Large scale colonization ship

kbd512 · 2020-09-05 13:42:24

Robert,

As expensive as this ship will be to build and operate, what would you tell people if it's lost because aerocapture fails?

Sorry about that $5B that we just incinerated, better luck next time?

We need a propulsion system that makes aerocapture superfluous.

Edit:
If you ruffle their feathers a bit by demanding artificial gravity and a true interplanetary transport system, when it's so obvious that it's needed even for exploration plans to stand a good chance of success, then good.

Last edited by kbd512 (2020-09-05 13:44:07)

RobertDyck · 2020-09-05 13:59:54

One basic fundamental of any project is it has to be profitable. And this is the primary source of revenue for Mars settlement. No bucks, no Buck Rogers.

tahanson43206 · 2020-09-05 19:26:23

For RobertDyck re #252, and topic in general ...

Thanks for confirming my guess that you are thinking of costs at this early stage of the design effort.

The risk of failure is going to be taken into account by your backers. And you are going to need a LOT of backers.

It seems to me that you have a pretty clear choice ... to become the lowest cost provider, or to become the safest provider.

You're NOT going to be able to do both.

The sooner you can confirm one path or the other, the sooner you can gather the appropriate support for whichever path you choose.

My guess is that people willing to put up millions of dollars for a share in a Mars venture are NOT the kind of people who will be impressed by nickel-dime savings, when the lives of their staff or relatives are at stake.

(th)

RobertDyck · 2020-09-06 04:35:49

tahanson43206: you're going to have to give up the claim that aerocapture is unsafe. I already explained, the only time NASA used it, they made a really fundamental mistake. Former navy engineers gave altitude in nautical miles, but they didn't say it was nautical miles, they said miles. Making such a dramatic mistake with units is unforgivable. Bureaucrats claim the technology is unsafe, but making such a fundamental mistake with units in any part of the mission would make it fail.

What do I have to do? Accuse you of slander?

tahanson43206 · 2020-09-06 06:26:49

For RobertDyck re #254

When you are ready you can delete #254, and I will happily delete this reply.

The character of a leader determines the behavior of subordinates.

Your enterprise is going to need thousands of subordinates .... you'll need hundreds of partners and thousands of workers, some of whom will be offering their services on a pro bono basis because they believe in the mission, and the quality of the management team.

Overnight I thought of examples of successful and unsuccessful leaders who were engaged in comparable undertakings.

The first that came to mind are Amundsen vs Scott.

Next would be Lindberg, whose meticulous planning allowed him to succeed when so many others had failed. [Wikipedia on Lindberg competitors]

Next would be Sir Ernest Shackleton, who brought his entire crew back (some close to death) from the disaster that struck his expedition.

In contrast, Sir John Franklin lost the entire crew due to a poor choice of a new technology for food preservation.

In the current time, ** someone ** is going to lead an effort that will result in safe delivery of passengers to Mars.

My guess is that whoever that person turns out to be, the person will place the safety of the crew and passengers at the highest priority.

At every point in planning, the leader (whoever it turns out to be) will anticipate failure and provide contingency plans

Above ** all **, the leader will demand sufficient funding to insure the expedition achieves a safe return even it it cannot stop at Mars.

That leader, whoever it may be, will provide an example of "safety first" thinking that will permeate the thousands of associates who will ultimately contribute to the successful return of the crew, even if the objectives of the expedition were not met.

(th)

SpaceNut · 2020-09-06 07:57:41

The mistake of unit problem is one where the computer is in charge of the flying, where men can not control what will happen. That flight path take unit of measure that we can not sense with accuracy to make changes at the time at which we need it.
The unit of measurement inconsistency to make persise maneuvers with is the issue and whom is lead or driving the ship is not something that we can do as we can not get all the measurement to make a calculation or to do the adjustment with.

One unit of measurement makes for safety as it removes all chances of error.

The difference of aerobraking to aerocapture is single pass into the mars atmosphere terminating in a landing using a tolerant heatshield and lots of fuel for rocket land rather than burn off the entry speed by looping through the air as many times as required with limited fuel use to make a slower speed landing possible on less fuel rocket mass.

