Margaritifer Basin (Margaritifer Trilogy Book 1) (13 page)

“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 demonstrated 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.”

“Then we blow the heat shield off
on the ground, jack up the capsule and set it down on top of the ascent stage.
And away we go.”

“Well, let’s run the numbers and
see. That’s a lot more to launch.”

From behind, Abby’s voice drew them
back out of their own little world, “Excuse me?”

Jeff turned to her, “Sorry, didn’t
mean to ignore you two.”

“That’s alright, you’re doing fine.
But I do have a question. You’ve said ‘tested and proven technology’. Doesn’t
sound to me like what you’re talking about is tested and proven.”

Gabe turned around, “Well, not
exactly in that sense. But all the parts are in fact tested and proven.
Essentially what I’m talking about is modifying a Gemini capsule by adding some
proven systems from MSL and Soyuz. We’re not really doing anything new, just
rearranging a few things. It’s sort of like taking a Chevy and dropping a Ford
motor and Chrysler seats into it. So long as they fit, no big deal.”

“Okay. Just thought I’d ask.”

Gabe turned back to Jeff, “But it
would be awful nice if we could get a test flight.”

Jeff smiled, warmed by the manner
in which she was using the word ‘we’. “Yeah, that would be nice. We could
launch one just about any time. But it would take a Falcon 9 to put it up.
That’s $35 million to launch it and drop it in the Mohave Desert just to see
what happens. And I don’t think any museum is really going to want to give up
their display. When we’re done with them, they’re just going to become the
center feature in a couple new impact craters. We’d need to dust off the plans
and build some. That doesn’t give us much time.”

Gabe sighed and rubbed her
forehead, “Tell me something I don’t know.”

“Anyway, my other thought was to
steal from Apollo Program technology and just build a slightly oversized LM,
and use it the same way – land in it, and take off in it.”