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#26 2018-04-30 16:37:49

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,452

Re: GPS system for Mars?

Louis,

Jet engines did not simply leap into existence in three years time.  In 1929, Frank Whittle received funding from his government to conduct basic continuous combustion engine research experimentation and to produce a working prototype jet engine.  The initial prototypes were built and tested many years before WWII started and the technology was progressively refined into the utterly reliable power plants that propel virtually every commercial airliner in the sky today.  That happened over the course of many decades and there was a slew of lethally catastrophic mistakes made along the way.

They didn't have an airplane with a jet engine in it for a decade.  When the first jet engines did actually generate enough power to get an airplane off the ground, critical components in the engine lasted for a few hours, after which they were no longer capable of functioning without an unacceptably high risk of catastrophic failure.  Many early jet engines did, in point of fact, explode in operation!  That is NOT the type of technology that you bet the lives of astronauts on when you have more reliable alternatives.  The military will try anything just to see if it works, despite a high risk of failure, because the military has a mandate to produce better technology than their adversaries in an attempt to save the lives of their people in times of war.

In WWII, we needed fast and maneuverable fighter aircraft to intercept and destroy enemy fighter aircraft.  Jet engines were the ultimate solution to the speed problem, but they also introduced an entirely new set of problems that everyone outside the lab was thoroughly unfamiliar with.  Mechanically, they were simpler than piston engines, but in terms of the required understanding of materials science, manufacturing tolerances, and the combustion principles involved, they were a leap ahead of existing combustion engine technology.  The reliability of the early jet engines was ignored because the need for greater speed was so painfully obvious.  In short, we were absolutely desperate and were literally throwing resources at anything we thought might work.

A laser communications system failure won't look nearly so dramatic from the standpoint of the satellite carrying the laser, thanks to decades of solid state electronics research and development, but if that system fails then the spacecraft that was relying on that positioning system to relay accurate positioning information may very well meet the exact same fate as early jet powered aircraft.  The "difference" between the jet engine and a laser communications system operating on another planet is that there is no mandate to unnecessarily hazard the lives of a dozen or more irreplaceable astronauts or colonists simply to use something that is slightly cheaper than existing alternatives.  It quite clearly won't be cheaper the very first time we lose one of those reusable interplanetary spaceships from bad navigational input data caused by using immature navigation systems.

If we kill a dozen astronauts or colonists in a single landing attempt, then the entire Mars exploration and colonization program will grind to a screeching halt.  FAA will pull BFR's flight certification so fast your idealistic head will spin.  Recall what happened as a result of the last Falcon 9 failure when the rocket was merely being fueled on the pad if you don't believe that.  Falcon 9 was grounded indefinitely until the cause of that failure was determined.  I'm done arguing this point because you're being deliberately obtuse about what our actual capabilities are.

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#27 2018-04-30 19:17:46

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,565

Re: GPS system for Mars?

Back to the GPS sat constellation which will be expensive even being stripped down and launched on the lowest cost launcher as the shear number of them that is required to make it as good as it can be for permanent settlement use.

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#28 2018-05-01 12:41:27

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,792

Re: GPS system for Mars?

Well I think you make the point for me: there may have been a long lead in period of research, but the project to build a working aeroplane took a relatively short period of time. 

We now have all sorts of ways of testing craft robotically which was not previously possible.  If you want, you can operate an aeroplane completely automatically without any humans on board. I am sure we could perfect a laser guidance system within a couple of years with the right amount of investment in terms of money and skilled labour.  I think NASA starves these crucial projects of cash and splurges it on things like Curiosity Rover which, although fun, don't give a very good return on investment and ISS.

kbd512 wrote:

Louis,

Jet engines did not simply leap into existence in three years time.  In 1929, Frank Whittle received funding from his government to conduct basic continuous combustion engine research experimentation and to produce a working prototype jet engine.  The initial prototypes were built and tested many years before WWII started and the technology was progressively refined into the utterly reliable power plants that propel virtually every commercial airliner in the sky today.  That happened over the course of many decades and there was a slew of lethally catastrophic mistakes made along the way.