RobertDyck · 2020-09-06 13:43:48

tahanson43206: You have been very encouraging. It's distressing that you use such hyperbole for such a fundamental technology. And as long as you claim passengers will be killed, no one will invest. However, as long as the venture is not profitable, no one will invest.

Perhaps we need to take a step back, to explain fundamentals. Successful business has shiny clean showrooms with latest technology. However, behind the door that says "employees only" it's entirely different. I could site 4 different computer repair stores in my city, all of which have bare 2x4 wall studs, floors that haven't been washed in years, and light fixture is a bare light bulb.

Three years ago I was hired to update cash registers for a chain of large retail stores. The stores updated their cash registers from Windows Embedded POS Ready 2009 (aka Windows XP with games removed) to Windows Embedded POS Ready 7 (aka Windows 7 Professional with games removed). Yes, that's right, they continued to run cash registers with Windows XP long after Microsoft marketing told everyone it was no longer supported. When they did upgrade, it was to Windows 7; yes *TO* Windows 7. They also upgraded their server *TO* Windows Server 2012. This deployment started September 2017, Windows Server 2019 was released October 2018, but Windows Server 2016 was available and they didn't use it. Furthermore, computers in the back office still ran Windows 7. However, they did upgrade counter thin-client workstations to Windows 10. Notice the trend: what customers see is shiny and the latest; what's behind the scenes is not. Successful business uses what works, not the shiny toy that some salesman is trying to push.

Mars Direct was proposed by Robert Zubrin and David Baker in 1990. President George H. W. Bush made a speech for long term funding of NASA on July 20, 1989, the 20th anniversary of the Apollo 11 Moon landing. NASA worked on a plan to do what the President asked, and came back 90 days later with that report. It called for $450 billion total, spread over several years. Congress balked! They rejected the plan because it was far too expensive. After Congress rejected it, Martin-Marietta asked their engineers to come up with a plan that Congress would approve. Their engineers split into 3 teams, one was Robert Zubrin and David Baker. Mars Direct was estimated to cost $20 billion for research, development, construction of infrastructure, and the first mission to Mars. Additional missions would cost $2 billion each. That initial $20 billion was in 1989 dollars, and would be spread over 8 years. Because of planetary orbits about the Sun, a mission is only possible once every 26 months, so the additional $2 billion (also in 1989 dollars) would be spread over 26 months. Or if NASA committed upfront to 7 missions, $30 billion for the program (again in 1989 dollars). That works out to "buy 6 missions, get one free!" Sounds silly, but that's how the numbers work out. But managers at NASA were not satisfied. The used ideas from Mars Direct, and devised the Mars Design Reference Mission. That had a cost of $55 billion including 6 missions. Congress looked at this and said you already increased the price from $30 billion to $55 billion, and you haven't even built any hardware yet. You're going to increase the price to the full $450 billion from the 90-Day-Report! Aren't you? So Congress said NO!

This is the point. Control cost, or you're dead.

GW Johnson · 2020-09-06 14:03:10

Multi-pass aerocapture can be made to work, just as RobertDyck says. But there are limits outside of which it cannot be made to work. Limits you cannot exceed.

Coming in straight off the interplanetary trajectory, you are approaching Mars (or Earth on the return) at speeds well above escape. The faster the interplanetary trajectory, the further above escape you are, as you make your approach.

For multi-pass aerocapture to work, you have to decelerate in the first pass from your approach velocity to a speed low enough to tolerate the period of the resulting elongated elliptical capture orbit. This orbit has its periapsis down in that atmosphere, for more braking upon every periapsis pass.

Each such braking pass lowers the apoapsis, until all the orbit is in the atmosphere, and you come down. Or unless you circularize at the appropriate apoapsis altitude.

An orbit with initially a weeks-to-months period, after you just endured months in space voyaging there, is just unacceptable for crewed vehicles. That period has to be measured in hours, or at most days.

The bigger that first-pass delta vee is, the deeper in the atmosphere you have to be, to get that much deceleration. That not only raises your deceleration gee and entry heating peaks (and the integrated accumulated heat you must also deal with), it also puts you ever more perilously close to the surface, especially at Mars. Because the air is so thin.

