If you had a 15-gallon tank, then the mass of your gas would be about 93 pounds; everything else would need to add up to 16 pounds, which is a total of 109 pounds. Taking 0.014% of that leaves you with only 0.015 pounds of groceries! One average-sized grape weighs about 0.015 pounds. That's what you get to bring home on a full tank of gas! As depressing as this analogy sounds, the brightest rocket scientists in the world would be thrilled to get that little grape back home. Welcome to the world of spaceflight and the tyranny of the rocket equation. This is the universe in which we live. Pegasus. Launch Sites If a spacecraft is launched from a site near Earth's equator, it can take optimum advantage of the Earth's substantial rotational speed. Sitting on the launch pad near the equator, it is already moving at a speed of over 1650 km per hour relative to Earth's center. This can be applied to the speed required to orbit the Earth (approximately 28,000 km per hour). Compared to a launch far from the equator, the equator-launched vehicle would need less propellant, or a given vehicle can launch a more massive spacecraft. A spacecraft intended for a high-inclination Earth orbit has no such free ride, though. The launch vehicle must provide a much larger part, or all, of the energy for the spacecraft's orbital speed, depending on the inclination. For interplanetary launches, the vehicle will have to take advantage of Earth's orbital motion as well, to accommodate the limited energy available from today's launch vehicles. In the launch animation below, the launch vehicle is accelerating generally in the direction of the Earth's orbital motion (in addition to using Earth's rotational speed), which has an average velocity of approximately 100,000 km per hour along its orbital path. Launch Complex-41 at KSC with an Atlas-V poised for launch. Previously. this was the launch pad for Voyager and Viking missions. In the case of a spacecraft embarking on a Hohmann interplanetary