Gabe stared at the board silently for a minute. “Huh. I’ll be damned. That’s not an entirely bad idea. Now why didn’t somebody think of that before?”
Jeff smiled, “Beats me.”
“So how do you plan on getting it there? There’s no launch vehicle available that can put that much mass into a Mars transfer trajectory.”
“Multiple launches, assemble it in low Earth orbit, then boost it on its way.”
She glanced over her shoulder at him, “You planning on doing the assembly yourself?”
“Nah. We’ll use a remote auto-docking system. They’ve come of age.”
“That’s still going to require an awful lot of thrust.”
“Yep. I figure a couple Centaur-3s and about 50 tons of fuel ought to do it.”
“50 tons of fuel?!” Abby gasped. “Didn’t you just say the ship only weighs 30 tons?”
“That’s right.”
“80 tons gives us just 30 tons of payload? That’s crazy.”
Jeff laughed, “Yeah, and that’s just the tip of the iceberg.”
Abby whistled through her teeth, “I had no idea.”
Jeff smiled at her, “And that, my dear, is why it’s so difficult and costs so much.”
Gabe glanced at him, “And why nobody’s done it.”
He returned her glance, “Yet.”
“Okay, so assemble in orbit, and you’re going to launch a Centaur-3 as a payload?”
“Yep.”
“What a waste.”
“No argument, but what’s the alternative? There’s no other way. There are no super-heavy lift vehicles available. We’ve got the Falcon, Atlas V and Delta IV heavies, and that’s pretty much it. The big boys – Saturn V, Ares V, shuttle – have either gone the way of the dodo or are vaporware. If you’ve got a better idea, I’m all ears.”
Gabe scratched her head and thought for a minute. “A few years back, Lockheed published a proposal to use a Centaur as part of a lunar lander, proposing to land the whole thing, with some kind of hab on the front.”
“Yeah, I remember reading about that. Weren’t they just going to use it as a fuel tank? The idea didn’t make much sense to me.”
“Yeah, but also remember that Skylab was essentially just a modified unused S-IVB left over from Apollo.”
“Ah, okay, I see where you’re going, but go ahead.”
“So, why not make use of the empty Centaur by landing it on Mars – they’re not heavy – and use it as a habitat?”
“Um, well, we could certainly take a look at it but, as I see it, the problem is, though a Centaur is arguably the greatest booster stage ever made, as a ready-to-occupy habitat it, uh… sucks. The effort and material required to make it habitable would be enormous. And the weight savings – the only reason to do it – is not that great, just a few tons.”
“I’m just thinking out loud.”
“Well you go right on thinking out loud, don’t let me stop you. There are no bad ideas and I’m perfectly willing to hear every last one of them.”
“How many payload packages do you plan on putting down?”
“I have no clue. 20, 30, 40, something like that. I was hoping to hire a Ph.D. in aeronautics to figure that out.”
Gabe nodded and laughed. “Uh huh. You do know they’re not all going to make it?”
Jeff was smiling. He now knew she was the right choice. “Probably not. So we build in some redundancy.”
Gabe shook her head. “Just out of idle curiosity, what’s the total launch mass of all this?”
“Who knows? Between payload, landers, boosters and fuel, jeez, I dunno, maybe a million pounds.”
Gabe’s jaw dropped. “A million pounds? That would take 20 launches! There aren’t that many heavy lifters available.”
“Well, there might be if we can corner the global market for the next four years.”
“Good luck with that.”
“But there is another possibility – Jupiters.”
“Jupiters? They’re still just conceptual.”
“Yeah, but there’s nothing special about them. Direct 2.0 calculated a four-year development timeline, and we’ve got four years. The shuttle’s dead and there’s God only knows how many leftover parts lying around. All we would have to do is get the government to release their surplus junk and museum pieces and get somebody to build ‘em.”
“What’s a Jupiter?” Susan asked.
