Smallest Human Ascent or Descent Lander for Mars Or Earth

RobertDyck · 2015-04-12 07:57:23

SpaceNut · 2015-04-12 16:29:34

Wow popcorn and where is the movie?
Oh I see still wanting a machine that is proposed... BAE to Offer Hybrid Electric Vehicle to Replace Army's Bradley Armored Personnel Carrier Shane McGlaun (Blog) - July 27, 2010 10:30 AM

The core hybrid vehicle platform from BAE is expected to tip the scales at 53 tons and meet the mobility requirements of the Army at that weight. The vehicle platform is designed to still meet mobility requirements of the Army at 75 tons. That extra weight range allows the vehicle to evolve as the needs and demands of the Army change.

But wait a minute its Hopes Dim for BAE’s ‘Green’ Combat Vehicle By Brendan McGarry Wednesday, January 22nd, 2014 5:40 pm

BAE conceived of a hybrid-electric vehicle that could operate on diesel or electric power, with lithium-ion batteries that recharge when braking. Think Toyota Prius, only super-sized and with tracks, armor and a gun turret. In addition to better gas mileage, the design would offer fewer moving parts and faster acceleration, officials have said.
Still, it’s no fuel-sipper. At a hulking 70 tons — about the weight of an Abrams and more than twice that of a Bradley — the vehicle would get less than a mile per gallon of fuel.
The Army in recent years repeatedly described the Ground Combat Vehicle as one of its top acquisition priorities. The service had planned to buy about 1,900 of the vehicles at a cost of as much as $17 million apiece, or $32 billion.

So lets get back to the topic which is smallest landing craft possible for mars of which a large mobile habitat is in another topic just waiting for details to show up in RV'ing mars....

Continues here Combining the Rover and Hab - Go RV'ing!

SpaceNut · 2015-04-12 17:07:03

The initial reason was sort of a means to stay with the current EDL of Mass profile that we have but to still make it safe for crews to land and go about the business of exploring, science and yes roaming in search of science and of exploration of the suroundings but that does not mean to be nomadic.

This mission was meant to be a can we survive if man must evacuate to Mars due to some catastorphy senario setting up a permanent shop to study that in its fullest from the start.

With that we are in agreement that we do need both styles sent to get the maximum effort from the first mission going forward. I see the nomadic part of Mars traveling from the outward parimeter of landing spiralling in towards the permanent habitat.

Do we have a topic for this... hum...????

RobertDyck · 2015-04-12 17:10:09

SpaceNut wrote:

Wow popcorn and where is the movie?

Antius started to debate kbd512. Let Antius argue, I'll just watch.

SpaceNut · 2015-04-12 18:41:01

LOL...
I see it now Yesterday 07:39:06 but in either case lets try to keep that little part of the mission in the RV'ing Mars topic.

Where are you now Antius....

Even the consumables still have not been nailed down in the imperical numbers topic from the ISS as to whether a cache system around the Mars equator or other such method will be possible if the EDL can not be met.

kbd512 · 2015-04-12 23:49:05

SpaceNut,

BAE's proposed hybrid-electric Bradley replacement is an entirely different vehicle from the M113 and MTVL (both of which are real, not proposed, vehicles in service with various North and South American, European, Middle Eastern, and Asian countries). I spoke to a former Army tank platoon commander (served in M1's, M2's, and M113's) about this on my flight from Houston to Atlanta.

The diversion from the OT had to do with the critique about landing a micro capsule off-course and not being able to reach the habitat. If the habitats are mobile and comes to you, then you wait in your capsule after you land for the mobile habitat to arrive or you cache supplies in and around the landing area.

The mobile mission architecture has everything to do with stated surface exploration objectives and keeping payload masses within the launch capability of one F9H. A beneficial side effect of mobile mission architecture is the ability to retrieve astronauts who have landed slightly off-course. Apart from astronaut comfort, one 40t or 80t stationary habitat module is not better than four 15t-17t mobile habitat modules. No matter the architecture, this mission costs too much to abandon because one of anything failed. It's also impossible to quickly (meaning with two or three missions) characterize Martian geology and resources if you're tied to a static or base site. I'm designing this mission as if we're only going to get two or three opportunities.

