Journey time to Mars...

louis · 2018-11-10 13:16:03

By the "only game in town" I meant the only organisation that will get humans to Mars any time soon. I didn't say they weren't dependent on NASA to do that. They are. For one thing - which you didn't mention - Space X can't currently replicate NASA space communications system.

kbd512 wrote:

Louis,
By that logic, SpaceX isn't in the game.
There would be no thin film solar arrays without NASA, although there is now.
There is no LOX/LCH4 plant without NASA.
There is no surface habitation solution without NASA.
There is no long duration life support equipment without NASA.
There is no adequate radiation protection without NASA.
There is no low-G / micro-G mitigation strategy without NASA.
SpaceX doesn't have trained astronauts, either, although there are other places to get them from besides NASA.
Did you catch on to the problems, yet?
Nobody has the solutions to all problems.

kbd512 · 2018-11-10 14:59:04

Louis,

The communications and sensor systems are mostly spin-offs of DoD projects. In that sense, not even NASA has an adequate communications system in place for human exploration of Mars. However, JPL's Deep Space Communications Network is the only system of its kind currently in operation and the only way to "phone home". Basically, the US Air Force or US Space Force needs to deploy assets to Mars and Venus to enable communications relay between Mars and Earth.

Despite your criticisms of NASA, the agency has killed more people in the pursuit of space exploration than all other public and private entities combined. If anything, NASA doesn't know when to say when. That is what bred the current atmosphere of extreme conservatism when it comes to space exploration. It has nothing to do with the agency's desire to prevent anyone from exploring space. It's very hard to explain to ignorant talking heads that the decisions the agency made made were not made with the benefit of hindsight. However, those same talking heads influence the electorate and their support for government funding for space exploration.

There's very little doubt in my mind that SpaceX will develop and eventually fly BFS, but there are physical limitations to every technology that have been pointed out by GW, Oldfart1939, and myself, which other people (inside and outside of NASA) are perfectly willing to ignore when it conflicts with their "gotta get there-itis".

I see what SpaceX is proposing as trying to make BFS a single solution to the plethora of unique problems associated with their goal of sending people to Mars. Basic math and physics says there's only so many things that a single vehicle can do acceptably well.

Here's what I do know:

For SpaceX to send people to Mars at all, they need outside help, and not simply help from government agencies.

1. We need JPL, DoD, and NASA to create a robust deep space communications network with communications and positioning assets spread throughout the inner solar system.

2. We need Orbital ATK, Lockheed-Martin, Boeing, and Aerojet-Rocketdyne to provide hardware for more efficient and cost-effective in-space propulsion.

3. We need Bigelow Aerospace to provide better habitation solutions that provide enough volume for continuous long term habitation.

4. We need ULA to provide Integrated Vehicle Fluids technology to reduce the mass and complexity of in-space maneuvering systems.

5. We need ILC Dover and Paragon SDC to provide advanced space suit and life support technologies.

6. We need universities, research organizations, and petrochemical corporations to provide ISRU / ISPP technologies for life support and propellant production.

7. Last but certainly not least, we need SpaceX to provide innovative and cost effective human-rated space transportion technologies.

We can pretend that any given company has the answers to all problems associated with sending humans to another planet, but cursory examination of the numerous and varied problems clearly demonstrates that such is not the case. What I've proposed takes nothing away from SpaceX's vital role in solving these problems, but they need to work with other companies that share their desire to go to Mars to achieve their objectives. If it's helpful to moving the project forward, I would also support leaving our government out of the decision making process. SpaceX and Bigelow Aerospace can decide on their own how to deploy a suitable habitation system, for example. Apart from meeting basic precautions against injury and death, which the government has a duty to provide oversight for, SpaceX can decide how and where to deploy cargo for human space flight.

That said, Elon Musk always seems to be the first to point out that there is no adversarial relationship between his company and NASA. The agency, to its credit, has a consistent position that their role is as an enabler for interested parties, such as SpaceX, not a roadblock to prevent technological progress. It should be noted that NASA and the US Air Force have consistently funded and backed SpaceX as a preferred launch services provider, to the tune of many billions of dollars. NASA recently accredited SpaceX's Falcon 9 rocket as a Category 3 launch vehicle, entrusted with our nation's most costly and sophisticated space exploration payloads. Similarly, the US Air Force entrusts Falcon 9 with their most expensive and highly classified national security payloads. If that weren't proof enough, neither NASA nor the US Air Force has ever uttered a cross word against SpaceX, unlike some of SpaceX's "old space" competitors, which have received scathing criticism for their inexplicable failures.

More funding for this endeavor would always be welcome, but our government has to weigh a number of competing priorities, all of which are more important than sending humans to another planet. I still believe that program progress is being made at best possible speed, given the inevitable setbacks and dead-end paths that are discovered along the way to the goal. Like you, I'm often frustrated by the apparent lack of progress. At the end of the day, everyone with any real knowledge of the numerous problems knows that this endeavor is far and away the most significant technological challenge of our time. If we still haven't made tangible progress in the next decade, then I may change my opinion. Right now, all I see is a lot of very promising technology that needs to be marshaled into a cohesive program. If SpaceX can do that on their own, then more power to them. If not, then a more comprehensive and systematic program needs to be implemented.

louis · 2018-11-10 17:38:30

I tend to think of JPL as surgically attached to NASA, owing to its financial dependence on NASA. JPL would never refuse NASA or a NASA-approved partner access to its space comms network, in my view. The Space X - NASA relationship is key.

Space X I don't think has killed anyone yet...I think NASA is risk averse regarding human exploration of the solar system, but that's more in the nature of an excuse than a genuine mindset (when they were putting humans into space, they were quite reckless post-Apollo).