They didn't have an airplane with a jet engine in it for a decade.  When the first jet engines did actually generate enough power to get an airplane off the ground, critical components in the engine lasted for a few hours, after which they were no longer capable of functioning without an unacceptably high risk of catastrophic failure.  Many early jet engines did, in point of fact, explode in operation!  That is NOT the type of technology that you bet the lives of astronauts on when you have more reliable alternatives.  The military will try anything just to see if it works, despite a high risk of failure, because the military has a mandate to produce better technology than their adversaries in an attempt to save the lives of their people in times of war.

In WWII, we needed fast and maneuverable fighter aircraft to intercept and destroy enemy fighter aircraft.  Jet engines were the ultimate solution to the speed problem, but they also introduced an entirely new set of problems that everyone outside the lab was thoroughly unfamiliar with.  Mechanically, they were simpler than piston engines, but in terms of the required understanding of materials science, manufacturing tolerances, and the combustion principles involved, they were a leap ahead of existing combustion engine technology.  The reliability of the early jet engines was ignored because the need for greater speed was so painfully obvious.  In short, we were absolutely desperate and were literally throwing resources at anything we thought might work.

A laser communications system failure won't look nearly so dramatic from the standpoint of the satellite carrying the laser, thanks to decades of solid state electronics research and development, but if that system fails then the spacecraft that was relying on that positioning system to relay accurate positioning information may very well meet the exact same fate as early jet powered aircraft.  The "difference" between the jet engine and a laser communications system operating on another planet is that there is no mandate to unnecessarily hazard the lives of a dozen or more irreplaceable astronauts or colonists simply to use something that is slightly cheaper than existing alternatives.  It quite clearly won't be cheaper the very first time we lose one of those reusable interplanetary spaceships from bad navigational input data caused by using immature navigation systems.

If we kill a dozen astronauts or colonists in a single landing attempt, then the entire Mars exploration and colonization program will grind to a screeching halt.  FAA will pull BFR's flight certification so fast your idealistic head will spin.  Recall what happened as a result of the last Falcon 9 failure when the rocket was merely being fueled on the pad if you don't believe that.  Falcon 9 was grounded indefinitely until the cause of that failure was determined.  I'm done arguing this point because you're being deliberately obtuse about what our actual capabilities are.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#29 2018-05-01 14:19:37

kbd512
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Registered: 2015-01-02
Posts: 3,452

Re: GPS system for Mars?

Louis,

NASA is working at best possible speed on a laser communications system and work started years ago.  The first operational test of the LEMNOS system aboard Orion is slated for 2019, as is the first operational test of the LCRD system is also slated for 2019.  If those projects work as intended, then I believe we can use it for BFR as well.  At that point, it becomes an engineering project rather than a science project.  Since NASA has successfully tested a laser communications system flown in space aboard LADEE and two upcoming projects to be launched next year, I don't believe they're starving these projects of funding.  NASA has also expressed a desire to use this system for deep space and Mars navigation and communication applications, so I'm pretty sure they even have that specific use case in mind.

LADEE began in 2008.

LCRD / LEMNOS began in 2011.

LEMNOS is the portion of the technology that flies aboard the Orion spacecraft and LCRD is the laser relay system that flies aboard a satellite to relay signals from LEMNOS to ground stations or other spacecraft.

That means it took about a decade to perfect the technology.  Try to wrap your head around the speeds and distances involved to understand why it's so complicated.  It's not simpler than microwave communications, but it does permit a much faster data transfer rates.

Think dust in the Martian atmosphere might attenuate the laser radiation like the comparatively dust-free atmosphere on Earth does?

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#30 2018-05-01 16:54:26

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,792

Re: GPS system for Mars?

https://www.nasa.gov/feature/langley/la … g-missions

I think it's the NDL that is the project of interest.

Some additional info:

https://www.lpi.usra.edu/opag/meetings/ … erdian.pdf

It's clearly pretty far advanced. But in my view projects like this could be accelerated.

