Yuri appeared over the rear of the Hope, and immediately told David he could light off the ion engines. He and Raoul re-entered the cargo bay, and Yuri turned on the pumps to repressurize it.
As soon as he returned to the passenger compartment, Dolf dove back into his tablet, which he had put into the communal docking station. He was punching keys frantically and talking nonstop to his fellows at Alcântara. He talked David through several short bursts of the small attitude jets to correct minor course discrepancies. All the crewmen were very busy, running post-launch checks of their assigned equipment.
Each of the crew reported to Control on their specialty, though Yuri did so in code words. Amazingly, it appeared that everything had gone exactly as planned, even to the fact that the Hope was still attached to the huge core stage. Unbelievably, there was even a small amount of fuel remaining in the core stage tank. The crew was jubilant, and over the radio, it sounded like the Control staff was having a party. Frank was again forced to remind the crew of the many ears listening to their every word.
Finally, it was 0900, 9 AM Alcântara time. Dolf grimaced in distaste as he flicked on the large main microphone.
"Good morning, Earth," he began. "This is Man's Hope calling, Rodolfo Ancara speaking. As you know, Mr. Weatherly decided that since this is man's enterprise, the people of Earth should be involved. He has broadcast the radio frequency we will be using, so you will be able to hear all of our contacts with Earth, including those with Alcântara Control. At the moment, this broadcast will have to be repeated to reach around the world, but Mr. Weatherly has arranged for this, as well as for language translations.
As we get farther from Earth, though, our beam will become wider, and weaker. Soon, it will cover the entire half of the Earth facing our position, and anyone with a sufficiently powerful antenna will be able to hear us direct. Mr. Weatherly is inviting everyone on Earth to accompany us on this mission. You will hear of our failures as well as our successes. Every day at this time, I will broadcast a briefing in English. They will be rebroadcast around the world, and translated. This is the first of those briefings.
"Many of you will have been surprised by our liftoff; it was far from conventional. In this first report, I would like to explain the reason for our unique method of departure.
"As many of you know, comets consist mostly of water ice. They have even been described as 'dirty snowballs'. Water consists of two elements, two atoms of hydrogen, and one of oxygen. This is why you sometimes hear water called H2O. Now, our main rocket engines are liquid-fueled, and use hydrogen and oxygen as their fuel. Some time ago, we decided that it would be very useful if we could retain the large tank and main engines, called the 'core stage', instead of dropping it, as is usual. Since the main engines on the core stage use hydrogen and oxygen, once we reach the comet, we hope to break some of the water ice down into hydrogen and oxygen, compress them, and refill the now-empty tank. While we do not expect to be able to liquefy the gases, we hope to compress them sufficiently to provide us some additional rocket boost, in case of an emergency.
"Now, a question that will occur to many is why we were able to do this, and other missions have not. The answer is that we stand on their shoulders. We were able to use the data that they, the pioneers, gathered for us. The information that they have gathered over the last fifty years told us how much boost was needed to lift how much weight, actually called mass, into how high an orbit. Those of you who are students, please ask your science teachers to explain the difference between weight and mass; it is a vital distinction in space. Here, nothing weighs anything; but mass is the same as on Earth. For those not in school, I recommend Google.
"Thanks to those previous missions," he continued, "we found that if we used larger than usual, three-stage booster rockets, we might get enough lift to permit us to keep the core stage, instead of discarding it. Please do not misunderstand. Our Commander had his finger on a button that would separate the core stage at an instant's notice, if necessary.
"However, we also realized that if we used a traditional launch pattern, where we would pause at Low Earth Orbit, and possibly again at geostationary orbit, we would not be able to sustain enough velocity to lift both our vessel and the core stage.
"We were very confident of our boosters and ship, so we decided that we would very carefully calculate our liftoff time, so that we would be able to boost straight into an orbit heading for the comet.
"We also listen to Earth news broadcasts, and have been hearing that we risked the lives of other astronauts by our 'reckless' departure. The only other astronauts in orbit at the time were on the International Space Station. That station was on the opposite side of the planet when we lifted. The only lives that were risked were our own.
"So, now we are on our way to Carter IV. Those of you with powerful telescopes may have been able to see us go outside and spread our solar panels. Those panels will enable us to use four ion engines. This means that instead of building up speed and coasting, the traditional means of space travel, we will have constant boost, all the way. As always, though, there is a down side. Ion engines provide a constant boost, but it is a very weak boost. Our acceleration, called 'delta-V', will be approximately one-thousandth of a 'G'. A 'G' is about 9.81 meters per second per second, or just over 32 feet per second per second. We will accelerate at one-one-thousandth of that, or .00981 meters per second per second, or .0032 feet per second per second.
"To put it another way, if we were starting from a standing start, with a velocity of zero, it would take us several days to build up to 60 miles per hour. But constant boost is cumulative. I recommend that you high school students ask your math teachers how fast we will be going when we approach the comet, and how long it will take us to get there. For simplicity's sake, I suggest using a starting velocity of 10,000 miles per hour. The comet's orbit is easily available on the Internet, but for your calculations, I suggest a distance of 266,000,000 miles.
"For those of you whose school days are far behind them, I will provide the answer tomorrow. If you have any questions you would like to ask us, Mr. Weatherly has set up a web site where you can post them. I will answer selected questions on these broadcasts as we progress. The website is www.man'shope.org. Until tomorrow, then, we hope you have a good day. For us, it is always a good day in space."
Chapter 8
Dolf sat back with a gusty sigh. "That is the hardest part of my job," he complained. "I sound like a schoolteacher."
David grinned. "You did great. I'd sign up for your course."
Dolf smiled broadly. "You already have. All of you have. You are a captive audience for these daily classes."
Ron grunted. "I am glad I brought plenty of music on SD cards!"
The next day, Dolf seemed particularly cheerful as he did his 'Daily Report'. He had received almost immediate feedback, most of it positive
"We have received much response to yesterday's report," he began. "Some teachers complained about being put 'on the spot' by their students, and several other teachers were concerned that the information I provided was insufficiently precise. Other listeners said that they wanted to hear reports of what is happening, not attend a math class.
"To all of you, I apologize. However, I must mention that space travel is all maths. To those math teachers that felt 'on the spot', I say that all that was required was the formula d=½at², with which every math teacher should be familiar. As for the imprecision, every capsule, every spaceship, every piece of space junk, is on an orbit. Now, orbital mechanics can become very complex very quickly. In addition, there are a number of factors involved that would cause a precise computation to require the services of a mathematician and a very powerful computer; for example, my problem did not include solar gravitational influences, or the fact that the comet is on an orbit of its own, which we must plan to intercept on a tangent. The person who asks 'when will you get there?' or 'how long will the trip take?' does not expect a scheduled arrival date. He merely wants an approximation, a reply accurate within an order of magnitude. And for the person who just wants me to answer the damned question, I reply that we cannot be sure, due to some of the factors I mentioned. But we expect to reach the comet in not less than four, and not more than six months. To be honest, I expect we'll reach it somewhere around the five-month mark. But scientists hate to be wrong, so I stand by the four-to-six month estimate.