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Tom Kalbfus

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Re: The SLS: too expensive for exploration?

Problem is, why do a few governments only, get to decide how much to invest in it? The government didn't invent the automobile, it didn't invent the airplane. No one in congress could simply pull the plug and then have no flights going to anywhere. The problem is the technology up to now for space flight hasn't been self-sustaining. No one has found a way for space exploration and settlement to fund itself, rather than going to various legislative bodies, hat in hand, begging for more money! If space exploration isn't dependent on government subsidy, then the government can't pull the plug.

A very good post I think! 

A lot of this has to do with the amount of effort - intellectual, cultural and resourcing - you are prepared to put in.  If no one had bought cars, then the development of automobiles would have been much slower.  Likewise, with space travel, if the USSR and USA not not invested huge resources in the 50s and 60s we would not have got very far. 

There is no doubt in my mind that humans to Mars, space colonisation and off planet ISRU have been the victims of under-investment.

I think one of the evolutions was from wood/ canvas to metals which was one thing that I can see from the images.

For sls the changes would seem to be the means to get to orbit to orbit and back with cargo loading being done by ion drive.

The next is mission duration without support from the earth surface on a regular scheduel to resupply what we need....

It just seems to me that waiting til 2043, when I will be 76 years old, seems like an awful long time to wait just to see 4 people walk on Mars. World War I is not long after Wilbur and Orville flew their Wright Flier, I think the progress they saw until 1943 was a lot more that NASA is assuming in this plan. I think by 1943, we could do a lot more than fly four people across the Atlantic.

I think the point is, I was born at an inflexion point in history, all the years before I was born, since the beginning of the 20th century was marked by the rapid advance of technology on all fronts, and suddenly after I was born, the brakes were applied and everything stayed pretty much the same, with only incremental developments in existing technology, which is what NASA seems to be assuming here. So why was the point of my birth so important as to cause the brakes to be applied soon after? Did they say, lets stop innovating? Why does the 21st century thus far look so much like the late 20th century. 50 years after the dawn of aviation, we had transcontinental flights across the Atlantic, but we're progressing through the so called "Space Age" like a crippled ant! I guess I am spoiled, throughout my childhood, I expected a great deal more technological progress that what actually occurred, children who were born around the year 2000, have grown quite accustomed to this nonprogress, it seems perfectly natural to them, while I was born when World War II was only a generation away.

http://blog.seattlepi.com/thebigblog/fi … _crop1.jpg
Seattle 1916
http://3.bp.blogspot.com/_FfetiF7C9vo/S … cident.JPG
1926
http://photos.francisfrith.com/frith/le … 87371x.jpg
1936
http://i.ebayimg.com/00/s/NjYxWDEwMjQ=/ … ~60_35.JPG
1946
http://4.bp.blogspot.com/-b3eR7Gq5i5M/U … 56+(3).jpg
1956
http://photos.francisfrith.com/frith/po … _large.jpg
1966
http://assets.blog.hemmings.com/wp-cont … 1_1500.jpg
1976
This sequence of pictures represents some of the technological progress up until I reach the age of 9
http://farm9.staticflickr.com/8096/8499 … b254_z.jpg
1986
http://www.foundsf.org/images/e/ee/Bayv … t-1996.jpg
1996
http://www.edinphoto.org.uk/0_STREET/0_ … nelson.jpg
2006
http://image.hotrod.com/f/116385254+re0 … six-15.jpg
2016
The 21st century has been rather mundane compared to what I was expecting.
http://www.seriouswonder.com/wp-content … tion-1.jpg

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,433

Re: The SLS: too expensive for exploration?

Now back to Say what...NASA examines options and flight paths for SLS EM-2 mission

Presently, EM-2 is baselined as a High Lunar Orbit (HLO) mission or maybe not as the “Evolution of Orion Mission Design for Exploration Missions 1 and 2” report, Orion and its crew, through the Trans-Lunar Injection (TLI) burn, will be placed into a free return trajectory to a nominal Earth Entry Interface condition.

or this path:

nah maybe this one:

Really more indecision....

kbd512

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Re: The SLS: too expensive for exploration?