There is a limit to this, beyond which you dare not go! I dunno which constraint bites you first: orbit period, gees, heating, or perilously-low altitude. It's not nearly as severe at Earth as at Mars. Because Earth has much thicker air, and all these things take place about 25-40 miles further up.

All of that is entirely separate from the uniquely-variable Martian air density at the entry range of altitudes. If you already have infrastructure in place so that the current density values are known in advance, you can allow for that as you make your final course adjustments during approach.

Not having those measurements in advance currently is mostly why we don't already use aerocapture routinely at Mars. That and the one mission failure from the stupid units mistake, which gave the technique an undeserved bad reputation.

That variability in entry density is also exactly why direct (single pass) entry and landing is the nail-biter that it is at Mars. Every entry is different because density is different, and you have to plan for all of that.

Which means you definitely have to plan on including the effects of that factor-2 variable density. So says the Justus & Braun "EDL tome". Which is where I got my Martian air density figures. They were (and are) the experts on this.

GW

Last edited by GW Johnson (2020-09-06 14:05:30)

SpaceNut · 2020-09-06 15:46:29

Its also why a night time entry is picked as the density is more predictable. They also are looking at about 3k altitude tangent to make that pass through the longest plus densest path.

RobertDyck · 2020-09-06 22:18:25

GW Johnson: Thank you. I was hoping you would contribute earlier. Thank you again.

You said that after a journey of months, you don't want an orbital period of months. Why not? I'm thinking of a presentation at a Mars Society convention by one employee of Robert Zubrin's company. Don't know if he still works there. He argued for a very high, very eliptical orbit. That means the spacecraft is barely in Mars orbit, so departing Mars does not require very much delta-V. Also remember, I said we would permanently park a SpaceX Starship on Mars to use as a shuttle from Mars orbit to the surface. That vehicle is originally designed to be able to achieve escape velocity and return to Earth, so rendezvous with a ship in high Mars orbit is quite possible.

Again, safety features I already described are: satellite network in Mars orbit to provide real-time updates of the upper atmosphere of Mars. This means detailed real-time data just before and during aerocapture. Also we don't require deep delta-V in the first pass through Mars atmosphere, just enough to enter orbit.

As for safety: the first mission with this ship must take 6 months transit from Earth to Mars. The reason is that's the velocity for free return. So if something goes wrong, the ship can use gravity of Mars to turn back toward Earth. Not a U-turn back the way it came, because Earth will have moved in it's orbit about the Sun. Gravity of Mars has to alter the ship's trajectory to head back to where Earth will be when the ship gets there. A 6 month transit is exactly that. Robert Zubrin and his team worked out that trajectory for Mars Direct, we should use it for this ship.

I emphasized cost. You realize that using aerocapture to enter Mars orbit, it costs less fuel to go to Mars than to the Moon. The reason is you have to use fuel to enter Lunar orbit, and more fuel to land. The fact that Mars takes less fuel may be counter intuitive, but it's true. However, it's only true if you use Mars atmosphere.

tahanson43206 · 2020-09-07 06:18:32

For RobertDyck re #260

Thank you for the details of your mission planning.

For GW Johnson re #258 ... thank you for once again trying to help to show how use of the atmosphere to slow a 1000 ton rotating ship full of people is risky.

RobertDyck ... you have made as clear as possible that you value cheap over safe.

There is a solution to allow for pulling more people in to help with design and planning.

You can split your options and hold off a final decision until you have more facts to work with.

Keep the form factor, but direct your teams to design for (a) atmosphere slowing at Mars and Earth and (b) use fuel and oxidizer to match orbits at Mars and Earth.

The cost of each of these options is not known at this time, and blocking your initiative from one of them means your rivals in other nations will develop the other option, at which point potential customers will weigh the value of their lives vs the cost of a trip.

Speaking of customers ... Set your price at a $1,000,000 (US) per customer for a round trip, so you have $1,000,000,000 to work with.

What can you do with that as a working per-trip income?

