Transterrestrial Musings

Comments

You do not need a communication satellite in halo orbit around EM-L2, you just put the CEV itself in a big enough halo orbit.

Posted by InfraNut at April 10, 2006 01:38 PM

It's not a space program, it's a jobs program.

By the way: I think "EM-Ln" is a poor choice of nomenclature for our circumlunar Lagrange points. It's too easy to think of EM as "Earth-Mars", for one thing. I propose that we either change the name to "Terra-Luna Lagrange Point n" (TL-Ln) or give the points georgraphical names. Terra-Luna Lagrange 1 could be Point Armstrong; TL-L2 Point Aldrin; and TL-L3 Point Collins. TL-L4 and -L5 might be named for Von Braun and O'Neill respectively. (We'll save the Sol-Terra points for Gagarin, Shepard, Goddard, Korolev, and G. Harry Stine.)

Posted by B-Chan at April 10, 2006 02:50 PM

Rand, I keep telling you guys this ATK architecture was done in August of 2004. They didn't need no stinking reports, they already had the hardware laid out. Everything since then is just backfill. L-2, though? Did they actually offer that with a straight face, or does TDRS peek around the Moon enough to give them operational confidence?

I've got a NASA handout that shows L-2 at 119,933 km from the center of the Moon, which is sensible as the balance point for Earth /Moon mass on one side and centrifugal force on the other) Anyone got the latest STK and can run a quick sim?

I disagree with B Chan. I don't think Earth-Mars with regards to Lagrange points. (¿Que?) The only real concern is confusing Sun-Mercury L-points for Sun-Mars L-points. I doubt we'll be getting around to putting Mercury to good use for a while, so I don't really think it's an issue for the near-future.

Besides, when I see EML-1 I think Emily. Anthropomorphising these things a bit always helps.

Posted by Ken Murphy at April 10, 2006 06:19 PM

The L2 rendezvous architecture has been around for a very long time. It was proposed by T.N. Edelbaum and R. Farquhar back in the late 1960s and early 1970s, so I think you could say that those eminent astrodynamicists could safely propose things like that with a "straight face." As far as the communications issue, this seems to keep tripping people up. Rather than being a hinderance, a CEV at L2 would be a fantastic communications link, provided that it was in a halo orbit that was always in view of the Earth. Farquhar showed how to do this 30 years ago. A CEV in a L2 halo could view the entire farside and make farside landings a piece of cake, from a comm perspective.

A Halo Orbit Lunar Station by R. Farquhar.

The Utilization of Halo Orbits in Advanced Lunar Operations by R. Farquhar.

Libration Point Rendezvous by T.N. Edelbaum.

BTW, there are no Earth-Mars libration points, so EM shouldn't confuse anyone except the astrodynamically non-astute.

Posted by SpaceFiend at April 10, 2006 06:30 PM

Rand

This time I completely agree with you! :)

Just wait, in a little while Solar Electric tugs will be put back in as well.

Dennis

Posted by Dennis Wingo at April 10, 2006 09:05 PM

Lunar LOX and re-useable LSAMs are the answer.

The current problem with a too heavy LSAM would appear to exist whether we fly sticks, EELV, Long March or shiny new SSTO RLV spaceplanes from NewSpace LLC.

Solar ion tugs? I can support that, also. :-)

= = =

Masten needs to win the lunar hopper challenge in October and then build us an authentic re-useable LSAM.

Posted by Bill White at April 11, 2006 08:50 AM

Ooops, a question for Dennis.

Solar electric - what do we use for fuel? I have read on the intarweb that terrestrial xenon supplies are insufficient for the massive commercial deployment of ion drive cargo vessels.

Is there something else we can use?

Posted by Bill White at April 11, 2006 08:52 AM

Other propellants than xenon can be used (e.g. cesium) but they're not as efficient. One interesting idea is to use buckyballs or other fullerenes, which has the advantage of being able to utilize carbonaceous material.

Posted by Rand Simberg at April 11, 2006 09:03 AM

Anyone got the latest STK and can run a quick sim?

No need for that. It's easily calculated by hand. Lagrange didn't have STK. ;-)

Posted by Rand Simberg at April 11, 2006 09:06 AM

As I understand it, when they tried using C60 as an ion propellant at JPL they found it decomposed too easily. The low MW fragments degrade efficiency.

Posted by Paul Dietz at April 11, 2006 09:59 AM

I hadn't seen that. I just recalled your earlier Usenet posts on the topic.

