OSP: Capsule v. Wings - if you had to choose right now

GCNRevenger · 2003-11-26 12:54:54

No form of X-38 could ever perform as a the crew transfer craft. X-38 was tailored to be a return vehicle only. Liftoff avionics, no docking hardware, solid-fueled OMS engine, only nine hours of life support, and no wheels for a 45mph hard landing. There isn't even a cockpit with any manual flight controls at all.

X-38 is so far removed from what Nasa needs for the CTV version of OSP that it shouldn't even bother; the costs of converting X-38 into a HL-20/Hermes style true spaceplane would probobly be higher than building just a baby HL-20/Hermes combined with the X-38's development costs.

RobertDyck · 2003-11-26 13:01:12

A lift body could, in theory, be able to integrate the OMS engines into the craft proper, which would simply negate the need an expendable "service module." That would add up to signifigant savings on every flight, for a modest design/building investment... I think the Air Force is getting ready to test a Peroxide/Kerosene OMS engine for their unmanned space bomber which would be ideal.

The HL-20 had its OMS engines/tanks integrated. That is one advantage over X-38 which had an expendable de-orbit module.

RobertDyck · 2003-11-26 13:05:04

X-38 did have a docking port, it would need one to connect to ISS. It also had maneouvering thrusters, they used cold nitrogen to avoid the posibility of damaging ISS. What it lacked was a radar system to target its docking. Is that really hard to add? After all, engineering design to upgrade X-38 to an OSP was performed when ESA was looking at it to launch on an Ariane V.

clark · 2003-11-26 13:17:01

GNC,

OSP is required to operate as a crew launch and return vehicle, which most certainly does not spend its entire mission in space. Wings are the superior choice for returning to Earth and could be built inherintly more reuseable.

OSP will be spending 280 days on orbit. If we give it wings, it means we are choosing to work between LEO and Earth, instead of trying to work between GEO and the moon.

This is all about raising the bar. But if we give OSP wings, we will spend billions of dollars to stay right where we are. We will then have to spend billions of more dollars to go further in after we are done spinning around in LEO.

Ditch the wings, build a capsule, which will meet our needs, and allow us to go even further, then try to implement a winged body on a second generation RLV utilizing new aerospike engines-scramjet-whatever. If you look at the state of the technology, you'll discover that in order to do the winged body justice, and to truly develop a second generation to the Shuttle, it will take another twenty years.

We can build a capsule to meet the 2008 deadline- we can do a winged body by 2008, but it won't be much of an improvement over the Shuttle.

I might also like to add that a capsule configuration allows for greater flexibility in docking different sized modules to the rocket- the Shuttle only had it's cargo bay.

Why will a lift body not be able to go beyond LEO and a capsule can? The shape does not matter when there is no air as you have pointed out clark, only structural stresses and mass.

Unused mass, or mass that has no purpose, still requires fuel to move in space. The fuel itself requires even more fuel to get it into space. Any reduction of useless mass is a good thing, like here on Earth.

A capsule OSP would be too heavy for a direct flight to the Moon or Lagrange anyway, so any incarnation would have to dock with an orbiting transfer/lander section, and if Nasa builds a dedicated manned Lunar transfer/lander, then a lift body would be even nicer.

I disagree. While maybe a Earth return OSP would be too heavy (I haven't the math to contend), a capsule configuration is still ideal. So guess what, we use the same factory to produce two different capsules- one with a return heat shield, another without. Same form.

Figuring out how to produce the things is a big part of how things get done, or if they are even considered. If you can cut costs based on the manufacturing side, then you take that into consideration on the design side. Look at the larger picture.

it will cost more to create a seperate winged body sapce ship as well as a capsule for anything beyond LEO. If we use the same basic design, then we can cut costs on development and testing. More bang for the buck!

Simply "have the army/navy pick them up" is a far stickier proposition than you may think... Unlike Apollo that was equitorial nearly, OSP will be returning from an ISS orbit which covers nearly the entire globe.

It returns on a ballistic trajectory with GPS tracking. The Russians have been returning people from ISS, so I don't think this is a major issue. We have a good idea on where the thing is going to come down- and if we pursue the capsule approach, we will have an incentive to get better at pinpoint landing in a capsule- a skill we definitely NEED for Mars or the Moon.

Plus, in order to return to proper medical care in only 24 hours from undock, a capsule would have to carry considerably more fuel for cross-range maneuvering.

Solution: In an emergency, bring a field medical hospital to them, wherever they land.

This is to say nothing of "what if" you have to come down in the water or far from civilization, that it may simply be hard to guarantee 24-hour-to-hospital even with extra fuel.

We can what-if either side of this to death. But i don't think these challenges are insurrmountable nor are they show-stoppers. So there is a small bit of risk that they might not reach the crew in less than 24 hours. There's a risk the winged body shape will blow a tire while landing and explode. ???