I see no real benefit to blowing our bankroll on a multi-person EDL vehicle that sees a few minutes of use with each mission, even though those seven minutes are critical to mission success. There's no such thing as simpler or easier when it comes to building it bigger, especially on Mars.

Getting back to the OT, Red Dragon only lands ~2t worth of people and supplies. Its landing capability in the highly variable Martian atmosphere is marginal. From a mathematics standpoint it's actually doable, but you're on thin margins with your propellant. My solution may require a sizable parachute and inflatable decelerator, but the mass of the landed payload (a human) is a more favorable portion of the total mass required for EDL. The only way giving up more mass for EDL makes sense to me is if the descent and ascent vehicle are one and the same.

As previously stated, for various reasons here on Earth any vehicle that goes through reentry is not reusable without substantial refurbishment at highly specialized facilities with sizable work forces that simply don't exist on Mars and won't exist in the immediate future. Obviously HIAD and ADEPT prevent the worst effects of reentry from adversely affecting the vehicle, but actual reuse has never been done.

If you land substantially off-course with any reasonably affordable EDL solution and don't have a mobile habitat or rover, the mission is still over, it just takes a little longer for the astronauts to run out of supplies and die. The alternative scenarios where you don't die if you land substantially off course involve using far more substantial and therefore expensive fully fueled ascent vehicles or landing the astronauts in the habitat module. I think we've come full circle and now we're right back to where we started.

Does everyone here want to wait another decade or so until NASA has funding for a necessarily large and expensive descent/ascent vehicle or an equally large and expensive stationary habitat module or consider comparatively inexpensive mobile habitats, small descent vehicles, and small ascent vehicles so we can afford to develop, test, and launch these mission hardware components? ISS, Orion, and SLS are funding nightmare scenarios that have become reality and aren't likely to go away in the immediate future.

kbd512 · 2015-04-13 00:33:38

Regarding the OT subject matter, all counter arguments up to this point have been that micro capsules are "unsafe" because you can become stranded if you land substantially off-course or that you can't land without retrorockets.

Reality would seem to indicate the following:

1. Absent a fully fueled ascent vehicle any substantially off-course landing has only one possible outcome and it really doesn't matter if you land the crew individually or together. With micro capsules, if something goes wrong, you kill crew members individually rather than collectively. Killing any crew member is really, really bad. Would killing the entire crew be any better? If so, how so?

2. It may or may not be possible to land without retrorockets, but no payload with the mass and parachute diameter I was thinking of has been landed. All landed payloads have been substantially heavier than what I proposed and therefore required retrorockets. Is there any hard data or mathematical model to indicate that landing a 150kg payload without retrorockets is impossible? I would immediately stop arguing the point if there is.

3. A fully fueled ascent vehicle atop the descent vehicle may present an abort option that micro capsules don't provide, but it will definitely not be comparatively inexpensive. Is there any concept or study that indicates that this proposed descent/ascent vehicle will be comparable in terms of cost, and therefore feasibility, to what I proposed?

I think we're all in agreement that Orion and SLS are a colossal waste of time and money that divert much needed funding and engineering effort away from development of hardware that's actually required for space exploration, but these programs have survived two administrations. Is there any reason to think these programs will go away after President Obama leaves office?

I would love to have multi-person descent/ascent vehicles and a Mars base. Even if we could afford multi-person descent/ascent vehicles and the other programs we're currently funding, would there be any funding left for MTV's and CL-ECLSS? We have to have all of the hardware components to execute the mission. Right now, because everyone seems to be stuck in the mud regarding what they really want to have, if only there was funding, we don't have a single piece of the required hardware.

GW Johnson · 2015-04-13 09:01:41

There are some limitations with chutes. One is speed at opening. They have that up to Mach 2.5 in very thin air with the ringsail designs. Ribbon chutes work to about Mach 2 in somewhat-thin air (Earth stratospheric), about Mach 1 to 1.5 at Earth sea level. It's an opening-shock thing. Materials are only so strong.