The current ALHAT scheme began in 2006:

https://en.wikipedia.org/wiki/Autonomou … _and_plans

So that's already 12 years ago. But lasers have been around since the early 60s and are an obvious technology to investigate in terms of hazard avoidance. So, I do think NASA are being incredibly slow.  This sounds more like a 3 year development project to me, assuming you throw enough resources at it.

NASA prioritises science spending over settlement, because of the way it creates its budgets:

http://www.sciencemag.org/news/2018/03/ … nding-plan

That's why there are no bases on the Moon and a NASA Mars mission is still a generation away at current rates of progress.


kbd512 wrote:

Louis,

NASA is working at best possible speed on a laser communications system and work started years ago.  The first operational test of the LEMNOS system aboard Orion is slated for 2019, as is the first operational test of the LCRD system is also slated for 2019.  If those projects work as intended, then I believe we can use it for BFR as well.  At that point, it becomes an engineering project rather than a science project.  Since NASA has successfully tested a laser communications system flown in space aboard LADEE and two upcoming projects to be launched next year, I don't believe they're starving these projects of funding.  NASA has also expressed a desire to use this system for deep space and Mars navigation and communication applications, so I'm pretty sure they even have that specific use case in mind.

LADEE began in 2008.

LCRD / LEMNOS began in 2011.

LEMNOS is the portion of the technology that flies aboard the Orion spacecraft and LCRD is the laser relay system that flies aboard a satellite to relay signals from LEMNOS to ground stations or other spacecraft.

That means it took about a decade to perfect the technology.  Try to wrap your head around the speeds and distances involved to understand why it's so complicated.  It's not simpler than microwave communications, but it does permit a much faster data transfer rates.

Think dust in the Martian atmosphere might attenuate the laser radiation like the comparatively dust-free atmosphere on Earth does?


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#31 2018-05-01 18:31:56

kbd512
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Posts: 3,452

Re: GPS system for Mars?

Louis,

NDL will fly in space for the first time aboard the Mars 2020 rover mission at the earliest.  A laser altimeter was first used in space aboard Apollo 15 flew in 1971.  LIDAR existed in the 1960's, but the computing power required to process any significant volume of data was beyond the capability of anything that would fit inside an aircraft, much less a spacecraft.  The current generation of rad hard processors has the computing power to process the input.

NASA prioritizes science because its reason for existing is space exploration, not space colonization.  Any base that NASA puts on the moon or Mars has to satisfy science objectives that only long duration surface habitation could satisfy.

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#32 2018-05-02 04:04:19

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,792

Re: GPS system for Mars?

It is my contention that more science will be done in the first year of Mars settlement than was done in the previous 50 years of absurdly expensive robot missions.


kbd512 wrote:

Louis,

NDL will fly in space for the first time aboard the Mars 2020 rover mission at the earliest.  A laser altimeter was first used in space aboard Apollo 15 flew in 1971.  LIDAR existed in the 1960's, but the computing power required to process any significant volume of data was beyond the capability of anything that would fit inside an aircraft, much less a spacecraft.  The current generation of rad hard processors has the computing power to process the input.

NASA prioritizes science because its reason for existing is space exploration, not space colonization.  Any base that NASA puts on the moon or Mars has to satisfy science objectives that only long duration surface habitation could satisfy.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#33 2018-05-02 04:16:11

elderflower
Member
Registered: 2016-06-19
Posts: 1,219

Re: GPS system for Mars?

Robot missions are nowhere near as expensive as human ones, Louis, and they don't put a crew at risk. They don't produce the information that a manned mission would but they have to be done before the human ones if only to identify design conditions and hazards prior to preparation of the manned/womanned missions.

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#34 2018-05-02 10:38:38

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,905
Website

Re: GPS system for Mars?

Louis:

Relative to your timeline complaint in post 28 above (which complaint I share,  by the way):

Development timelines today throughout NASA and all of DOD are tied up in their own underwear with bureaucracy,  quite unlike WW2 or even the 1960's.  The new DARPA guy knows this,  because the new USAF undersecretary rubbed his nose in it.  So he wants to do something about that.  Wouldn't even have come up if she hadn't prodded him,  they have been comfortable in their bureaucratic swamp for decades now.  The latest issue of AIAA's magazine "Aerospace America" has an article in it on this very topic.