I agree NASA doesn't know when to say when. It's basically because it's been captured by scientists rather than engineers, explorers or visionaries. Science is pretty much infinite in its curiosity - so they pursue just about everything spreading themselves way too thinly. It's absurd, because if NASA had got us to Mars say 20 years ago, the amount of scientific info we would have gathered would be stupendous in comparison to the paltry amounts gathered by all those robot rover and similar missions.

I definitely don't agree with you about the BFS. It is certainly the right solution in the current space era. Think of how many commercial road vehicles on Earth don't go around carrying their maximum cargo weight but are used profitably, but it is the maximum that gives the flexibility. The BFS will of course be modified for its different uses, but those are minor technical changes. By pooling development costs over about seven discrete applications coming into play over maybe 20 years, Space X have found the perfect way to spread development costs across a range of products. It's pure genius! I admit I got it wrong because I tended to "think small" as the way to get to Mars when all along Musk had the right approach: think big! There may have been a fair amount of serendipity involved (otherwise why would Musk have taken that Shuttle-like Falcon 9H detour) but all's well that ends well.

Space X are not claiming they have all the answers. In fact they have issued an open invitation to companies to come up with Mars Mission solutions.

Regarding your points:

"1. We need JPL, DoD, and NASA to create a robust deep space communications network with communications and positioning assets spread throughout the inner solar system."

Yes I would basically agree with that. I doubt Space X have the wherewithal to do it themselves (given the need for big ground stations which can't just be magicked up in a few years).

"2. We need Orbital ATK, Lockheed-Martin, Boeing, and Aerojet-Rocketdyne to provide hardware for more efficient and cost-effective in-space propulsion."

Eventually maybe but for now methane rockets are fine and dandy and will get us to Mars - and back.

"3. We need Bigelow Aerospace to provide better habitation solutions that provide enough volume for continuous long term habitation."

I was a Bigelow fan but there development programme seems v. slow. I doubt Space X actually need them for anything. I am now tending to favour on site construction of habitats - from units that are largely self-assembly.

"4. We need ULA to provide Integrated Vehicle Fluids technology to reduce the mass and complexity of in-space maneuvering systems."

Will be interested to hear more about that as I don't follow.

"5. We need ILC Dover and Paragon SDC to provide advanced space suit and life support technologies."

I think Space X are involved in some space suit development programme with NASA already. Certainly this is something that would be largely contracted out.

"6. We need universities, research organizations, and petrochemical corporations to provide ISRU / ISPP technologies for life support and propellant production."

Yes, this is definitely the case. This is one of the most concerning areas for me. If Space X are making substantial progress in these areas they are keeping it very secret! You would think a Mars-centred company would have as much of this on their website as their rockets. That said, Space X does have to be careful. We know Russia and China for sure aggressively hack commercial firms for technological development. A softly-softly approach may be wise to keep competitors at bay.

"7. Last but certainly not least, we need SpaceX to provide innovative and cost effective human-rated space transportion technologies."

That'll be the BFR-BFS you're talking about!

kbd512 wrote:

Louis,
The communications and sensor systems are mostly spin-offs of DoD projects. In that sense, not even NASA has an adequate communications system in place for human exploration of Mars. However, JPL's Deep Space Communications Network is the only system of its kind currently in operation and the only way to "phone home". Basically, the US Air Force or US Space Force needs to deploy assets to Mars and Venus to enable communications relay between Mars and Earth.
Despite your criticisms of NASA, the agency has killed more people in the pursuit of space exploration than all other public and private entities combined. If anything, NASA doesn't know when to say when. That is what bred the current atmosphere of extreme conservatism when it comes to space exploration. It has nothing to do with the agency's desire to prevent anyone from exploring space. It's very hard to explain to ignorant talking heads that the decisions the agency made made were not made with the benefit of hindsight. However, those same talking heads influence the electorate and their support for government funding for space exploration.
There's very little doubt in my mind that SpaceX will develop and eventually fly BFS, but there are physical limitations to every technology that have been pointed out by GW, Oldfart1939, and myself, which other people (inside and outside of NASA) are perfectly willing to ignore when it conflicts with their "gotta get there-itis".
I see what SpaceX is proposing as trying to make BFS a single solution to the plethora of unique problems associated with their goal of sending people to Mars. Basic math and physics says there's only so many things that a single vehicle can do acceptably well.
Here's what I do know:
For SpaceX to send people to Mars at all, they need outside help, and not simply help from government agencies.
1. We need JPL, DoD, and NASA to create a robust deep space communications network with communications and positioning assets spread throughout the inner solar system.
2. We need Orbital ATK, Lockheed-Martin, Boeing, and Aerojet-Rocketdyne to provide hardware for more efficient and cost-effective in-space propulsion.
3. We need Bigelow Aerospace to provide better habitation solutions that provide enough volume for continuous long term habitation.
4. We need ULA to provide Integrated Vehicle Fluids technology to reduce the mass and complexity of in-space maneuvering systems.
5. We need ILC Dover and Paragon SDC to provide advanced space suit and life support technologies.
6. We need universities, research organizations, and petrochemical corporations to provide ISRU / ISPP technologies for life support and propellant production.
7. Last but certainly not least, we need SpaceX to provide innovative and cost effective human-rated space transportion technologies.
We can pretend that any given company has the answers to all problems associated with sending humans to another planet, but cursory examination of the numerous and varied problems clearly demonstrates that such is not the case. What I've proposed takes nothing away from SpaceX's vital role in solving these problems, but they need to work with other companies that share their desire to go to Mars to achieve their objectives. If it's helpful to moving the project forward, I would also support leaving our government out of the decision making process. SpaceX and Bigelow Aerospace can decide on their own how to deploy a suitable habitation system, for example. Apart from meeting basic precautions against injury and death, which the government has a duty to provide oversight for, SpaceX can decide how and where to deploy cargo for human space flight.
That said, Elon Musk always seems to be the first to point out that there is no adversarial relationship between his company and NASA. The agency, to its credit, has a consistent position that their role is as an enabler for interested parties, such as SpaceX, not a roadblock to prevent technological progress. It should be noted that NASA and the US Air Force have consistently funded and backed SpaceX as a preferred launch services provider, to the tune of many billions of dollars. NASA recently accredited SpaceX's Falcon 9 rocket as a Category 3 launch vehicle, entrusted with our nation's most costly and sophisticated space exploration payloads. Similarly, the US Air Force entrusts Falcon 9 with their most expensive and highly classified national security payloads. If that weren't proof enough, neither NASA nor the US Air Force has ever uttered a cross word against SpaceX, unlike some of SpaceX's "old space" competitors, which have received scathing criticism for their inexplicable failures.
More funding for this endeavor would always be welcome, but our government has to weigh a number of competing priorities, all of which are more important than sending humans to another planet. I still believe that program progress is being made at best possible speed, given the inevitable setbacks and dead-end paths that are discovered along the way to the goal. Like you, I'm often frustrated by the apparent lack of progress. At the end of the day, everyone with any real knowledge of the numerous problems knows that this endeavor is far and away the most significant technological challenge of our time. If we still haven't made tangible progress in the next decade, then I may change my opinion. Right now, all I see is a lot of very promising technology that needs to be marshaled into a cohesive program. If SpaceX can do that on their own, then more power to them. If not, then a more comprehensive and systematic program needs to be implemented.

