Moon, Mars, or Asteroid? Which is the best goal?

[EarthlingX]

2. Gravitational loss requires bigger engines to create enough thrust for launch and landing. Much smaller engines, like those used for RCS could be used for the asteroid mission, thus improving mass ratio. I also suspect that hydrazine, as an example, has much less of a problem with evaporation than hydrogen, which improves overall system Isp, among other.

Why not...

In Robert A. Heinlein's classic novel The Moon Is a Harsh Mistress, rebelling Lunar colonists convert a kilometers-long mass driver system that delivers raw materials to Earth into a railgun that lobs metal-clad rocks, then commence an orbital bombardment.
One of the first depictions of a mass driver for space exploration was in the 1936 movie Things to Come.
http://en.wikipedia.org/wiki/List_of_electromagnetic_projectile_devices_in_fiction

A launcher like that could actually work on the moon unassisted, with no atmosphere.

You have to land there first, more or less on the same spot, and not only one time. Then you have to support building site, for quite some time before it is done. Mucho dinero.

 

[rockett]

You have to land there first, more or less on the same spot, and not only one time. Then you have to support building site, for quite some time before it is done. Mucho dinero.

Why not robots? Can be teleoperated almost live from Earth, much easier than on Mars or an asteroid. Russians did that a long time ago.
http://en.wikipedia.org/wiki/Lunokhod_2

 

[HopDavid]

A launcher like that could actually work on the moon unassisted, with no atmosphere.

You have to land there first, more or less on the same spot, and not only one time. Then you have to support building site, for quite some time before it is done. Mucho dinero.

I think we have to ask ourselves what the goal of our manned space program is.

If the end goal is a LEO station, it is not worth the expense.

If the end goal is flags and footprints on an asteroid or Mars, it is not worth the expense.

The only thing that justifies the expense, in my view, is settlement of space.

The taxpaying public has a short attention span. Asteroids and Mars have infrequent launch windows. The time it would take to establish worthwhile infrastructure would be too much for that short attention span. We would have a repeat of Apollo.

----

The ULA architecture for the moon was estimated to be 7 billion dollars per year. It could be less now that massive ice deposits have been discovered at the poles.

The ULA architecture calls for propellent depots to be supplied with small to medium lift vehicles. Atlas Vs, Falcon 9s, Russian as well as Chinese space craft. This could generate the flight rate that would finally allow rocket makers to enjoy economies of scale and amortize their design expense over many units. Propellent depots could be supplied as well as used by many entities. This could be a start towards a competitive space commodities market.

From LEO, lunar launch windows occur every two weeks. We could actually build usable infrastructure on the moon within a short time frame and plausible budgets.

At first the water and other in situ resources on the moon would help alleviate the expense of a lunar base and travel from the moon. After time, lunar propellent could be exported to EML1 and LEO. By the time this happens, building a lunar rail gun would be much less expensive than it would be with our present capabilities.

The moon offers an opportunity to develop less expensive access to space as well as usable infrastructure.

Other destinations offer flags and footprints.

If flags and footprints is the only payoff, Human Space Flight is an abominable waste of taxpayer money and should be eliminated.

 

[EarthlingX]

You have to land there first, more or less on the same spot, and not only one time. Then you have to support building site, for quite some time before it is done. Mucho dinero.

Why not robots? Can be teleoperated almost live from Earth, much easier than on Mars or an asteroid. Russians did that a long time ago.
http://en.wikipedia.org/wiki/Lunokhod_2

Project-M ? It still needs to get financed, and since HLV is supposedly more important than technology development, it will be a tough one. If you take your time to read their page, you will see they are fighting for scraps. Good luck.

btw, Russians did a lot of stuff a long time ago, and they still do things which NASA doesn't, like automatic docking, for one, and there's more. I think most, if not all firsts, up to the Lunar landing, were Russian. I'm not sure how this relates to NASA, unless there will be international effort to do it, which would be very nice. Not much talk about that though, well, at least not in America.

ESA is planning Lunar lander too : ESA's Lunar Lander

If they wanted to do Lunar railgun they would have to make one on the Earth first. Sounds like technology development, lot of time, and a lot of money. I would love it though, just can't believe it's going to happen. It has better chance in Europe or Japan, even China, since they all have at least some technology to start with. I can't remember any maglev trains in USA or even high speed trains .. ?

I think i heard about plans to get one in California, but i'm not sure how that goes ?

Anyway, if you already have fuel depots in place, which would be nice, why not go for an extended flight to an asteroid, just to see if your tech is ready at least for empty space, before you get down into lunar dirt, or marsian, perhaps a bit later ?

