Manned missions into space -- a waste?

[patnray]

How would the denizens of 1000 AD have proposed getting to Mars?

On the Chariots of the Gods?

 

[Larspeart]

How would the denizens of 1000 AD have proposed getting to Mars?

BIG catapult?

 

[Larspeart]

On the Chariots of the Gods?

Now THAT guy is a Woo Woo. Damn G. Hancock. . .

 

[Walter Wayne]

It isn't just a question of finding a source of energy. Relativity places some severe constraints because mass increases as velocity increases...

The human cargo also places some constraints. Extreme acceleration is not an option. Acceleration must be limited to something around 1 g.

Here's a puzzle for those with time on their hands: Assume you have a space ship with an unlimited energy supply and a non-inertial propulsion system that can produce 1 g of acceleration when the mass of the ship equals the rest mass. Assume the mass of the ship does not change except for the relativistic increase due to velocity. How long would it take (measured by an observer on earth) to get to a star 10 light years away (remember you can only accelerate for half the journey, then you must deccelerate)?

The problem in such long term travel is in fact the energy required to maintain such an acceleration. Running your numbers we actually get favourable results.

I'll use an acceleration of slightly less than g to simplify calculations. (An acceleration of 1g is an acceleration of 1.08 lightyears/year²). I'll use an acceleration of one lightyear/year² (An acceleration of 0.925 g's). So accelerating for half the journey, gives us an acceleration distance of 5 lightyears.

Distance according to stationary observer: 5 light years.
Time according to stationary observer: 5.92 years
Max velocity: 0.986 c
Shipboard time: 2.48 years

Double this to account for slowing down and we get: 4.96 years of ship board time to reach 10 light years out in 11.84 earth years.

Given communication times, earth will start receiving telemetry back in about 22 years.

Walt

 

[patnray]

I get about the same numbers asuming a constant acceleration of 1 g.

But I specified a propulsion system capable of 1 g AT THE REST MASS. I guess I should have said a propulsion system that produces a constant FORCE that results in 1 g acceleration at the rest mass. My point was that the relativistic mass increase will add substantially to the journey time given a propulsion system with finite power...

 

[patnray]

Back to a more realistic subject, here is a Scientific American article on what it would take for a series of manned missions to Mars.

 

[Walter Wayne]

I get about the same numbers asuming a constant acceleration of 1 g.

But I specified a propulsion system capable of 1 g AT THE REST MASS. I guess I should have said a propulsion system that produces a constant FORCE that results in 1 g acceleration at the rest mass. My point was that the relativistic mass increase will add substantially to the journey time given a propulsion system with finite power...

And relative to itself the ship is always at rest. The earth sees the ship as getting heavier, but the ship and people in it still perceive themselves as being at rest mass.

If one accelerated at 1g with respect to earth for one year, one would be travelling at 1.08 c.

Walt

 

[DanishDynamite]

There is an aspect of this discussion which I don't think has been addressed yet. The aspect I'm thinking of is the fact that the major players in off-Earth exploration are all government funded. And the size of government funding (in democratic countries) is ultimately a reflection of public support. And public support is usually dependent on the "Wow!" factor. And the "Wow!" factor in the aerospace sector is often associated closely with manned expeditions.

That said, I'm pro any initiative which ultimaly results in additional funds being allocated to space exploration, in any form. The Earth is a tiny "pale blue dot" much too exposed to the variances of the Universe.

 

[Skeptician]

Re: Re: Re: Re: Re: Re: Manned missions into space -- a waste?

Ian's not off here (I'm amazed too )

Ian is a woo woo. Therefore he is a inferior being!

Only skeptics have the intellect to work out how to travel to the stars!!

 

[Psiload]

Re: Re: Re: Re: Re: Re: Re: Manned missions into space -- a waste?

Ian is a woo woo. Therefore he is a inferior being!

Only skeptics have the intellect to work out how to travel to the stars!!

Oh, look... Rational is starting up a little sock puppet theatre.

Now where did I put that Ignore button? Ah, there it is... *poof*

 

[Soapy Sam]

I'm so dim, I can't really understand the question.

What the blue blazes is the point of exploration at all, if you don't go yourself?

 

[shecky]

I'm so dim, I can't really understand the question.

What the blue blazes is the point of exploration at all, if you don't go yourself?

Indeed. They should have stuffed a man inside the Beagle2 playload.

 

[Kevin_Lowe]

While I applaud epepke's statement, and the wonderful way he expressed it, I've got to say that I don't think humanity is in any danger of losing its explorers. When Columbus sailed the ocean blue, Mallory climbed that big rock that was in his way, and, yes, when Tom Hanks and Kevin Bacon had that bit of trouble on Apollo 13, the vast majority of people on this earth were more likely to have said something like what Kevin Lowe has expressed (probably in the same harsh terms). There will always be people who oppose change.