Oldfart1939 · 2018-11-11 00:20:23

Regarding the communications for mars missions, please see my post #36 of this thread.

louis · 2018-11-11 17:45:16

I took a look - but it seems to me if you have a working communications system in place why would you reinvent the wheel.

I am sure the communications system can be improved upon, but that could be done incrementally. The most important thing I think is to ensure that for Mission One we have a really big communications transmitter that can send back lots of data (so far, it seems to me, they have been very small). I don't think there's any problem with catching the data back on Earth.

Oldfart1939 wrote:

Regarding the communications for mars missions, please see my post #36 of this thread.

SpaceNut · 2018-11-11 18:09:01

But its not yours in the case of Space x and does not mean that they will be willing to share the technology.

Oldfart1939 · 2018-11-11 20:40:22

Having a dual purpose GPS and communications constellation is one of the HIGHEST priorities necessary before any major mission/expedition. This is entirely possible with the FH system Would also allow refinement of the necessary guidance package for the BFR. Would be a great private/public partnership project. NASA supplies the satellites, SpaceX the vehicle and launch support, Could still reclaim the 1st stage boosters.

SpaceNut · 2018-11-12 09:31:25

The twin cube sat's will tell us a huge amount as to how much larger they will really need to be for encircling mars. Even if these are made 4 times larger to give more fuel and power its still not a billion dollar effort as most that are around earth are for each unit.

kbd512 · 2018-11-12 14:49:08

Louis,

We have low data rate communications for scientific probes. That's not the same thing as having a wide enough pipe for crewed missions. Why do you think NASA is working on laser communications? Even their science missions are becoming limited by available bandwidth as the computing power of the latest generation of rad-hard solid state electronics produces reams of data to send back to Earth.

As to your other points:

Methane is "just fine" if you want to spend lots of money on flying gas to orbit. For this to be economical for potential paying customers, a better propulsion system is required. That's what combined chemical and electric propulsion provides. No Methalox rocket engine has flown to space yet, so it's flight heritage is zero. Hall thrusters, on the other hand, are far more of a flight proven in-space propulsion technology.

SpaceX "actually needs" inflatables that Bigelow Aerospace makes to live inside something other than the rocket. There's no permanent human presence on Mars if SpaceX's rocket is the only habitable place on Mars. If the rocket has to leave Mars to come back to Earth, do the people already on Mars hold their breath until another rocket shows up or do they leave in the habitable structure on Mars?

Integrated Vehicle Fluids (IVF) is all about using the vehicle's main engine propellants (LOX/LCH4 in SpaceX's application, or LOX/LH2 in ULA's RL-10 application) for the reaction control system, rather than lower-Isp storable propellants like NTO/MMH, which incurs additional mass / complexity / hazard / cost penalties (and if you ever run out of whatever type of Hydrazine you're using, you can't get any more, except from Earth). Further, it provides main propellant tank pressurization and electrical power by burning the propellant in a conventional piston-driven combustion engine (a massively de-rated / de-tuned race car engine). Recall that the only Falcon rockets that blew up were destroyed by their Helium COPV's required to pressurize the LOX and RP1 tanks. When your propellants are all cryogenic and your IVF can regulate tank pressure and temperature, you'll last a lot longer.

The reason the ISRU/ISPP is "so secret" is that nothing is happening, outside of the lab experiments done at NASA. That's the "big secret". Nobody has the answer to this problem yet. If they did, you'd see patent filings for the technology so someone else didn't "discover it" and patent it first. I've seen nothing and can only assume that there's no progress.

louis · 2018-11-12 15:41:47

kbd512 wrote:

Louis,
We have low data rate communications for scientific probes. That's not the same thing as having a wide enough pipe for crewed missions. Why do you think NASA is working on laser communications? Even their science missions are becoming limited by available bandwidth as the computing power of the latest generation of rad-hard solid state electronics produces reams of data to send back to Earth.

