I found information about the diameters of the fuel tank and SRBs. Based on this, I estimate the total frontal area to be around 1200 sqft. With a Cd of 0.66, that would make the force at maxQ around 40% of what you estimate, thus consuming around 10% of the thrust. I readily concede that mine are also rough estimates.
But the real point is that the dynamic pressure has a reasonably sharp peak: it’s only above half maxQ for about a minute, and drops to zero at about 2 minutes into the launch. This is why I think the atmosphere isn’t truly a huge obstacle - basically, it’s isn’t all that thick.
I think we’ll find that if and when a rocket lifts off from Mars carrying astronauts home to Earth, the cost of their launcher will definitely be in the multi-billion-dollar area.
There are a couple other factors to consider:
[ul]
[li]The Shuttle throttles down near max-Q to reduce stresses on the structure. If it weren’t for the atmosphere, the Shuttle would be able to maintain 3-G (or whatever) acceleration all the way, which would make for a quicker and more fuel-efficient trip.[/li][li]Very roughly speaking, aerodynamic forces scale as square of size, while weight scales as cube of size. It may not be a significant effect for a Shuttle-size rocket, but it’s more significant (relative to other forces) for a 2-man capsule. Even more so for a small unmanned rocket, like you’d need for an unmanned sample-return mission.[/li][/ul]
But I concede that “huge obstacle” may have been an exaggeration. On the other hand, if we didn’t have an atmosphere at all, all we need to do is accelerate horizontally to 7 km/s, instead of having to gain altitude first. Then again, you’d have to do that on Mars as well…
A Mars mission would doubtless use a small landing vehicle a la the Apollo LM.
The real problem will be the “mother ship”. Just one problem to consider: just how big a “pantry” will you need to feed, say, three guys for eighteen months? And then there are the hydrogen and oxygen tanks needed to feed the fuel cells that would provide water and electricity.* This sucker would have to be huge.
It would have to be assembled in earth orbit (or, some have suggested, lunar orbit). Not an insurmountable problem. In the early years of the “moon race” NASA briefly considered such an “earth rendezvous” approach; the Soviets, as I recall, pursued that idea somewhat longer (which may be why they never got a manned spacecraft to the moon).
And give how utterly tedious such a long flight would be, we’d have to allow our crewmembers generous-sized Personal Preference Kits so they could take along enough books, crossword puzzles, playing cards, girlie magazines, whatever, to pass the time. . . .
True, and that might make things easier (e.g. some sort of linear rail accelerator could give a rocket some useful initial velocity). But think of the really nasty problem you’d have with returning from orbit: no atmospheric braking would mean you’d need the about the same amount of fuel to de-orbit as it now takes just to get there.
Indeed, it’s interesting to note that if Mars had no atmosphere, landing there would be enormously more challenging than it already is.
SF authors long ago realized the difficulty of bring along enough food, water and air for long space trips, so they came up with the idea of the Hydroponics Section, wherein plants were grown to recycle waste and turn the CO[sub]2[/sub] to O[sub]2[/sub] as well as provide food. But I’m not sure if most of the writers realized that the majority of the human occupied parts of the ship would have to be in this section in order to be anywhere close to a sustainable system.
If you give them a liberal bandwidth allowance, they could download lots of that on the way.
Not bloody likely. The cost of developing a high-speed internet connection that works over interplanetary distances (and the cost of installing, powering, and maintaining the antenna) ensures that it will be sized to meet mission needs and not much else. I think it’s far more likely that they’d get a WinXP machine and several fully-patched slightly-older games (e.g. SimCity, Civilization IV, Starcraft) if NASA decided they needed recreation. Or maybe a Wii – how fun would that be in zero-gee?
Shuttle astronauts are usually working their butts off doing seven grillion experiments, so I imagine these astronauts would probably also have at least a nine- or ten-hour work day full of experiments (aside from their housekeeping chores).
why not use a aircraft come space vehicle,you leave the earth in aircraft mode then when you get as high as is possible go into rocket mode.
or am i missing something
To reach orbit requires a monster amount of fuel, and thus a giant launch vehicle to hold it. Much of this fuel is burned within the first two minutes of the flight, at which point your giant vehicle is a useless container. So there will need to be stages, and the thing that actually recahes orbit will necessarily be a small part of the size of what was launched.
There have been proposals for fully reusable space shuttles. Here’s an image of one; the booster vehicle would have separated at a height of 25 miles or so and soon been back on the ground. The cost of this approach was reckoned to be unacceptable.
In theory you could gain an advantage by launching your space shuttle from an aircraft flying at, say, 50,000’. In practice, the payload of the largest aircraft is a tiny percentage of what even a small space shuttle plus the fuel to reach orbit would weigh.
I always wondered about that–will NASA et al force their astronauts to keep to the same insanely busy schedule, or will they allow them to have ample downtime? If the former, I can envision a “work stoppage” at some point by Mars-o-nauts . (Say around month 4.)