It gets better... a capsule, in any form, by nature of its ballistic trajectory will expose the crew to 3-5G loads. No matter the shape. Thats the way it is. This is not a good thing when flying back deconditioned or injured crewmen; Nasa even considerd changing the seat arrangement on Shuttle to make the return flight easier on them.

Someone scientifically gifted enough to figure out a way to reduce the g load on a returning capsule? It may not be a 'good' thing, but I don't think it's a show stopper. Witness the continued and functioning Astronauts from ISS on the Soyuz.

Check the thing between flights, shine it up, and its ready to go... a far cry from having to half-dismantle a capsule to replace its ablative shield every mission.

The Shuttle is practically dismantled and put together all over again- each and every tile has to be inspected. it's insane. The major portion of a heat shield on the capsule is the lower portion facing re-entry. A wing shape, you're looking at a larger surface area, and the possibility of damage to neccessary pieces of the wing shaped body that may render it broken in the atmosphere (look at what happened to Columbia). Wings were a liability, not a plus.

Please also remember, that this cross-range landing was an Airforce requirement, not a NASA one.

Bill White · 2003-11-26 13:18:12

No form of X-38 could ever perform as a the crew transfer craft. X-38 was tailored to be a return vehicle only. Liftoff avionics, no docking hardware, solid-fueled OMS engine, only nine hours of life support, and no wheels for a 45mph hard landing. There isn't even a cockpit with any manual flight controls at all.
X-38 is so far removed from what Nasa needs for the CTV version of OSP that it shouldn't even bother; the costs of converting X-38 into a HL-20/Hermes style true spaceplane would probobly be higher than building just a baby HL-20/Hermes combined with the X-38's development costs.

Here is the key question (IMHO) on X-38:

Is it cheaper to build an additional OSP CTV and leave it permanently parked at ISS or is it cheaper to build a stripped down X-38 to leave permanently parked at ISS. If all goes well (no emergency evacuations of ISS) X-38 would =NEVER= be used for any real life operation, other than training or testing, right?

If ISS suffers emergency pressure breach which required rapid evacuation, there simply would be no time to fly OSP up to recover the crew, right? Therefore, an emergency CRV would never be available for any task except as an ornament attached to ISS, just in case. . .

RobertDyck · 2003-11-26 13:28:44

Remember, I was saying the interplanetary spacecraft for Mars should be reusable. It would travel from Earth orbit to Mars, then aerocapture into high Mars orbit. The Mars ascent vehicle would carry astronauts back to the interplanetary spacecraft, which would travel back to Earth and aerocapture into Earth orbit. To do that you need a crew taxi to get astronauts to the interplanetary spacecraft. After they return to Earth orbit, you can use the same crew taxi to go fetch them. There is no need for an OSP to go anywhere other than Earth orbit. As an emergency backup, stick a couple Soyuz capsules on the interplanetary spacecraft. If it fails the insertion into Earth orbit then the Soyuz capsules can directly enter. And you don't need the orbital or service modules of Soyuz, just the descent module. Two astronauts per capsule plus enough room for samples equal to an astronaut's body weight, his spacesuit and seat. If you send 6 astronauts instead of 4, then the emergency escape pods don't have room for the samples, but you can still design for 2 Soyuz capsules.

Rather than re-inventing a capsule that already exists, develop something new: a space taxi both for ISS and to deliver crew to the Mars ship.

clark · 2003-11-26 13:33:26

Robert,

Does a space taxi need wings?

Designing something new presents new opportunities, but takes more time, and costs more.

We need something now, and cheap. Or am I just seeing it wrong? ???

RobertDyck · 2003-11-26 13:56:19

A lifting body based on HL-20 or X-38 should not take long to develop. And we can proceed with development of the Mars spacecraft concurrently. If you use the same universal docking port as the ISS, then the Mars spacecraft is not dependant on a particular space taxi. Hell, you could use a couple full Soyuz to get your astronauts to interplanetary spacecraft. Or the old Space Shuttle if the powers-that-be decide to restore it to flight.

clark · 2003-11-26 14:08:27

But does a space taxi need wings?

We understand the 'capsule' concept. We have experience with the shape, and we know it can take us to at least the moon. Relying on a third party, such as Russia, for our Human-to-Space service is untennable, and risky. It also flies in the face of our stated policy of dominating space. If you want to do something like that, you have to do for yourself.

We update the Apollo capsule, make the neccessary changes to pressurization, and start working on making the landings more controlled, and less g intensive.

We then have a supplemantary space taxi for the ISS by 2008- thereby relegating the space shuttle to the scrap heap. We free up the Shuttle funds for development of the moon and other space infrastructure. We work on a heavy lift vehicle, so when the moon and GEO become more important economically- we're positioned to gain market share as a nation.

