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Impatience Limits Space-Travel


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#1 gsmonks

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Posted 06 November 2015 - 10:05 AM

NASA is very slow to realise some very simple facts, and one that has been bugging me for many decades is simple impatience when it comes to getting stuff off the ground and into space.

When the Saturn V was first introduced, I couldn't help but wonder why such a big machine was used to ram a comparatively small payload into orbit. It seemed to me to be terrifically impatient and inefficient.

Here's why:

The highest anyone has sent a professional helium balloon up into the air is 53 km, which is roughly half-way to space.

Space begins at roughly 100 km.

So why has no one built a big honking helium-filled permanent platform for launching space hardware?

Imagine winching a mighty Saturn V, plus various other stages, to such a platform, and launching it from there?

Also- what's the tearing rush to get to Mars? We could be colonising the red planet already if we weren't worried about getting there FAST. Send lots of stuff by way of low-thrust snap-apart reusable pre-fab spare parts, let it take its sweet time getting there, and park tons of stuff in Mars orbit for later use.

Slow is far cheaper than fast.
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#2 Woodmansee

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Posted 09 November 2015 - 06:15 PM

Altitude is not the most important part to get into space and stay there. You need velocity. Even if you were 200km high, you would fall right back down to Earth unless you had sufficient velocity to stay in orbit.

So while launching from a high altitude platform would save some effort in that your launch vehicle would not have the friction of low altitude, it would still have to be huge and go fast to achieve orbit in space. The cost of such a platform has been looked at and generally does not make up for the added advantage.

What does help is having a launch base as close to the equator as you can so you can get as much of the Earth’s rotational speed to help you achieve orbit as possible. That’s why Sea Launch floats down to the equator, and why the ESA launches from French Guiana.

Take a look at this site for more explanation http://solarsystem.nasa.gov/basics/bsf3-4.php

As for the hurry to get to Mars, I don’t think understand what you mean by trying to get to Mars fast.  It takes a certain velocity to change from Earth’s velocity around the sun, to Mar’s velocity around the sun. A Hohmann transfer does this with least energy. See http://solarsystem.nasa.gov/basics/bsf4-1.php

The fuel needed depends on the exit velocity of the rocket (see the rocket equation below). So it doesn’t matter if you use slow acceleration or fast. However, most rockets with a very high exit velocity (like an ion engine) have very low thrust, so to use these very fuel efficient rockets you need a power source (solar electric energy or nuclear) and a lot of time.

https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

Once at Mars, you cannot just “park” without significant maneuvers (i.e. fuel) to slow down to get into Mars orbit. This is more fuel.

If you don’t make new fuel somehow on Mars (in-situ fuel production) which is being developed, then you have to carry the fuel to get back and that’s a huge load

One major drawback with taking longer than 9 months to get to Mars (which is typical of a low energy impulsive maneuver and then coasting) is that the risk is greater as the human body is exposed to high interstellar radiation for longer periods of time, and a higher likelihood of a solar eruption of radiation killing the crew. That’s not even taking into account the muscle and bone loss if the habitat isn’t spun in some way to simulate gravity.

So it’s not impatience limiting space travel, it’s physics, and funding limitations.

Edited by Woodmansee, 10 November 2015 - 01:52 PM.


#3 gsmonks

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Posted 10 November 2015 - 07:54 AM

Why is your font so microscopic? I had to read your post with a magnifying glass.

I wasn't referring to manned missions. I was referring to unmanned supply drones slowly making their way to Mars and into Mars orbit. Perhaps even going into geostationary orbit and descending slowly, by balloon, on a carefully-chosen windless day.

It seems to me that the trick is to get mountains of supplies there, past the point of redundancy.
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#4 Woodmansee

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Posted 10 November 2015 - 01:55 PM

Sorry about the font size. I write in another app then cut and paste here and it got messed up. I will try and fix it with an edit.

