Celestia Forums

Greetings, I have not posted in a quite a while but I assure you I am still alive and well. That said I'm really curious as to what you guys think about NASA's current plans to land a man on the moon by 2020 or so, and whether or not those plans will actually produce any tangible results.

My feeling is Project Constellation will be canceled in the next Presidency, with a higher probability of President Bush's "Vision" for Space Exploration dying young if the next President is a Democrat. Many effective arguments can be made that NASA's ambitions for manned spaceflight are cutting into its ability maintain its investment in scientific research. The demise of the Terrestrial Planet Finder, even in its most simple form is one case which could be used to illustrate this point. A further complication is the extreme unpopularity of anything and everything President Bush does. The new congress, under a new President may even like the idea of a man on the moon, but it might be more politically popular to oppose and dismantle such plans if they can be tied to Bush.

If I had to make a prediction today, my feeling is that at most only the Ares I and Orion CEV will ever be built. They will have one purpose, to go to the ISS. I don't expect the Shuttle program to be resurected, nor do I expect the US to go without a manned program entirely. I do think we wont be leaving LEO anytime soon, and partly I think NASA is to blame. Project Constellation strikes me as a bureaucratically bloated and inefficient program. I do hope I'm wrong, but what are your thoughts on the Moon Program, will it even make it into the next decade of the century?

Apollo7,

Unfortunately, as posed, your questions violate the guidelines of the Celestia Web forum. They are very much political in nature.

If you want to discuss the technical feasibility of the various aspects of the program, that probably would be OK, but, by themselves, expressing opinions without the numerology to back them up is a no-no. People get too worked up over them and the resulting arguments convince nobody.

Sorry.

Politics aside...
I think the effort of putting a man on the Moon and then bringing him home again, is a waste of time and effort... it's been done already. I think any future Moon venture should be one inwhich scientists strive to build a permanent working base there, one which could be used as a stepping-stone for future missions to Mars and elsewhere. While focused as such on the Moon, unmanned intelligent probes can continue to be used to spearhead future exploration until the next big step outward - such as a base on Mars.

The exploration of space will continue, that's going to happen no matter what or who. People need to realize that and either get with the program or get left behind... and that goes for any Nation, any Party.

LordFerret wrote:Politics aside...
I think the effort of putting a man on the Moon and then bringing him home again, is a waste of time and effort... it's been done already. I think any future Moon venture should be one inwhich scientists strive to build a permanent working base there, one which could be used as a stepping-stone for future missions to Mars and elsewhere. While focused as such on the Moon, unmanned intelligent probes can continue to be used to spearhead future exploration until the next big step outward - such as a base on Mars.

The exploration of space will continue, that's going to happen no matter what or who. People need to realize that and either get with the program or get left behind... and that goes for any Nation, any Party.

Perhaps the problem is that it's not been done...

I think any future Moon venture should be one in which scientists strive to build a permanent working base there, one which could be used as a stepping-stone for future missions to Mars and elsewhere.

That's the plan. We're not going back for goofs.

Over at the Planetary Society Weblog, Emily Lakdawalla reports on a presentation at the 39th meeting of the AAS Division of Planetary Sciences by Paul Abell from NASA's Johnson Space Center on the feasibility of a manned mission to a near-Earth object using the Crew Exploration Vehicle...

The basic mission profile would be a dual launch, with the Orion capsule launched on one rocket and an interplanetary transfer vehicle on another. The two would dock in Earth orbit and then depart for a near-Earth object, on a mission that would take 90 to 180 days with a 14-day stay at the near-Earth object; they would leave the transfer vehicle behind and just return with the Orion capsule. Abell's team even searched the current NEO database and found eight objects that have orbits that are close enough to Earth's to be feasible targets for such a mission, launching in the 2015-2030 time frame.

So, it may be possible, but what's the point of such an exercise? It would, Abell said, "expand human capability beyond Earth orbit, and actually start exploring the solar system." The astronauts could assess the resource potential of NEOs and gain operational experience peforming complex tasks with crew, robots, and spacecraft under micrograivty conditions, with Mars being the eventual goal. From a science standpoint, Abell said, the rationale is "sample return, sample return, sample return," with all the science benefits that having pristine chunks of space rocks to analyze in Earth laboratories gives you. I was most happy about the last of his rationale slides, which looked at what the public would get out of it. It would be an unprecedented deep space voyage -- an amazing adventure. It would "put humans demonstrably on the way to Mars while doing science, gaining understanding of potentially hazardous objects that would be useful in developing mitigation strategies."

A moon landing may not be the only possible near-term objective of the new manned spaceflight program.

- Hank

... they would leave the transfer vehicle behind and just return with the Orion capsule.

And that I have a problem with. Why is it we must always leave such "garbage" behind? Why not launch this left-over crap into the sun?