After this time- about 20 years, our hypersonic research should be coming to frutition. We can then develop a truly second generation winged body RLV that drasticaly reduces cost to space. This in turn fuels space commerce because now people are going up (since costs are coming down) and there are a few places they can go (like a decommisioned ISS that acts as a tourist rest stop).

We need things now. If we go with a winged body, it will reduce our chances to go further in space. We didn't go very far with the Shuttle, we went to the moon with a capsule.

Let go of the Buck Rogers future.

GCNRevenger · 2003-11-26 14:15:25

With the cost of building X-38 starting to mount up to over half a billion dollars, and HL-20 only projected to cost two billion, and all of these estimates probobly low by around 100% knowing contractors, building X-38 and OSP would be more expensive than building just OSP and leaving a copy of it docked at ISS perminantly.

Now, how many times must I say it, a tiny lift body is not like shuttle! Even if it did use tiles, there would only be a few strong ones, not the thousands on Shuttle! Dealing with a small spacecraft is infinatly easier than having to prepare the US's "Battlestar Gallactica" for launch. HL-20 is just so much smaller that it isn't that hard to service. No massive ultra-high-pressure LH2/LOX engines, no hydraulics, no truckloads of equipment to remove, and all the systems are accessable through convienant hatches:
http://oea.larc.nasa.gov/PAIS/HL-20-fig6.gif
It could even have a METAL heat sheild.

There is no good reason that a lift-body ship could not also travel to the Lunar surface or to GEO or to Lagrange, none at all. Let me reffer you to a concept cooked up by the Pentagon in ages past...: http://www.astronautix.com/articles/lunpter1.htm Yes, that caption with the lifting body and super-trans-stage does indeed read "LUNAR LANDER." Capsules hold NO SPECIAL MONOPOLY over space travel outside of LEO. A capsule can do it, well guess what, a lift body can too.

Instead of building capsules AT ALL, we build only one ship, a HL-20 style craft. This craft could handle all the crew launch/return needs from LEO, and could be mated to a tranfer/lander stage for travel outside LEO. No version of the EELV boosters could carry a capsule or lift body AND the fueled trans-stage/lander to a Lunar transfer orbit, they are all just too small, thus the extra weight of HL-20 would not be a signifigant launch issue. There would be no need for this heat-shield-less flying capsule cockpit thingie for another space craft, HL-20 OSP IS the spacecraft. Flying one ship and one ship only means you have to develop one manned ship, which would probobly more than make up for the small extra launch mass requirements. "More bang for your buck!"

Furthermore, as i've mentioned on more than one occasion in these various threads, the only way man will REALLY leave the Earth for keeps is when we move away from this "save ever gram" style of thinking. An extra metric ton or two that a mini-HL-20 might weigh is simply worth the extra launch mass. Its worth it, its as simple as that.

There needs to be a little clarification about the return mission... it cannot be planned on any convientant schedule. If there is a disaster on ISS, the capability should exsist to come back down immediatly. Without a large number of landing sites, this is hard to do without ladening your capsule with large fuel tanks like on Soyuz. With HL-20 it would be easier, since it can simply use its orbital momentum, with the aid of lift and control surfaces, to fly hundreds of miles to safety. Plus, if a capsule goes off course during re-entry, then you are out of luck and have to come down near your re-entry vector, with HL-20 you just turn and glide. The number of field hospitals that would have to be air-portable through the world to meet Nasa's 24-hour mark would be rediculus.

I would also like to note more about where HL-20's G-loading advantage comes from... from the more mild re-entry dynamics, which translates into lower heating, which translates into a lighter heat shield than is possible with the firey death plunge capsules.Wings are an ADVANTAGE when done properly, not a liability.

Bill White · 2003-11-26 14:40:35

With the cost of building X-38 starting to mount up to over half a billion dollars, and HL-20 only projected to cost two billion, and all of these estimates probobly low by around 100% knowing contractors, building X-38 and OSP would be more expensive than building just OSP and leaving a copy of it docked at ISS perminantly.

=IF= this is true, I am largely content concerning cancellation of X-38, except,

--> What is the per copy cost of additional X-38/OSP?

--> Cancellation of X-38 only makes sense =IF= OSP gets funded, right? Otherwise with no OSP and no X-38 the ISS starts looking like a huge white elephant.

Instead of building capsules AT ALL, we build only one ship, a HL-20 style craft. This craft could handle all the crew launch/return needs from LEO, and could be mated to a tranfer/lander stage for travel outside LEO. No version of the EELV boosters could carry a capsule or lift body AND the fueled trans-stage/lander to a Lunar transfer orbit, they are all just too small, thus the extra weight of HL-20 would not be a signifigant launch issue. There would be no need for this heat-shield-less flying capsule cockpit thingie for another space craft, HL-20 OSP IS the spacecraft. Flying one ship and one ship only means you have to develop one manned ship, which would probobly more than make up for the small extra launch mass requirements. "More bang for your buck!"