Problem is, why do a few governments only, get to decide how much to invest in it? The government didn't invent the automobile, it didn't invent the airplane. No one in congress could simply pull the plug and then have no flights going to anywhere. The problem is the technology up to now for space flight hasn't been self-sustaining. No one has found a way for space exploration and settlement to fund itself, rather than going to various legislative bodies, hat in hand, begging for more money! If space exploration isn't dependent on government subsidy, then the government can't pull the plug.

Tom,

At present, only governments are investing serious funding into human space flight activities.  The cost of launching rockets with payloads of any substantial mass is so prohibitively high that only public funding can pay for the expenses associated with this activity.

You pretty much hit the nail on the head, with respect to why it is that there is not greater private investment into space flight activities.  Apart from government contracts, there's no identified economic incentives for settlements on other planets and no business case for undertaking commercial activities in space, such as mining.  There's enough materials resources available in our solar system to sustain us indefinitely.  Our little corner of the Milky Way is chock full of metals, minerals, and gases that are extremely costly here on Earth.  Even if we found an asteroid comprised of pure platinum, the cost of taking the materials back to a processing facility is greater than the cost of the materials.

The most profound stumbling block, with respect to the affordability of space flight activities, has been the monumental cost associated with development and production of rockets that are used for a few minutes to escape Earth's gravity and then subsequently dumped into the ocean like trash.  If you told American Airlines or even the US Air Force that you'd sell them a $100M+ aircraft that they could fly for 10 minutes and then the aircraft would be destroyed and they'd have to pay for a replacement, they'd look at you like you'd lost your mind.  Well, that's exactly what we have with current rocket technology.  And some of those rockets cost substantially more than $100M.

Our government won't stop funding space exploration activities.  There's simply too much to lose.  Believe it or not, even within our Congress and Senate, there are people who understand that not every research and development activity has immediate and clearly defined payoff.

SpaceNut

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Re: The SLS: too expensive for exploration?

Precision meets progress in welding on SLS liquid oxygen tanks for the Block I configuration of the rocket.

Towering more than 200 feet tall with a diameter of 27.6 feet, the core stage will store cryogenic liquid hydrogen and liquid oxygen that will feed the vehicle's RS-25 engines.

SpaceNut

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Re: The SLS: too expensive for exploration?

So why is Nasa still playing games with what engines are to be used and with what contract shall they be used at what cost....
MSFC propose Aerojet Rocketdyne supply EUS engines  has issued a “Justification for Other Than Full and Open Competition (JOFOC)” solicitation in support of sole sourcing RL10 engines for the Exploration Upper Stage (EUS) from Aerojet Rocketdyne. The document calls for an initial order of 10 engines to cover the first two flights of the Space Launch System (SLS) with the powerful upper stage.

with just 4 engines used per stage thats just 2 flights....

The order of 10 engines (eight flight-assigned engines and two spares) has a cost figure, although that figure was redacted from the document.

The contract has an estimated period of performance from the date of execution through December 31, 2023 – although engine delivery is required two full years ahead of the expected launch dates.

Funny no contract cost....and it takes 2 years to make them....wow

RobertDyck

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Re: The SLS: too expensive for exploration?

So why is Nasa still playing games with what engines are to be used and with what contract shall they be used at what cost....

The initial plan was to switch to this new upper stage after the crewed EM-2 mission. However, as previously reported by this site, NASA wishes to advance this plan.

The debut of SLS will be known as the “Block 1”, sporting a Delta Cryogenic Second Stage (DCSS), renamed the Interim Cryogenic Propulsion System (ICPS) for SLS. The original plan called for two DCSS orders (EM-1 and EM-2) before NASA placed a stop work order on the second unit.