It takes a couple of years even to propose something to the government,  under rules that disqualify almost all but the long-favored contractors (yes,  the game is rigged). 

Then it goes through 3+ years of fundamental testing to verify that it might work,  on the government's schedule,  not what it might really take. 

Then there is around 5-10 years of development efforts that produce prototype hardware that might work,  again to a schedule driven by the government's whims,  not reality. 

Then there is at least 2 more years' tests to show that it really works.

Then 3+ years of operational testing before it gets fielded. 

It's been like that since the 1970's.  ~20+ years is what it took to get the F-22 into USAF hands.  It ain't right,  but that's the way it certainly really "is".

Contrast that with the far-less bureaucratized way of doing things that existed before and up into WW2:  the P-51 went from idea to a flying prototype in 120 days.  About a year's testing showed it to be inadequate.  Borrowing a better engine from the Brits,  plus a 4 bladed prop to match,  turned it into a very effective fighter in about another year.  2 years vs 20 years today.

I know that the technology of a fast piston-prop airplane is simpler than a gas turbine supersonic airplane.  But back then,  fast piston prop was every bit as challenging to them,  as supersonic gas turbine is to us,  today. 

The problem is too much bureaucracy run by idiots who not only cannot do any of the things they contract for,  they now no longer even fully understand any of the things they contract for.  "Boilerplate" requirements by the boxcar load,  instead of a kid's toy wagon-load of requirements that are actually pertinent.  And so forth.

NASA's SLS and its former Constellation/Aries program are really one long program going back over 20 years now.  And it has yet to fly.  Why should that surprise anyone?  Just the latest example in the launch business.  The F-35 is the latest in the airplane business (started 30 years ago,  it did!)

GW

Last edited by GW Johnson (2018-05-02 10:43:47)


GW Johnson
McGregor,  Texas

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

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#35 2018-05-02 10:50:34

Oldfart1939
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Registered: 2016-11-26
Posts: 1,835

Re: GPS system for Mars?

GW-
I support your comments in entirety.

The SLS will be obsolete before it's first flight--if that ever happens. Both Blue Origin and SpaceX are moving faster than the government paperwork money program (workfare) for the favored contractors. There will be a Bezosville on the Moon, and a flourishing Muskquett on Mars for NASA to stay when they finally pull their collective heads out of their as**s.

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#36 2018-05-02 14:39:16

kbd512
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Registered: 2015-01-02
Posts: 3,452

Re: GPS system for Mars?

GW,

We could test that theory.  Let's determine how long it takes the Federal government to design a modern equivalent of the P-51D.  The only requirement is that they develop an aircraft with equivalent performance specifications.  Give them 120 days to construct a working prototype.

Nobody makes Merlin engines anymore, so give them the option to use turboprop engines.  Doesn't matter what it looks like, so long as it performs.  If it can fly X number of miles per hour with Y payload to Z distance, they get a pass on the issue of how long it takes to do something on account of the level of sophistication of modern design.  If they fail, then we no longer issue cost plus contracts for engineering development efforts since it's blatantly obvious that they're not performing to standard and the increasing sophistication of modern aerospace design has little to do with their lack of performance.

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#37 2018-05-03 03:12:41

elderflower
Member
Registered: 2016-06-19
Posts: 1,219

Re: GPS system for Mars?

You don't need to do all that GW. Embraer/Shorts already make a similar machine to the plane you envisaged. The RAF use it for training. It can come with the facility to be fitted with bombs, rockets and guns.

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#38 2018-05-03 16:42:21

kbd512
Administrator
Registered: 2015-01-02
Posts: 3,452

Re: GPS system for Mars?

Elderflower,

This is more of a test to see if they can replicate 1940's aircraft tech in 120 days.  If they can't, then that means all the better tools and materials, education, and design technology haven't produced a system that can get things done in a reasonable amount of time.