I might very well agree with this. Let me read more about HL-20 or a mini HL-20.

What are the odds Congress will fund something like this?

RobertDyck · 2003-11-26 14:54:51

The X-38 had a budget of $1.2 billion including all development from concept study, to production of 2 flight units. With all the redesigns and changes of what they were trying to do, the budget got over-run to $2 billion. However, that budget amount was never spent because the project was cancelled.

GCNRevenger, there are two reasons I'm not advocating an OSP of any sort beyond Earth orbit.
1) The heat shield for re-entry from interplanetary velocity is significantly higher. There is no need to put that on a vehicle which is used primarily for trips to LEO.
2) I'm pretty much ignoring the Moon. A spacecraft for Mars will require much more room than a seat for each astronaut (cosmonaut, taikonaut, euronaut, chimponaut. Ack let's stick to one word.) A spacecraft for Mars will require at minimum a bunk for each crew member, exercise equipment, and some place for them to do work. The little staterooms in Robert Zubrin's habitat look perfect. I said exercise equipment is minimum, artificial gravity is better if it can be done. Sending just a capsule or lifting body on a 6 month journey to another planet is just not enough. You don't want to use something that big as a space taxi; it would be as big as the current Shuttle. And you don't want to send the full size Shuttle to Mars, the fuel required for something that big would be prohibitive. So a dedicated interplanetary spacecraft is required.

Bill White · 2003-11-26 15:09:25

GCNRevenger, there are two reasons I'm not advocating an OSP of any sort beyond Earth orbit.

Does this suggest building an OSP for Earth/LEO/lunar operations and something bigger for interplanetary operations?

With that "someting bigger" never actually landing on any planetary surface?

Robert, would the TransHab inflatable be sufficiently durable for multiple round trips from Earth to Mars? How would the heat shields be serviced or replaced?

clark · 2003-11-26 15:09:39

Thank you Robert!

your points are all well taken.

And GNC, you make a convincing case.

GCNRevenger · 2003-11-26 16:57:16

Wow this thread is h-o-t...

The theme of the thread is what form OSP ought to take, not to much should one be built or not... It really depends on priorities:
1: If we want to take ISS beyond core complete, OSP is required
2: If routine transit to Lunar suface or station, OSP could serve as a transfer/lander vehicle, eliminating the need for another manned spacecraft.
3: In the event that "Shuttle II" takes extra time to man-rate, a mission to Mars built and tested in LEO will need a crew transfer vehicle, one which is preferably American.
Of course OSP would not be used for any trip more than about a week one way, it would obviously only be a tiny fraction of whats needed for a multi-month Mars ship.

The one achillies heel of a lift body that everybody parades as its death-knell is that it would be difficult to make it capable of direct re-entry from a Moon-to-Earth transit speed. I think it could be possible to only skim the atmosphere and areobrake, but this would not be ideal. Everybody recall that transit/landing module? For there to be any real substantial flights to and from the Moon, a reuseable transfer/lander vehicle could take advantage of Lunar fuel (if there is water ice) to make flights back and forth from the Lunar surface and Earth orbit, carrying OSP. If there is no water ice on the Moon to at least make rocket fuel, then there is no point going back at all.

As much as I would love to drop everything; ISS, Shuttle, OSP and start on a Mars program, I don't think that is going to happen. Even if Nasa has the technology, no country has the confidance or the will to follow through on such a long term project at the moment. So... with the Moon close by, and the chance of water on it, it would be better than going in circles.

The object is to leave this planet and use as little of its reasources as possible - to LIVE - out of the cradle... Mars is the ideal destination, but since that is not "in the cards" at the moment, a Lunar colony sustained water ice in the regolith is the next best thing that we can do today, and OSP is a great way to get there.