I wasn’t specifically talking about crewed missions (except in the last paragraph), the rocket equations apply to every mission. Did you look at the referenced links?

A minimum energy transfer from Earth to mars is always going to require a delta V of about 3 kilometers/sec. This is true whether it is a slow acceleration or a couple or rapid impulsive maneuvers.  It doesn’t matter how long it takes to get there. It is the same whether it is a crewed mission or cargo mission.  Using the rocket equation we can calculate the fuel based on the fuel efficiency of the rocket (or specific impulse, Isp). See
https://spaceflights...ket/rktpow.html

With a conventional non-cryogenic rocket the Isp is about 320 which means 62% of the initial mass will be fuel (that’s a lot). This is of the spacecraft after launch. And when you add structure, navigation controls, communications, etc, this leaves not a lot for payload (maybe 15%).

With a conventional non-cryogenic rocket the Isp is about 320 sec which means 62% of the initial mass will be fuel (that’s a lot). This is of the spacecraft after launch. And when you add structure, navigation controls, communications, power, etc, this leaves not a lot for payload (maybe 15%).

With a ion engine or other system with continuous low thrusts the Isp is much higher, say 2000 sec which means only 15% of the initial mass will be fuel. However, this type of spacecraft has huge poer requirements with either require a nuclear reactor (not done) or very large solar arrays and associated hardware, which take up much of the spacecraft mass. When you add structure, navigation controls, communications, power, etc, this leaves a lot more for payload, (maybe 30% to 50%) but is also very expensive.

The point is that sending things slowly to Mars is not cheap or easy. The speed that you get there doesn’t matter, because it’s the speed you need to be going to stay there that matters. Think of it as catching an aircraft flying over your house at low altitude. Even if you could jump up to it you couldn’t catch a ride on that aircraft unless you were going close to the same speed as the aircraft to grab on.

#5 gsmonks

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Posted 10 November 2015 - 06:05 PM

What's needed are substations, an on-Mars refuelling system, an orbital fuelling station, permanent stations around both planets, larger ships built of snap-together components, and much larger ships with heavy shielding.

Financed by a mega-lottery corporation.
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#6 Orpheus

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Posted 10 November 2015 - 10:01 PM

To be quite honest, I've come to think that Elon Musk's obsession with Direct-to-Mars NOW! is daft. In fact, I'm inclined to think that even he knows it, but also knows that he'll be "forcibly subverted" into lesser missions (like further exploration of the Moon) by a combination of NASA and Congressionally-sculpted programs ["a subcontractor in every district" is too much pork for them to ignore]. I like to think that his public obsession is partly a bargaining chip ("What if he sends a Mars lander without us?")

Whether he's entirely on an even keel or not, he's already done more (and spent more) than any lottery prize in history. I'm glad that SOMEONE will keep making serious, monomaniacal, strides toward Mars and beyond.

There are so many issues to be resolved that even a small 1 year expedition to Mars in his lifetime is an iffy proposition. On the other hand, it should be doable with foreseeable refinement of current technology (i.e. no "new science", just a lot of engineering work and a fair bit of research into humans in non-Earth environments). It's so daunting, that I'm glad SOMEONE is committed to try -- and is cutting a path for other wealthy visionaries like Jeff Bezos (Amazon/Blue Origins), Robert Bigelow (Budget Suites/Bigelow Aerospace), John Carmack (Id video games + Oculus VR/Armadillo Aerospace) -- and about a dozen other serious companies by visionaries without $100Ms in disposable wealth [from Peter Diamandis' X Prize Foundation, the Ozmen's Sierra Nevada Corp., right on down to the father and son Masten Aerospace

There have been a LOT of illustrious ventures since 1975, by dedicated [and qualified] heroes, that simply folded for one reason or another. It's tough to be the point of the spear on top of all the technical challenges.

