SCIENCE & TECHNOLOGY

Towards a reusable space vehicle
Radhakrishna Rao
N
O doubt, the unexpected failure of India’s three-stage high performance Geosynchronous Satellite Launch Vehicle powered with an upper cryogenic engine stage to place 2168-kg. INSAT-4C communications spacecraft into orbit during its space journey on July 10 is a setback to the Indian space programme.

Low-cost housing
Lieut-Col B.K. Sodhi (retd)
E
ACH one of us wants to make our own home at the earliest possible, but house-making is the “costliest lifetime investment”, and most of us can hope to afford this, only after the hard-earned saving of over 20 years. Hence, economics of construction is of paramount importance for most of us.

Pollen bees, wild flowers in decline
B
EES and the wild flowers they pollinate have declined significantly across large tracts of northern Europe, according to one of the most comprehensive surveys of pollinating insects.

Prof Yash Pal

Prof Yash Pal

THIS UNIVERSE
PROF YASH PAL

If we throw a stone upwards it comes down because of the gravitational force. What will happen if the stone crosses the air boundary? Will it move or be steady in space?



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Towards a reusable space vehicle
Radhakrishna Rao

GSLV-FO2 before launch
GSLV-FO2 before launch

NO doubt, the unexpected failure of India’s three-stage high performance Geosynchronous Satellite Launch Vehicle (GSLV) powered with an upper cryogenic engine stage to place 2168-kg. INSAT-4C communications spacecraft into orbit during its space journey on July 10 is a setback to the Indian space programme. But the Indian space scientists who are now in the midst of probing the reason for the failure of GSLV are confident of readying the space vehicle for a successful launch in the near future.

Clearly and apparently, launch failures are a common feature of the global space activities. There is hardly a space faring nation that has not suffered reverses and setbacks in its space programme.

But not one to lose heart, Indian Space Research Organisation (ISRO) is quietly and efficiently working on developing an integrated scramjet propulsion system with a view to reducing the cost of delivering a satellite payload into the orbit.

With the current genre expendable space boosters based on chemical propellants it costs anything between $ 10,000 and $ 12,000 to deliver a kg of payload into the near-earth orbit. As such scramjet or supersonic combustion that operates on the air-breathing propulsion system is considered the most ideal option for reducing the launch cost. USA, Australia and Japan are among a handful of countries that are involved in testing and perfecting this frontier technology for the next generation, reusable space vehicles.

For instance, recently the USA tested successfully a hydrocarbon fuelled scramjet engine, paving the way for the next step towards a hypersonic vehicle.

On its part ISRO is preparing the ground for testing its integrated scramjet system — as ongoing research on supersonic combustion — using a two stage sounding rocket.

As part of its advanced technology initiative in the area of air breathing propulsion, ISRO had sometime back successfully accomplished the design, development, characterisation and realisation of Scramjet through a series of ground tests. These tests achieved a stable combustion for nearly seven seconds with an inlet Mach number of 6.

As pointed out by ISRO, “the development of scramjet system is quite complex and it involves a number of technological challenges, especially those relating to the mixing of very high speed air with fuel, achieving stable ignition of flame holding in addition to ensuring efficient combustion within the practical length of the combustor”.

Not surprisingly then, ISRO considers this a significant breakthrough in the context of this technology being in a very nascent stage of development the world over.

According to J.D.A. Subramanyan, Project Director of the air breathing propulsion project at the Thiruvananthapuram-based Vikram Sarabhai Space Centre (VSSC), the largest Indian space establishment advanced reusable launch vehicles based on air breathing propulsion could help bring down the launch cost by a substantial extent.

As pointed out by him the cost could be brought down by reducing the size and recovering and reusing the hardware. “More importantly, reducing propellant is imperative for low cost access to space as propellant forms about four-fifths of the launch vehicle mass at take off’, quips Subramanyan.

Meanwhile, a Rs 60-million state of the art facility meant to test and study the air breathing scramjet engines is being set up in Bangalore by ISRO in association with the National Aerospace Laboratories (NAL). This facility is crucial for building a reusable space vehicle operating on air breathing propulsion system.

A technology demonstrator of this reusable vehicle expected to be ready by 2010 is considered a first vital step towards the ultimate development of a two stage to orbit space vehicle.