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#39 2018-05-03 16:43:13

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,565

Re: GPS system for Mars?

GW was trying to point out that under the correct conditions of management, A fixed drive to create and funding to make it happen on a schedule for a quick turn can happen.

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#40 2018-05-03 16:54:39

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,792

Re: GPS system for Mars?

I think it is just a given that where you have sufficient willpower backed by resources and managerial competence you get accelerated technological development.  That's the lesson of war throughout history, the Cold War and - more recently - the era of tech multi-billionaires seeking to realise the dreams of their childhood.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#41 2018-05-04 10:13:43

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,905
Website

Re: GPS system for Mars?

Naw,  it's about vast quantities lobby money (a euphemism for bribes) corrupting government into total inaction and incompetence.  This has been building exponentially since gearing up for war production during WW2.  Since then it has gotten much worse and spread far beyond the defense sector of the economy.  It's not limited to just the US,  either. 

I see EAA members building high-performance propeller airplanes in a handful of years,  financed entirely out of their own pockets.  Some of these are analogs to the P-51 project of WW2. 

On the other hand,  I see a government that spends billions looking for a close ground attack bird to replace a still-perfectly-good A-10,  without much to show for it so far.  The best candidates seem to be pre-existing single-engine turboprop airplanes refitted to carry weapons,  as Kbd512 mentions.  But I see a government unwilling to select and buy one.  Dithering,  waiting to see where the most lobby money will come from,  apparently.

GW

Last edited by GW Johnson (2018-05-04 10:15:11)


GW Johnson
McGregor,  Texas

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

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#42 2018-05-04 15:56:05

kbd512
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Registered: 2015-01-02
Posts: 3,452

Re: GPS system for Mars?

GW,

My idea for a true replacement of the A-10 was an X-Wing facsimile with a composite armored fuselage for the pilot, avionics, fuel cells, landing gear, and weapons bay.  It would have four engines based upon the RamGen technology with 3D vectoring nozzles for short takeoff / landing and four aeroelastic wings to function as air brakes in a diving attack.  The wing tips would carry air-to-air weapons or sensor pods.  The ordnance would be carried in an internal weapons bay running the length of the fuselage or hard points mounted to the fuselage.  The primary armament would be configurable, anything from a standard rotary cannon to a 105mm howitzer firing guided projectiles, rail gun, or laser.  For strike missions, the primary armament could be replaced with bombs or missiles.  The airfoils would remain clean to maximize performance.  It would be optimized for low speed flight, but still be capable of flying at high subsonic speeds for dashes to and from the target area.  Some low-RCS features would be incorporated where feasible, but it would not be a true stealth aircraft.  The landing gear would be flat-folding tracks instead of wheels to both minimize the internal volume occupied by the landing gear and minimize the result of a puncture from ground fire.  The control systems would be comprised of triple redundant electrical actuators instead of hydraulics, to include the brakes.

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#43 2018-05-05 08:27:54

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,905
Website

Re: GPS system for Mars?

If it were up to me, I'd give serious consideration to digging the tooling out of the scrapyard at what was Fairchild aviation,  and opening up the A-10 production line again.  Similarly,  if the tooling still exists in the scrapyard,  one might consider opening up the production line for the A1 Skyraider again.  Well-proven in combat (Vietnam).

Another leading contender would be the turboprop Tucano or Super Tucano.  Fairly fast,  maneuverable,  carries a heavy load.  The Tucano has seen combat in the Falklands.  It's not the only single-engine turboprop candidate out there,  either.

Another good candidate would be simply adding armaments to an Air Tractor cropduster.  Maneuverable,  carries extreme loads.  Tougher than an old boot, so adding hard points for weapons should be easy.  Replace the chemical tank with another fuel tank for more range. 

There are more really good candidates just like those,  all seriously proposed.  Any could have been flying years ago. 

It's only my opinion,  but I really do believe the long dithering on this is just public servants fishing for lobby money/bribes to get rich.