RobertDyck · 2003-11-27 08:50:27

Let's talk about the Moon. There is no CO2 on the Moon, so Robert Zubrin's ISPP technique will not work there. Ice found by Lunar Prospector is tiny crystals spread thinly over a large area, so I don't think you'll find a convenient mine for rocket fuel. However, there is lots of aluminum. The most abundant compound in lunar soil is silicon dioxide (rock or sand), the second most abundant compound is aluminum oxide, third is iron oxide. Since everything is oxides, the most abundant element is oxygen, the second is silicon, the third is aluminum, fourth is iron. Aluminum is the primary fuel for solid rockets, with a pinch if iron oxide as a catalyst. Solid rockets normally have a solid oxidizer, something that releases oxygen when it gets hot. They also have a rubber binder. The rubber has two purposes: hold everything together, and convert the heat from burning aluminum into thrust. Aluminum oxidises into aluminum oxide, which is solid. Although it produces more heat that burning hydrogen, that does not translate into expanding gasses so it does not translate into thrust. When rubber gets hot it vaporizes and breaks down into other gasses that expand easily with heat. So rubber translates heat into thrust. But the Moon doesn't have either hydrogen or carbon to make rubber. I suggest powdered aluminum fed directly into a rocket combustion chamber with the same powder handling equipment used for industrial manufacturing. Feed liquid oxygen as the oxidiser. Use an excess of liquid oxygen so the heat will boil the excess LOX and use that to generate thrust. The specific impulse will not be as good as LH2/LOX, but it is a fuel you can make from lunar soil. Therefore, it is Lunar ISPP. The key technology will be the rocket engine. Can you design a powder fuel pump that operates at rocket engine pressure and throughput?

The vehicle for the Moon will require a landing rocket and legs for a tail-down landing. That will look quite different from a horizontal landing, wheeled aircraft. You don't need wings or a shaped lifting body for the Moon, you don't need any heat shield, you don't need aerodynamic control surfaces, but you do need control rockets and tail-down landing. With its lower thrust requirements I would argue it is quite different than a reusable spacecraft design for a planetary atmosphere. You don't need a separate orbital transfer vehicle and lander for the Moon, the lander could travel from Earth orbit to the Lunar surface. The only part that could be applicable to Earth orbit that isn't useful to the transit and lunar surface would be a heat shield for aerocapture and aerobraking. So I argue for a dedicated Lunar vehicle.

This gets to one point that Robert Zubrin raised. He wanted to use the Martin vehicles for a Lunar mission so they can be proven on the Moon before going to Mars. If your sole focus is Mars that may make sense, but a Lunar mission does not require the addition space that the Mars habitat provides. The whole mission architecture of aerocapture or direct atmospheric entry and ISPP for the return to Earth does not follow on the Moon, so the ERV is not applicable. That means the Mars vehicles are not applicable; we would need a dedicated Moon spacecraft. That raises into question the applicability of any attempt to prove equipment on the Moon for a mission to Mars. In fact, as a few Mars Society members have pointed out, the total delta-V for a Moon mission and back is greater than Mars due to aerocapture and ISPP. How much hardware for a Lunar mission would really be applicable for a Mars mission? If we only get one extraterrestrial destination, I pick Mars.

RobertDyck · 2003-11-27 09:03:33

Robert, would the TransHab inflatable be sufficiently durable for multiple round trips from Earth to Mars? How would the heat shields be serviced or replaced?

Hopefully TransHAB is sufficiently durable for multiple round trips. I'm afraid I don't really know. For a micrometeoroid shield it uses multiple layers of nomex, open cell foam, and ballistic kevlar fabric. The nomex breaks the micrometeoroid into fragments, the foam holds the nomex away from the kevlar so the fragments can separate, then the fragments are stopped by the kevlar. Kevlar is the same fabric as bullet-proof vests. TransHAB uses 3 layers of this sandwich. Eventually the micrometeoroid shield will accumulate enough holes that it won't function safely anymore, but I don't know how long that would take. The ideal would be to put one on ISS so we could see how long it lasts in space.

A heat shield for aerocapture must endure a lot of heat, but not as much as direct entry. You can design it as a radiative heat shield rather than ablative. So it gets hot and radiates heat into space. You probably want to use some sort of stand-off between the heat shield and the spacecraft. A solid radiative heat shield should be reusable so many times that it would last longer than the solar panels. We have seen with Hubble that solar panels accumulate micrometeoroid damage and have to be replaced, but Hubble has its third set now so that proves they can be replaced.

GCNRevenger · 2003-11-27 23:01:49

I would love to set out on a trip to Mars, but that is still a far bigger undertaking than a trip to the Moon if for no other reason the sheer distances involved. Zubrin's MD concept is also shakey due to many shortcomings and frankly is simply not very robust. A really robust mission that would actually permit real work to be done is a major national decision that would take a great deal of investment... which is just not going to happen any time soon.

I agree that using the Moon as a testing ground for Mars hardware is not a good idea. Hence, the Moon itself should be the destination. At the very least, it would be good experience in having humans live further from Earth with a minimum of imported reasources. Any activity that advances that capability is a worthwhile investment.

Although the idea of using metalic aluminum and LOX for fuel is a interesting idea, I doubt that it would be practical. You can't really "feed" solid aluminum powder at the nessesarry pressures into the reaction chaimber: the fuel must be pushed into it (hence the extremely powerful turbopumps) to achieve decent thrust per amount of engine weight. A solid-core hybrid engine somehow based on aluminum without the polybutadiene binders would also be difficult to operate and probobly be of low performance. You must also consider the huge energy investment in seperating and cracking the aluminum oxide, which I am certain is at least as bad or worse than cracking water.

