Towards a reusable space vehicle
Radhakrishna Rao
IN a major breakthrough towards the goal of developing an operational supersonic combustion technology, which holds the key to building a reusable space vehicle or a high speed, ultra fast aircraft for civilian or military uses, Indian Space Research Organisation successfully carried out the design, development and characteristics realisation of the supersonic combustion ramjet (Scramjet) early this year.

Trends
Stone-age skeleton
A 260,000-year-old partial skeleton excavated in northwestern China 22 years ago represents our largest known female ancestor, according to a new analysis of the individual’s extensive remains.

Prof Yash Pal

Towards a reusable space vehicle
Radhakrishna Rao

IN a major breakthrough towards the goal of developing an operational supersonic combustion technology, which holds the key to building a reusable space vehicle or a high speed, ultra fast aircraft for civilian or military uses, Indian Space Research Organisation (ISRO) successfully carried out the design, development and characteristics realisation of the supersonic combustion ramjet (Scramjet) early this year.

In a series of ground tests carried out by the Thiruvananthapuram-based Vikram Sarabhai Space Centre (VSSC), the largest Indian space establishment entrusted with the responsibility of designing, developing and building launch vehicles, was able to demonstrate a stable supersonic combustion for nearly seven seconds with the inlet Mach No of 6, or six times the speed of the sound.

Of course, this demonstration of the feasibility of the Indian scramjet forming part of the advanced technology initiative of ISRO was achieved under laboratory conditions. In the next stage of scramjet development, ISRO is planning to flight test an integrated propulsion system made up of elements such as an air intake, combustor and nozzle by making use of a two stage RH-560 sounding rocket.

This test likely to take place in 2007 will test scramjet’s performance under lower atmospheric conditions. According to sources in ISRO, the development of an air breathing propulsion system based on scramjet will pave the way for an “easy, efficient and routine” access to space through a reusable space vehicle. Clearly and apparently, this propulsion system can also be used in a missile system with a devastative impact.

As things stand now, the scramjet technology is in a very nascent stage of development. Excepting USA which has successfully carried out demonstration of supersonic combustion for a short while in flight conditions, work on supersonic combustion design in other countries such as Japan, China, Russia, Australia and Europe are in a very preliminary stage.

Clearly and apparently, the motivation for ISRO to develop launch vehicles working on the air breathing propulsion system lies in the need to reduce the launch cost by a substantial extent. The currently used expendable space vehicles stuffed with chemical fuels are quite costly to operate. And the cost of launching a kg of payload with this type of space vehicle works out to anything between $ 12,000 and $ 15,000. As pointed out by G. Madhavan Nair, Chairman, ISRO, “if we have to make the access to space more affordable, we may need to bring down the cost of launching a kg of payload to something like $ 1,000 per kg.”.

As it is, in a space vehicle equipped with an air breathing propulsion system there is no need to loft huge quantities of oxygen required for burning the fuel. For an air breathing engine is designed to suck the oxygen from its surrounding and use it for burning the onboard fuel. In a conventional launch vehicle both the oxygen and the fuel need to be carried onboard with the result that the weight of such a launcher goes up by a considerable extent. As such the weight of a space launcher equipped with an air breathing system gets reduced by a substantial extent.

This, in turn, translated into an increased launch capability making for a reduced launch cost. However, since the air breathing propulsion system has the capability to operate only during the atmospheric phase of the flight, they always need to be adopted along with the conventional rocket booster stage for meeting the final orbital velocity requirements.

Without doubt, developing an operational scramjet system is a complex and challenging task. And as things stand now, it may be difficult to forecast as to when India’s own reusable space vehicle based on an air breathing propulsion system will be ready for take off. As it is, the development of scramjet system involves a number of new and novel technologies, including the mixing of the very high speed air, achieving stable ignition and flame holding in addition to ensuring combustion within the practical length of the combustor.

Trends
Stone-age skeleton

A new analysis of a partial stone age skeleton, including this skull, identifies it as coming from the biggest known female among human ancestors. Rosenberg

A 260,000-year-old partial skeleton excavated in northwestern China 22 years ago represents our largest known female ancestor, according to a new analysis of the individual’s extensive remains.

This ancient woman puts a modern twist on Stone Age human evolution, say Karen R. Rosenberg of the University of Delaware in Newark, Lü Zuné of Peking University in Beijing, and Chris B. Ruff of Johns Hopkins University School of Medicine in Baltimore. The fossil individual’s large size and the apparent adaptation of her body to cold conditions are “consistent with the idea that patterns of human anatomical variation that we see today have deep evolutionary roots,” Rosenberg asserts.

Now known as the Jinniushan specimen, she stood roughly 5 feet, 5-1/2 inches tall and tipped the scales at 173 pounds, the three anthropologists estimate.

THIS UNIVERSE
PROF YASH PAL

Why do rigid thinkers deny the concept of time travel?

You can dream about time travel but how do you “think” about it when it implies that a river would start going backwards till it climbs the Himalayas and become snow again? I suppose when we think of time travel we do not mean that time flows backwards, but as a happening where we are transposed to another period in time. It is not possible to imagine a way in which any desired transposition would take place, for anyone who wishes, and then events would progress forward as they always did?

There are questions related to conservation of energy and momentum. In the ordinary world that we know and understand this cannot be allowed. As far as romance and fantasy are concerned it is marvellous to be able to transpose oneself. We are blessed with memories that can be randomly addressed in ways as selective as we desire. I suggest that is the best way of time travel available to all of us, even the rigid thinkers.

Why do tears taste salty?

Salt is an important component of our bodies. One of the reasons for this is that the sodium ions released when salt is dissolved in water serve as essential carriers of electrochemical signals that allow us to function in an integral way. Without signaling a body cannot remain alive.

Salt is found in our blood, in our cells, indeed in all parts that are wet. It is no surprise, therefore, that all secretions of water from our body are salty. This is true of perspiration, which performs an important role in maintenance of our body temperature and it is also true for tears from our eyes. Incidentally, our eyes do not water only when we are sad. A little secretion from our eyes is almost continuous. This is to keep our eyes clean. The fluid that wets our eyes, and sometimes comes out as copious tears also contains, besides salt, a chemical called Lysozyme, which destroys bacteria that might infect our eyes.

Tears also come to other animals and birds. Like they do for us, for them also they perform the functions of cleaning and protecting their eyes. For the ocean-going birds the tears are a bit oily to protect their eyes from salt spray!

It is interesting to realise that frequent blinking of our eyes serves the same function for eyes as the movement of windshield wipers on the front window of our car on a slightly wet day. A thin, uniform layer of the tear fluid allows us to see clearly. The more we learn about the control and maintenance systems of our bodies, the more are we impressed with their virtuous ingenuity. It is hard to believe that all this was a part of an original design. It is more likely that the incomplete and imperfect designs did not survive. All of us now living are the efficient survivors of a long chain of evolution.