1636 The China Venture – Snippet 35
“Prepare for hot inflation,” Mike warned the ground crew, and waited for them to nod acknowledgment. Several of them came over and stood on either side of the basket, ready to hold it down if the balloon started to lift off before Mike was ready.
Mike knelt in the space between the basket and the burner, so he could access the burner controls. He angled the burner a bit upward and sighted along it, confirming it was pointing down the throat of the envelope. He pushed down repeatedly on the pump handle, pressurizing the fuel, and lit the pilot light.
“Test blast!” said Mike, and opened the fuel valve on the burner. A blue flame jetted out; Mike confirmed that it was clearing the fabric and the sailors on throat duty.
“One thousand one, one thousand two ….” Mike counted to himself. After six seconds, he shut the valve for three seconds, giving the fabric, not to mention the sailors, a chance to cool down.
Zheng Zhilong tapped Jim’s shoulder. “In the days of the Song, our armies used a Pen Huo Qi, a Sprayer of Fiery Oil, against the Mongols. But I think it made a different kind of flame.”
“The burner for the balloon breaks the oil up into extremely small droplets; when they are ignited, they are turned immediately into gas. It is the burning gas you see here.”
“It is a substance like air, but with different properties. This gas burns. There are other gases that burn, too, like the gas that rises from swamps, or the fire-damp in a coal mine. ”
As Mike continued the intermittent blasts of fire, the balloon started to rise.
He turned in Jim’s direction and made a throat-cutting gesture. “Blower off!”
Jim turned off the supply of fuel to the blower engine. The fan would keeping running for a minute or so, turning ever more slowly as it did so.
The throat crew gently released the balloon and came around to hold the back of the basket as it tilted backward. At the same time, the crown line crew allowed the crown to rise, but not too quickly.
Jim was pleased to see the ease with which the men went about their work. He and Mike Song and several other members of the mission staff had been trained in balloon operation prior to leaving Grantville, but most of the ground crew were simply sailors. Obviously, they have experience handling lines for sails and they’d gotten some training before the Rode Draak left on the mission in September 1634. But since then, on the voyage itself, they could only give the crew some reminder lectures and practice some aspects of the ground handling. The balloon could not be safely inflated on board a ship not designed for the purpose.
But all seemed to be going well. The inflation was proceeding as smoothly as it had during their test run the day before, even though the crew knew they had to impress their distinguished visitor.
Once the fan of the blower had stopped turning, Jim tilted it backward and slid it back some feet, well away from the basket. In the meantime, Mike stood up and adjusted the burner orientation to keep it centered on the mouth of the envelope.
When the basket was inclined perhaps thirty degrees from the horizontal, Mike stepped back into it, and the throat crew rotated the basket upright. The balloon was also vertical, and bobbing with its mouth perhaps a foot away. Mike pointed the burner straight up and pulled in the mouth so it was directly over the burner. He then tied the mouth to the frame so it would stay that way.
The crown line crew brought the line to the pilot, who fastened it to the frame, and they joined the throat crew around the basket. “Weight on!” he called, and all four put all their weight on the top of the basket, while keeping their feet on the ground.
It was time for Zheng Zhilong to board. Mike offered him a hand, but Zhilong declined.
Mike bowed to him once he was settled in the basket. “Admiral Zheng, there’s something very important that I tell you. Please don’t take offense, but this balloon is my ship and I am the captain. You must obey my orders.”
Zhilong smiled. “It appears that sailing the sea and sailing the air have much in common. It will be as you direct.”
Mike gave the burner a one second burst and studied the movement of the balloon.
“Light hands!” The ground crew eased up, leaving their hands on top of the basket so that they could put weight back on quickly if so commanded.
Mike gave the burner another short burst. The balloon rose off the ground, but too quickly for Mike’s taste. “Weight on!”
He waited a few seconds. “Light hands!”
The balloon remained steady, the basket perhaps a foot above the ground.
“Ready?” he asked Zhilong.
The admiral pointed up at the sky.
“Hands off!” The crew let go of the basket and backed away from it.
Mike released the tie-off, and gave another short burst with the burner.
Slowly, the balloon rose into the morning air.
“We are already higher than the crow’s nest on the tallest ship I have ever set foot on,” marveled Zhilong.
“That’s what, seventy feet? The tethers will let us go several times as high, although I don’t want to go so high that the ropes are taut.”
As Mike answered, he briskly opened the burner valve, and three seconds later, closed it again. The balloon, which had started to descend, resumed its ascent.
“How do you decide how often and how long to apply the flame?” asked Zhilong.
“I like to make each burn exactly the same–I aim for a three second full burn–and just adjust the frequency of burns to the situation; how high up we are, how fast are we ascending or descending, and where I want to end up.”
“Ah. We are higher now. It seems to be windier, too.”
“We’re at about two hundred feet now. Wind speed tends to increase with altitude. But just so you know, the only reason we feel the wind is that we are tethered. If the balloon were flying free with the wind, we’d accelerate up to the wind speed, and then, traveling with the air current, we’d feel nothing.’
“So why doesn’t that happen with a ship?”
“There’s more resistance, so you probably don’t reach a ground speed of much more than maybe half the wind speed.”
Zhilong leaned over the railing of the basket, looking northwestward, toward the channel lying between Jinmen and the island immediately to its west. “There! That’s one of my ships!”
“How can you tell?”
“Look at the foresail.” The foresail bore the character “Zheng.”
“So how far can we see now?”
“We’re at two hundred feet, soâ€¦ I’d say a little over seventeen miles. Weather permitting, and no hills in the way, of course. With a thousand foot single tether, we could see almost forty miles.”
“So let’s go higher!” said Zhilong. “At least to the limit of the tether.”
“It’s not a good idea. If we released the tether and free-ballooned up to eight thousand feet, which is as high as lowlanders like us can go without risking mountain sickness, we could see over one hundred miles. Forgive me, Admiral, but this is a test flight, and you are an important personage. I’ll feel a lot happier once you’re safely back on solid ground.”
Zhilong smiled. “I understand. Not good for business to have an admiral fall over the side, whether at sea or in the air. But first, may I try a burn myself?”
“Be my guest.”