 

[rockett]

If they wanted to do Lunar railgun they would have to make one on the Earth first. Sounds like technology development, lot of time, and a lot of money. I would love it though, just can't believe it's going to happen.

Looks like NASA is seriously considering it for Earth use. Even research on it would tell us a lot of what would be needed for a Lunar version:
Emerging Technologies May Fuel Revolutionary Launcher
http://www.nasa.gov/topics/technology/features/horizontallaunch.html

 

[oldAtlas_Eguy]

Railguns are a nice idea except: they operate by using low voltage and high current which requires a lot of low resistence metal like copper 1 to 2 MT of it to propel a 100kg object at 300m/s using a very large room full of batteries 15 to 30 MT that charge over several hours for a single launch. I saw the USAF's railgun in 1990 and what it took to make it work. The setup used $1 million dolars worth of Deep discharge marine batteries tied into a soild copper busbar that was 5 inches thick by 12 inches wide that ran from the ~ 10,000 batteries to the railgun. It took nearly a full day to charge all of the batteries. The railgun I saw was only a test article but the disadvantages for use in space are clear. A Linear electric motor is better because it dosen't use the high currents that is used in a railgun, trading length for lower currents. Lower currents equals less weight and also less energy storage requirements which also adds weight.

 

[rockett]

Railguns are a nice idea except: they operate by using low voltage and high current which requires a lot of low resistence metal like copper 1 to 2 MT of it to propel a 100kg object at 300m/s using a very large room full of batteries 15 to 30 MT that charge over several hours for a single launch. I saw the USAF's railgun in 1990 and what it took to make it work. The setup used $1 million dolars worth of Deep discharge marine batteries tied into a soild copper busbar that was 5 inches thick by 12 inches wide that ran from the ~ 10,000 batteries to the railgun. It took nearly a full day to charge all of the batteries. The railgun I saw was only a test article but the disadvantages for use in space are clear. A Linear electric motor is better because it dosen't use the high currents that is used in a railgun, trading length for lower currents. Lower currents equals less weight and also less energy storage requirements which also adds weight.

According to the article they are looking at a number of options. I was only using the term "railgun" in a generic sense.

A couple of quotes from the article:
http://www.nasa.gov/topics/technology/features/horizontallaunch.html

A rail launcher study using gas propulsion already is under way, but the team is applying for funding under several areas, including NASA's push for technology innovation, but the engineers know it may not come to pass.

Different technologies to push a spacecraft down a long rail have been tested in several settings, including this Magnetic Levitation (MagLev) System evaluated at NASA's Marshall Space Flight Center. Engineers have a number of options to choose from as their designs progress.

 

[oldAtlas_Eguy]

Use of an electric Mass Driver on the moon or even as a way of shipping cargo from an asteroid or changing its orbit, picking timing direction and velocity of firings would be challenge. The Mass driver can impart most of the delta V from the asteroid to get a payload back to earth as long as the asteroid is large, if the asteroid is small the Mass Driver would be used as a reaction engine to change the asteroid’s orbit. For a medium to large asteroid a 1MT payload shot out at 4km/s enough delta V can be done to get the payload to do an aerobraking to a LEO orbit at earth or to be captured at a Lagrange point with a small delta V onboard rocket. A 4km/s 1MT object would impart 0.5 m/s on a 8000MT asteroid for each payload launched. If used as a payload launcher it would increase the asteroid’s elliptical orbit.

Electric Mass Drivers may become more common as both cargo shippers and as reaction engines since they are so well understood, have high efficiencies, and is robust. It is only in getting higher efficiencies and lowering the system weight that is such an engineering challenge. This brings us back to Earth to LEO launch costs. As Launch costs go down so does development costs for equipment sent to space.

I did some wattage calculations for electric linear electric motor launchers and a 1MT payload at 4km/s with a 20km length track takes 122mega watts of power during the acceleration. If some high rate discharge storage is used then the power source could be the same as proposed for most of the VASIMR tugs of 10Mw. Using capacitors for the temp power storage at 10 to 1 charge to discharge rate, a max of 32 launches per hour can be done, or 32 MT per hour.

Sorry my EE background is showing.

 

[rockett]

Electric Mass Drivers may become more common as both cargo shippers and as reaction engines since they are so well understood, have high efficiencies, and is robust. It is only in getting higher efficiencies and lowering the system weight that is such an engineering challenge. This brings us back to Earth to LEO launch costs. As Launch costs go down so does development costs for equipment sent to space.

Sorry my EE background is showing.

Glad of it! My engineering classes in college are extremely rusty from disuse.