Surely that just because the probes are small. Won't Space X be able to take a large transmitter dish with them?

As to your other points:
Methane is "just fine" if you want to spend lots of money on flying gas to orbit. For this to be economical for potential paying customers, a better propulsion system is required. That's what combined chemical and electric propulsion provides. No Methalox rocket engine has flown to space yet, so it's flight heritage is zero. Hall thrusters, on the other hand, are far more of a flight proven in-space propulsion technology.

The cost of space transport is not relevant if Space X are making a profit. They can definitely make a profit at $10,000 per kg in my view. Mass colonisation can follow later on.

SpaceX "actually needs" inflatables that Bigelow Aerospace makes to live inside something other than the rocket. There's no permanent human presence on Mars if SpaceX's rocket is the only habitable place on Mars. If the rocket has to leave Mars to come back to Earth, do the people already on Mars hold their breath until another rocket shows up or do they leave in the habitable structure on Mars?

It's not clear to me they need a Bigelow inflatable. If they have a pressurised Rover vehicle that can be used for temporary accommodation on the surface (probably no more than one or two sols) before the hab is constructed. I envisage that being semi-automatic assembly.

kbd512 · 2018-11-12 19:00:58

Louis,

The data rate isn't solely determined by the size of the satellite dish. There's a little more to it than that. This was something I dealt with in the Navy. The size of our satellite dish wasn't what typically degraded data transmission rate. A bigger dish could help, but only to a point. Lasers can transmit more data at higher rates with a greater signal to noise ratio than is practical for the types of radio frequency communications equipment in common use for long distance communication purposes. The frequency of the carrier signal and the error rates from poor signal quality have a lot to do with it.

They can't make a profit without a product people can afford to buy. Ask people you know how many of them would sell everything they own to move to Mars to live in a tent and tend to a farm like a farmer does. Get back to us after you do.

SpaceX doesn't absolutely have to buy an inflatable from Bigelow Aerospace, but no other company I know of makes inflatables that have been long duration tested in space. I find the idea that they could make their own to be possible but implausible. It's taken decades to develop the technology.

louis · 2018-11-12 19:27:47

kbd512 wrote:

Louis,
The data rate isn't solely determined by the size of the satellite dish. There's a little more to it than that. This was something I dealt with in the Navy. The size of our satellite dish wasn't what typically degraded data transmission rate. A bigger dish could help, but only to a point. Lasers can transmit more data at higher rates with a greater signal to noise ratio than is practical for the types of radio frequency communications equipment in common use for long distance communication purposes. The frequency of the carrier signal and the error rates from poor signal quality have a lot to do with it.

Well your experience is interesting but I guess whatever the method (dish or otherwise): (a) there is a relationship between mass of equipment and strength of signal (so the question is simply how many tonnes do we have to take to Mars to be able to return rich quantities of data e.g. real time video*) and (b) our receiving dishes on Earth are geared to receive extremely weak signals (because we are looking into the far reaches of the cosmos).

* I am guessing we can probably do that with 5 tonnes (plus using our PV energy system), but happy to be persuaded otherwise.

They can't make a profit without a product people can afford to buy. Ask people you know how many of them would sell everything they own to move to Mars to live in a tent and tend to a farm like a farmer does. Get back to us after you do.

You've got it the wrong way round. The profit initially comes from sources such as Space Agencies, universities, TV companies, newspaper groups, major websites, big manufacturing firms, tech companies - all of whom, taken together, control trillions of dollars of expenditure. Mass colonisation lies much further down the road - at least 20 years after landing and probably more like 50 years.

SpaceX doesn't absolutely have to buy an inflatable from Bigelow Aerospace, but no other company I know of makes inflatables that have been long duration tested in space. I find the idea that they could make their own to be possible but implausible. It's taken decades to develop the technology.

I wasn't suggesting Space X make inflatables...in fact it's because Space X are using the BFR rocket I think inflatables might not be that appropriate. They are a bit of a pain, really.

I am thinking much more "flat pack assembly". But with a degree of self-assembly. So, essentially you have aerogel sandwich panels. some of these can be hinged together. There will be some final assembly work involving bolts being screwed into position and internal sealant application. Once assembled they will be boxes standing on adjustable leg to ensure good horizontal alignment. There would need to be separate assembly of adjoining pressure chambers.

The advantage over Bigelow would be that these units could be larger (given the limitations placed upon hab size by the diameter of the BFR, if you are using inflatables - remembering they aren't that small when deflated).

A big single Bigelow inflatable will be a difficult item to offload from the BFR. How much will it weigh? How do you get it to the desired location? Individual panel sections are much easier to offload and then assemble at the desired location.

SpaceNut · 2018-11-12 20:02:07

No one gets a free ride and the individual will need to invest, on not just the trip to mars but as well in the survival of oneself once there.

Laser communications is a straight line of sight and is in usually non visible frequencies where there is less interference that are stationary. Uplinks from surface will not be laser due to atmospheric attenuations and trying to target a moving target limits the possible use for Low mars orbits and will require geosynchronous satellite for mars and for earth to create the link required.

Even with the speed of laser light the time delays are at its Closest approach: 182 seconds, or just over 3 minutes. and at its Farthest approach: 1,342 seconds, or just over 22 minutes.

Inflateables will only make the grade for use as to when they contain more than the air it takes to inflate them, have more than 1 to 2 connecting points, have airlock capability....