As it is, the first stage of this hypersonic space vehicle that could accelerate to the speed of up to Mach 10 is designed to return to earth after its separation from the second stage.

It would then land on a runway like a conventional airplane. On the other hand, the second stage on completion of its mission would land vertically by making use of a parachute.

Indian President Dr A.P.J. Abdul Kalam, who was the architect of India’s first civilian space vehicle SLV-3, has all along been vigorously highlighting the need for India to develop the technology for building a reusable space vehicle. Technology developed for a reusable space vehicle could also be used for building an aircraft capable of ferrying passengers at hypersonic speed.

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Low-cost housing
Lieut-Col B.K. Sodhi (retd)

EACH one of us wants to make our own home at the earliest possible, but house-making is the “costliest lifetime investment”, and most of us can hope to afford this, only after the hard-earned saving of over 20 years. Hence, economics of construction is of paramount importance for most of us.

To help a common man, well tried and time tested tips are given. We need to learn from two existing examples of Jaipur and Chandigarh, as 60 to 70 per cent houses are sited in NW — SE orientation, which “avoids Harsh SW Hottest summer sun and welcomes SE winter sun” This simple correct orientation makes our living comfortable with minimal loads of airconditioning and heating loads which will save money as well as conserve scarce energy.

Window area needs be around 10 per cent of floor area, beautifully done in both cities, but recent western trend being copied blindly, against our climate is a disturbing trend.

It is very important to note that “window area is four to five times costlier” than masonry. Bigger windows means also “higher energy costs, curtains and of course, uncomfortable artificial living”.

A nearly square house plan, is far more cheaper than a rectangular house plan. Savings, may be around 25 per cent due to lesser perimeter wall lengths (20x20-80 and 10x40-100) which will also reduce energy loads.

Local Materials — Bricks and Stone — are the cheapest, as beautifully practiced, in both Capitols. In our climate, 60 per cent heat comes from roof, and needs be suitably insulated, to reduce recurring lifelong extra energy costs.

This can also be attended to through efficient under roof ventilation and nearly white roof surface to reflect away maximum heat.

Again, external surfaces need be whiter, particularly on south, south west and west facades.

Height of ceiling should be as low possible, around nine feet height, is more than sufficient in most of our houses. Higher height means higher cost as “Ten feet height will amount to 11 per cent costlier as compared to nine feet high house”. A seven-feet high airconditioned room, without a ceiling fan is the cheapest, as being done in hills. Maximum common walls, in form of row housing, is another shining example of mass housing, at Jaipur and Chandigarh.

Common walls save money, as well as save extra recurring energy costs with lesser exposed surfaces to heat, for comfortable living.

Time tested use of flyash up to 30 per cent both for brick making and for cement concrete will conserve fertile soil, save cement, money as well as provide stronger structures. 175 Micron PVC as DPC will save money as well as save us one week of curing time required for 1:2:4 PCC.

Both masonry work and plaster work needs be in “lime surkhi mortar” as Lime Surkhi Plaster becomes stronger with aging as Stucco Plaster done since centuries, in our temples and monuments.

Most of us need to understand that cost of a RCC or MS sheet or PVC water tank is same i.e. around Rs 4 per litre but life of PVC tank is far less than RCC and MS sheet rather “Brick /Fibrocement tanks are the cheapest as well as durable”.

Cost of foundations in case of a Two/Three/ Five/Ten Storied house is around 17%, 8.4%, 7.96% and 5.6% respectively. Therefore, most of housing should be four/five storeyed with Brick Load Bearing walls. Lack of curing, is a norm at most of sites, and is a very serious matter, as 1:6 weekly cured plaster is far better than 1:3 cement plaster, with superficial curing. Most of manual construction being done at 99% of sites required 33 grade cement only, but even 43 grade cement is not available on demand. 53 Grade Cement is also costlier than both 33 and 43 Grades and is useful only on fully/partially mechanised projects. These fundamental, time tested tips need be disseminated for benefit of common man to save our scarce national resources.

Aging stars slow down

WHEN you’re young and single, it’s easy to dance fast. But when little ones are on the way, the dance tends to slow down. And so it seems to be with stars and the planet-forming disks that orbit them.

