BENGALURU: The Indian Space Research Organisation (Isro) early on Sunday successfully conducted the reusable launch vehicle (RLV) autonomous landing mission
or RLV-LEX at the Aeronautical Test Range (ATR) in Challakere,
Chitradurga, some 220km from Bengaluru. The space agency used a scaled
down version of the RLV technology demonstrator (RLV—TD).
The space
agency used a scaled down version of the RLV technology demonstrator
(RLV—TD). The actual vehicle will be 1.6 times larger than the one used
on Sunday.
Isro chairman S Somanath said: "We'll have a few more
landing experiments with different conditions to prove the ruggedness of
the algorithm and hardware that we've put in. This paves the way to
development of the ORV and puts us a step closer to having India's own
re-usable launch vehicle."
Isro said it was for the first time in the
world that a winged body was carried to an altitude of 4.5km by a
helicopter and released for carrying out an autonomous landing on a
runway. RLV is essentially a space plane with a low lift to drag ratio
requiring an approach at high glide angles that necessitates a landing
at high velocities of 350kmph.
The RLV took off at 7.10am by
IAF’s Chinook helicopter as an underslung load and flew to a height of
4.5km. Once the predetermined pillbox parameters were attained, based on
the RLV’s mission management computer command, the RLV was released in
mid-air, at a down range of 4.6km.
Release conditions included 10
parameters covering position, velocity, altitude and body rates, etc and
release was autonomous RLV then performed approach and landing
manoeuvres using the integrated navigation, guidance & control
system and completed an autonomous landing on the airstrip at 7.40am.
“It
went on exactly as planned and all parametres were met,” S Unnikrishnan
Nair, director, Vikram Sarabhai Space Centre (VSSC), told TOI.
Stating
that it then achieved the autonomous landing of a space vehicle, Isro
added, the landing was carried out under the exact conditions of a space
re-entry vehicle’s high-speed, unmanned, precise landing from the same
return path as if the vehicle arrived from space.
“Landing
parameters such as ground relative velocity, the sink rate of landing
gears, and precise body rates, as might be experienced by an orbital
re-entry space vehicle in its return path, were achieved. The RLV-LEX
demanded several state-of-the-art technologies including accurate
navigation hardware and software, Pseudolite system, Ka-band radar
altimeter, NavlC (Indian GPS) receiver, indigenous landing gear,
aerofoil honey-comb fins and brake parachute system,” it said.
LEX
utilised several indigenous systems developed by Isro. “The digital
elevation model of the landing site with a Ka-band radar altimeter
provided accurate altitude information. Extensive wind tunnel tests and
simulations enabled aerodynamic characterisation prior to the flight.
Adaptation of contemporary technologies developed for RLV-LEX makes
other operational launch vehicles of Isro more cost-effective,” Isro
said.
The RLV-LEX demonstrated one of the critical technologies — the
approach and autonomous landing on a runway and has put the RLV
programme one step closer to an orbital re-entry experiment (ORE), for
which the vehicle will be scaled up.
In ORE, a wing body called
Orbital Re-entry vehicle (ORV) will be taken to an orbit by an ascent
vehicle derived from the existing GSLV and PSLV stages and stay in orbit
for a stipulated period, re-enter and land in a runway autonomously
with a landing gear.
Before the RLV-LEX Isro had done the RLV-TD
HEX-01 (hypersonic experiment) mission in which it validated autonomous
navigation, guidance & control, reusable thermal protection system
and re-entry mission management. Now that LEX is done, Isro will need to
integrate both for the ORE.
Carried out on May 23, 2016, the RLV-TD
HEX was a 770-second suborbital flight and designed to land on sea. The
experimental mission saw the HS9 solid rocket booster carrying RLV-TD to
a height of about 65km from where the vehicle began its descent
followed by atmospheric re-entry at around Mach 5 (five times the speed
of sound).
Isro, which has been working on this technology for more
than a decade, decided to develop it primarily to address the cost and
time issues. “The cost of access to space is the major deterrent in
space exploration and space utilisation. A reusable launch vehicle is
the unanimous solution to achieve low cost, reliable and on-demand space
access,” Isro has said.
However, mastering this technology will
provide multiple other benefits, including in development of different
types of launch vehicles, space transportation and so on. While the ORE
will be a major milestone, the RLV-TD is only a technology demonstrator
and the development of an actual re-usable launch vehicle will take more
time.
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