SearchTerm:MarsMissionPlan

(th)

SpaceNut · 2020-09-07 16:29:49

cheap does not mean unsafe as quality control with cost control using current technology not extreme tech to achive the goal.

no where is it more unsafe to aerocapture or to aerobrake as they both enter the atmosphere at super speed due to journey time and earths escape speed. The difference comes to amount of fuel to land as when its done wrong they both equal ka..spat….

https://ntrs.nasa.gov/archive/nasa/casi … 056070.pdf
Mars Aerocapture Systems Study - NASA

https://tfaws.nasa.gov/TFAWS03/Data/The … undsen.pdf
Aeroheating Thermal Analysis Methods for Aerobraking Mars …

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

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

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

tahanson43206 · 2020-09-07 18:26:27

For SpaceNut re #262

I try to keep up but now and then the regular contributors to this forum leave me behind ...

In your post #262, you referred to aerocapture and to aerobrake ways of slowing a space vehicle.

Please take a moment and explain the difference?

(th)

RobertDyck · 2020-09-07 18:48:37

tahanson43206 wrote:

Speaking of customers ... Set your price at a $1,000,000 (US) per customer for a round trip, so you have $1,000,000,000 to work with.

No. As an example, a technician in Toronto loses his job. Because Toronto is so expensive, and employment is unstable, he decides to move to Mars. I have said the cost is sell your house, sell your car, liquidate your life insurance and pension plan, your entire life savings. But for a tradesman, how much is that? I said Toronto has unreasonably high housing costs. An example is a townhouse in Toronto, real life today. Canadian Dollars is often represented as "CAD". Purchase price of the townhouse: CAD$500,000, 1 bedroom, 1 bath, 670 square feet. Real estate ad claimed it has a view of Lake Ontario, but an actual photograph shows a townhouse with a balcony, no yard, sidewalk running across the townhouses, each unit facing a concrete block wall across from the sidewalk. Down the sidewalk are buildings, viewed over one building is the spire of the CN Tower. No view of the lake at all. Say the man paid 5% down payment. Add mortgage insurance fee. Monthly payment including property tax: $2,188.96 That's with current interest rate from Royal Bank, and I looked up Toronto property tax rate. Assume 30 year amortization. And found 41% of homes in Toronto have 1 adult. After 10 years accumulated equity: $132,381.39 Subtract from that real estate agent's fee, and lawyer fees for closing. Also remember, in Canada you don't get any money for "selling" your life insurance. And most employers do not offer any sort of pension buy-out. If you're close to retirement and your employer wants you to leave, you may be given an offer to "buy out" your pension, but that's rare. If you're still in your 30s or 40s, you will not be offered anything. So this individual can afford US$100,000 = CAD$130,938.04 ticket price. Nothing more. So a single bunk in an economy class cabin is US$100,000, with the passenger sharing a cabin with 5 strangers. That's 6 people per cabin.

Ticket price breakdown:
economy bunk: US$100,000
whole economy cabin: US$500,000
"single" cabin (same size with just one queen-size Murphy bed): US$500,000
Club cabin (twice the floor area of economy): US$1,000,000
Premium suite (4 times floor area of economy): US$2,000,000
Luxury suite (16 times floor area of economy): US$8,000,000

Note: only 2 Luxury suites on the ship. One Luxury suite can be subdivided into 4 Premium suites, or 8 Club cabins, or a combination. Price is constant per floor area, so it doesn't matter what configuration as long as all suites are booked.

Now assume: 162 economy cabins, on average 5 passengers per cabin.
90 single cabins: all booked
8 premium suites: all booked
(162 x US$500,000) + (90 x US$500,000) + (8 x US$2,000,000) = US$142,000,000
Yes, that's US$142 million.

That's total revenue per trip. With 6 month transit per voyage, only one round trip every 26 months. How many trips to pay for construction of the ship? How much to pay crew salaries? How much to pay for food? How much to pay for fuel and other supplies? How much to pay for maintenance?

This appears that ticket prices will have to be several times these prices for the first few trips. But will have to come down to these prices for on-going trips. The example tradesman can just barely afford a ticket at these prices, so could not afford one at several times.