.

louis · 2018-11-12 20:19:50

SpaceNut wrote:

Inflateables will only make the grade for use as to when they contain more than the air it takes to inflate them, have more than 1 to 2 connecting points, have airlock capability....

.

And also not be so big and heavy that offloading them from a BFS is an extremely difficult exercise - remember even if you can get it in the hold - can you get it through the cargo door? And there has to be a door of some type because of the structure of the rocket. I think you could end up with quite a small Bigelow structure. Bigelows are better adapted to launch into orbit.

kbd512 · 2018-11-12 20:32:12

Louis,

With a better deep space communications network in place, the communication system on the lander or base could weigh tens of kilograms. Anyway, I think the point is lost on you.

Regarding profitability, maybe from space agencies. Apart from that, I don't see most of what you proposed happening in the near future. It's too expensive to send a small science payload to LEO for all but the largest corporations and space agencies. Universities could work out some sort of ride sharing, so I could see that happening. I'm not sure what tech company needs to send something to Mars to test it, so I don't see that happening.

Regarding lego buildings, we already hashed out why that won't work. No pressure vessel is built that way and there are very real engineering reasons why they're not. I wasn't suggesting that the inflatable should have anything installed in it, unlike the space station modules, so it could also be relatively compact for storage purposes.

The BA-2100 module is expected to have a mass between about 65t and 70t when minimally outfitted (life support, avionics, power, etc), but they're saying it could weigh up to 100t when chock full of consumables and scientific equipment. BFS is supposed to have 1,000m^3 of pressurized volume. The BA-2100 is supposed to have 2,250m^3 of pressurized volume. A single BA-2100, with well over double the pressurized volume of the BFS, could easily hold enough consumables for a 2 year transit. If it uses the upper stage of a BFR, without the heat shield and wings, then it could combine Raptor and SEP technology into a purpose-built vehicle that leverages the best features of inflatables combined with SpaceX and Aerojet-Rocketdyne propulsion technology. The walls of the BA-2100 are just over 4 feet thick, comprised of many layers of fabric that perform much better than Aluminum and Carbon Fiber when it comes to stopping MMOD. It's 12.6m in diameter and 17.6m in length. I can promise that a carbon composite ship that only weighs 85t will be nowhere near as durable as the inflatable. A Raptor-enabled Falcon 9 Heavy upper stage should be able to orbit the beast and a LOX/LH2 upper stage would have no issue doing that.

louis · 2018-11-13 04:32:59

kbd512 wrote:

Louis,
With a better deep space communications network in place, the communication system on the lander or base could weigh tens of kilograms. Anyway, I think the point is lost on you.

Indeed but to get your better space communications network you will have to launch hundreds of tonnes into space on multiple launches, all requiring planning and resources.

While a well functioning space communications network is desirable and will be realised eventually, at this stage it makes much more sense to take a big transmitter.

Regarding profitability, maybe from space agencies. Apart from that, I don't see most of what you proposed happening in the near future. It's too expensive to send a small science payload to LEO for all but the largest corporations and space agencies. Universities could work out some sort of ride sharing, so I could see that happening. I'm not sure what tech company needs to send something to Mars to test it, so I don't see that happening.

Tech companies already spend billions on PR of one sort or another. I think all the big ones: Google, Microsoft, Apple, Vodafone, Samsun, Sony, Facebook etc will want to have a "presence" on Mars for PR purposes. Space X, if they have any sense won't be giving away that presence for free.

Regarding lego buildings, we already hashed out why that won't work. No pressure vessel is built that way and there are very real engineering reasons why they're not. I wasn't suggesting that the inflatable should have anything installed in it, unlike the space station modules, so it could also be relatively compact for storage purposes..

I think this needs further discussion and research. From what I am reading on the net, it is suggested a Mars surace hab would need to be able to withstand 2000 pounds of pressure per sq. foot. But pressure vessels like submarines have to withstand in excess of 40,000 pounds per sq. foot. I've no idea whether the direction of pressure makes a difference.

Not sure if I am reading this right but the hab needs to survive pressure around 15 psi if the figure I quoted is correct whereas some bolts can survive pressures of 120,000 PSI...

https://www.greensladeandcompany.com/wp … %20PSI.pdf

Bolt fastening doesn't seem to be a problem per se. I presume for the panels you might choose a strong honeycomb structure filled with aerogel and of course you'd be using whatever metal or alloy provides greatest strength in context.

kbd512 · 2018-11-13 05:57:24

Louis,

Regarding using the existing communications network, I'll present Exhibit A, which is the Sabatier reactor aboard ISS. It has as many parts as a jet engine. Unlike a jet engine, where you have a bunch of little parts that all do the same thing, all the little parts do different things in the Sabatier reactor. They tried to fix it on orbit where high data rate communications were available to provide HD video of the problem to the engineers at NASA. Eventually they gave up and shipped a new unit to ISS. You don't have months to fiddle with a problem related to the life support equipment, nor days in most cases. That's how long it could take to transmit a few minutes worth of video clear enough to determine what you're looking at. You either get useful information to the people who can help you or you're screwed. A bigger satellite dish won't help. From years of actual personal experience using satellite transceivers aboard Navy ships, this just won't work the way you want it to work. I've said what needed to be said about this point and you can believe what you choose to believe.

Your bolted-together square steel or composite lego building won't hold air. 15psi means 2,160 pounds of pressure per square foot. Over a wall the size of a useful building, you need to either put the entire pressure vessel in tension or accept that the building will get unacceptably heavy, very quickly. All that extra weight to try to make a square building into a pressure vessel isn't worth it. Even if you were willing to pay the mass penalty, the structure would still prematurely crack and fail at the interfaces between the joints and/or fasteners. Putting a bolt through a hole in a wall that will inevitably deform under load doesn't make the structure airtight, either.