The other limitation that I am aware of is canopy loading to achieve an opening at all. If there's not enough weight, too big a chute doesn't open correctly. I don't have any figures, but it's something that is real. For a given payload size, it limits the single canopy diameter. Probably a different value at Mars than here, but I don't know. Maybe the JPL guys have figures for that.

Based on the probes sent to Mars so far, up to around a ballistic coefficient of 100 kg/sq.m you can use heat shield, then chutes, the subsonic terminal rocket braking fairly easily. Above 100 kg/sq.m, things get squirrely at best, and you end up with airbag and skycrane schemes. Microcapsule or not, with a man on board, it'll be difficult to get under 100 kg/sq.m unless the inflatable heat shield technologies actually pan out. Those are still quite experimental.

The most-ready technology would be supersonic retro-propulsion, but right now only Spacex does it, and it's still pretty experimental until Dragon does propulsive landings, and they have some success landing those first stages. I rather think both the retropulsion and the inflatable/extendible heat shield stuff will fully mature about the same time in the near future. Spacex may or may not demo stage landings before the soft heat shield crowd demos their items, I dunno. Dragon v2 will fly retropulsive quite soon, I think.

The other issue is landing accuracy. If you have a maneuvering vehicle during hypersonic entry, you have some capability to adjust downrange and cross-range to hit a desired target. With plasma-induced radio blackout this is inertial guidance, not radio homing during entry. It requires a very precise start to the descent trajectory, something easily available if starting from a well-characterized orbit, not easy at all if doing a direct entry from deep space. Your control toward the aim point on a parachute is poor-to-nil. It's during the terminal rocket braking that you regain aimpoint control, to whatever extent is possible. That's where a homing beacon helps, there and at start-of-descent.

This landing accuracy issue is avoided if you land only a single vehicle at each site. Site precision is then not required. But if you intend to land multiple vehicles at a site, this is an issue that requires a working solution, no way around that. If you dispense with the chute and start retropropulsion much earlier at end of hypersonics, higher up, then you have much better homing control over your landing point.

All of these approaches can be made to work. Some will be easier to implement than others, and all are going to need some level of development and trials. The real question is what is likely to be ready "in time to make the trip". This has to be decided much earlier than most folks think, at the mission architecture/launch vehicle requirements stage. It seriously affects those design choices.

Advice from an old development engineer: don't incorporate a totally-new technology development into your flight hardware prove-out program. If you do, you will never fly. Go with technologies already mature enough to use "now".

GW

Last edited by GW Johnson (2015-04-13 09:10:02)

Antius · 2015-04-13 12:17:38

SpaceNut wrote:

LOL...
I see it now Yesterday 07:39:06 but in either case lets try to keep that little part of the mission in the RV'ing Mars topic.
Where are you now Antius....

As always, too much work to do and not enough time. I will reply in detail in due course. Just a few thoughts to throw into the discussion...

Mars gets colder than anywhere on Earth, litterally cryogenically cold, and it is that cold everywhere at night. This presents some materials problems for a rover, as flexing parts like the chassis cannot be made from ordinary steel. On Earth, we can get around the problem by adding more manganese to steels thereby reducing their brittle transition temperatures, but Mars is far too cold for that.

Austenitic stainless steels would retain their strength, as would aluminium alloys, I'm not sure about marageing steels. Aluminium alloys are undesirable, as they have a finite fatigue life and a chassis will be flexing a lot. An aluminium chassis would need to be designed to minimise bending strain and a rover would need some sort of flight history to ensure a margin of safety. Aluminium alloys could be used in wheels that are not subject to heavy strain. Again, getting around these problems ruins a lot of the weight advantages of aluminium. For obvious reasons, you would not want to use aluminium in vehicle tracks. Stainless steel would do better, but it does not have the strength-weight of some of the stronger non-austenitic steels.

Tyres present a design problem, as most polymers would be brittle at Mars night time temperatures. This supports your decision to opt for a tracked vehicle, but it comes at the cost of additional weight. An imperial walker would be good from the point of view of dust contamination, but suffers stability issues, not to mention a lot of complex control issues and moving parts.

Not an easy design project, especially when you consider that breaking down in the middle of nowhere could easily be fatal.