GW


GW Johnson
McGregor,  Texas

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

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#44 2018-05-05 08:42:51

Oldfart1939
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Registered: 2016-11-26
Posts: 1,835

Re: GPS system for Mars?

The A-10 Warthog was designed around the 30 mm Gatling gun, a weapon known to strike fear in the hearts of enemies. Position of the armored engine nacelles made the a/c very hard to shoot down or significantly damage.

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#45 2018-05-05 18:12:58

kbd512
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Registered: 2015-01-02
Posts: 3,452

Re: GPS system for Mars?

GW,

I doubt the tooling to mass produce A-10's still exists and is usable.  If it does and the manufacturing plant could be re-opened for reasonable cost, then we should probably do that until we can devise a better aircraft for close air support and interdiction missions.  If not, then I see no reason not to drive technology forward.

I feel the same way about this new laser navigation and communication technology that Louis proposed using to reduce mass, therefore cost, and to improve upon the reliability and precision of legacy positioning systems.  That's why I didn't argue the point.  After reading about what the laser mapping and navigation technology can do, relative to legacy GPS, I think it's worth the money and effort to develop and field extreme precision navigation and extreme bandwidth communication systems.

My point, which he ignored like all other points I try to make about the current state of technology, is that it's not quite ready for prime time.  He seems to think that because someone somewhere did an experiment with laser navigation that that is somehow equivalent to having human space flight rated hardware ready to launch or that such a system is literally just around the corner, despite all past evidence about other sophisticated technology development programs like jet engines and radar indicating that it's at least a decade or two before any fundamentally new way of doing something becomes reliable enough to bet human lives on.  Talking about what could possibly happen in the future is not the same thing as having an operational system that does "X".  You and I both seem to understand that, but I don't get the sense that Louis does.

LIDAR existed shortly after lasers existed.  The reason it's still not the primary navigation aid is that existing technologies work well enough in most cases and the atmosphere can distort or otherwise attenuate laser radiation.  That said, NASA seems very intent on employing this tech to assure the success of landings and communications on Mars and as a fan of better technology, I think that's a good thing.  I'll concede that if NASA can successfully demonstrate the technology on two or more robotic missions and two or more human mission aboard Orion, then it should be used in the interest of the benefits it bestows upon craft so-equipped.

There are endless complaints about the cost of military and aerospace technology, but those of us who are a bit older should probably remember that we're sending our sons and daughters to the government.  My expectation is that they be returned to me alive and well, if it all possible.  There are or will be times when conflicts or other forms of adversity like living on another planet will be unavoidable, so I think having the best equipment, training, and mindset are critical ingredients to success in any complicated endeavor.  This is the fundamental point of better technology development.

When the first human learned to throw rocks or spears at animals intent on eating them, human life was improved.  All technology development thereafter, even those with the inherently destructive purpose of warfare, have ultimately bettered human lives (not all lives, obviously, but exceptions don't invalidate the general rule).  After weapons that could annihilate all living things were invented, the basic technology still held the promise of being used to better human lives and was, in fact, used for that purpose as well.

I find the notion that we don't know how to design and build affordable and dependable attack aircraft or laser navigation and communications system for use on another planet to be unacceptable.  If there are individuals or bureaucracies within NASA or external to NASA that are needlessly inflating the cost or increasing development time, then those obstacles should be removed ASAP.  However, I do not believe there is any systematic attempt on NASA's part to deny technology to space exploration companies.  To use a laser analogy, there seems to be a coherency problem on NASA's part.  All of this technology development is useful, but there is no over-arching plan to combine all of these technologies into a system of systems intended to enable long duration human space exploration and colonization.  In contrast, the robotic exploration program is extremely mission and target focused, achieving exploration goals in time frames from 5 to 10 years, on average.

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#46 2018-05-05 19:00:41

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,929
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Re: GPS system for Mars?