Aeroject Rocketdyne makes RL-10 engines. The manufacturer has changed ownership several times since the 1960s. Delta Cryogenic Upper Stage is manufactured by United Launch Alliance. I'm sure this is corporate lawyers and Congressional lobbyists don't want to lose the contract for that second upper stage.

Funny no contract cost....and it takes 2 years to make them....wow

Yea

GW Johnson

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From: McGregor, Texas USA

Registered: 2011-12-04

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Re: The SLS: too expensive for exploration?

The guys who actually produced RL-10's at Rocketdyne long ago are now all dead or retired. 

Corporations,  especially those undergoing mergers and acquisitions,  never encourage employees to document anything but what the contract requires. 

Contract requirements ARE NOT WRITTEN by engineers,  which is why contracts never required any of those people to write down everything needed to produce an RL-10 from the cookbook. 

Corporate management likes to believe it can hire high-school dropouts cheap to produce any technology from the cookbook,  which is AT BEST an egregious fallacy.  Precisely because they always refuse to pay for a real,  comprehensive cookbook. 

That's why I keep saying rocket science IS NOT science.  It is at most 40% science,  it is about 50% or more art that no one ever paid to have written down,  and it's about 10% blind dumb luck,  or maybe more.  And that's in production work.  In R&D,  the art and luck percentages are higher still.  Been there and done that.  Seen it from the inside.  Trust me,  I speak the truth.  And it's true of all engineering,  not just rocketry. 

Given that any cookbooks are woefully incomplete,  then why should it surprise any of you that RL-10's cost a whole lot more in smaller numbers today,  than 50 years ago? 

Same company identity does not matter.  What matters is the people who did it before,  who are now no longer there.  The real question is:  did the company pay to have them train on-the-job the next generation,  or not?

My experience says they did not.

GW

Last edited by GW Johnson (2016-04-08 17:42:51)

---

GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

SpaceNut

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Re: The SLS: too expensive for exploration?

Rather than trying to machine many of the parts they are looking towards the use of 3 D printing to help with the art of manufacturing a steady state device...with pieces that are assembled into the RL-10....

GW Johnson

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From: McGregor, Texas USA

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Re: The SLS: too expensive for exploration?

3-D printing is great,  except that I am very skeptical of the mechanical properties of 3-D printed metal parts.  Nothing I have seen suggests those properties are any better than a sintered-metal part. 

Those are relatively weak,  and very susceptible to brittle failure behavior.  Hardly any ductility or resilience at all.  That is one lousy material to make a highly-loaded pressure-vessel part,  like a rocket chamber,  or a nozzle,  or an injector plate,  or anything at all to do with a turbopump assembly. 

I wouldn't bet a plug nickel on the reliability of an RL-10 made that way.  It'd very likely shatter like glass upon ignition,  especially if cold. 

I would't want a hand wrench or a socket set made from stuff like that. 

GW

---

GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

RobertDyck

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Re: The SLS: too expensive for exploration?

There are several different technologies all called "3D printed". Two general categories are additive of subtractive. Subtractive is nothing more than a CNC milling machine. Additive is more efficient in terms of material, it doesn't waste as much. There are many methods for plastic, but the only additive method I've heard of for metal is to blow powdered metal onto a form and melt the powder with a high intensity laser. That's the same process as sintering, just using a computer controlled method of delivering material instead of a mould. So it *IS* a sintered metal part. This would have all the issues GW Johnson raised.

What does SpaceX use? I saw a video, a tour of the facility by Elon Musk himself. At one point he showed the machines, they're CNC milling machines. That produces much higher quality part than sintering. What do the others use?