If there is insufficent water ice in the Lunar soil to make signifigant amounts of rocket fuel, then we should forget the Moon and focus on Mars hardware even if budgets will be slashed and public interest dissapates, since we really have no place else to go.

RobertDyck · 2003-11-28 09:41:50

I would love to set out on a trip to Mars, but that is still a far bigger undertaking than a trip to the Moon if for no other reason the sheer distances involved. Zubrin's MD concept is also shakey due to many shortcomings and frankly is simply not very robust.

Ooh, arguing against a Mars mission on a message board for a society dedicated to sending a Mars mission as soon as possible. That is at best brave.

Dr. Zubrin's Mars Direct concept has a small return vehicle, but other than that it is sound. I have argued for updating the mission plan with modern 21st century technology and improving the return vehicle, but that does not mean the original idea was flawed. I will not be cowed into advocating Robert Zubrin's idea with no improvement, if that is your intent. Neither will I stand by while someone calls his mission plan "shakey".

Let's put it simply. We can go to Mars, we can go now, we would have been on Mars in 1999 if Congress approved Mars Direct in 1990/91. We don't need multiple decades of new technology development. In fact, we don't need any new revolutionary technology at all. A nuclear engine would be nice, but it isn't necessary at all. A new spacesuit is required, but we can use mid-to-late 1960's technology to do it. A closed loop recycling life support system is required, but the proposed system for the US habitat on ISS is good enough.

The Moon has one simple flaw: Been there, done that. What would we prove by going there again? There aren't sufficient resources to sustain a self-sufficient colony. It would be a great location for telescopes, but you don't need a permanently manned facility to operate a telescope. We have talked about Lunar water before; water ice found by Lunar Prospector is just not concentrated enough as a source for rocket fuel.

Keeping public interest will require a rapid series of significant achievements. That means go to Mars and keep going. You can't stop. In fact, the two years between manned missions are too great to sustain public interest. It will require continuing reports from Mars similar to the photos from MGS and Odyssey. That shouldn't be hard, just schedule regular video reports from the astronauts. Build a greenhouse and use Mars resources to build a simple shelter, demonstrating a colony could be established. You could follow the Mars landing with construction of a planet imaging interferometer telescope on the Moon's equator. That telescope could take an image of an Earth size planet orbiting another star. Now THAT would get the public's interest. But constructing a telescope is no way to start a sustained human presence in space; we will need a Mars base. We can also mine asteroids for rocket fuel and precious metals. Once asteroid mining companies start making a fortune on precious metals it will get the attention of big business. But it all has to start with a manned mission to Mars.

Palomar · 2003-11-28 10:04:29

I would love to set out on a trip to Mars, but that is still a far bigger undertaking than a trip to the Moon if for no other reason the sheer distances involved. Zubrin's MD concept is also shakey due to many shortcomings

*Care to elaborate on what you mean by "many shortcomings" in Zubrin's Mars Direct plan?

Not a challenge; I'm simply curious is all.

[I'm really surprised at how many people on the message board are in favor of returning to the moon prior to heading out for Mars. I've read their posts in that regard and despite stating their opinions on that matter (often very well), I'm not persuaded in the least]

--Cindy

GCNRevenger · 2003-11-28 13:54:08

Hey, don't get me wrong, I would love to go to Mars... But be realistic, there just isn't going to be any Mars mission for quite some time. Going to Mars is a big deal and that will take alot of time and money; things that Nasa neither has nor is likly to be given to that degree.

Since Nasa has to go some place to avoid irrelivence, this destination needs to be close at hand: the Moon, provided there is water ice, will have to do. All tests of the amount of water ice on the Moon have been inconclusive, but if there really isn't any, then Nasa's energies will have to wait for better days with the goal in mind of developing the tech for really robust Mars missions.

If we go to Mars with anything less than colony first and exploration second, MD will turn into Apollo, and we will leave almost as quickly as we came. We COULD try go to Mars today with current technology, but I think it would be a bad idea. We really need better propulsion and to cast off the "save every gram" philosophy of spaceflight, it just doesn't provide needed margins. Even a solid core NTR rocket is only a marginal improvement.

If science and exploration are the goal, which could be served by MD or similar system well enough, then there won't be a "after Mars Direct." MD and our current technology is obviously insufficent for building and tending a signifigant Mars base... it is however good enough for a perminant Moon base, provided there is water ice there. The ultimate reality TV series?

The object of human spaceflight is the real core of this debate I think... I believe it should be to get humanity of this rock for good, and a Moon base would bring this capability closer to our species.