#7 gsmonks

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Posted 11 November 2015 - 09:42 AM

I see reliance on technology as part of the problem. I see Mars as a "stuff, not technology" problem. For example, heavily-shielded spacecraft. No technological finesse needed. Lots of pressurised greenhouses for producing food and oxygen. Making cement out of Mars materials and building underground structures in order to save heat, and for safety purposes. Turning water into hydrogen for fuel cells. And otherwise sending tons and tons of simple, redundant stuff, with a minimum of technology.

All of the aforementioned we could be sending to Mars en masse right now.
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#8 Woodmansee

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Posted 18 November 2015 - 04:36 PM

There are different ideas about what is technology. It is true that no new breakthrough technology developments based on new physics are needed to go to Mars. On the other hand, to my mind, anything that hasn’t been done before is new technology.

There is a lot of new technology in your proposal. There are lots of things that don’t exist right now (and therefore we don’t have the technology). For example: We do NOT have the capability to "send tons of simple, redundant stuff” to Mars. We haven’t built spacecraft that could put tons of stuff in Mars orbit or the surface (they are much smaller). We don’t have the launch vehicle capability to push large spacecraft on its way to Mars. We don’t know what foods will grow in space. We don’t know how to make cement out of Mars materials. We haven’t built greenhouses on other planets or in space. We do not have the capability to put Earth moving equipment (or rock moving) on Mars to build underground structures like we would on Earth. We don’t know how to extract useable water from the soil on Mars (assuming we could find large enough deposits).

All of these are big technology developments that will take years and a lot of funding. Some of which NASA and others are working on (for example growing lettuce from a watered pillow on the ISS, or developing a larger launch vehicle, or working on extracting oxygen from the CO2 on Mars) while other technologies are not being developed yet.

I’m not saying we shouldn’t make that invest in new technology, we should, but it isn’t as simple as you want to believe. Also, back to your initial point, impatience in the speed we get to Mars has nothing to do with it.

Finally, once you develop the technology, doesn’t it make more sense to test whatever you make on Lunar missions before sending it to Mars. For example, if you developed robotically built pressurized greenhouses, and underground structure robotic builders, wouldn’t you test them on Luna first so that if something goes wrong (as they always do) you could much more easily send a mission to figure it out and fix the problem before the next iteration of the hardware.

Edited by Woodmansee, 18 November 2015 - 04:41 PM.


#9 gsmonks

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Posted 18 November 2015 - 10:47 PM

We have the ability to build really big space vehicles right now. We just aren't doing it.

We could be using the same snap-together technology used to build scaffolding and crane-towers. We could be building an in-space "warehouse" to store these materials. We could be putting reusable fuel canisters into space. We could be putting reusable and redundant power-supplies, fuel cells, and engines, into such a facility. We could be putting a similar facility into Moon-orbit for shuttling material back and forth. We could be sending ad hoc snap-together "shuttles" to and from the Moon on a weekly basis if the will was there.

Many theorists have already adopted the crane-tower-like model of snap-together-and-apart ad hoc spacecraft. The snap-together parts supply the ad hoc structure, engines, fuel tanks, living-quarters, etc., can be inserted and snapped in as required.  We've had living-quarters of a sort on the Moon already. The same idea, only much larger, will work for Mars travel.

One of the major clunkers of that The Martian movie was the use of human poo to grow stuff. Soil samples from the Moon were used to grow stuff, using only seed and water. There were pictures in the paper of plants growing like gangbusters in Moon soil. No $hite.

One of the major flaws in modern fabrication methods is in making things just strong enough to hold together. Anyone who has sat at the wing-seat of a jetliner and watched the wing go up and down has seen this in action.

What's needed for Mars is buildings that are thick, strong, robust, redundant, built underground and semi-underground for protection and heat-conservation.
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#10 Woodmansee

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Posted 23 November 2015 - 01:31 PM

‘Snap together’ technology isn’t as easy as you make it sound. Connections that ‘snap’ together easily also come apart easily (with tragic results). Fasteners that hold things strongly take time to screw and tighten, bond, and/or weld – which also make them difficult to take apart and reconfigure. Care must be taken with wiring connectors that ‘snap’ together to ensure pins don’t get bent. And fluid transfer connectors moving gas or liquid often leak, which is why we prefer all welded systems (and then check the welds with x-ray, redoing some of them).