SpaceNut

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Re: The SLS: too expensive for exploration?

http://www.nasa.gov/exploration/systems … ector.html

The component was manufactured using selective laser melting. This method built up layers of nickel-chromium alloy powder to make the complex, subscale injector with its 28 elements for channeling and mixing propellants. One of the keys to reducing the cost of rocket parts is minimizing the number of components. This injector had only two parts, whereas a similar injector tested earlier had 115 parts. Fewer parts require less assembly effort, which means complex parts made with 3-D printing have the potential for significant cost savings. Early data from the test, conducted at pressures up to 1,400 pounds per square inch absolute and at almost 6,000 degrees Fahrenheit, indicate the injector worked flawlessly.

http://www.nasa.gov/centers/marshall/ne … ngine.html

A NASA team moved a step closer to building a completely 3-D printed, high-performance rocket engine by manufacturing complex engine parts and test firing them together with cryogenic liquid hydrogen and oxygen to produce 20,000 pounds of thrust. “We manufactured and then tested about 75 percent of the parts needed to build a 3-D printed rocket engine,” Seven tests were performed with the longest tests lasting 10 seconds. During the tests, the 3-D printed demonstrator engine experienced all the extreme environments inside a flight rocket engine where fuel is burned at greater than 6,000 degrees Fahrenheit (3,315 degrees Celsius) to produce thrust. The turbopump delivers the fuel in the form of liquid hydrogen cooled below 400 degrees Fahrenheit (-240 degrees Celsius).

http://www.popularmechanics.com/space/r … -15146569/

Vickers says, an engine injector made with conventional fabrication techniques of molding and welding might cost in the range of $250,000. "We hope to reduce that by a factor of 10 and get in the range of $25,000," Vickers says. "That's huge when you start talking about reducing the cost." Production times could also dwindle from six months to just weeks.

http://www.aerospace-technology.com/new … ne-4759158

The test firing was conducted using cryogenic liquid hydrogen and liquid oxygen that produced 20,000p of thrust.

For the last three years, the team at Marshall have been working with several groups to build 3D printed parts, including turbopumps and injectors, and test them separately.

However, they have recently tested the parts together by connecting the parts in the same way as in the case of a real engine, although the parts were not packed up together to look like a typical engine.

Seven tests were conducted during the recent test and the longest was ten seconds.

The 3D printed demonstrator engine had to undergo all the extreme environments, experienced inside a flight rocket engine during the test.

NASA Alabama Marshall Space Flight Centre additively manufactured demonstrator engine project manager Elizabeth Robertson said: "We manufactured and then tested about 75% of the parts needed to build a 3D printed rocket engine.

http://www.3dprinterworld.com/article/s … d-printing

The group recently test fired the metallic engine fueled by kerosene and liquid oxygen creating 200 pounds of thrust.

SpaceNut

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Re: The SLS: too expensive for exploration?

I look at actions (money is involved) not words (talk is cheap).  I think based on actions for many years that NASA really,  really doesn't want to send men anywhere but cis-lunar space on missions of 2 to 4 weeks duration.  They only want to reprise Apollo and similar,  with men.  If that were not true,  then we would be building something other than a botched reprise of a Saturn moon rocket with shuttle technology,  and something more than Apollo-on-steroids for a cramped capsule to ride in. 

If NASA was serious about sending men beyond the moon,  they'd already have been working on this issue.  Or,  they'd be chomping at the bit to try an idea like this.  If I can sit down and come up with ideas like this in under half an hour, how come they haven't already done so?

Well,  THAT'S why I say they really don't want to send men to Mars. 

Musk does.

I hope his people see this.

GW

repost reflects sentiment of Nasa's SLS program....

To which we need Space x and others to start to fund the flights via the cheaper access to space and by providing the products that are needed.

Tom Kalbfus

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Re: The SLS: too expensive for exploration?

Well you know what SLS stands for SLOW! I think the SLS can be sold to somebody who could pick up the pace a bit. If SpaceX is a big success, there will be would be competitors who might like to get a head start by buying the SLS, and will get investor money to complete it, instead of going to Congress for appropriations. Perhaps someone can figure out how to reuse the lower stages of the SLS, seeing how they use Shuttle Engines, and those are designed to be reused anyway!

SpaceNut

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Re: The SLS: too expensive for exploration?