Look at the shape of any pressure vessel. Why are all of them a bunch of smooth curves instead of squares / cubes or triangles / pyramids? Why are aircraft windows rounded? Google "de Havilland Comet" to find out why.

Aerogel foams suitable for structural applications in composites are substantially heavier than carbon fiber. They have a lot of good qualities that make them useful as insulation and they're mostly fireproof. However, the honeycombs you mentioned tend to be lighter and stronger still, even when the honeycomb material is a high strength Aluminum alloy sandwiched between carbon fiber. The use of fabrics is about ultimate durability, more predictable failure modes, not producing secondary particle showers from ionizing radiation (GCR's) striking thin metal cans, and total cost for a given pressurized volume.

louis · 2018-11-13 07:29:35

kbd512 wrote:

Louis,
Regarding using the existing communications network, I'll present Exhibit A, which is the Sabatier reactor aboard ISS. It has as many parts as a jet engine. Unlike a jet engine, where you have a bunch of little parts that all do the same thing, all the little parts do different things in the Sabatier reactor. They tried to fix it on orbit where high data rate communications were available to provide HD video of the problem to the engineers at NASA. Eventually they gave up and shipped a new unit to ISS. You don't have months to fiddle with a problem related to the life support equipment, nor days in most cases. That's how long it could take to transmit a few minutes worth of video clear enough to determine what you're looking at. You either get useful information to the people who can help you or you're screwed. A bigger satellite dish won't help. From years of actual personal experience using satellite transceivers aboard Navy ships, this just won't work the way you want it to work. I've said what needed to be said about this point and you can believe what you choose to believe.

Well my Exhibit B is the Apollo Mission coms. We got pretty good live video back from the lunar surface, using a dish with 1960s technology.

https://ntrs.nasa.gov/archive/nasa/casi … 015392.pdf

I am sure we can do even better now. The distance from Mars is much greater of course. But I think that's where you are back to a more powerful transmitter and a more sizeable dish.

Your bolted-together square steel or composite lego building won't hold air. 15psi means 2,160 pounds of pressure per square foot. Over a wall the size of a useful building, you need to either put the entire pressure vessel in tension or accept that the building will get unacceptably heavy, very quickly. All that extra weight to try to make a square building into a pressure vessel isn't worth it. Even if you were willing to pay the mass penalty, the structure would still prematurely crack and fail at the interfaces between the joints and/or fasteners. Putting a bolt through a hole in a wall that will inevitably deform under load doesn't make the structure airtight, either.
Look at the shape of any pressure vessel. Why are all of them a bunch of smooth curves instead of squares / cubes or triangles / pyramids? Why are aircraft windows rounded? Google "de Havilland Comet" to find out why.

I accept fully the preferred shape for pressure vessels is rounded. I just think there may be methods of of creating assembled panel buildings under pressure. We're often told in a Mars setting that things "aren't possible" but they prove to be some years later.

I think a kind of bulkhead arrangement would work internally. So maybe say a 20 feet x 20 x 7 hab would be constructed of sixteen 5 x 7 x 5 panels. These could be bolted on to internal struts at floor and ceiling level and also bolted on to struts that pass horizontally between the floor-to ceiling struts (maybe at a height of 2.5 and 5 feet. Electromagnets could be used to give added assurance of panels being aligned with no possibility of major leakage, sealant having also been applied to all joins. I feel like such a construction would be possible.

Aerogel foams suitable for structural applications in composites are substantially heavier than carbon fiber. They have a lot of good qualities that make them useful as insulation and they're mostly fireproof. However, the honeycombs you mentioned tend to be lighter and stronger still, even when the honeycomb material is a high strength Aluminum alloy sandwiched between carbon fiber. The use of fabrics is about ultimate durability, more predictable failure modes, not producing secondary particle showers from ionizing radiation (GCR's) striking thin metal cans, and total cost for a given pressurized volume.

I am proposing that the whole of the hab is covered in regolith for radiation protection. I suggest that the hab come with an external frame that can be fitted to facilitate the piling of regolith on top and at the sides.

Last edited by louis (2018-11-13 07:31:23)

kbd512 · 2018-11-13 14:14:23

Louis,

The moon is only a quarter million miles away and has direct line-of-sight (LOS) to the Earth. Believe it or not, even way back in the 1960's, LOS communications equipment was up to the task of transmitting voice and grainy video images. At standard frame rate, 1080p video is 8 megabits per second (mbps). Current networks are currently capable of about a quarter of that. The new Ka-band satcom equipment is capable of 100mbps. The laser communications systems NASA has tested in space are capable of as much as 600mbps and possibly as high as 1,024mbps.

The Lunar Lasercom Space Terminal (in lunar orbit) demonstrated transmit throughputs between 40mbps to 622mbps at a 1550nm wavelength and 10mbps to 20mbps receive. The Lunar Lasercom Ground Terminal (White Sands Complex, New Mexico) demonstrated 10mbps to 20mbps transmit and 40 to 622mbps receive. Compared to the satcom antennas, these things are lightweight and tiny and the 20mbps data rates were completely error-free, which means no retransmission of lost data was necessary.

Anyway, ISS, Orion, Earth ground stations (JPL), and another satellite demonstrator program known as the Deep Space Optical Network is being readied to transfer data at 1,244mbps. Performance will be achieved using 76We (with a 31% power margin) to the entire space terminal, with 4We powering the laser itself. The target system mass for the space terminals is 28kg (with a 30% mass margin). A low data rate radio beacon is used to both steer the beam onto the target back on Earth and to transfer data at low rates. The space terminals feature rad-hard electronics (20,000 rad) and isolation mounts to prevent any vibrations from affecting where the laser is pointed.