Posted by Rand Simberg at April 11, 2006 10:02 AM

The "not enough xenon" argument is overstated. Bismuth is the other realistic possibility for ion propulsion (mercury has been suggested, but people worry about it depositing on the spacecraft). See

A Solar Electric Propulsion Cargo Vehicle to Support NASA Lunar Exploration Program,” Proceedings, 29th International Electric Propulsion Conference, Nov., 2006

For everything you want to know about SEP

Posted by brian d at April 11, 2006 11:00 AM

Folks

I do know that Mike Griffin was under the impression that Xenon supplies were insufficient to support a cislunar and solar system solar electric propulsion system. Nothing could be further from the truth.

Do a search on the AIAA site for a paper by Verhey on available supplies of Xenon. There is over 100 million tons of Xenon in the atmosphere and with existing thruster technology the amount required to move 60 metric tons of payload to the Moon and return the system is only about 22 metric tons. You do the math.

With a modest capital expense and a couple of years of lead time, global production of Xenon, now at about 50 metric tons per year can easily be expanded to 100 metric tons per year.

I have an NDA with a major supplier and can't say a lot more but today, I can lay my hands on as much Xenon as I need for the foreseeable future.

If by some circumstance Xenon was in short supply (it is about $1000-1200 a kg) Krypton can be used. It is only about 5% less efficient as a fuel than Xeon and is 20 times more plentiful in the atmosphere. It is about $50 per kg.

Xenon supply problems are a red herring.

Bismuith can be used as well but it does have some problems in that you have to keep the plumbing heated at all times to around 40 degrees C in order for it not to solidify and clog the plumbing. However, for really high performance systems and in the future, it looks very interesting.

A very good thing about Xenon or Krypton is that there are no toxicity or plume impingment issues to deal with or problems in having it around humans.

Dennis

Posted by Dennis Wingo at April 11, 2006 09:38 PM

Xenon supply problems are a red herring.

Good. Some google and some bookmarks and I can push this rumor from my mind.

I can lay my hands on as much Xenon as I need for the foreseeable future.

I betcha you can't "lay you hands on" much Xenon at all. Wouldn't it escape through your fingers?

;-)

= = =

The Farquhar papers cited above are quite interesting. Humanity needs two EML stations.

An EML-1 "Gateway Station" and also a Farside "Farquahar Station" in an EML-2 HALO orbit. Having both would be a real beginning towards genuine cislunar infra-structure.

At NASASpaceflight.com the idea was floating to use LSAM ascent stages to assemble a rudimentary EML-2 station during VSE missions that rendezvous there. EML-2 rendezvous does appear to require less delta V than LUNO rendezvous and allows global lunar access.

Very interesting issues that apply whether humanity uses EELV, da' Stick, that proposed 25 MT Long March 5 or the NewSpace LLC SSTO RLV.

Posted by Bill White at April 11, 2006 09:57 PM

Bill

Actually, with solar electric propulsion you either

a) Don't need the Heavy lifter.

b) can increase the cargo delivered from 21.5 metric tons to over 50 metric tons per mission.

The ESAS architecture fumbled this one.

Dennis

Posted by Dennis Wingo at April 12, 2006 06:19 AM

Rand writes:

I like a Lagrange rendezvous point, but all of the analysis that we did at Boeing indicated that L-1 was a better choice than L-2. The advantage of L-1 is that it's always visible from earth, and it's a relatively short trip home from there. We were strongly driven in our trades by NASA demands (unreasonable ones, in my opinion) that astronauts be able to get home in an arbitrarily short amount of time. The disadvantage of L-1 is the propulsion cost, and L-2 is indeed more efficient from that standpoint. But it wasn't considered in the Boeing CE&R studies because of the trip-time constraint. Its other problem is that unlike L-1, which is continually visible from earth, L-2 never is. For communications, a relay satellite in a halo orbit, or a series of them in lunar orbit, will be required.

Based on this, switching to an EML-2 rendezvous may actually make a whole lot of sense and demonstrates that NASA is looking at cutting away at some (at least) of these possibly unreasonable NASA demands.

The studies linked by SpaceFiend from 1972 suggest that an EML-2 HALO orbit retains full visibility with Earth with negligible increases in delta V for lunar access.

Posted by Bill White at April 12, 2006 08:48 AM

Ooops, I meant to mention, I like solar electric tugs, a whole lot. For whatever my opinion is worth. ;-)

Posted by Bill White at April 12, 2006 08:50 AM

If mercury is ruled out due to deposition concerns, how is bismuth any better? The boiling point of Bi is over 1500 C. This should solidify on exposed spacecraft surfaces. Indeed, deposition of Bi at room temperature is cited as an advantage since it makes ground testing easier (no cryogenic pumping of the vacuum chamber is needed).

Perhaps the real concern is toxicity of Hg making ground testing more difficult. Or maybe Hg would react with spacecraft materials, like aluminum, to a greater extent than Bi, and the higher vapor pressure means more gets inside the spacecraft?

