ISRO Launch Vehicles

Indian Space Research Organisation

Server sky's best first use is rural computing in the developing world, and India's rural half billion could connect with their cell phones, through antenna panels on cell towers, to a modest server sky array. 12 low-population arrays can provide overlapping broadband coverage to villages up to the northern mountain valleys. Assume 12 "open" and 12 "managed" arrays in the first launch.

India has the technology to manufacture and assemble all components of Server Sky, except for some of the hafnium-gate integrated circuits, which (in 2013) must be made by Intel. Intel offers this technology to outside manufacturers under contract.

Using small 5300 5 gram thinsat arrays, spot size would be larger, but adequate for gigabit communication per village and small town. Assuming 50% extra weight for extra delta V to m288 and for apogee insertion motors (reusable in the future as ballast), and 3 spare launch bundles for backup, the entire system could launch with one 1000kg-to-LEO booster, or with 25 40kg-to-LEO boosters.

Server sky thinsat arrays are both much lighter than big-iron comsats, they are 7 times closer to earth than GEO, and can focus on much smaller ground spots. While a GEO comsat can focus on regions, server sky can focus down to city blocks, and multiplex transmit beams, while ground antennas can rapidly sequence between arrays .

ISRO's Launchers

first launch

LEO kg

GTO kg

GEO kg





high success rate








All vehicles launch from the Satish Dhawan Launch Centre (formerly the Sriharikota High Altitude Range ) at 13°43′12″N in Andhra Pradesh, 80 km north of Chennai (on India's southeast east coast). All these vehicles are larger than needed; perhaps they can launch many more than 25 arrays, selling them to other operators. Keep in mind that the arrays around the earth and below the horizon from India (70% of the total!) can serve other parts of the globe until they return to India's sky.

Estimated capacity to m288

The ISRO website claims 1600 kg "satellites" to a sun synchronous 620 km orbit, and a 1050 kg satellite to GEO. Does this include the apogee kick motor in the weight of the satellite? The above numbers from wikipedia are larger, but appear to be gross weight including AKM. Assume an inclination of 98 degrees for the 620 km orbit, meaning the plane of the orbit is 8° west of north.

Oversimplifying the trajectory a lot, a transfer orbit from sea level at 13.7 degrees north (est 6377 km radius perigee) to 620 km average altitude (6271+620 = 6991 km radius apogee) has a semimajor axis of 6684km, and an eccentricity of 0.04593 . v0 is 7730.5 m/s, vp is 8085.6 m/s, and va is 7375.5 m/s. The earth rotates at 7.292e-5 radians per second, or 465 m/s at 13.7N . We need to be moving north (or south) at 8085.6*cos(8°) = 7929 m/s, and retrograde by 8085.6sin(8°) + 465 = 1590 m/s for a total launch delta V of 8087m/s .

The apogee circularization is to an orbit with v0 = vp = va = 7550.9 m/s . The delta V is 175 m/s . The total delta V from Satish Dhawan to 620km orbit is approximately 8260 m/s .

The delta V to GTO from Satish Dhawan is about 9960 m/s . The delta V to m288 transfer AND insertion is around 9780 m/s . The mass is inversely proportional to the exponential of the deltaV divided by VE, the effective exhaust velocity (very crudely, this is for a curve fit). A change from 8260 to 9960 m/s (1700 m/s) reduces payload weight by a fraction of 1.54 or so, thus VE = 1700/ln(1.54) = 3880m/s .

Interpolating to 9780 m/s suggests a mass advantage over GTO of exp( (9960-9780)/3880 ) or 5%. Using the 1200kg to GTO number above, we get 1250 kg to m288, and using 1050 kg to GTO we get 1100 kg to a circular M288 orbit.

PSLV notes

ISRO notes

ISRO (last edited 2014-09-04 19:25:49 by KeithLofstrom)