Are we talking military combat aircraft? Ok. Canada was heavily pressured to purchase F-35 aircraft. All of America's allies were. Congress would not allow the F-22 to be exported, even to Canada. The first production run of F-22 was completed, the second contract didn't happen. The manufacturer was disappointed, wanted some way to recover the money they expected from the second contract. So they increased the price of F-35, and used their lobbyists to convince US government officials to pressure allies to buy them. Canada just won't pay the high price after the increase, and Canadian air safety rules prohibit any single-engine aircraft from flying over open water farther than gliding distance back to shore. That's why Canada didn't buy F-16 in the late 1970s, and why Canada won't buy F-35 today. And you could cite other problems with the aircraft.

Gary's arguments about A-10 Warthog are very valid. However, just for the sake of clarity, I'm going to bring up the opposing argument. Surface-to-Air missiles can and have inflicted serious damage on A-10 aircraft; fixed installations, ground vehicle launched, and shoulder launched. The A-10 is wonderfully adapted to the roles of tank hunter and close ground support, but the problem is these missiles. It's not just engine location; A-10 compressor blades are designed to take damage yet still operate. It can withstand small arms fire such as bullets from combat riffles, without any impact. But missiles? That's what makes it vulnerable. In Iraq they started using F-16 aircraft for the roles A-10 had done. F-16 has no armour, but it flies high and fast. F-35A was supposed take over roles of A-10 and F-16, F-35B would take over roles of AV-8B, and F-35C would take over roles of FA-18C. F-35B has proven to be too big and heavy, an assault carrier cannot carry has many aircraft if it has F-35B. F-35C still looks good, but the 'A' variant has serious issues. However, I still have to point out, what about missiles?

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#47 2018-05-05 19:41:21

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 18,565

Re: GPS system for Mars?

I do think that we have drifted long enough on what could be for earths Airforce but points are well taken in that we could be doing better for a lot less money.

The Insight has two communication cube sat's are passengers for that mission so we will learn if size really matters

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#48 2018-05-06 09:08:02

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,905
Website

Re: GPS system for Mars?

Well,  the original thread title here was GPS for Mars.  I see no reason why something like a Falcon-Heavy could not fling a few satellites of that type to Mars.  Takes a stage of some kind to do the delta-vee into Mars orbit,  but so what?  Just get on with it. 

If some sort of laser navigation system could be shown to work as well or better,  I don't object to doing that instead.  I don't care,  as long as there is a way to to precisely aim direct-entering spacecraft toward the entry track that lets them hit their landing targets.

Nobody will need communication during the plasma-sheathed entry.  That may or may not ever be doable,  but why bother when you don't need it?  At Mars (like Earth) those intervals are but a single handful of minutes long.  Inertial guidance is well proven,  and has no perceptible drift on timescales like that. 

That'll put you within around +/- 2-3 km of your aim point. If you're small ballistic coefficient and using chutes,  wind drift raises that to nearer +/- 5 km landing error.  By the way,  ringsail and ribbon chutes that you can deploy while supersonic are simply not steerable items.  Probably won't ever be,  not in any of our lifetimes.

If you're big ballistic coefficient and come out low,  you will be using retropropulsion,  which is inherently steerable,  as the rocket engines must be gimballed just to achieve stable flight at all.  That's where a beacon on the site might cut km-size landing errors to just several meters.  Timelines will be nail-bitingly short,  so a human or robot pilot will have little time to see-and-avoid any obstacles like boulders or gullies or small hillocks in the way. 

On a large vehicle like BFS,  visibility of the site from the flight deck is going to be awfully bad,  without some sort of TV in the tail.  That's subject to electronic failures and to foreign object damage from the jet blast-thrown rocks,  and sooting damage from the engines themselves.

Those are all things to think very carefully about.  They make a good argument for building large paved pads to land BFS's on,  as the preferred thing to do.  That won't be possible for the first landings,  but it will be necessary later,  in order to cut down the crash rate.

GW

ps -- as to A-10 tooling,  I think Kbd512 is most likely right.  It was probably gone long ago.  Different companies do this differently.  At LTV Aerospace in the 1960's and 1970's some of the tooling from WW2 was still out on the back lot. It didn't look very good,  but heavy steel is often refurbishable anyway.  Most prefer the $ to be had from scrapping.