Well if you didn't like all of Mars Direct Robert why didn't you say so? Ecrasez, I don't like Mars Direct for a number of reasons, such as:
1: Low masses to Mars for anything not involving the Hab or ERV with associated equipment, which will promote Apollo style "been there beat the commies done that" thinking. There is hardly enough mass for science gear.
2: Due to direct flight any failure caused by Earth launch, which is hard on a spacecraft, would be catastrophic. The HAB has no abort mode of itself; when the SRBs are lit on the Cape' its Mars or bust.
3: The artifical gravity scheme is frightening from a reliability standpoint, and the lack of artifical gravity for the baseline MD is unacceptable considering the length of the trip either direction. The maximum should be four months on either leg.
4: Insufficent radiation shielding on any of the modules, in Mars Direct or the Nasa DRM. A (rather heavy) water or polymer cosmic radiation shield is a must.
5: Inherint unreuseability, which further promotes "yay Mars, now lets go home" philosophy, combined with low down-mass to Mars makes any sort of perminant base using the system difficult.

The list goes on... now about OSP, for which the thread is about...

Using a lift body OSP for Earth/Moon-Moon/Earth travel is not such a bad idea I think... of course you don't need wheels or wings or heat shields for Lunar travel, but you will want a reuseable cargo lander/transfer vehicle that can haul alot of mass, which could simply mate with OSP in LEO and carry it down tail-first to the Moon, like the Air Force's LUNEX concept. The USAF even thought a lift body could be hardend enough to perform direct re-entry at Earth from Lunar transfer velocities. Building two manned ships with similar abilities that neither can make it to the Moon on their own via a EELV does not make sense to me.

Ah and the much heralded asteroid mining... I hate to continue playing wet blanket, but I don't think that is going to happen, not to Earth anyway. If you mine alot of precious materials, which is a difficult proposition as it is, then they aren't so precious anymore, are they? If you could ship a hundred tons of diamonds down every month, the diamond market would collapse... This is to say nothing about the economics of pushing very heavy things, like Platinum, back to Earth and re-enter them intact with signifigant mass... On the distant-distant horizon, maybe a space elevator to astroids pushed into Earth orbit, but not any time in our lifetimes.

dicktice · 2003-11-29 10:12:03

Too pessimistic! How about considering: Tethered propulsion (1) to discover promising asteroids inside Earth-orbit (2) ditto out to mine the inner asteroids for water ice and any other consumables (3) Lunar orbiting the resulting resources (4) access these for exploiting the Moon. All based on having the ISS in place as the necessary way-station and anchor for the tethered orbital transfers. Solar-steam jet propulsion, radiation shielding and cracking by electrolysis for H2 and O2 fuel components, subsequent to the asteroid ice becoming available. The OSP's, and tugs and manned-Mars would naturally follow, in that order. Sounds do-able, and as adventurous as need be to keep us taxpayers who care entertained, seems to me. . . .

GCNRevenger · 2003-11-29 13:09:27

I think that any sort of rotating tether system is still a distant technology if it is possible at all. The USAF can't even make an autopilot that can do mid-air refueling with planes going similar speed to hook up a hose, the ability to connect structurally to a teather accuratly as it wizzes by is impractical, if you could do the timing reliably at all. Picking up paylaods from the ground sounds like a nightmare to do accuratly, and won't the tether end be traveling at extremely high speeds? What if you miss and hit your pick-up pad? BOOM, ready made space inertia powerd kenetic missile. No mechanical or especially no manned system could survive the acceleration of a ground pickup either.

Making a tether strong enough in the first place is questionable even with the coming of continuous carbon nanotube polymer composits. Then there is the question if the tether could withstand micrometeoroid impacts at all... If there is any incarnation of a tether, it will be in the form of a space elevator that stays put. Also, a Lunar space elevator is impractical given the Moon's rotation and orbit. But in any event, I say with certainty that an Earth space elevator that can do more than haul small satelites is some distance away.

I reiterate that mining asteroids for minerals is a terrible idea economicly, since flooding the market with cheap precious minerals would destroy said market. Base minerals are much easier to mine here and will be for the foreseeable future, even with low ore quality, compared with how hard it would be to push an asteroid or its ores back to Earth.

Now, if you found a dead comet with alot of water ice, then it might be useful to mine it for rocket fuel, but any sort of operation will have to be highly automated, since Astronauts can't spend more than about 6mo up before getting dangerously deconditioned. Such a zero-G mining aparatus would be pretty heavy and extremely expensive too I imagine.

I would be interested to see a cost comparison between water mining and simply launching 120 tons of LH/LOX from Earth with SDV to a LEO "gas station" equipped with boiloff liquifiers. If Nasa does SDV right, and scuttles as much of the Shuttle = Manned overhead, each SDV could perhaps cost only a quarter billion apiece or less.