RobertDyck · 2020-09-07 18:55:03

tahanson43206 wrote:

For SpaceNut ... you referred to aerocapture and to aerobrake ways of slowing a space vehicle.
Please take a moment and explain the difference?

If I may...

Aerobraking means a satellite or spacecraft orbiting a planet dips into the upper atmosphere as it passes the low point of it's orbit. This causes drag, which slows the vehicle. That drops the high point of the orbit. At some point the spacecraft must use fuel to raise the low point of its orbit out of the atmosphere.

Aerocapture is a special type of aerobraking. It means a spacecraft arriving at interplentary speed, for example travelling from Earth to Mars, arrives at full speed. As the spacecraft drops into the planet's gravity well, it gains more speed. It dips into the upper atmosphere of the planet to cause drag. That must slow the spacecraft sufficiently in just one pass to enter planetary orbit. It could be very high orbit, and very elliptical. That would mean the high point of the orbit is very high indeed, but unless the spacecraft actively does something, the low point will still pass through the planet's atmosphere in the next pass of the low point of its orbit.

So aerocapture to enter orbit, aerobraking to drop into lower orbit.

tahanson43206 · 2020-09-07 19:42:16

For RobertDyck re 264 and 265

Thanks for both posts ... this is just to acknowledge ... I'll study 264 tomorrow.

In the mean time, 265 covers the difference nicely!

http://newmars.com/forums/viewtopic.php … 20#p171920

SearchTerm:Aerocapture
SearchTerm:Aerobraking

(th)

kbd512 · 2020-09-08 07:41:32

Robert,

If people don't have enough money to move between cities in Canada to improve their personal economic situations, or to improve their education or professional skills, then there's no way that they're moving to Mars on the basis of economics. There's no economic case to be made for moving to Mars at this time, full stop. The very first person has yet to set foot on Mars, so we need to estimate costs based upon the tonnage of everything required to send them there and keep them alive there.

The entire point behind this endeavor is that it's a backup plan for human civilization, essentially the world's most expensive science experiment. It's going to take years to figure out how to live on Mars at all, assuming 2/5g is not a serious problem for human physiology, a question which absolutely nobody knows the answer to. In order to determine how well humans will fare on Mars, we need a way to reliably deliver a significant number of them to Mars to increase the number of data points we have. In essence, and out of necessity, they're human guinea pigs, same as the astronauts we send to ISS.

What we should be trying to do is to reduce the marginal cost for sending the next human to Mars. The only way to do that, on account of the round trip transit time, is using very large ships that can carry lots of people per trip. The ship in question needs to have a reasonably long service life, but building it strong enough for functionally infinite service life is both impractical and unnecessary.

You might find 1 out of every 1,000 or perhaps 10,000 people who is willing to sell everything they own and move some place where there's a significant likelihood of serious injury or death. From that pool of willing applicants, you have to identify those who have the money to spend to simply make the trip and the technical knowledge / skills / experience to merely survive. In simple terms, only tax payers or private venture capital firms are going to pay for something like this.

You will find that in most countries, 1% of the population are willing to devote significant monetary resources to space exploration.

Every industrialized nation on the planet has enough combined wealth to build a rocket and capsule system to send a human into space. Thus far, Russia, America, and China have actually done it. It's been 59 years since the very first person was launched into space. Since that time, a grand total of 550 people have EVER been into space, out of a total of about 7B people alive today and 107B people who have ever lived. As such, astronauts represent about 0.00000008% of Earth's current total population. In order to have any chance at all of recruiting enough qualified applicants, we'd have to accept most of the 12,000 to 18,000 NASA astronaut applicants, many of whom are sent away due to health problems or failing various tests.

Let's say we could muster 7K qualified applicants after we thoroughly train and evaluate their performance. That's 0.000001% of Earth's population. Assuming 4K came from America and the rest came from the rest of the world, that's 0.00001% of America's population, yet each launch opportunity will deliver more than an order of magnitude more people into space than have ever been to space up to this point.