Jeff turned to her and smiled. “A great big rocket. They’re based on the Space Shuttle; uses the same external fuel tank and solid rocket boosters – SRBs – but moves the engines to the bottom of the fuel tank and the payload up top in a conventional inline configuration. All the parts are tried and tested, man-rated, and have been flying for 30 years. Like I said, it’s just a matter of building them. The Jupiter-130 will lift around 140,000 pounds into low Earth orbit, more than double the current top heavy lifter, a Falcon Heavy, and the Jupiter-246 will lift over 200,000 pounds. Further, the 246 has a big second stage, not unlike the S-IVB third stage used on the old Apollo-era Saturn V, but a lot bigger. That can be used to boost us into Mars trajectory and eliminate the need for all those Centaurs.”
Abby whistled under her breath.
“Yes, but I’m not buying it,” Gabe said. “You couldn’t possibly build and test fly the thing in four years.”
Jeff smirked. “Maybe, maybe not. But who said anything about testing it? We build it and we go.”
“You’re going to launch in an un-tested rocket? Are you crazy?”
“Well, I wasn’t planning on riding the thing, there are plenty of man-rated vehicles around now. We’ll use it, or them, for cargo.”
“And if it, or them, don’t work?”
“Then I’m out another couple hundred million and take what’s left and go lie on a beach in Bermuda, and y’all are back in the unemployment line. Gabe, that’s the only way this can work. It’s the only way it’s affordable. No frills. No years of engineering design, testing and redesign – we haven’t the time or money. If we need something new, we design it, build it, and fly it. If it works, great. If it doesn’t we call it quits and find something else to do.”
“Right. Okay, well…” Gabe rubbed her forehead, “… getting back to Mars, even if you do get all these payloads down, they’ll be scattered over a couple thousand square kilometers. How are you going to find ‘em and retrieve ‘em?”
“Well, we retrieve them with rovers; either remote control or manned. And we find them by first putting down something akin to a military grade TACAN: radio direction finding and distance measuring, like a commercial aviation VORTAC but more accurate. Then, as each module comes in, following chute deployment and as it’s approaching the ground, it reports its location, direction and distance from the TACAN. Then we go get it. Further, since the guidance systems can utilize the TACAN, drops should be a lot closer, as they’ll have a good, consistent target.”
“Huh. So the TACAN’s ground zero? That’s not a half-bad idea.” She moved on down the board. “So this is our base of operations? What are these?”
“Habitat modules.”
“Tuna cans? You couldn’t come up with anything more original?”
“Oh, I had a lot of ideas, but fact is aluminum cans are still the easiest, cheapest, and most practical.”
“How big are they.”
“Tiny. Outside dimensions are about twelve feet in diameter and six and a half feet tall, with three inch insulated double walls.”
“Oh my god, it’ll be like living in a refrigerator carton.”
Jeff chuckled, “Pretty close. But everyone will have their own refrigerator carton that they can call home and get away from the rest of us.”
Gabe sighed and shook her head, “This just gets better and better. Why so small?”
“Weight. The MSL descent stage is limited to 1875 pounds. Bigger tuna cans means bigger descent stage, more fuel, bigger and heavier lifting body, bigger launch vehicles – everything gets bigger
and heavier all the way back to the launch pad at Kennedy. We have to draw the line somewhere.”
“Okay, what’s this?”
“Bigelow Aerospace Sundancer.”
“Really? Like the one they just put in orbit?”
“Exactly.”
“That’s the transit habitat?”
“Yep.”
“Interesting. Out and back? Same module? Kind of small isn’t it?”
“Yep, same one. Home sweet home. The Beverly Hilton it ain’t, but it’ll do. And it’s not all that small. Around 6500 cubic feet, that’s about the same volume as the surface habitat.”
Gabe nodded. “Okay, so the transit vehicle consists of the Sundancer and an Apollo or Orion-like CEV?”
“Yeah, command and service modules.”
“What’s this can up front?”
“Provisions.”
“You can’t get provisions for a seven-month trip in the Sundancer?”
“Sure, but we’ll need to have enough with us for the return trip as well.”
“You’ll bring all the return trip provisions with you rather than send them separately and resupply once you get there?”
“Yeah, have to.”
“Why?”