In the long run, when ice cracking and zero-G mining becomes much more refined, then the ease of mining asteroids for water might make sense. However, even this is questionable if a Scramjet SSTO really could make simply hauling up Earth fuel competitive as Nasa seems to think.

ISS is useless for travel beyond LEO. The amount of propulsion required to push the ISS out of the "Russian Partnership" orbit and down to equitorial is substantial, and I don't think ISS will be in service long enough to make such a large project worthwhile. Nor is ISS very useful in the first place for basing such missions... what do you really need? A truss for some fuel tanks, some solar pannels, and boiloff liquifiers. It doesn't even need to be manned with the aid of a orbital tug and docking beacons. Everything but the tanks could be lofted with a single SDV launch.

If your ship requires some assembly, then it should be done like the first componets of ISS; two modules, one with propulsion for docking mates with the other at least structurally. An OSP crew goes up and attaches any hoses and wires then does startup and testing. Or if it is more than two modules, or perhaps you are building a space station, a refuelable orbital tug would be ideal. Perhaps it could be powerd by nuclear electric, with its excelent fuel efficency?

I have little faith in taxpayer attention span... as much as I hate the analogy, manned spaceflight must take a more "highway building" stance: start a perminant manned base on the Moon (provided fuel is easily available) with no "end of life" as with ISS, and make the investment so irrevocable that the future government just can't pull the plug.

RobertDyck · 2003-11-29 14:48:39

I have already said that water ice found by Lunar Prospector is too spread-out to be economically mined for rocket fuel. Furthermore, telescopes have to be located on the lunar equator if that are to be able to view the whole sky. The equator is a long way from either pole. One reason I agrued for aluminum powder as rocket fuel is that is the only resource I know of that will be available at the lunar equator. If it can't be used for rocket fuel, then let's give up on the moon.

Getting back to the topic for this thread: capsule vs. wings or lifting body. I argue for a dedicated surface to LEO crew taxi for all missions. Mars should have a reusable Earth orbit to Mars orbit transfer vehicle. Any moon mission should also have a reusable transfer vehicle, but since the moon is airless such a vehicle could go from LEO to the lunar surface. That requires a reusable OSP that can go from Earth surface to LEO and back. All capsules to date have been expendable, and designing a reusable capsule would fight against the tendencies of the contractors to build a copy of what they have already done. A lifting body is not as heavy as wings, and all designs to date have been reusable. (Well, the de-orbit module of X-38 wasn't reusable.) A shallow entry to permit use of existing reusable heat shields are difficult to control with a capsule, but easy for a winged or lifting body vehicle. The cross-range flying capability of a winged or lifting body vehicle was argued by yourself in this thread, GCNRevenger. You could use skids to land on a salt flat, meadow, farmer's field, or other open land. You could also use wheels to land at any airport in the world, and there are a lot of them now. It would be easier and less expensive to recover a lifting body vehicle that could be carried on a flat bed medium truck with dual rear axle and a truck crane, than an ocean recovery fleet. Then you could drive it back to Florida.

GCNRevenger · 2003-11-29 17:47:10

If memory serves, there was some question about the calibration of said insturment... in any event, we won't know for sure unless we send a rover with soil oven and a mass spectrometer or somthing, which Nasa ought to make priority one after launching Pluto Express. I agree that any base in a signifigant gravity well without a mostly indiginous supply of fuel is a bad idea, but don't write off the Moon just yet.

I also had a little brainstorm... since there is alot of oxygen on the Moon in the form of oxides and such, I wonder, could a NTR engine be built to operate on LOX instead of LH? I think the Russians thought about using Ammonia back in the Apollo days in their NTR, though handling multi-thousand-degree oxygen gas would present engine corrosion issues. The Russian engine would have had similar Isp to regular LOX/LH, though Ammonia is much lighter than Oxygen per mole. With the plentiful supply of ultraviolet light, you could also make all the Ozone you could ever want, if there is a good use for it. It is a somewhat more powerful oxidizer than Oxygen, but a pain to handle.

Carrying OSP out to the Moon would save having to build a second manned ship at all, though keeping OSP in LEO would probobly make it easier to build. A LEO-to-Moon transfer/lander would be very desireable for cargo duty, and I guess making a manned version would not be that hard considering the benign envelope it would operate in. Maybe it could be TransHab based and both models areobrake into LEO?

I pretty much agree with the rest of your post, except that flying a lift body or winged ship back down is somewhat more delicate than the "sledgehammer" capsule aproach. Shuttle has done a marvelous job, though probobly no true lift body or winged craft will meet Nasa's "dead stick" requirement for surviveable re-entry without getting pretty heavy... I think Nasa ought to have its head examined for safety-parinoia over this one. If you don't have power, then chances are you are hosed anyway.

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