Mars Reconnaissance Orbiter can transmit at a maximum data rate of 5.2mbps and it takes 1.5 hours to transmit a single HiRISE image back to Earth. The new Lasercom system would require approximately 22.5 seconds to complete that task. Anyway, the new system is supposed to be a part of NASA's / JPL's 2022 mission to the asteroid named "16 Psyche".

Since SpaceX is already providing the launch services for this program and has been involved for years now, I don't see what the issue would be with them using it for communications purposes.

How NASA's New Mars Rover Will Phone Home

Excerpt from the article:

...
Controllers on Earth will have three ways of hailing Curiosity as it trundles around Gale Crater. Two are direct links through NASA's Deep Space Network, a worldwide collection of antennas. It provides both a fixed low-gain antenna, best for basic commands and emergencies, and a pointable high-gain antenna for complex commands. [11 Amazing Things NASA's Mars Rover Can Do]
Curiosity also has a higher-speed ultra-high frequency (UHF) communications system that can send signals to spacecraft orbiting Mars, which in turn would relay them to Earth.
To send back imagery, Curiosity must stay in touch with the Mars Reconnaissance Orbiter and Mars Odyssey spacecraft, two probes orbiting Mars that each can talk to the rover twice a day. (Odyssey is currently recovering from the loss of one of its three reaction wheels.)
"The high-gain antenna only gives us a moderate amount of bandwidth," Vasavada told SPACE.com. "We can transmit a series of commands every morning. But it's not enough to transmit hundreds of images every day."
...

Each minute of 1080p video to demonstrate a problem to mission control would take at least 4 minutes to transmit. Opinions on the matter clearly differ, but I think that means we need better comms. The upgrade to Ka-band comms and a small constellation of orbital COM/NAV/GPS satellites would be what I would think is the bare minimum necessary to ensure that the crew has adequate support. We're talking about 500kg class satellites using electric propulsion. Falcon 9 Heavy can already deliver 16t to Mars, so why not use CC-SEP to send the satellites to their destination and then ring the planet with high data rate Lasercom and Ka-band satcom relays? This would be a JPL task, anyway.

This square pressure vessel idea is becoming every bit as silly as what Dook proposed. Nobody runs a giant MRI machine to maintain the structural integrity of a square steel pressure vessel while its loaded with computers and humans not undergoing medical treatment. That's what you're now talking about doing. The rounded pressure vessel idea isn't an engineering suggestion, it's an engineering fact. Submarines are made of welded (not riveted or bolted together) HY80 or HY100 steel a half inch thick. Obviously somewhat thinner steel could be used, but it's still a recipe for failure. No engineer would ever propose doing something like that, just to prove that a square pressure vessel could also work. It's an utter waste of available tonnage.

Oldfart1939 · 2018-11-13 15:17:58

Louis-

To minimize the exchanges we're seeing here, you really need to buy a copy of Bob Zubrin's "Entering Space." It's really the way to satisfy your thirst for the knowledge you seem to be seeking. The simple and one-line answer to the problem of data transmission rates is POWER. The 300 We Plutonium sources on the various space probes does not allow much data to be transmitted from Jovian and Saturnian space, and even less from beyond.

Last edited by Oldfart1939 (2018-11-13 15:30:22)

louis · 2018-11-13 17:07:18

Here's what I said.

"The distance from Mars is much greater of course. But I think that's where you are back to a more powerful transmitter and a more sizeable dish."

The Mars Reconnaissance Orbiter seems capable of transmitting back 6 megabits per second...which is four times the recommended Nexflix streaming amount...

https://en.wikipedia.org/wiki/Mars_Reco … ons_system

The amplifier(s) seem to consume about 200We. I don't know how much other power is used.

We clearly need something larger than the MRO transmitter but maybe not a lot more powerful.

Oldfart1939 wrote:

Louis-
To minimize the exchanges we're seeing here, you really need to buy a copy of Bob Zubrin's "Entering Space." It's really the way to satisfy your thirst for the knowledge you seem to be seeking. The simple and one-line answer to the problem of data transmission rates is POWER. The 300 We Plutonium sources on the various space probes does not allow much data to be transmitted from Jovian and Saturnian space, and even less from beyond.

SpaceNut · 2018-11-13 17:40:26

But it could not able handle multiple on the surface items trying to send data back to earth as it was not designed for that purpose for continous communications. Case in point we are on the night side of the planet and we need to talk. The MRO is orbiting at a different rate but is not geosynchronous so we are waiting for alignment to happen to recieve its information from the surface and many hours later relay them when aligned for earth transmission. Then depending on orbit season we could be waiting beyound the solving time required any where from the 4 to 22 minutes to hear back if we are on the right side of the alignment otherwise we are waiting for the relay to happen to the surface.

louis · 2018-11-13 18:41:41

We lived with that on the lunar Apollo missions (dark side of the orb)...I think we can live with it on the Mars Missions.

It's useful to have contact with Earth but essentially when you send people to Mars, you send them as autonomous units. It's misleading to think of there being a "ground control".

Regarding information carried on the BFS, compared with when the lunar missions were taking place we can now carry whole libraries on memory sticks and we can put a lot of AI on the BFS - to diagnose faults and suggest solutions. If there is something that needs fixing it will be better to have those systems on board, rather than waiting anything up to 44 minutes for an answer.

