[tiki12revolt]

Employing high-altitude balloons to cut down on launch costs is potential feasible, as traditional launches can run into the tens of thousands of dollars (or more) per lb.

One potential problem with going small on the rover end is that the prize stipulates that the rover must travel a prescribed distance on the lunar surface, and going too small will make traversing distance a much greater obstacle that it already is. Additionally, how would one power the antenna necessary to communicate with earth (I am thinking specifically of battery power only, and I think it would in and of itself weigh more than a pound)?

[gravitycop]

Employing high-altitude balloons to cut down on launch costs is potential feasible

How would high-altitude balloons reduce launch costs?

[stcredzero]

Not by much. Most of the energy cost of a launch to Earth orbit involves getting to orbital velocity. Getting an object that high is pretty easy by comparison.

(Get out your physics textbook and compare the kinetic energy of something going Mach 24 to the potential energy of something dropping 100 km.)

I'd expect a mistake like this from a high school student or a freshman. If you're not clear about this, then you have a perhaps a bit of homework to do before posting questions about space to a social news site that prides itself on informed, intelligent discussion.

Perhaps start with Zubrin's _Entering Space_. Any number of books about the space program will do as well.

[wlievens]

I don't think a person should "do his homework" before asking a mere thought-provoking toy question. However naive the question, it has potential for informed, intelligent discussion.

[stcredzero]

Not if you're off by an order of magnitude!

[ErrantX]

It's entirely logical: you just have to think outside the box (big enough baloon vs. small enough vehicle: plus it overcomes some of the niggly "near ground" effects [why do you think so many next-gen space vehicle designs launch from Airplanes??])

The physics is there and probably workable.

(EDIT: my initial thoughts would tend towards a high altitude launch of several smaller sized vehicles that re-assemble on the lunar surface... or interact there. S o for example someone above mentions the comms issue: a static relay planted on the surface interfacing with a seperate rover device would probably work well. In fact I would launch 2 or 3 of each type (assuming cost could be kept low) to ensure that you got at least one functioning pair :D)

[stcredzero]

Jet airplanes also give you something like 600 mph of initial velocity. In the case of Pegasus and Space Ship One, they are like the first stage rocket.

The Rocket Equation is pretty nasty. When your required delta-v goes up, your reaction mass requirement goes up faster than a polynomial function. Saving the initial 600 mph is very significant. Balloons -- only sounding rockets use those, but they don't do anything but gain altitude anyhow. If you need escape velocity or orbit, then they are pretty much useless. (You might as well build a slightly bigger rocket.)

Please actually do the physics before you post vacuous statements like:

The physics is there and probably workable.

People are having "intelligent discussions" about balloon assisted launch? Eternal September has gotten to HN!

[ErrantX]

I have done the physics: or spoken to people that have.

In fact I have seen a successful small rocket launched from a 100 ft high ballon platform (the physics is painful but it is possible).

Other ideas like centrifuge acceleration I know have been discussed: and I personally see potential in them (Ammers & Myers, Oxford University Press, 2006 I think: I'll try and dig out a reference #).

With equal respect I suggest you actually try to think outside the box before posting vacuous statements stating it is impossible.... ;)

EDIT: BTW you do know NASA have recently been exploring the possiblity too.... admittedly for low earth orbit sattelites (and i know that a major problem is breaking that barrier - but it is proof of an initial concept....)

The crucial data is that ballons can carry rockets to a MUCH higher altitude than planes. The reduced drag at that altitude means a lot less propellant is needed (and even a solid fuel propellant could suffice).

NASA has plans for a ballon that can carry up to a ton of equipment to a height of 33Km which is pretty good!

You've also missed the point of the airplane: 600MPH is frankyl nothing (4% of the speed required for LEO). The important thing is the lowered drag and kinetic requirements to get the payload to LEO.

[gravitycop]

You've also missed the point of the airplane: 600MPH is frankyl nothing (4% of the speed required for LEO).

Small increases in speed would indeed be relatively unimportant in regard to only a final stage. When, instead, an increase in speed affects an entire rocket stack, it becomes important, since lower stages are exponentially more massive than upper stages. For the same reason, it can be important to launch from the equator, since equatorial launch provides 465 m/s of speed, not only for the final payload, but for the entire rocket stack.

[gravitycop]

I have seen a successful small rocket launched from a 100 ft high ballon platform

That was a sounding rocket. As Stcredzero wrote in the message you responded to, "Balloons -- only sounding rockets use those." http://en.wikipedia.org/wiki/Sounding_rocket

http://www.astronautix.com/lvs/rockoon.htm

[gravitycop]

traditional launches can run into the tens of thousands of dollars (or more) per lb.

$8.90/lb. http://neverworld.net/truax

http://news.ycombinator.com/item?id=429099

[tiki12revolt]

assuming we take SpaceX on their word, that the "Falcon 1 is the world’s lowest cost per flight to orbit of a production rocket", and take the cost and payload weight right of the website, then for a 1010 kg payload at $9.1M, that works out to be roughly, $4095 / lb.

from: http://www.spacex.com/falcon1.php