any more G than we've got now, Qoqol, all the way to Mars. Our maximum acceleration will be 1/3,000th-G."

"One three-thousandth?" exclaimed T'an, shaken out of his Oriental calm. "Jonner, the Marsward will blast away at one or two Gs. How do you expect to beat that at 1/3,000th?"

"Because they have to cut off and coast most of the way in an elliptic orbit, like any other rocket," answered Jonner calmly. "We drive straight across the system, under power all the time. We accelerate half way, decelerate the other half."

"But 1/3,000th!"

"You'll be surprised at what constant power can do. I know Baat, and I know the trick he's going to use. It's obvious from the blastoff time they arranged. He's going to tack off the Moon and use his power right to cut 20 days off that regular 237-day schedule. But this tug-boat will make it in 154 days!"

They took aboard the 200-ton landing boat. By the time they got it secured, the radio already was sounding warnings for blastoff.

Zero hour arrived. Again Jonner pulled levers and again the faint glow appeared around the tail of their distant tug. Across space the exhaust of the Marsward XVIII flared into blinding flame. In a moment, it began to pull ahead visibly and soon was receding like a meteor.

Near the Radiant Hope, the space station seemed not to have changed position at all.

"The race is not always to the swift," remarked Jonner philosophically.

"And we're the tortoise," said T'an. "How about filling us in on this jaunt, Jonner?"

"Is should, Jonner," agreed Qoqol. "T'an know all about crazy new engine, I know all about crazy new orbit. Both not know all. You tell."

"I planned to, anyway," said Jonner. "I had figured on having Serj in on it, but he wouldn't understand much of it anyhow. There's no use in waking him up."

Serj was the ship's doctor-psychologist and fourth member of the crew. He was asleep below on the centerdeck.

"For your information, Qoqol," said Jonner, "the atomic engine produces electrical energy, which accelerates reaction mass. Actually, it's a crude ion engine. T'an can explain the details to you later, but the important thing is that the fuel is cheap, the fuel-to-cargo ratio is low and constant acceleration is practical.

"As for you, Tan, I was surprised at your not understanding why we'll use low acceleration. To boost the engine power and give us more Gs, we'd either have to carry more fuel or coast part of the way on momentum, like an ordinary rocket. This way's more efficient, and our 63-day margin over the Marsward each way is more than enough for unloading and loading more cargo and fuel."

"With those figures, I can't see how Marscorp expects to win this competition," said T'an.

"We've got them, flat, on the basis of performance," agreed Jonner. "So we'll have to watch for tricks. I know Marscorp. That's why I arranged to take aboard that G-boat at the last minute. Marscorp controls all the G-boats at Marsport, and they're smart enough to keep us from using them, in spite of the Space Control Commission. As for refueling for the return trip, we can knock a chunk off of Phobos for reaction mass."

The meteor alarm bells clanged suddenly, and the screen lit up once with a fast-moving red line that traced the path of the approaching object.

"Miss us about half a mile," said Jonner after a glance at the screen. "Must be pretty big ... and it's coming up!"

He and T'an floated to one of the ports, and in a few moments saw the object speed by.

"That's no meteor!" exclaimed Jonner with a puzzled frown. "That's man-made. But it's too small for a G-boat."

The radio blared: "All craft in orbit near Space Station 2! Warning! All craft near Space Station 2! Experimental missile misfired from White Sands! Repeat: experimental missile misfired from White Sands! Coordinates...."

"Fine time to tell us," remarked T'an drily.

"Experimental missile, hell!" snorted Jonner, comprehension dawning. "Qoqol, what would have happened if we hadn't shifted orbit to take aboard that G-boat?"

Qoqol calculated a moment.

"Hit our engines," he announced. "Dead center."

Jonner's blue eyes clouded ominously. "Looks like they're playing for keeps this time, boys."

The brotherhood of spacemen is an exclusive club. Any captain, astrogator or engineer is likely to be well known to his colleagues, either personally or by reputation.

The ship's doctor-psychologist is in a different category. Most of them sign on for a few runs for the adventure of it, as a means of getting back and forth between planets without paying the high cost of passage or to pick up even more money than they can get from lucrative planetbound practice.

Jonner did not know Serj, the Radiant Hope's doctor. Neither T'an nor Qoqol ever had heard of him. But Serj appeared to know his business well enough, and was friendly enough.

It was Serj's first trip and he was very interested in the way the ship operated. He nosed into every corner of it and asked a hundred questions a day.

"You're as inquisitive as a cadet spaceman, Serj," Jonner told him on the twenty-fifth day out. Everybody knew everyone else well by then, which meant that Jonner and Qoqol, who had served together before, had become acquainted with T'an and Serj.

"There's a lot to see and learn about space, Captain," said Serj. He was a young fellow, with fair hair and an easy grin. "Think I could go outside?"

"If you keep a lifeline hooked on. The suits have magnetic shoes to hold you to the hull of the ship, but you can lose your footing."

"Thanks," said Serj. He touched his hand to his forehead and left the control deck.

Jonner, near the end of his eight-hour duty shift, watched the dials.

The red light showing the inner airlock door was open blinked on. It blinked off, then the outer airlock indicator went on, and off.

A shadow fell across Jonner briefly. He glanced at the port and reached for the microphone.

"Careful and don't step on any of the ports," he warned Serj. "The magnetic soles won't hold on them."

"I'll be careful, sir," answered Serj.

No one but a veteran spaceman would have noticed the faint quiver that ran through the ship, but Jonner felt it. Automatically, he swung his control chair and his eyes swept the bank of dials.

At first he saw nothing. The outer lock light blinked on and off, then the inner lock indicator. That was Serj coming back inside.

Then Jonner noted that the hand on one dial rested on zero. Above the dial was the word: "ACCELERATION."

His eyes snapped to the radio controls. The atomic pile levers were still at their proper calibration. The dials above them said the engines were working properly.

The atomic tug was still accelerating, but passengers and cargo were in free fall.

Swearing Jonner jerked at the levers to pull out the piles aboard the tug.

A blue flash flared across the control board, momentarily blinding him. Jonner recoiled, only his webbed safety belt preventing him from plummeting from the control chair.

He swung back anxiously to the dials, brushing futilely at the spots that swam before his eyes. He breathed a sigh of relief. The radio controls had operated. The atomic engines had ceased firing.

Tentatively, cautiously, he reversed the lever. There was no blue flash this time, but neither did the dials quiver. He swore. Something had burned out in the radio controls. He couldn't reverse the tug.

He punched the general alarm button viciously, and the raucous clangor of the bell sounded through the confines of the ship. One by one, the other crew members popped up to the control deck from below.

He turned the controls over to Qoqol.

"Take