The missile threat to things like A-10 is quite real,  particularly IR-guided shoulder-fired stuff,  for which dropping chaff is useless,  and flares are of limited value if the seeker is a staring array.  The towed RF decoy has already proven to be effective,  and there have been towed IR concepts bandied about for decades now,  with none ever actually developed and deployed.  I worked on one of those. There's still good reasons to think it would be successful and effective.

There's a mix of people on these forums.  Not many have heavy-duty engineering backgrounds.  That's why there is so much failure to distinguish a science experiment from a real ready-to-use technology,  and consequently such unrealistic expectations about how long it should take to get something ready. 

That being said,  I think that perception problem is compounded by a blind trust in how effective and logically-motivated government agencies are to actually get something done.  In point of fact,  the only thing in this world more brain-dead than a set of government agencies is an empty dry skull. 

That last is why I am much more a fan of the likes of Spacex and Blue Origin (and others) than NASA or ESA or the rest of those. I only saw this later in life.  After watching 40 years and $trillions spent on never traveling beyond orbit except as robots.

Last edited by GW Johnson (2018-05-06 09:25:20)


GW Johnson
McGregor,  Texas

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

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#49 2018-05-06 09:55:45

clark
Member
Registered: 2001-09-20
Posts: 6,264

Re: GPS system for Mars?

It is not a failure of background GW, it is a failure to recognize a troll. louis is either (a) delusional or (b) yanking the collective chain. Enjoy the tea party.

As for GPS on Mars; what is the point? Something like that is needed if we have a more robust Mars-centric exploration program. We don't.

Entire universe and somehow we need to prioritize GPS on Mars? Fling a couple satellites at Mars? Sure, no problem, let's just torch 20 million for some hardware to do something with limited immediate value.

I did enjoy the government agency quip though. Having been to places without an equivalent EPA, FDA, DOE, or [ohmygod] NASA, I think the alternative is not ideal. Large groups of people develop internal inertia, it is not a government thing. The broad stroke being painted here is lazy.

Oh, and A-10. Because somehow that is relevant and I want to belong.

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#50 2018-05-06 10:53:16

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,835

Re: GPS system for Mars?

I believe it was a big mistake on part of SpaceX to abandon the Red Dragon missions(s). A successful retropropulsive landing could have achieved many things discussed here on this thread as well as many others. The Dragon capsule could have been the entire stationary science lab as well as the radar transponder for a subsequent larger and manned lander. If it had been equipped to drop the heat shield, could have had an onboard drill system and penetrometer to determine weight bearing properties of the regolith at the landing site. It could also incorporate an extendable camera mast for photography of the immediate vicinity of the site where landed and out to a radius of several kilometers. With a good PV array, could be kept running for a long time. It would allow incorporation of a larger Moxie unit to test the on-Mars efficacy of such a system. It could also do a survivability test of the new Kilopower nuclear reactor generators. But given the aggressive nature of SpaceX, all this could be assembled in time for the 2020 Mars window.

Incorporated in the Dragon trunk could be 3-4 GPS satellites for in Mars orbit deployment. Two such identically equipped Red Dragon missions could establish a minimum constellation of GPS satellites, as well as establishing some data regarding two of the proposed landing sites, as well as having 2 additional radar transponders on the planetary surface. My cost estimate for doing this might be around $400 to $500 Million for the pair of missions. Launching these about 30 days apart using a Block 5 Falcon Heavy system (reusable), would go a long way towards answering some of the questions that I and other astute posters here have posed. If the Block 5 Falcon Heavy were to be used there could be as many as 3 launches for construction of the Mars GPS system, and accomplishing a lot of landing zone knowledge.

Overall, I would counsel SpaceX to take a more conservative approach to things, with several pioneer type missions including a GPS constellation concurrently with landing site evaluations. They could conceivably repeat this approach for the 2022 launch window, along with (perhaps) a BFR lander (maybe). If there cold be as many as 18 GPS satellites in the Mars constellation, it would go a long way in enhancing BFR landing accuracy.

Last edited by Oldfart1939 (2018-05-06 11:01:36)

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