Scientists have long reckoned that the disks of gas and dust that can turn into planets might be putting the brakes on young stars, which can spin around in half a day or less if nothing tugs on them, researchers say.

“We knew that something must be keeping the stars’ speed in check,” Luisa Rebull of NASA’s Spitzer Science Center said in a statement. “Disks were the most logical answer, but we had to wait for Spitzer to see the disks.”

The orbiting Spitzer telescope sees the cosmos through infrared radiation, which makes it particularly good at finding the disks that swirl around stars, because the dust in the disks is heated by starlight and glows in infrared light. — Reuters

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Pollen bees, wild flowers in decline

Numbers of the Andrena hattorfiana bee are declining in line with the field scabious flower
Numbers of the Andrena hattorfiana bee are declining in line with the field scabious flower

BEES and the wild flowers they pollinate have declined significantly across large tracts of northern Europe, according to one of the most comprehensive surveys of pollinating insects.

Scientists examined hundreds of wildflower sites in Britain, the Netherlands and Germany and found that the diversity of bees had fallen in 80 per cent of them over the past 25 years.

The researchers said wild-flowers that rely on specialist species of bees for pollination had also declined suggesting the two were caught up in a vicious cycle of decline.

The authors of the report, in the journal Science, believe intensive farming and pesticides, as well as the loss of wild habitats, may be helping to cause the widespread fall in the diversity of bees and wildflowers. “We were shocked by the decline in plants as well as bees,” said Koos Biesmeijer, a researcher at the University of Leeds. “If this pattern is replicated elsewhere, the pollinator services we take for granted could be at risk, and with it the future of the plants we enjoy n our countryside.

— By arrangement with The Independent, London

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THIS UNIVERSE 
PROF YASH PAL

If we throw a stone upwards it comes down because of the gravitational force. What will happen if the stone crosses the air boundary? Will it move or be steady in space?

Air does not shield gravity. It only provides a frictional drag to a moving object. So let us forget about the air boundary for a while. If there were no air the ball will keep moving up, slowing down bit by bit. As it goes away from the earth the force of gravity also decreases, essentially inversely as the square of the distance from the centre of the earth.

Finally the stone will come to a stop and start falling down. It will come down with the speed at which it was thrown up. The kinetic energy lost on the way up is regained on the way down. It cannot stop and become steady. However, you can throw it in such a way that it also has a forward motion. It is like a goalkeeper kicking soccer ball high and towards the opponent’s goal. The ball follows a curved path. Suppose there was no air to provide friction and the goalkeeper was a superman. He could kick the ball with such a speed that its parabolic path would never hit the round earth. The ball would be continuously falling towards the earth but, because of its forward motion, it would keep missing it. The ball would have become a satellite of the earth!

Of course, it is possible to give the ball such a velocity that it completely escapes the confines of the earth gravitational field. Not only that, we could send it outside the solar system. (In practice giving a single large kick would not work because that would wreck the ball. We would instead use rockets that increase the speed more gradually.)

Incidentally, the orbital velocity of a near-earth satellite of the earth is 7.9 kilometres per second, while the escape velocity is 11.3 km per second. These values depend on the mass of the earth.

Armstrong and his friends landed on the moon and hoisted the US flag on its surface. But we can see that the flag is fluttering even though there is no air on the moon. How did it happen?

You may not recall but no movies of the fluttering flag are available. I do not know of anyone who has seen a movie of that flutter. Perhaps no movies were taken. If they had been we would have found that there is no flutter. The flag must have been cleverly designed using a material stiffer than cloth and molded into shape to simulate appropriately the folds and wrinkles of a fluttering flag.

When we pour water over quick lime it emits heat. How does it happen?

All chemical reactions involve an exchange of energy some of which often manifests itself in terms of heat.

Quick lime is calcium oxide, which is prepared by heating limestone to a temperature of the order of 900 degrees Celsius. The reaction produces, in addition, carbon dioxide. When calcium oxide, or quick lime, is mixed with water a chemical reaction occurs producing calcium hydroxide and a lot of heat.

The chemists say that the reaction is highly exothermic. Therefore, the answer to your question is that here you are talking of a highly exothermic chemical reaction. Incidentally calcium hydroxide is the chemical name of slaked lime, that is used for white washing our walls and some people eat in their “PAAN”.


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