Posted by Paul Dietz at April 12, 2006 09:04 AM

EML2 is also an excellent departure point for low-thrust vehicles to Mars or the asteroids...the "spiral-out" time would be almost negligible.

Posted by SpaceFiend at April 12, 2006 09:18 AM

Paul,

Everything you say about mercury and bismuth is pretty much true. I was pushing mercury because it's much cheaper than Xe, and easyer to store and feed. You pretty much hit on it, ground testing is a pain so I got shot down. I think the deposition problems could be worked, solar panels are pretty hot.

Posted by brian d at April 12, 2006 09:42 AM

Has anyone considered an L-point fuel depot based on using LiH? Ship LiH from Earth and LOX from Luna. You could even set up a fuel depot on the moon and drop containers of LiH via airbag crash landing for collection and processing.

I love the solar ion tug idea Dennis is pushing but pushing H2 or CH4 to an L point (EML-1 or EML-2) via a long slow ion journey and then storing it would seem to pose a huge boil off problem. But, Wikipedia tells me LiH has a density of 780 kg per cubic meter with basically no vapor pressure. That means no boil off right? Suppose its two years from LEO to EML-2 via a long and winding Lo road powered by solar ion? Do we care?

Package it in a water tight container (heh!) and ship to LEO however is cheapest. Then use a solar ion tug to transport to your fuel depot. Ship some water the same way.

Whenever you want H2, mix LiH + H2O. Ka-boom. H2 is released, captured and bottled for fuel.

Then use the LiOH as your CO2 sorbent. That releases more H2O.

Okay, Li2CO(3) then ends up being a processing dead end (slag for a radiation shield?) but that Li molecule would seem to save a whole lot of expense by avoiding LH2 or CH4 boil off.

Hmmmm . . .

Time to write some more sci-fi stories premised on LiH.

Cool!

Posted by Bill White at April 12, 2006 10:19 AM

Okay a downside is that only 1/8th of the mass of LiH is hydrogen but in exchange for that you save the need to deploy a power supply to crack water into H2 and O.

And a space station will need CO2 sorbent in any event and it could sell excess LiOH sorbent along with H2 fuel.

Posted by Bill White at April 12, 2006 10:43 AM

Bill: another interesting property of LiH is that you can crash land it on the moon at lunar escape velocity and the liberated kinetic energy, even if entirely converted to heat in just the LiH, is insufficient to melt the material (IIRC). No airbags needed, assuming you can get the fragments out of the regolith.

Lithium really shines as a propellant if you have fluorine-based oxidizers, but that's a dangerous and expensive game, and fluorine is much less abundant than oxygen in ET materials.

Posted by Paul Dietz at April 12, 2006 11:05 AM

I wonder if heavy metal halides have been looked at as ion engine propellants. The boiling points of metal halides are often lower than the metals they contain, and the molecular weight of the gas is higher. Granted, you'd lose if the molecules didn't hold together through the ionization process.

Posted by Paul Dietz at April 12, 2006 11:09 AM

Thanks, Paul.

As I think about this, LiH would seem useful if only as a cheap method for cracking the H2 out of H20 in lieu of using nuclear reactors and electrolysis. The extra H atom and unlimited CO2 sorbents are just gravy.

Not that I oppose nukes (I emphatically do not) but they are heavy and expensive and cannot be crash-landed on the moon with minimal packaging.

Using chemical rockets and soft landing the basic ratio is 5 to 1 for mass in LEO versus mass on the lunar surface, right? 5 kg in LEO will yield 1 kg on Luna. With a re-useable solar ion tug and lunar crash landing with miminal packaging, that should improve well past 2 to 1, just thinking off the cuff.

With airbag delivery, I want to play lunar golf.

Let the various lunar package delivery companies send in their packages at a shallow angle and let 'em bounce aiming for a target crater well equipped with video cameras and a target flag. I'd watch that on Terran TV.

= = =

I am trying to think about how to do ISRU with low capital investment rather then engineering elegance being the driving metric. Maximum use of passive solar energy and mimimum use of intricate hardware and other ideas along those avenues.

Posted by Bill White at April 12, 2006 11:47 AM

> Actually, with solar electric propulsion you either

> a) Don't need the Heavy lifter.

You don't need a heavy lifter with or without solar electric propulsion.

However, the architecture proposed by Andrews did include a new heavy lifter. An Atlas 5 with Zenit strap-ons is not an "off the shelf" EELV.
With a payload of 40,000 kg, the "Expendable Common Booster" would have been the second only to the Saturn V as the heaviest rocket ever developed in the United States.

> or

> b) can increase the cargo delivered from 21.5 metric tons to over 50 metric
> tons per mission.