LordFerret wrote:

... they would leave the transfer vehicle behind and just return with the Orion capsule.

And that I have a problem with. Why is it we must always leave such "garbage" behind? Why not launch this left-over crap into the sun?

Beacuse of $$, I'm guessing.

It's expensive to launch stuff into the Sun. The Earth's orbital velocity is 30 km/s, which is rather a lot to cancel.

selden wrote:Apollo7,

Unfortunately, as posed, your questions violate the guidelines of the Celestia Web forum. They are very much political in nature.

If you want to discuss the technical feasibility of the various aspects of the program, that probably would be OK, but, by themselves, expressing opinions without the numerology to back them up is a no-no. People get too worked up over them and the resulting arguments convince nobody.

Sorry.

Looks like you were too late Selden.

chaos & hungry -

Of course there's a dollar amount attached to this, but my guess is - that dollar is already spent and there. Wouldn't there be some fuel left-over upon arrival, perhaps even a lot if an ion propulsion system was used?

I'm not suggesting a direct path to the sun, just a good nudge in the proper direction to let gravity and time and orbits do their thing.

LordFerret,

I'm afraid you've missed the point: the amount of energy (or delta-v = change in velocity) needed to change the orbit of an object that's in the Earth's orbit so that it even comes close to the Sun is tremendous. That's why the Messenger probe to Mercury has had to use multiple planetary flybys in order to shed enough speed to get close to that innermost planet.

I understand that Selden, but I'm afraid I still don't see the issue there.

This probe will have already matched velocity with the NEO it's to visit. The gravity of the NEO would be minimal compared to Earth's, and wouldn't the probe be far enough out that Earth's influence be minimal as well? I keep thinking about the Dawn Mission probe, which will be flying about making visits to both Vesta and Ceres!... and with that in mind, I just don't see why my suggestion can't be accomplished.

If anything...
"In the question and answer session that followed, someone pointed out that if they visited a small-enough body, they could accidentally do a gravity tug on the asteroid, one of the mitigation strategies suggested by Rusty Schweickart and the B612 Foundation. A manned vehicle will be pretty massive -- it could prove the concept, at least, but it's something they'd better plan carefully for, lest they accidentally tug their near-Earth object nearer to Earth!"
...I see that as reason enough to consider the idea. And aside from the gravity-tug, what about the mass they intend to leave behind on the thing?

LF,

Leaving the junk on or near the asteroid is easy. The point about visiting a specially chosen NEO is that its orbit is very similar to that of the Earth -- so relatively little energy / delta-V is needed to get back and forth to it. Remember, they're not proposing visiting some random object, but , rather, visiting one that they find which has an orbit that's easy to match.

In contrast, getting something into an orbit which grazes the sun requires a large delta-V. You have to eliminate the velocity which is preserving the current near-circular orbit.

And you still have the problem that after it falls down near the sun, it'll be "falling" right back out at you. One of the non-intuitive effects in astrodynamics is that when one applies acceleration, one is actually affecting the altitude of the orbit 180 degrees away. Accelerating at apohelion, for example, one actually is raising the altitude of the orbit's perihelion, not changing the altitude of the apohelion.

This probe problem is known in physics as the "satellite paradox". Of course, it isn't a real paradox. It's just that the interpretation of the probe dynamics (change of orbit in the "gravitational well") isn't very obvious, from an intuitive point of view.

There are some good descriptions of this "paradox" in the American Journal of Physics (AJP). For example, there was a first description of it in this article :

http://scitation.aip.org/getabs/servlet ... s&gifs=yes

I also suggest reading this paper :

Satellite Orbit Paradox : A General View
Leon Blitzer
AJP Volume 30
August 1971
Page 882

Actually it's probably easier to launch stuff out of the solar system than into the Sun.

Escape velocity from the Sun at a distance of 1 AU is 42 km/s, and the orbital motion of the Earth gives us 30 km/s already.

That leaves a delta_v of 12 km/s to escape the solar system, as opposed to 30 km/s to hit the Sun.

chaos syndrome wrote:Actually it's probably easier to launch stuff out of the solar system than into the Sun.

Escape velocity from the Sun at a distance of 1 AU is 42 km/s, and the orbital motion of the Earth gives us 30 km/s already.

That leaves a delta_v of 12 km/s to escape the solar system, as opposed to 30 km/s to hit the Sun.

Therefore this mean that if a spacecraft cost, to say, 500 million of $ to go out of the solar system, the acceleration's business require that the spacecrafts which hits the Sun will cost 500 x 30/12 = 1250 millions of dollars? The propulsion's method issue sound as an excuse at this point...

Thanks for the information (Selden) and resources (Cham), it's apparent I need to read more on this ... though already the explanations given do paint a better picture for me. I appreciate it.