SpaceNut wrote:

But it could not able handle multiple on the surface items trying to send data back to earth as it was not designed for that purpose for continous communications. Case in point we are on the night side of the planet and we need to talk. The MRO is orbiting at a different rate but is not geosynchronous so we are waiting for alignment to happen to recieve its information from the surface and many hours later relay them when aligned for earth transmission. Then depending on orbit season we could be waiting beyound the solving time required any where from the 4 to 22 minutes to hear back if we are on the right side of the alignment otherwise we are waiting for the relay to happen to the surface.

Last edited by louis (2018-11-13 18:42:06)

louis · 2018-11-13 19:16:26

Sorry missed this earlier, so have covered some of this in subsequent posts.

I suppose the issue is why does MRO take so long to send just a photo when the Netflix streaming standard is only 1 MBPS? Clearly something is missing...Does the signal spread out and take longer to capture at the Earth end? I admit to being confused.

I'll take a look at the link your posted.

kbd512 wrote:

Louis,
The moon is only a quarter million miles away and has direct line-of-sight (LOS) to the Earth. Believe it or not, even way back in the 1960's, LOS communications equipment was up to the task of transmitting voice and grainy video images. At standard frame rate, 1080p video is 8 megabits per second (mbps). Current networks are currently capable of about a quarter of that. The new Ka-band satcom equipment is capable of 100mbps. The laser communications systems NASA has tested in space are capable of as much as 600mbps and possibly as high as 1,024mbps.
The Lunar Lasercom Space Terminal (in lunar orbit) demonstrated transmit throughputs between 40mbps to 622mbps at a 1550nm wavelength and 10mbps to 20mbps receive. The Lunar Lasercom Ground Terminal (White Sands Complex, New Mexico) demonstrated 10mbps to 20mbps transmit and 40 to 622mbps receive. Compared to the satcom antennas, these things are lightweight and tiny and the 20mbps data rates were completely error-free, which means no retransmission of lost data was necessary.
Anyway, ISS, Orion, Earth ground stations (JPL), and another satellite demonstrator program known as the Deep Space Optical Network is being readied to transfer data at 1,244mbps. Performance will be achieved using 76We (with a 31% power margin) to the entire space terminal, with 4We powering the laser itself. The target system mass for the space terminals is 28kg (with a 30% mass margin). A low data rate radio beacon is used to both steer the beam onto the target back on Earth and to transfer data at low rates. The space terminals feature rad-hard electronics (20,000 rad) and isolation mounts to prevent any vibrations from affecting where the laser is pointed.
Mars Reconnaissance Orbiter can transmit at a maximum data rate of 5.2mbps and it takes 1.5 hours to transmit a single HiRISE image back to Earth. The new Lasercom system would require approximately 22.5 seconds to complete that task. Anyway, the new system is supposed to be a part of NASA's / JPL's 2022 mission to the asteroid named "16 Psyche".
Since SpaceX is already providing the launch services for this program and has been involved for years now, I don't see what the issue would be with them using it for communications purposes.
How NASA's New Mars Rover Will Phone Home
Excerpt from the article:
...
Controllers on Earth will have three ways of hailing Curiosity as it trundles around Gale Crater. Two are direct links through NASA's Deep Space Network, a worldwide collection of antennas. It provides both a fixed low-gain antenna, best for basic commands and emergencies, and a pointable high-gain antenna for complex commands. [11 Amazing Things NASA's Mars Rover Can Do]
Curiosity also has a higher-speed ultra-high frequency (UHF) communications system that can send signals to spacecraft orbiting Mars, which in turn would relay them to Earth.
To send back imagery, Curiosity must stay in touch with the Mars Reconnaissance Orbiter and Mars Odyssey spacecraft, two probes orbiting Mars that each can talk to the rover twice a day. (Odyssey is currently recovering from the loss of one of its three reaction wheels.)
"The high-gain antenna only gives us a moderate amount of bandwidth," Vasavada told SPACE.com. "We can transmit a series of commands every morning. But it's not enough to transmit hundreds of images every day."
...
Each minute of 1080p video to demonstrate a problem to mission control would take at least 4 minutes to transmit. Opinions on the matter clearly differ, but I think that means we need better comms. The upgrade to Ka-band comms and a small constellation of orbital COM/NAV/GPS satellites would be what I would think is the bare minimum necessary to ensure that the crew has adequate support. We're talking about 500kg class satellites using electric propulsion. Falcon 9 Heavy can already deliver 16t to Mars, so why not use CC-SEP to send the satellites to their destination and then ring the planet with high data rate Lasercom and Ka-band satcom relays? This would be a JPL task, anyway.
This square pressure vessel idea is becoming every bit as silly as what Dook proposed. Nobody runs a giant MRI machine to maintain the structural integrity of a square steel pressure vessel while its loaded with computers and humans not undergoing medical treatment. That's what you're now talking about doing. The rounded pressure vessel idea isn't an engineering suggestion, it's an engineering fact. Submarines are made of welded (not riveted or bolted together) HY80 or HY100 steel a half inch thick. Obviously somewhat thinner steel could be used, but it's still a recipe for failure. No engineer would ever propose doing something like that, just to prove that a square pressure vessel could also work. It's an utter waste of available tonnage.

kbd512 · 2018-11-13 19:17:06

Louis,

This is about mission control engineering assistance with complex system problems, not real-time monitoring, although the laser data transmission rate is sufficient for a couple of life feeds and mission control's delayed monitoring of vital systems to predict failures. The laser based systems are clearly far superior to the radio frequency systems, if the subsystem mass, power, and signal quality are considerations. Most other people seem to think that they are.

MRO can't transmit its own data back in a timely manner, but now we're going to run a mission with humans and robots all over the planet?

Not.

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