If each full ride only costs $100K, which seems extremely unlikely without mass space transport on a scale never achieved before, then the American tax payers are on the hook for $400M, or 2% of NASA's total yearly funding. If SpaceX really can launch for $10M, then the minimum launch cost for each 5,000t ship is $500M, assuming Starship can deliver 100t to LEO with full reusability. If each ship costs $2B to construct, can transport 500 people per voyage, and can conduct 10 voyages over its operational life, then each passenger would have to contribute $220K just to pay for the cost of the ship and the fuel to reach the ship. If 600t of Aluminum fuel is required per trip for a fusion driven engine, then you can add another $120K per head for the Aluminum fuel costs. So, now we're up to $330K per person to pay for transportation, assuming each Starship delivers 500 passengers / colonists per flight. In terms of merely paying for the transportation and ship construction costs, it's $165M per flight. If the ship is fully loaded for each voyage, then transportation costs are $1M per person, meaning each colonist represents a million dollar investment, so quite similar to initial training of a US military C-17 pilot, except that the $1M is just the transport cost, not the cost of training. Astronaut training is about $15M. Obviously we don't have to train everyone to do science experiments, but we do have to train them to do EVAs and space-based construction tasks.

Bottom Line:

This is going to be a government-funded project, out of necessity, wherein member nations pool their capital and labor resources to deliver a tiny fraction of their population to another planet in order to determine the feasibility of interplanetary travel, commerce, and life off-Earth. The cost would be so astronomical using chemical propulsion that it won't be feasible for those being transported to ever pay for it, so fusion driven rockets are required, and those cost estimates are for 1-way transport to Mars only. Training is extra, additional supplies are extra, etc. I'm sure Uncle Sam could pay for the training, though, since we pay to train military jet pilots already, about $5M to $10M per pilot.

GW Johnson · 2020-09-08 07:44:31

To answer Robert's question about not spending months in an aerobraking orbit: this is bad psychologically. It is one thing to spend months in space on the voyage, looking out the porthole at unmoving stars. It is quite another to spend more months in space looking at your destination right out the porthole. Your colonists will be more like ordinary people than trained and disciplined astronauts.

I will say that the use of aerocapture and aerobraking puts very severe design constraints on what your transport's shape can actually be. And, having it spin during entry is probably not a good thing as regards control. You probably cannot use a spinning wheel design for this. Nor would my spinning baton work for this. Be also aware that peak deceleration gees during each braking pass will be a number closer to 10 than 1 gee.

GW

tahanson43206 · 2020-09-08 08:01:05

Reference Tag: http://newmars.com/forums/viewtopic.php … 41#p171841

SearchTerm:RemoteWork
SearchTerm:Teleoperation

Edit#1: Reference Tag: http://newmars.com/forums/viewtopic.php … 19#p171919

SearchTerm:Customers
SearchTerm:WhoAreMyCustomers

(th)

Last edited by tahanson43206 (2020-09-08 09:24:17)

kbd512 · 2020-09-08 08:19:39

GW,

The only practical and proven-to-work way to decelerate a multi-thousand-ton colonization ship is using a propulsive burn, not some 10g glowing-hot roller coaster ride through the atmosphere.

As sailors, we often operated within sight of land during combat operations. A few people had problems with this, but the overwhelming majority didn't. We need some kind of "boot camp for Martians" as part of the initial training program. The colonists should be considered to be the civilian arm of the Space Force. It'll be much like joining the Coast Guard. You still need people who know how to follow orders and get jobs done without a lot of petty bickering. Kids who grew up on farms won't have too many problems, for example.

RobertDyck · 2020-09-08 10:01:16

kbd512 wrote:

If people don't have enough money to move between cities in Canada to improve their personal economic situations, or to improve their education or professional skills, then there's no way that they're moving to Mars on the basis of economics.

A lot of people do not want to move to smaller cities in Canada. They move to Toronto or Vancouver, then complain about housing cost. Is it stupid? Yea. I use this as an example because housing cost is so high, which means selling the townhouse will result in significant money. You realize selling a house elsewhere in Canada would be a larger house, but less money. That doesn't improve ticket price for Mars.

kbd512 wrote:

The entire point behind this endeavor is that it's a backup plan for human civilization

No, it's not. People will make decisions based on their personal lives, not some egalitarian principle.

kbd512 wrote:

You might find 1 out of every 1,000 or perhaps 10,000 people who is willing to sell everything they own and move some place where there's a significant likelihood of serious injury or death.