Some are thinking of lunar mass drivers, even as manned spacecraft launchers. Here is one general and two technical articles.
http://www.permanent.com/t-massdr.htm
THE ARTEMIS PROJECT
Launch from Luna
Section 2.10
http://www.asi.org/adb/02/10/mass-driver-intro.html
MASS DRIVER UP-DATE
http://www.nss.org/settlement/L5news/1980-massdriver.htm
What do you think?

A mass driver for lunar launch (artist's conception - NASA)

 

[oldAtlas_Eguy]

The NSS article had some interesting side notes. One of them was a H.G. Wells chemical cannon launcher for payloads. This would work on the moon. Use liquid hydrogen and oxygen in a gun as the propelant to produce the over preasure in the gun to accelerate a payload. It requires no complex power system and has only two disadvantages one the propelant manufacture from water ice and the other the weight of the gun. If in 1960's they could impart nearly 9km/s velocity on an object at sea level on earth with a short barrel, I am sure it could be done with a little bit longer one and in a vacuum :shock:

 

[rockett]

The NSS article had some interesting side notes. One of them was a H.G. Wells chemical cannon launcher for payloads. This would work on the moon. Use liquid hydrogen and oxygen in a gun as the propelant to produce the over preasure in the gun to accelerate a payload. It requires no complex power system and has only two disadvantages one the propelant manufacture from water ice and the other the weight of the gun. If in 1960's they could impart nearly 9km/s velocity on an object at sea level on earth with a short barrel, I am sure it could be done with a little bit longer one and in a vacuum :shock:

Very good point. I think we have a tendancy to overcomplicate solutions. Or maybe we could even use a lunar lava tube
http://articles.cnn.com/2010-01-01/...unar-base-lava-flows-lunar-surface?_s=PM:TECH

 

[oldAtlas_Eguy]

Very good point. I think we have a tendancy to overcomplicate solutions. Or maybe we could even use a lunar lava tube
http://articles.cnn.com/2010-01-01/...unar-base-lava-flows-lunar-surface?_s=PM:TECH

Yes, a 1km length lava tube would work. Line it using lunar aluminum or tungsten and it would be easily big enough to launch 10+MT payloads or even 100MT payloads.

 

[rockett]

Yes, a 1km length lava tube would work. Line it using lunar aluminum or tungsten and it would be easily big enough to launch 10+MT payloads or even 100MT payloads.

Not sure this would work for manned use though. Some of the accelerations I've read say 5,000 to 20,000 G's.

Here's an article and video from early this year about a new design for a space cannon:

Space cannon to shoot payloads into orbit (w/ Video)
http://www.physorg.com/news183023838.html

 

[EarthlingX]

A couple more pictures in this thread :
QuickLaunch's Spacegun

another thread :
Rail gun or space cannon to launch to Orbit

 

[SteveCNC]

that cannon seems a little dangerous as far as methods go of propelling an object off the moon , personally I prefer a maglev system , more controllable for any size payload to any orbit desired depending on placement . With the new high energy capacitors being developed each electro mag could hold it's own charge for use on demand .

 

[neutrino78x]

If they wanted to do Lunar railgun they would have to make one on the Earth first. Sounds like technology development, lot of time, and a lot of money. I would love it though, just can't believe it's going to happen.

Looks like NASA is seriously considering it for Earth use. Even research on it would tell us a lot of what would be needed for a Lunar version:

Most definitely. I heard NASA is working on maglev assist. In other words, use magnetic levitation track to accelerate the vehicle to the point that an airbreathing rocket can be used, then activate the rocket. Or even use a normal rocket, but just give it a boost in speed.

Check out Hypersonic MagLev Group.

--Brian

 

[neutrino78x]

Not sure this would work for manned use though. Some of the accelerations I've read say 5,000 to 20,000 G's.

That's right, any of these cannon technologies, where you accelerate the thing until it leaves the device, so it has to be going fast enough to reach orbit, involve high accelerations like that. It would be good, for example, launching fuel to dock with a fuel depot, though.

--Brian

 

[neutrino78x]

The only thing that justifies the expense, in my view, is settlement of space.

I agree, although colonization itself should be done by private enterprise, at the expense of private enterprise. Government could go to establish infrastructure for private enterprise to follow and establish a colony where people are born and live their whole lives, but the people who go and live there should be private individuals going at their own expense.

The moon offers an opportunity to develop less expensive access to space as well as usable infrastructure.

My question about the moon, though, is who would own it? Do people get to own land on the moon? Of course, that is true on Mars too, and we need a new Outer Space Treaty where people are allowed to own land on other celestial bodies. I would say the Moon should be like Antarctica, owned internationally, whereas Mars can have private ownership.

