Launch Vehicles. Based on fact and informed speculation. Credit Norbert Brugge[568]
The exhaust from this chamber is used drive turbo pumps that deliver the LH2/LOX into the main combustion chamber. Developing this engine was a huge achievement following over two decades of development. ISRO is now beginning to develop a Semi-Cryogenic Engine with a large capacity of (SCE-200).[569] Semi-cryogenic engines use LOX and kerosene rather than LOX and LH2 as propellants. ISRO plans to use its own formulation of kerosene that is referred by some as Isrosene. A future ULV would have solid strap-ons, a semi-cryogenic second stage and with CE-25 cryogenic third stage with an increased payload to GTO of 10 tonnes. In 2015, India signed a further MoU with the Russian Federation. The remit of this MoU is not clear but likely to include progress with the SCE engine technology.[570] The current design of ISRO’s future launch vehicles will continue to use solid boosters (up to S250), a semi-cryogenic first stage (using the SCE-200) and a larger cryogenic second stage (up to CE-60). ISRO plans introduce semi-cryogenic technology for the first time with the ULV and HLV but probably not until the next decade. ISRO’s designs for launch vehicles in the future do not involve a radical new technology but envisages an increasingly larger first stage (solid), enhanced second stage (semi-cryogenic) and third stage (cryogenic). Given that semi-cryogenic propellants were first used in the German V2 missiles during World War II and in the launch of Sputnik in 1957, ISRO is joining late. Just as with the PSLV and GSLV, multiple configurations are envisaged for ULV and HLV. Not all initial designs make it beyond the design phase.
Version
Booster
Stage 1
Stage 2
LVM3[571]
2 × S-200
L-110 (UDMH/ N2O4
Vikas-X 2
L-25 (LH2/LOX)
CE-20
ULV Light
6 × S-13
L-160 (Kerosene/LOX)
SCE-200
L-30 (LH2/ LOX)
CE-20
ULV Heavy
2 × S-200
L-160 (Kerosene/LOX)
SCE-200
L-100 (LH2/LOX)
CE-20
; HLV
S-250
5 X L-200 (Kerosene/LOX)
SCE-200
L-100 (LH2/LOX)
CE-60
SHLV
5 X SCE-200
5 X L-200 (Kerosene/LOX)
SCE-200
2 x L-100 (LH2/LOX)
CE-20
Table 10‑12 Potential Future Launch Vehicles. Credit Norbert Brugge
The typical cost of placing 1 kg payload in Earth orbit is about $20,000 (Rs.0.13 crore). Although the fuel used by a launch vehicle is around $300,000 (Rs.2 crore), the cost of the single-use launch vehicle is about $60 million (Rs.400 crore).[572] Reusable launch vehicles are a key area for development but ISRO is currently at a very early stage. The potential future launch vehicles listed above is a product of informed speculation based on public presentations by senior ISRO personnel rather than formal policy announcements. [573]
Reusable Launch Vehicle (RLV)
The USSR had briefly demonstrated its capability in reusable space vehicle with Buran, but it was the US, through the space shuttle, that proved launch vehicle reuse was technically possible although the economic benefits were not as substantial as first envisaged. While still in its early stages, India too is working on its Reusable Launch Vehicle (RLV) and the ‘two-stage-to-orbit' (TSTO) concept. A TSTO concept relies on a vehicle with two stages to get to orbit, one of which may be expendable. In January 2007, ISRO conducted Space Capsule Recovery Experiment usually abbreviated to SRE-1. For the first time ISRO recovered the vehicle it had sent to space. This demonstrated ISRO’s ability to perform experiments in space, de-orbit the spacecraft for a safe re-entry and recover it intact from a predefined location after splash down. The SRE-1 was a small capsule of 550 kg and conducted two onboard experiments during its 12 days in Earth orbit. Through SRE-1, ISRO proved its subsystems for navigation, guidance and control at hypersonic re-entry, thermal protection system, parachute deployment and recovery following re-entry. While ISRO demonstrated its capability to recover a spacecraft after launch, it was only the payload, not the launch vehicle that was recovered.