These are your potential Mars settlers. It has been done before. The United States likes to talk about Pilgrims being the first settlers to found the US. History is actually more complicated, but those pilgrims did sell everything and move to a far distant land to start over. And yes, it was dangerous.

kbd512 wrote:

Every industrialized nation on the planet has enough combined wealth to build a rocket and capsule system to send a human into space. ... This is going to be a government-funded project

No, it's not. If government was going to do it, they would have done it by now. After Apollo 11, NASA said their next major goal was Mars, and they would send a human mission to Mars in 1981. Then they said 1983, the next launch opportunity. Then they said they would get back to us. They never did. George H. W. Bush tried to give NASA a long term mandate, but Congress rejected the 90 Day Report. Mars Direct tried to show how to do it cost effectively, but a couple problems. Even though NASA had committed to a 4 person crew since 1965, when they saw the Mars Direct mission plan they wanted to expand crew to 6. And they wanted to abandon ISPP in favour of bringing return propellant from Earth. By the way, Mars Direct included aerocapture, not direct entry, and not propulsive orbital entry. All these changes ballooned the price, so Congress wasn't willing to pay. There has been excuse after excuse. Government isn't going to do it. Ever. Period. Get over it.

Private enterprise will go to Mars, or humans will never set foot on the Red planet. Period.

RobertDyck · 2020-09-08 10:07:00

kbd512 wrote:

The only practical and proven-to-work way to decelerate a multi-thousand-ton colonization ship is using a propulsive burn, not some 10g glowing-hot roller coaster ride through the atmosphere.

No, it's not. Nothing is "proven" for a multi-thousand-ton ship. The only ship to the Moon is Apollo. For Apollo 15 and later (larger spacecraft) CSM massed 28,800kg and LM massed 16,400kg; total 45,200kg = 45.2 metric tonnes. 45 is not "multi-thousand". And unmanned Mars orbiters are smaller. And aerocapture is does not have to be 10G. Expect much lower acceleration.

kbd512 · 2020-09-08 12:52:02

Robert,

If people don't want to move to smaller cities in Canada, then they're not going to want to move to a non-existent city on Mars that they have to build from the ground-up, or underground, and stand a better than average chance of dying in the process. By their own logic, there's no reason to move to a "smaller city", and "Mars City" still has a population of zero. You have to be pretty desperate to move to an entirely different planet where you can't go outside without considerable personal protection. The pilgrims wanted to move to a place where they could escape religious persecution, but nobody told them that they would need a space suit to merely walk around outside. This is the 21st century and the only people who would potentially go aren't in any real danger of religious persecution and their chances of mere survival are far better here than on Mars. Beyond that, the Pilgrims were farmers who had a plan to farm and trade when they arrived, so what's our plan for farming on a planet with no usable air or water or soil or trading when everything has to be imported from tens of millions of miles away?

Apple has enough money to start their own space program, but they're not doing that, are they? Government is. Government contracts made it possible to travel into space to begin with, because no company would develop the technology to go into space with no other way to make money off of it. SpaceX is dependent upon NASA and satellite launch contracts. If private industry was going to do this on their own, then by your own logic they would've done it already since they developed the technology for the government to use and NASA allows corporations to license all the technology they develop.

We have multi-thousand-ton ships here on Earth. All of them use propulsion to stop at ports. They don't ram into the pier to reduce velocity. GW already told you that single-pass aerocapture is more like a 10g deceleration than a 1g deceleration. I know, engineering doesn't work the way fantasy does, but he's an actual aerospace engineer and he told you what would be required to capture into orbit using the atmosphere, but you don't like the answer so you're going to ignore it. I don't wonder at all about why we haven't made as much progress as we did in decades past. This type of thinking is what's caused the slowdown in human advancement. Someone says, "there's a minefield over there that you can't go through", but then someone like you says, "we'll develop the technology to go through it", whereas an aerospace engineer looks at the same problem and asks, "Why not go around it?". When the technology to go through the minefield doesn't materialize as fast as you'd like it to, you proclaim that the government is balking at the challenge, blissfully unaware that they've already killed many, many people attempting to use technology to go through it.