The way that the contract writing has been presented I would not put it past the contractors to have clauses that state they can only sell to Nasa for the parts that are made for the SLS.
The RS25 engine is also no longer made and only so many remain to remanufacture if we were able to get them back from the depths of the ocean after each flight as there is no landing pad available for such a large rocket except for landing on hard bare earth....
Plus doing so would be a 40 percent cut in payload to earth orbit....
I agree that the snails pace of designing and building the SLS is and has become way to long but how do we speed such things up?

SpaceNut

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Re: The SLS: too expensive for exploration?

Orbital ATK completes installation of world's largest solid rocket motor

Orbital ATK in partnership with NASA, has completed installing the second Space Launch System (SLS) booster qualification motor, QM-2, in a specialized test stand in Utah in preparation for a June 28 static-fire test. QM-2 is the second of two Orbital ATK-developed motors to support qualification of the boosters for NASA's SLS, which is a heavy-lift rocket designed to enable exciting new deep space exploration missions. The first qualification motor, QM-1, completed a successful test last spring. last year's QM-1 test validated motor performance at the upper end of the propellant temperature range, Orbital ATK personnel are cooling QM-2 to 40 degrees Fahrenheit to test its lower temperature capabilities against the required temperature range.

Orion Exploration Mission-1 Crew Module Pressure Tested

Spacecraft Approved for Assembly of Secondary Structures

In order to certify the structural integrity of the crew module it was outfitted with approximately 850 instruments and subjected to 1.25 times the maximum pressure the capsule is expected to experience during its deep space missions. That means about 20 pounds per square inch of pressure was distributed over the entire inner surface of the spacecraft trying to burst it from within. As a next step, the team will use phased array technology to inspect all of the spacecraft's welds in order to ensure there are no defects.

On the make work side of the coin "A network of hundreds of suppliers representing 49 states supports the SLS and Orion programs. Orbital ATK has 29 key SLS booster suppliers across 16 states including Alabama, Arizona, California, Connecticut, Indiana, Kentucky, Massachusetts, Minnesota, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Texas, Utah and Wisconsin."

Tom Kalbfus

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Re: The SLS: too expensive for exploration?

I wonder if a Falcon 9 could be substituted for Solid Rocket and placed on the side of the SLS. Solid rockets have the advantage when you want to store them someplace for a long time without worrying about the liquid fuel boiling off, someplace like a missile silo for instance. I think a good application for a solid rocket motor would be in the ascent stage of a Lunar Lander, the solid rocket would have enough propellant for a return to Earth directly from the moon's surface. some finer control rockets would adjust the trajectory so that it enters the Earth's atmosphere at the right angle so it neither burns up or skips off into space. This would imply that part of the ascent stage would be an Orion capsule. Of course the moon lander would have to be more massive as a result. I think perhaps in orbit assembly would be useful here. A solid rocket motor ascent stage would make it as reliable as an ICBM in its silo, Astronauts can explore the Moon's surface for as long as they like without worrying about the ascent stage, and when they are ready, they get onboard and press the button, the flight computers and reaction jets do the rest after the solid rocket underneath ignites.

RobertDyck

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Re: The SLS: too expensive for exploration?

Graphite-Epoxy Motor (GEM) is the solid rocket for Delta IV and Atlas V, and proposed for Vulcan. GEM 40 has specific impulse of 274s at high altitude (near vacuum), or  245s at sea level. Apollo Lunar Module ascent propulsion system used N2O4 / Aerozine 50, with Isp=311s. Liquid methane boils at -161.49°C at 1 atmosphere pressure, and LOX at -182.962°C. The surface of the Moon is -123°C in shade. LOX/LCH4 could be kept liquid in space with sufficient insulation because space is -270.45°C in shade. Spacesuits are rated for +120°C to -150°C, sunlight vs shade. A service module using LCH4/LOX would require very good insulation, and probably a radiator in permanent shade. A lunar spacecraft is expected to operate in 24/7 sunlight, and sit in direct contact with the ground. When the ground is in sunlight. Raising it off the ground with legs and multi-layer insulation help, but LCH4/LOX doesn't sound like the right choice for a lunar lander. Serivce module yes, but not LM. However, you suggested solid. Main engines of the ATV are R-4D-11 use MMH/N2O4, Isp=312s. Would that be a better choice for the Moon?