--Brian

 

[bdewoody]

It is just because an asteroid has little or no gravitational influence that makes going to one impossible with current technology. For a manned space vehicle to get to a destination with acceptable quantities of fuel the destination needs to help by grabbing the vehicle to establish an orbit and then to land. This makes the moon the only logical choice for manned missions in the immediate future. Since we can't keep the ISS operating without constant resupply and repairs from the ground I don't give a Mars mission much of a chance of bringing them back alive.

It has been done a number of times, it's no big deal. Hover at a few feet, shoot a penetrating projectile and reel the vehicle down. The moon and Mars need landers based on the surface as well as in orbit. Built of structurally identical Modules, each self sufficient for months in a failure of adjacent Modules.

What has been done a number of times? I only recall one little probe landing on one asteroid. The mass of that probe was miniscule compared to a manned vehicle and it also took several years for it to get there, or did you forget that detail. Show me how it is possible for a manned craft with a crew of even only three and all of the support gear, food & water and fuel to get to an asteroid, orbit it, land on it and then return to earth within the time limits of the fuel and food carried. Remember once you get that hulking manned spacecraft to an asteroid you must match velocity and direction using fuel as the asteroid won't help you with its gravity well. Then take off from that asteroid and change direction again to get to earth before you die of starvation.

 

[scottb50]

What has been done a number of times? I only recall one little probe landing on one asteroid.

Hayabusa orbited Itokawa for months and landed upon it at least twice. NEAR Shoemaker landed, more or less, on 453 Eros. The moon, Venus, Mars and in a matter of months Mercury have all been landed on, the mechanics and physics are the same.

 

[bdewoody]

What has been done a number of times? I only recall one little probe landing on one asteroid.

Hayabusa orbited Itokawa for months and landed upon it at least twice. NEAR Shoemaker landed, more or less, on 453 Eros. The moon, Venus, Mars and in a matter of months Mercury have all been landed on, the mechanics and physics are the same.

No they are not. First don't include the moons or planets in your statement. They all have gravity wells that help to pull in the vehicle to a safe orbit. Little tiny probes such as near and Hayabusa had vast amounts of power compared to their mass and were not manned. A large manned vehicle would fly right by an asteroid and hardly be affected let alone pulled into orbit. My statements were directed soley at the idea that we can fly a MANNED mission to an ASTEROID with current technology or technology under development. The moon is the only destination that we have the capability to send men/women to for the immediate future which is what we need very soon.

 

[EarthlingX]

When spacecraft visit ISS they are not pulled in by gravity, same thing with asteroid, they first station-keep, than dock.

If you can't go to an asteroid, there is nothing you can do on the Moon either. There will be needed more capabilities and technologies for the Moon than an asteroid, not to mention costs.

Program for just one destination is very uninspiring, it's a big Universe.

 

[rockett]

When spacecraft visit ISS they are not pulled in by gravity, same thing with asteroid, they first station-keep, than dock.

If you can't go to an asteroid, there is nothing you can do on the Moon either. There will be needed more capabilities and technologies for the Moon than an asteroid, not to mention costs.

So when are we sending a mission to weld on a docking ring? Getting there is not the problem., keeping station is not the problem either. Staying on the surface to do meaningful work is a problem. In addition, unless it's a "boots and flags" operation with a very quick turnaround you would have to provision for a year or more.
http://en.wikipedia.org/wiki/Delta-v_budget

Near earth objects are asteroids that are in orbits that are within the orbit of Mars. The delta-v to return from them are usually quite small, sometimes as low as 60m/s, using aerobraking on Earths atmosphere (substantial reentry shields would be required).[10] The orbital phasing can be problematic; once rendezvous has been achieved, low delta-v return windows can be fairly far apart (more than a year, often many years), depending on the body.

However, the delta-v to reach them is usually rather higher, over 3.8 km/s,[10] which is still less than the delta-v to reach the moon's surface.

With respect to landing on the moon, we have the tech now, we only need to build it. We have done a lot of experimentation with regard to living there too. Real time teleoperated rovers could prepare the way...

 

[Yuri_Armstrong]

I would rather see a lunar base, but at least the asteroid mission will give the program direction.

 

[rockett]

I would rather see a lunar base, but at least the asteroid mission will give the program direction.

Unfortunately, a direction that probably wouldn't survive another administration. There is simply too much to be done to even make it possible (even the ISS couldn't go a year or more without resupply, let alone a spacecraft, for example), and it would be incredibly expensive for the results acheved (can't see it leading to a sustainable architecture for exploration). It might also be too easily perverted into another "boots and flags" stunt.

Once we commit people (bunches of them), such as to a base, it's a lot harder to back down.