“What if we get there and can’t land? Look, with only two launch windows available, a lot of the stuff we’ll need to get down to the planet, live there, and get back off will be in the air while we are. What if something doesn’t make it? I don’t know about you but, all things considered, I’d rather not be marooned on Mars or lost in space for the rest of eternity. So, Plan B would be to abort the landing, do a powered swing-by, and head straight home. But, that would mean another year in space, and we’d need the provisions for it.”
Susan grimaced. “Nineteen uninterrupted months in space?”
Jeff smiled. “Yeah. I grant it wouldn’t be fun, but it sure beats the alternative.”
Gabe nodded. “Okay, I like that. That’s the safety valve.”
“Correct.”
“Alright. Um, but assuming all goes well and you do go into orbit and land, when you’re ready to go home, where’s the fuel? Or are you taking that along also? And, if so, where is it? I’m just guessing, but it seems to me your combined arrival and departure Delta-V is around four kilometers per second. I don’t know what the dry mass of this is, but off the top of my head I’d guess around 30 tons. That’s a lot of fuel.”
“Yep, that’s pretty close and, yes it is.”
“You’re going to go with the manufacture methane and LOX on the planet approach? How will you get it into orbit?”
“Nah, can’t be done.”
“So you are taking all the return fuel with you?”
“Have to. First, the only methane/liquid oxygen engines around are XCOR’s and Pratt Whitney’s CECE. And they’ve only been tested a couple times and never flown. The CECE is RL-10 based and a pretty good engine, but on it’s best day the XCOR only puts out 7500 foot-pounds of thrust. That may be enough for the ascent vehicle, but nowhere near enough to get us home, let alone lift 26 tons of methane and LOX off Mars for the return trip. Can’t be done. We’d have to build a massive ship on the surface and bundle about nine engines like a Falcon. And that ain’t gonna happen. No, safe bet is to take the fuel with us.”
“Okay, but where is it?”
“We’ll send it separately. If we use an Apollo-like service module, that’ll get us into orbit. Barely, but it’ll do. But for the return trip we’ll need something a bit bigger – I’m thinking something about the size of a Centaur V.”
Gabe frowned. “Um, have you solved the long-term hydrogen boil-off problem?”
“No. We’ll need to build a new booster. Suppose we take a Centaur V-2, replace the RL-10s with AJ-10-137s, gut the tanks, and, uh, basically convert it to hypergolic fuel. Shouldn’t be that hard. Then we wrap it in an aeroshell and heat shield and, to conserve fuel, get it into orbit with an aerocapture.”
Gabe’s eyebrows popped up. “Yikes! That’s never been done.”
“Yeah, but it is possible, isn’t it?”
“Yes.”
“Okay, well, if it’s possible then it’s doable. So, let’s do it.”
“And, what will you do if it doesn’t make it?”
“Plan B. And when we get home we say we gave it the old college try. Okay, we didn’t quite make it to Mars, but we got closer than anyone else has, or probably will in our lifetimes, and we write books and go on the lecture circuit at $50,000 an hour, and satisfy ourselves with holding a whole bunch of space travel records.”
Gabe chuckled, then stared at the boards for a time, rubbing her lips with a finger. “Huh, it might just be possible.”
Jeff smiled. “I’m glad you think so.”
“But you’re going to fuel the ascent vehicle on the surface?”
“Again, have to. It’s too heavy to land in one piece. I thought about bringing nitro-tet and hydrazine with us. Stores well, hypergolic, reliable, it works. But I think we can get away with methane/LOX for the ascent, maybe. Gonna need to talk to XCOR and Pratt Whitney and think about it some more. But honestly, I’m not real big on the in situ return fuel manufacturing idea. Awful lot of pitfalls and problems. It’d sure be a lot easier just to bring it with us.”
She moved on a bit further. “Solar cells for the Sabatier reactor? Tracking?”
“Don’t know. The tracking mechanism is awfully heavy.”
“You’ll only get four or five hours a day out of them without tracking. Why not nuclear?”
“In the entire history of the American space program we’ve launched exactly one nuclear reactor, while the Russians have launched more than 30. Unlike the rest of the ‘civilized’ world – and for reasons passing understanding – America has a fear of nuclear power that borders on hysterical paranoia. Even if a suitable reactor were available, the government’s not going to let us launch one.”
