Enligt källan minskade Hermes i en månad så att Den kinesiska booster kan leverera resupply-sonden:
“Iris is a point-thrust craft,” Venkat said. “Hermes has a constant-thrust ion engine. It’s always accelerating. Also, Hermes has a lot of velocity right now. On their current Earth-intercept course, they have to decelerate for the next month just to slow down to Earth’s speed.”
Chapter 16.
och
Taiyang Shen är en rakett som ursprungligen utformades för att ge en mycket tung sond till en heliocentrisk omlopp (det vill säga att bana Sun, i det här fallet mellan Mercury och Venus). På grund av det har det mycket bränsle (i tekniska termer: mycket delta-V), så att det går hela vägen till Mars, eller i det här fallet - för att fånga upp Hermes :“Well,” Venkat began, “if they did this ‘Rich Purnell Maneuver,’ they’d start accelerating right away, to preserve their velocity and gain even more. They wouldn’t intercept Earth at all, but would come close enough to use a gravity assist to adjust course. Around that time, they’d pick up a resupply probe with provisions for the extended trip.
Ibid.
“It’s the Taiyang Shen’s booster, sir. Our engineers have run the numbers, and it has enough fuel for a Mars injection orbit. It could get there in four hundred and nineteen days.”
Ibid.
och
“Earlier,” Teddy said, “you mentioned a supply probe for Hermes. We have that capability?”
“Yes, with the Taiyang Shen,” Venkat said. “We’d shoot for a near-Earth rendezvous. It’s a lot easier than getting a probe to Mars, that’s for sure.”
Ibid.
Och senare för CNN: s Mark Watney-rapport :
“Hermes isn’t going to orbit Earth,” Venkat said. “It’s just passing by on its way to Mars. And its velocity is huge. We need a booster capable of not only escaping Earth’s gravity but matching Hermes’s current velocity. Only the Taiyang Shen has enough power to do that.”
Chapter 19; italics author's, bold emphasis mine.
Om hur Watney kunde fånga Hermes - var det genom att ducka mycket tyngd och att vara mycket lycklig. För det första hade MAV lite bränsle kvar från sin första landning. Watney gjorde ännu mer bränsle och drogade allt möjligt, till och med säkerhetskopior och vissa säkerhetssystem.
“Next up,” he continued, “We’re ditching all life support. The tanks, pumps, heaters, air lines, CO2 absorption system, even the insulation on the inner side of the hull. We don’t need it. We’ll have Watney wear his EVA suit for the whole trip.”
[. . .]
“We’ll remove the nose airlock, the windows, and Hull Panel Nineteen.”
Venkat blinked. “You’re taking the front of the ship off?”
“Sure,” Bruce said. “The nose airlock alone is four hundred kilograms. The windows are pretty damn heavy, too. And they’re connected by Hull Panel Nineteen, so may as well take that, too.”
[. . .]
“We’ll also have him remove the back panel of the pressure vessel. It’s the only other panel he can remove with the tools on hand. Also, we’re getting rid of the auxiliary fuel pump. Sad to see it go, but it weighs too much for its usefulness. And we’re nixing a Stage One engine.”
“An engine?”
“Yeah. The Stage One booster works fine if one engine goes out. It’ll save us a huge amount of weight. Only during the Stage One ascent, but still. Pretty good fuel savings.”
Chapter 25
Observera att Hermes också var tvungen att vara kvar på banan och använda Martens slanghot. Annars, även med sina jonmotorer, skulle de ta för lång tid att återvända till jorden, och skulle dö även med försörjningssonden närvarande.
“It’s a flyby,” Venkat said. “Hermes isn’t going into Martian orbit. If they did, they wouldn’t be able to get back. They need their velocity for the return trajectory.”
Chapter 21.