Seriously, I think some of you believe that whenever engineers haven't solved a problem yet that it's a question of intelligence or effort or money, rather than asking the right question or accepting the limitations of current technology and finding an alternative solution.

The right question to ask is:

How can I get a multi-thousand-ton ship to capture into a stable orbit around another planet without putting everyone onboard the ship at risk of the consequences of an inadvertent reentry or failed capture at interplanetary velocity?

There's one correct answer to that simple question. The ship should be under power and the power should be used to slow the approach for a comparatively benign capture. It doesn't require the ship's structures to withstand multiple times the force exerted by gravity here on Earth, nor temperatures that will melt light alloys, nor risk becoming another smoking crater in the ground if atmospheric density calculations are ever so slightly off-nominal. No ring of satellites to measure air density with great precision is required, either. There's far too much hand-waving of the engineering complexity of any prospective solution.

The one satellite that aerocaptured into Mars orbit had a very low ballistic coefficient, along with a very low mass to surface area ratio. Beyond that, it was an experiment, and provided a single data point to us. It proved that aerocapture does work, but that's very, very far from any sort of universal solution that works no matter what the ballistic coefficient is, mass to surface area ratio is, or the rigidity of the structure slamming into the atmosphere is. There's a general principle in aerospace engineering that says you build a structure as strong as it absolutely needs to be, but no stronger. That principle exists because otherwise the flying qualities of machines designed without such regard would be very poor.

SpaceNut · 2020-09-08 18:02:38

kbd512 you have given the reason that others say we are wasting money on space in general that the money would be better suite for man on earth...ect all that socialism babble....

The reason one moves away from cost is to lower it....knowing all to well that it costs you time on the road....

We are not going to mars for convience of anything being nearby and its the frontier men that did explore and made a life of it away from the cities....

kbd512 · 2020-09-08 18:44:37

SpaceNut,

I disagree with the basic premise or assertion that money spent on space-related infrastructure and colonization is in any way "wasted". I'm simply trying to point out that there is no economic case to be made for moving to Mars at this juncture in our history. That is a stumbling block for all of our ideas about how to go about colonizing Mars. There is no immediate economic payoff, even though the future economic payoff could be more money than anyone ever imagined. As of right now, the money changes hands between the government and universities and aerospace corporations. If we were after some type of immediate economic payoff, then we're talking about asteroid mining.

Anybody who thinks aerospace and defense technology doesn't have a future payoff should really stop using the internet and GPS and their laptop / cell phone / tablet- all of that was the result of aerospace and defense technology spin-offs handed over to the private sector. Everything that makes modern life possible started life as an aerospace or defense program, period and end of story. It doesn't matter if people like the way technology is developed or not. If you want better technology, then that's the only realistic way you're going to get it. SpaceX didn't invent modern rocket engines, they just took the work from technology that started life in government programs and refined it to the nth degree using... US Air Force rocket engine program funding. This idea that SpaceX is out there, all by themselves, doing something that's never been done before, is pure fantasy. What they're doing is taking existing technology and refining it to the point that it's practical for something like Mars colonization, though I'd say truly affordable rockets goes far beyond enabling a Mars colony.

We're going to need people in government to have just a tiny bit of foresight or forward-thinking, unlike most people here on Earth, so that we can get the funding required by companies like SpaceX, who are quite serious about wanting to explore and colonize Mars, to get the tools and technologies they need to do that. And yes, I completely agree that the frontier mentality is required for this endeavor to work. I also believe that it fundamentally can and will work, but that the correct thought process about the motivations and reasons for colonizing Mars need to be transparent to all who witness them. Basically, someone needs to get in front of the American tax payers and convince them that the reason we need to spend money on space exploration and colonization is to ensure that humanity always has a "better tomorrow" in its future. I think the task of colonizing our solar system, and eventually our galaxy, is so big that someone needs to convince the tax payers of other nations that humanity needs to move beyond the cradle of life to take our place amongst the stars.

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