I'm all up for change. I'm very exited about all the nifty change I hope to live to see.

I'm just not up for idiocy. There are all sorts of cool but dumb things we could do. We could build more pyramids, or build an underwater colony where everyone drives submarines, or build a nine hundred foot high statue of Pee Wee Herman, or make a giant diamond-encrusted teepee where okapis play. We could in Xanadu a stately pleasure dome decree. We could send someone to Mars. Or we could do something useful instead.

And there will always be costs associated with change. Yes, manned exploration is currently costly. And how are reductions in cost acheived? Through economies of scale. The first, and second, and tenth manned mission will always be costly, whether it's done now or a millenium from now. It is only by repeatedly sending missions that the cost will go down.

What a silly claim.

The cost will go down because our science and engineering will advance anyway. The real cost will go down because the amount of energy we have to utilise will increase anyway. The longer we wait, the less a manned mission will cost in terms of the world's productivity.

Mars and the rest of the universe will still be there in a few hundred years.

 

[Skeptical Greg]

.................................

Mars and the rest of the universe will still be there in a few hundred years.

Perhaps the best point anyone has made IMHO...


Actually they (... Mars and the rest of the universe) may not be there next week.. If not, it doesn't matter what we do today, but it seems reasonable to proceed as if they will be there...

 

[Graham]

Mars and the rest of the universe will still be there in a few hundred years.

And in a few hundred years there'll still be people saying that an, what's more, they'll still be right.

If we're going to start sometime, why not now?

Graham

 

[Correa Neto]

...
Name a goal that could be better achieved with a manned ship...

Just a few:

- Unravel the stratigraphy of martian sedimentary deposits and collect the samples that are more likely to contain microfossils.

- Locate and analise places where there is more chance to find any existing martian lifeforms.

- Repair tasks that could be done by EVA.

- Changing spare parts of internal equipment.

- Avance through rough terrain, by feet or driving a vehicle.

Note that some of these tasks would require robots with an AI much more sophisticated than what we have today or on the next few years (OK, vague term) unless some breakthrough shows up. Others would be achieved by remotely operated vehicles, but the delay time is too big when you are considering a mission, say, to Mars. Could be done on the Moon, but not on Mars. As a matter of fact they could be done in Mars, if the veihcle is piloted by someone on a ship orbiting the planet.

As I wrote before, space exploration is to be made by a combination of manned and unmanned missions. The exact ballance will depend on technological advance, avaliable money, political circunstances (the most dificult ones to deal with) and mission goals. A typicall exploration program would be, in my opinion, something like this- robotic vessels making the first surveys, locating targets for manned missions (that will be made with support from a number of robotic and/or remotely controlled vehicles). And, in harsh environments (Venus comes in to mind), or on very long range missions, robotic probes are the answer.

We have important and interesting things to do here? Yes. We have important and interesting things to do "up there"? Yes. I say we should go for all of them.

It will take a long time untill we develop space flight to a safe technological level? Yes. It will take long time to have colonies or permanent bases on the Moon or Mars? Yes. It will take a long time before we need to leave Earth? Yes.

Should we start to develop space technology so soon? Yes, why not?

Space exploration is the sort of subject where one should not adopt radical positions such as "ban all manned flights" or "lets go there now" positions. Neither the "lets not spent money up there in space, but down here on Earth" or the "lets put billions at once in that space program" work. As in most subjects in real life, radicalism is unproductive and must be avoided.

Useless, IMHO, is to dump hundreds of billions in weapons, that will never be used (at least we hope so), but thats for another thread.

 

[patnray]

Just a few:

- Unravel the stratigraphy of martian sedimentary deposits and collect the samples that are more likely to contain microfossils.

No reason this could not be done with remotely operated/robotic machines.

- Locate and analise places where there is more chance to find any existing martian lifeforms.

Already being done by satellite.

- Repair tasks that could be done by EVA.

Less critical with unmanned craft. Robust, flexible, and redundant design would allow for recovery from many problems.

- Changing spare parts of internal equipment.

See above.

- Avance through rough terrain, by feet or driving a vehicle.

No reason this could not be done with remotely operated/robotic machines.

As you point out, even a manned mission will require sophisticated robotic equipment to support it. Since this technology is so critical, I think its development should be the first priority. I think it is a waste to commit to a huge manned program with poorly defined goals. It will drain dollars from worthwhile projects. Whether a moon base is necessary, or even useful, to manned Mars mission is an open question. Why commit to it now? I'd prefer to see us get as much as we can from unmanned missions first and use what we learn to guide us to a rational decision about manned programs with clearly defined goals.

 

[Correa Neto]

- Unravel the stratigraphy of martian sedimentary deposits and collect the samples that are more likely to contain microfossils.

No reason this could not be done with remotely operated/robotic machines..

