Dead on Mars

Later, Tomcat said, “In human aeronautics, 99% of the problems faced were a result of insufficient power. As long as there was enough power, none of the problems were problems.”

The final 1% was the fault of conventional frameworks.

…

“We all know that if a body is thrown from the sky on Earth, it will be a free-falling body, but it’s not truly a free-falling body.”

“Because of air resistance?” Mai Dong asked.

“Yes, this object will keep accelerating, but it won’t go on forever,” Tomcat said. “At a particular point in its descent, gravity and air resistance will achieve a balance, resulting in terminal velocity.”

Tang Yue and Mai Dong nodded. It was easily comprehensible as it was in high school physics.

“This is influenced by the density of the air, and in physics, there’s a term known as the ballistic coefficient. The Martian atmosphere’s ballistic coefficient is extremely low, which also means that the atmosphere can hardly provide enough resistance to achieve a balance of forces,” Tomcat said. “If we throw a powerless Eagle down, its deceleration will happen extremely slowly. And when its height drops to 40,000 meters, its speed will still exceed Mach 15. The surface temperatures will rise to 2000°C. This is also why we need the heat-resistant tiles.

“In the 20th and early 21st century, many Martian probes perished because of this. The speed was just too fast for them to land successfully.

Tomcat shrugged its shoulders.

What was destroyed in the descent was Martian probes. The most classic example was the European Space Agency’s Beagle 2. The poor lander remained in the desert to this day.

“A lander’s normal descent is this: It enters the atmosphere from an altitude of 125 kilometers. At this time, its speed should be about 5 km/s,” Tomcat used a pen to demonstrate it to the two others. It raised the pen in its paw high before stabbing it down. “85 seconds later, it will inflate an entry device for the first stage of the deceleration. Within that 85 seconds, its altitude will drop to 90 kilometers, enduring the peak heating.

“The entry device will reduce the Eagle’s speed to below Mach 2. This is a Mach number that can withstand the deployment of a parachute. At 10,000 meters, the lander will deploy a parachute with a diameter of thirty meters.” Tomcat spread its paw above the pen to indicate the parachute. “The parachute will reduce the speed of the Eagle to subsonic speeds until the lander reaches a height of 1000 meters. It will then abandon the parachute and activate the rocket engines to change its attitude to begin a powered descent.”

Tomcat slowly placed the pen vertically on the table.

These were things Mai Dong and Tang Yue knew as well. During their training prior to the mission, they had been briefed in detail about the spacecraft’s operational principles.

Tomcat was repeating it again today.

“Why is the process so complicated?” Tomcat asked. “Why does it need to be so complicated?”

Before waiting for their answer, Tomcat answered, “It’s because there’s not enough power. We lack the power from rocket engines to provide a reverse thrust the entire time. Chemical rockets are too inefficient,” Tomcat said. “A rocket’s thrust is mostly pushing itself, with tonnes of its mass being fuel, and the rounding errors are the load.

“In an ordinary descent, it’s not practical to have the rockets produce a reverse thrust the entire time. That will require the Eagle’s cargo and command module to be filled with propellant. The lander will become a flying fuel tank,” Tomcat continued. “But that’s in normal circumstances. What we are going to do is an abnormal descent… We don’t care about efficiency or cost, nor do we care about the hundreds of tonnes of fuel. All we care about is that rounding error!”

Tomcat raised its paw and pointed at Mai Dong, enunciating each and every word: “A rounding error of 60 kilograms!”