So? According to Andrews, each Expendable Common Booster would cost $240 million. That works out to $6,000/kg. No matter how many times you call that "cheap," it is very expensive by the standards of the "semi sentient bags of water" that you wanted to pay for all this.

Andrews's estimate for the inital program, through the first lunar base, was nearly $100 billion. The solar electric stage alone was estimated at $6.3 billion. Those numbers are not substantial cheaper than "Apollo on Steroids."

You and Bill obsess over reducing the cost of getting from LEO to the Moon, Mars, and Beyond but we don't even have an affordable way of getting to LEO. That's like worrying about the cost of airline tickets to Australia when you can't even afford a ride to the airport.

Worse, the workers who are trying to build the airport (ISS) don't even have affordable rides, for themselves or their building materials. An "Expendable Common Booster" won't change that. Neither will solar electric propulsion. No matter how many times you chant "launch costs don't matter," launch costs do matter. Lower launch costs are the key to doing everything you want to do in space. Even von Braun, on his better days, realized that.

Posted by Edward Wright at April 12, 2006 01:14 PM

Edward, the Golden Spike was driven when railway lines from California (going east) met up with railway lines going west. The English Channel Chunnel was built digging in both directions.

Having safe reliable proven lunar access technology to merge with low cost Earth-to-LEO transport will allow lunar access very much sooner and will allow greater return on investment for NewSpace compared with LEO tourism as the only revenue source. Its called "parallel processing" :-)

Besides, if littering the Atlantic sea floor with SSMEs is dumb, throwing away an LSAM after one use is double dumb.

Posted by BIll White at April 12, 2006 01:39 PM

The English Channel Chunnel was built digging in both directions.

I don't think that analogy shows what you want it to show. The Chunnel's been a major economic boondoggle.

Posted by Paul Dietz at April 12, 2006 02:04 PM

Touche' ;-)

Posted by Bill White at April 12, 2006 03:06 PM

> Edward, the Golden Spike was driven when railway lines from California
> (going east) met up with railway lines going west.

And if Grandma had wheels, she would be a Buick.

Newt Gingrich, who is a professional historian, has often written about space and transcontinental railroad. He notes that, "We built the transcontinental railroad with government incentives but without a government bureaucracy of railroad builders."

So, how does the Golden Spike prove the need for a government transportation bureaucracy on the Moon?

> Having safe reliable proven lunar access technology to merge with low
> cost Earth-to-LEO transport will allow lunar access very much sooner

Did the proven Apollo technology allow ordinary Americans to have lunar access much sooner? No, it ensured that no one else would try to go to the Moon for more than 30 years.

What makes you think a new lunar lander that's just as expensive (and just as dangerous -- hypergolics are not "safe" or "reliable" ) will bring people running?

I can't think of a better way to frighten investors away from the Moon than to have a NASA Administrator loudly proclaim that the only way to get there requires a $100-billion investment.

> Besides, if littering the Atlantic sea floor with SSMEs is dumb, throwing
> away an LSAM after one use is double dumb.

SSMEs aren't contaminated by highly toxic, hypergolic propellants after one use. The Shuttle RCS system, which does use hypergolics, is enormously expensive to refurbish, even on Earth. On the Moon, it would be much harder.

Someone who wanted a reusable lunar lander would be better off starting from scratch than trying to convert the misbegotten LSAM. Any chance that LSAM would be safe or reliable went out the window when NASA decided to go with the "proven" technology instead of "risky" methane.

At least you finally admit that a reusable vehicle doesn't have to take decades to develop. Now, if we could just get you to consider reusable vehicles that are not based in insane LSAM technology. :-)

Posted by Edward Wright at April 12, 2006 05:49 PM

A reuseable LSAM would not use hypergolics.

Masten for example is working on a very nice pressure fed methane fellow that might well be ideal.

Posted by Bill White at April 12, 2006 08:36 PM

> A reuseable LSAM would not use hypergolics.

> Masten for example is working on a very nice pressure fed methane fellow that might well be ideal.

Yes, but Masten's "fellow" is called "XL" -- not "LSAM."

LSAM is NASA's fellow.

Are you under the impression that Masten is working for NASA on LSAM?

Or have you just decided, for some bizarre reason, to start calling all lunar landers LSAMs? Like calling all cars BMWs? If so, please stop. It's hurting my brain. :-)

More importantly, if your "reusable LSAM" is really Masten's XL, why do you keep saying things like, ""NASA should build and deploy genuine LSAMs as soon as possible and let the private sector buy some" -- as if anyone in the private sector afford a genuine NASA LSAM?

Why don't you say, "Masten should build and deploy some XLs and let the private sector buy some"?

Posted by Edward Wright at April 12, 2006 11:12 PM

A retraction to the original article has been released.

Posted by hi at April 13, 2006 11:30 AM

Post a comment