Yes, there are plenty of reasons. You will have to create a machine smart enough to dodge its way through a crevasse or erosional rille, identify and measure the layers, and select the most promising ones to be sampled. A remotely operated machine could do the trick on them Moon, but on Mars (or some other more distant target), delay time would be too great. You would need, as I said, someone operating it from a closer distance- a manned mission.

-Locate and analise places where there is more chance to find any existing martian lifeforms.

Already being done by satellite.

Yes, but not on a detailed scale. You must have a machine able to go to the sites and prospect them. Then it would have to turn rocks, dig the soil, look for some suspicious-looking stains, colect the samples and take them to a lab for analisys. The same restrictions of the above item apply.

- Repair tasks that could be done by EVA.

Less critical with unmanned craft. Robust, flexible, and redundant design would allow for recovery from many problems.

Yes, but this can make them almost as costly as a manned mission, and without the flexibility in terms of repair and improvising that a crew has. A manned craft can make last-minute course corrections, for example, that would not be possible due to the delay time on missions to Mars, for exmple. Would a manned lander land on a crater? And even if it did, the crew could get out the lander and place an antenna over the crater´s rim.

- Changing spare parts of internal equipment.

See above.

Exactly. See above.

- Avance through rough terrain, by feet or driving a vehicle.

No reason this could not be done with remotely operated/robotic machines.

See the first and second items.

As you point out, even a manned mission will require sophisticated robotic equipment to support it. Since this technology is so critical, I think its development should be the first priority. I think it is a waste to commit to a huge manned program with poorly defined goals. It will drain dollars from worthwhile projects. Whether a moon base is necessary, or even useful, to manned Mars mission is an open question. Why commit to it now? I'd prefer to see us get as much as we can from unmanned missions first and use what we learn to guide us to a rational decision about manned programs with clearly defined goals.

The commitment to a very bold mission right now can be disputed, I agree on that. As I wrote, the key is to achieve a ballance between manned and unmanned missions. Manned missions are usefull in a given set of contitions and goals, robotic probes are usefull on others, and they are complementary. If NASA guys know how to do their job (I belive they know how to- but sometimes they just can´t do it they way they should do for political reasons), they will send an armada of robotic probes before the manned missions, therefore developing the needed technologies and locating suitable targets to be studied by scientists, not millitary pilots.

 

[patnray]

Yes, there are plenty of reasons. You will have to create a machine smart enough to dodge its way through a crevasse or erosional rille, identify and measure the layers, and select the most promising ones to be sampled.

Exactly. You haven't convinced me this can't be done with a combination of AI and remote data analysis. Transmission delays preclude remote control for time critical events like landing. Once positioned in front of an interesting feature, however, there is plenty of time to analyze data and send instructions. Your argument seems to be that you can't imagine a machine sophisticated enough, so it can only be done by men.

Yes, but not on a detailed scale. You must have a machine able to go to the sites and prospect them. Then it would have to turn rocks, dig the soil, look for some suspicious-looking stains, colect the samples and take them to a lab for analisys.

Or your robo-prospecting machine can do all that and analyze samples on the spot using IR, UV, and chemical means. You seem to be saying men would have to go there and analyze the rocks to determine if men should go there.

Yes, but this can make them almost as costly as a manned mission, and without the flexibility in terms of repair and improvising that a crew has. A manned craft can make last-minute course corrections, for example, that would not be possible due to the delay time on missions to Mars, for exmple. Would a manned lander land on a crater? And even if it did, the crew could get out the lander and place an antenna over the crater´s rim.

Still not nearly as costly as a manned mission. You are correct that a lander cannot be remotely piloted from earth. But that does not mean it cannot have enough intelligence to make decisions and course adjustments as it lands. In fact, this will be crucial in delivering supplies and equipment in advance of a manned mission. Air bags just won't cut it when delivering fuel or power plants...

The fact is, most of the exploration will be done by machines, even on manned missions. The presence of men will be mostly window dressing...

 

[juryjone]

I'm just not up for idiocy.

[snip]

What a silly claim.

OK, so I'm a silly idioy. Thank you for confirming the most minor point in my post - that you are unnecessarily harsh and judgmental.

Let's move on to something of substance...

The cost will go down because our science and engineering will advance anyway. The real cost will go down because the amount of energy we have to utilise will increase anyway. The longer we wait, the less a manned mission will cost in terms of the world's productivity.

Mars and the rest of the universe will still be there in a few hundred years.

Please explain the shuttle to me. Is the cost of using the shuttle less because the world's productivity has expanded so greatly in the past thirty years or because using a reusable vessel is cheaper when there are a large number of launches to be made?

Which is likelier to get a better return over a shorter period of time (ignoring the fact that world productivity will increase and large-scale interplanetary travel may not happen) - your increase in world productivity or my economies of scale?