Your ‘snap together’ technology doesn’t exist, and until someone can develop and demonstrate snap together cars and aircraft, it’s not going to be used in space either.

Also, unless you have crewed missions (and the whole point is to make things before crews get there), all of this snap together items would have to be built and tested robotically. So, tt just makes more sense to build what you need on Earth and then send it than to build in space when you don’t have to build it there.

Some things can be built in space. The ISS is an example. Each of the modules were specially built and tested on Earth with a lot of time and effort over years (i.e. lots of $). Then later with heavy lift launches sent just into orbit to assemble the ISS in space. I would hardly call this ‘snap together’ or easy.

Soil samples from the Moon were used to grow stuff, using only seed and water.” [citation requested]. The only food grown in space that I am aware of the lettuce recently grown in specially made ‘pillows’ on the ISS. Plants need nutrients from the air, water, and/or soil. Lunar and mars regolith is totally dead, so if you plant things in them then the nutrients have to be provided by either fertilizer, or in the water (so not the distilled deionized water used on crewed missions). See http://aces.nmsu.edu/ces/yard/2002/121402.html

Engineers design things just as strong as they need to be, and no more. There are industry accepted (and government regulated) factors of safety rules that are followed for those aircraft wings and other items to make them safe. If they were so stiff that they didn’t flex, then the aircraft would be so heavy it would never take off. The factors of safety on building are much higher, because weight isn’t as much of a factor. For spacecraft, mass is a HUGE factor, and an overdesigned high mass spacecraft is one that never gets launched.

I agree that a long term habitat would need to have a “thick, strong, robust, redundant, built underground and semi-underground for protection and heat-conservation.” However, a smaller inflatable habitat that is carried in one piece is much easier for a short duration mission. To build something there requires heavy equipment. Getting the construction equipment to Mars (or hopefully the Moon first to test it) is a difficult problem that requires new technology. A standard backhoe or bulldozer wouldn’t work because, 1) way too heavy to get there, 2) no free oxygen to burn to run the engines, 3) cannot be operated robotically or by a human in a space suit. Making a small light backhoe or dozer doesn’t work right, because it is in part the heavy mass of the machine that allows the dirt to be moved instead of the machine to be moved. The lower gravity does make that dirt to be moved lighter (but same mass) but also makes this a harder problem as there is less traction for the machine.

Again, my point is not that these things cannot be done, but they are not easy and take time and money to develop the new technologies needed, a lot more investment than is currently allocated.

#11 gsmonks

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Posted 24 November 2015 - 01:51 AM

The moon soil used to grow stuff was on Earth, not in space. It was a CBS/Walter Cronkite story on television in the 70's. You'd have to contact CBS and get them to go through their archives in order to get your citation.

Snap-together technology already works just fine. We use it in mining and engineering already. There's nothing tougher than hydraulic lines, and they've been using snap-together technology for many decades.

Snap-together pre-fab superstructure is low-tech, reliable, and dependable. Fluid and gas connectors have nothing whatever to do with tinker-toy superstructure. They're a secondary matter. And there are bazillions of examples of low-tech solutions here on Earth to look to in terms of design. Space-bound variations have to be developed, but already have their analogue in existing designs.