Tom Kalbfus

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Re: The SLS: too expensive for exploration?

Graphite-Epoxy Motor (GEM) is the solid rocket for Delta IV and Atlas V, and proposed for Vulcan. GEM 40 has specific impulse of 274s at high altitude (near vacuum), or  245s at sea level. Apollo Lunar Module ascent propulsion system used N2O4 / Aerozine 50, with Isp=311s. Liquid methane boils at -161.49°C at 1 atmosphere pressure, and LOX at -182.962°C. The surface of the Moon is -123°C in shade. LOX/LCH4 could be kept liquid in space with sufficient insulation because space is -270.45°C in shade. Spacesuits are rated for +120°C to -150°C, sunlight vs shade. A service module using LCH4/LOX would require very good insulation, and probably a radiator in permanent shade. A lunar spacecraft is expected to operate in 24/7 sunlight, and sit in direct contact with the ground. When the ground is in sunlight. Raising it off the ground with legs and multi-layer insulation help, but LCH4/LOX doesn't sound like the right choice for a lunar lander. Serivce module yes, but not LM. However, you suggested solid. Main engines of the ATV are R-4D-11 use MMH/N2O4, Isp=312s. Would that be a better choice for the Moon?

I think since Moon missions are expensive, expect around 1 or 2 a year, given that they are expensive, we will want long stays on the Moon, kind of like ISS crew rotations. I think a manned mission on the Moon lasting 6 months would not be unreasonable, so we would want a lander that could last just as long, we wouldn't want fuel boil off to limit the duration of the crew's stay. I'm not sure we need a service or command module in Lunar orbit either. Before the Apollo architecture, there was a proposal to have command module on the ascent vehicle, that way you don't need a lunar orbit rendezvous. The Ascent module accelerates to lunar escape velocity towards Earth, and can do so at any time. So in an emergency the crew could be headed towards Earth in minutes.

remember this? We could build a version that could carry an Orion module from the Moon's surface all the way back to Earth.

Last edited by Tom Kalbfus (2016-05-14 13:35:04)

RobertDyck

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Re: The SLS: too expensive for exploration?

Hypergolic fuels don't boil off: Aerozine 50, UDMH, or MMH. That's why they're used. N2O4 oxidizer doesn't boil off either. Density of N2O4 changes with temperature, but you just design a tank to take it at whatever temperature in the environment it will operate.

The reason Apollo was changed to CSM & LM was because direct launch would not fit on a Saturn V. It required Saturn C8, aka Nova.

Tom Kalbfus

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Re: The SLS: too expensive for exploration?

Then why do ICBMS use solids? Why don't they use hypergolic fuel in ICBMs? ICBMs are designed to sit in a silo and launch at a moments notice, they are designed to be reliable. Wouldn't you want that for an Earth return vehicle. Also what happens if something goes wrong with the Command Module when the astronauts are on the Moon's surface? Also isn't there the option of in orbit assembly? That is what you are proposing for Mars Missions.

RobertDyck

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Re: The SLS: too expensive for exploration?

Russian ICBMs do use UDMH & N2O4. American missiles use solids for the reasons you gave. They built them to do the job, so what if they're heavy. They're just transported by truck to a silo, then sit in a silo for years. They aren't intended to be delivered to the Moon.

Liquid rockets can be throttled, and launch abort is possible. With a solid you hit the "fire" button, then forget about it. Do nothing until it blows up on the enemy target.

Tom Kalbfus

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Re: The SLS: too expensive for exploration?

Russian ICBMs do use UDMH & N2O4. American missiles use solids for the reasons you gave. They built them to do the job, so what if they're heavy. They're just transported by truck to a silo, then sit in a silo for years. They aren't intended to be delivered to the Moon.

Liquid rockets can be throttled, and launch abort is possible. With a solid you hit the "fire" button, then forget about it. Do nothing until it blows up on the enemy target.