“NASA and DOE are working on one.”
“Yeah, but they’ve been working on it for six years and don’t anticipate having a functional prototype for another eight. We could use radioisotope thermoelectric generators, but RTGs can barely produce enough power to run the lights in this room. And besides, how well would you sleep knowing there was twenty pounds of plutonium under your bed? Still, a reactor is something we might look for elsewhere; Russia, China, Europe, maybe even Japan or India. We can make some calls. But even if we could find one, there are still logistical problems. Shielding makes them awfully heavy, and if you skip the shielding then you have to locate it a considerable distance from your base of operations, and then you’ve got miles of cabling to deal with. Ultimately nuclear is the best solution, but I just don’t think it’s ready for prime time. No, I think we’re probably going to be stuck with a combination of solar, hydrogen fuel cells, and plain old generators.”
“Okay, getting back to the landing, if you’re in a high orbit how do you get down?”
“Same way everything else goes down. We have a lifting body ship up their waiting for us, or that comes along with us. We transfer to it, strap in, fire up a service module to deorbit, get into a landing trajectory and down we go.”
“Just another pallet of cargo, huh?”
“That is one way of looking at it.”
“So you’re really not talking ‘Mars Direct.’”
“Oh, bits and pieces here and there but, overall, no. Look, let’s face it, Mars Direct, Mars Semi-Direct, Mars Oz, Mars for Less… all of those Mars XXX plans have the same fundamental flaw – they require technology that doesn’t exist. They require power from nuclear reactors that don’t exist, and nobody’s gonna let you launch even if they did. They require landing masses on Mars that can’t be done, and they require lifting return trip fuel loads from the planet in ships that can’t be landed. So they’re all wonderful exercises and may someday come to pass but, for now, they’re all just so much science fiction. My plan is to use what exists and what we know works, or can be demonstr
ated to work by the time we go.”
“No argument. So, okay, your plan is to… holy crap! You’re gonna land four people on Mars using an MSL-like lander?”
“Maybe. It certainly is an option. And why not? If it can soft land the MSL, it can soft land four people.”
“Wow. That’d be one hell of a ride. You figure what, about 9 Gs?”
“Hard to say. I haven’t run the Monte Carlo trajectory profiles, a bit beyond my skill level, that’s why you’re here. But if we can hold entry interface to around 5400 meters per second and, I dunno, say, 11.5 degrees, shouldn’t be more than around six Gs. Pretty uncomfortable for a couple minutes, but not dangerous.”
“We’ll need some software, and a good computer.”
“Agreed. I already have JAQAR’s software and some industrial strength multiprocessor PCs but, yeah, we’ll need more.”
Gabe thought for a minute. “Why not a Soyuz?”
“Too heavy. Awkward size. Designed for three. It’s either too big or too small.”
“There’s got to be a better way.” She stared at Jeff’s crude drawing, scratching her temple. “How about a pair of Gemini capsules? You want ‘off the shelf’? They’ve flown a dozen times and we could probably rent a truck and steal a couple from museums. Seats two, lot lighter than a Soyuz.”
Jeff furled his brow, “No, still awfully heavy. I was hoping for a descent capsule that weighs in about the same as an MSL rover, around 850 kilos, with crew. A Gemini capsule weighs well over twice that.”
“You were going to consider crew safety and comfort at some point, weren’t you?”
“Yeah, the thought had occurred to me. After all, I’ll be one of those passengers, and I’m not all that anxious to cash in my chips just yet. So, I’m not saying no, just saying… In any case, in a couple months we’ll know whether or not MSL works, then we can reevaluate… if necessary.”
Gabe waved him off, “What if we steal a little Soyuz technology. Put an MSL chute in the nose of a Gemini capsule and punch holes in the heat shield for some solid fuel rockets. Then just soft land the thing on the heat shield.”
Jeff tilted his head as if he were looking at the problem from all angles. “Uh, yeah, that could work. But it’s still heavy.”
Margaritifer Basin (Margaritifer Trilogy Book 1) Page 11