Gas-line couplings affixed to flexible hoses work on the same principles here on Earth as they do in Space. The coupling mechanisms use pressure to lock and hold, with a spring-loaded collar being the release mechanism. What we don't have in Space, at present, is redundant stock to draw from, the way you do in a machine shop. In a shop, when working on hydraulics, you'll often crack open a brand-new hose with bad connectors. In Space you don't often have the option of tossing such items aside for repair. That is something that absolutely must change. There should be a Space-warehouse full of redundant, reusable, interchangeable parts.
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#12 Woodmansee

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Posted 03 December 2015 - 01:13 PM

“There's nothing tougher than hydraulic lines.” Um yes there is. Hydraulic fluid doesn’t leak easily (large molecules). High pressure helium (~4500 psi) is normal on spacecraft pressurization systems and is much harder to prevent leakages. All mechanical systems will leak, especially ones with disconnecting o-rings, and a leak on a long duration space mission is mission critical. This is why all pressure systems for long space missions are usually welded.

Space-bound variations have to be developed…” My point exactly. They would have to be developed, and currently there is no need or funding for this.

“There should be a Space-warehouse full of redundant, reusable, interchangeable parts.” This would be a massive investment for even one of these. And space isn’t all one place, so many would be needed for each possible mission.

Currently, an individual design for a specific mission with pre-defined needs is the only affordable method as it doesn’t require a massive infrastructure that you are talking about.

#13 gsmonks

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Posted 04 December 2015 - 10:08 AM

View PostWoodmansee, on 03 December 2015 - 01:13 PM, said:

“There's nothing tougher than hydraulic lines.” Um yes there is. Hydraulic fluid doesn’t leak easily (large molecules). High pressure helium (~4500 psi) is normal on spacecraft pressurization systems and is much harder to prevent leakages. All mechanical systems will leak, especially ones with disconnecting o-rings, and a leak on a long duration space mission is mission critical. This is why all pressure systems for long space missions are usually welded.

Space-bound variations have to be developed…” My point exactly. They would have to be developed, and currently there is no need or funding for this.

“There should be a Space-warehouse full of redundant, reusable, interchangeable parts.” This would be a massive investment for even one of these. And space isn’t all one place, so many would be needed for each possible mission.

Currently, an individual design for a specific mission with pre-defined needs is the only affordable method as it doesn’t require a massive infrastructure that you are talking about.

What's needed is a massive infrastructure, publicly funded, and funded by many types of investment.

Financially-speaking, NASA makes the same mistake as charities: raise money, spend it, raise money, spend it, in a never-ending cycle. Absolutely insane way of doing things. What they should be doing is raising money, investing it, spending the dividends and/or interest, until enough capital and resources have been accrued that you have a self-sustaining entity.
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#14 Woodmansee

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Posted 04 December 2015 - 11:42 AM

NASA, like any other federal agency, is required by law to spend it's budget annually. It is prohibited, by law, from making investments with it's funding.

Also, even if congress changed the law and NASA was allowed to do so, all of the present programs NASA does currently does would be canceled. Lots of people would be out of work, and lots of companies (large and small) would be hit hard as contracts get canceled. In short, it would be tragic.

#15 gsmonks

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Posted 04 December 2015 - 12:37 PM

View PostWoodmansee, on 04 December 2015 - 11:42 AM, said:

NASA, like any other federal agency, is required by law to spend it's budget annually. It is prohibited, by law, from making investments with it's funding.

Also, even if congress changed the law and NASA was allowed to do so, all of the present programs NASA does currently does would be canceled. Lots of people would be out of work, and lots of companies (large and small) would be hit hard as contracts get canceled. In short, it would be tragic.

Who said anything about NASA?

I did, of course, but there should be an autonomous civilian space agency.
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#16 G-man

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Posted 10 December 2015 - 12:53 PM

Ummm ... NASA IS an autonomous civilian space agency.  Perhaps you mean a "Private" (as in corporate operated) as opposed to "Public" (government-operated) agency.

And even there, the Private Consortium would be obliged to meet the same safety standards required of NASA.  Even more, the massive infrastructure you're proposing is simply prohibitive in cost and time to pursue as this would all come out of the Consortium' pockets, and then it is only after the infrastructure is in place can they start to see a return on investment.  Afterall, private industry survives on making money, and if there is no money, private industry has no incentive to pursue your plan.

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