Why would you want to abort the launch if you are lifting off from the Moon? If you landed safely somewhere after aborting the launch from the Moon, you are still going to die when your air runs out. An aborted launch on the Moon is not the same as an aborted launch on Earth. On Earth if you land safely, you can go to a hospital, get checked out and go home. On the Moon, if you land safely, you just wait to die, or maybe wait to be rescued, that means of course that NASA cancels the next mission to launch a rescue mission of the stranded astronauts!

We've been lucky in the space program, whenever there was a failure, the astronauts either died immediately or were saved, as in Apollo 13, there was no failure where the astronaut we're doomed and they had days or weeks to think about it as their supplies ran out.

How does this scenario strike you. Suppose there are astronauts on the Moon, and we have a fuel tank explosion in the command module as its orbiting the Moon (such as had occurred during the Apollo 13 mission for instance), leaving it as a useless piece of space junk. Now the Lunar ascent stage can reach Lunar orbit and it runs out of fuel with no command module to take them back to Earth, or the astronauts can choose to remain on the Moon and wait to die there. Which would you prefer?

RobertDyck

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Re: The SLS: too expensive for exploration?

Solid Isp=274s. MMH/N2O4 Isp=312s. Why would you chose something worse?
Throttle=Good. No control=Bad.
I'm arguing for essentially the same fuel used by Apollo. This exact fuel mixture was used by Apollo SM thruster quads. Apollo ascent stage used Aerozine 50; the difference between MMH and Aerozine 50 is technical, we've already discussed it. And I'm sure you and everyone reading this knows that.
These are storeable propellants, meaning they don't boil off *AT ALL* in Lunar conditions. That includes UDMH, MMH, Aerozine 50, and oxidizer N2O4. That's why they were used. I don't think I'm being unreasonable when I say the same fuel system as Apollo is preferable to solids.

RobertDyck

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Re: The SLS: too expensive for exploration?

Here's a question: what would it take to store soft cryogenics? I said above that good multi-layer insulation plus a radiator exposed to the cold of space should do it. Is that enough? What happens when the craft manoeuvres? Should the craft be designed with a gas capture tank for boil-off, and refrigeration pump for liquefaction? Or active refrigeration without capturing boil-off?

Note: a couple reasons Lockheed-Martin won the contract for Orion was the air-bag landing system, and use of LCH4/LOX for the service module. Both have been removed.

Tom Kalbfus

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Re: The SLS: too expensive for exploration?

Solid Isp=274s. MMH/N2O4 Isp=312s. Why would you chose something worse?
Throttle=Good. No control=Bad.
I'm arguing for essentially the same fuel used by Apollo. This exact fuel mixture was used by Apollo SM thruster quads. Apollo ascent stage used Aerozine 50; the difference between MMH and Aerozine 50 is technical, we've already discussed it. And I'm sure you and everyone reading this knows that.
These are storeable propellants, meaning they don't boil off *AT ALL* in Lunar conditions. That includes UDMH, MMH, Aerozine 50, and oxidizer N2O4. That's why they were used. I don't think I'm being unreasonable when I say the same fuel system as Apollo is preferable to solids.

Also how long can the command module stay in lunar orbit? Lunar orbit isn't stable. Anything left in Lunar orbit is eventually going to crash into the Moon, and with the traditional Apollo architecture, a return to Earth depends upon docking with the Command Module in orbit around the Moon. What if something happens with the command Module, as had happened on Apollo 13? Now they say those astronauts were lucky that the accident occurred on the outbound leg of their journey and not when it was orbiting the Moon and two astronauts were on the Moon's surface!

You know its a pity those Nova rockets didn't get built, they would have been great for going to Mars! There is no reason why they couldn't be built today, especially is we made the lower stages landable and reusable using the same techniques SpaceX used. We could build a Nova version of the SLS and reuse the bottom stage!

Last edited by Tom Kalbfus (2016-05-15 07:07:21)