None of this was an issue for the original lunar rovers because their design lives were short and they were only used during the lunar day.

kbd512 · 2015-04-14 03:54:23

Antius wrote:

As always, too much work to do and not enough time. I will reply in detail in due course. Just a few thoughts to throw into the discussion...
Mars gets colder than anywhere on Earth, litterally cryogenically cold, and it is that cold everywhere at night. This presents some materials problems for a rover, as flexing parts like the chassis cannot be made from ordinary steel. On Earth, we can get around the problem by adding more manganese to steels thereby reducing their brittle transition temperatures, but Mars is far too cold for that.

This is the primary concern I had for the running gear and tracks, the entire vehicle, actually. The extreme cold is the biggest problem. Heating is the obvious solution, but that requires a lot of power.

Antius wrote:

Austenitic stainless steels would retain their strength, as would aluminium alloys, I'm not sure about marageing steels. Aluminium alloys are undesirable, as they have a finite fatigue life and a chassis will be flexing a lot. An aluminium chassis would need to be designed to minimise bending strain and a rover would need some sort of flight history to ensure a margin of safety. Aluminium alloys could be used in wheels that are not subject to heavy strain. Again, getting around these problems ruins a lot of the weight advantages of aluminium. For obvious reasons, you would not want to use aluminium in vehicle tracks. Stainless steel would do better, but it does not have the strength-weight of some of the stronger non-austenitic steels.

Aluminum alloys were selected for the M113 over the steels available in the 1950'S because the aluminum alloys increased chassis rigidity to the point that reinforcement was no longer required.

Antius wrote:

Tyres present a design problem, as most polymers would be brittle at Mars night time temperatures. This supports your decision to opt for a tracked vehicle, but it comes at the cost of additional weight. An imperial walker would be good from the point of view of dust contamination, but suffers stability issues, not to mention a lot of complex control issues and moving parts.

The UHMWPE running gear and rubber tracks would require embedded heating elements to survive Martian nights and using compounds with low Tg would be required. I'm also concerned about the increased UV exposure. I'm less concerned about the corrosive salts, but it's something that requires more data to characterize.

Antius wrote:

Not an easy design project, especially when you consider that breaking down in the middle of nowhere could easily be fatal.
None of this was an issue for the original lunar rovers because their design lives were short and they were only used during the lunar day.

Nothing is easy about Mars. Rovers are no exception.

RobertDyck · 2015-04-14 06:11:19

kbd512 wrote:

The UHMWPE running gear and rubber tracks would require embedded heating elements to survive Martian nights and using compounds with low Tg would be required. I'm also concerned about the increased UV exposure. I'm less concerned about the corrosive salts, but it's something that requires more data to characterize.

UHMWPE becomes brittle at temperatures below -150°C. That's a concern for Earth orbit or interplanetary space, but Mars at night does not get that cold. In fact, the lowest temperature I saw recorded by Mars Global Surveyor for the southern pole was -140°C. And I doubt you would send humans to a Martian pole.

It's not advisable to expose UHMWPE to temperatures above 80 to 100°C for long periods of time. But the highest temperature I saw from MGS was +24°C. Some people claim they saw a few degrees above that, but don't expect Mars surface to get above +30°C. Ever. So high temperatures are not a concern. UHMWPE can withstand temperatures on Mars. However, UV is another concern.

UHMWPE is a marvellous material. Sold under brand names Spectra or Dyneema, these are the core for mountain climbing ropes. I have hoped that it could be used as a tether for spin to produce artificial gravity. Temperatures swings in LEO exceed this materials limits, both high and low. Is it possible to design a sleeve to protect a rope core of UHMWPE? The goal of the sleeve would be to moderate temperature between the extreme heat of direct sunlight, and extreme cold of shade in space. That's two sides of the same rope, and the rope would be rotating so alternately exposed to sunlight or shade. It should be possible. But that's for LEO or interplanetary space. UHMWPE would not have a temperature problem on Mars; UV perhaps, but not temperature.

Last edited by RobertDyck (2015-04-14 06:23:24)

kbd512 · 2015-04-14 18:05:50

RobertDyck wrote:

UHMWPE becomes brittle at temperatures below -150°C. That's a concern for Earth orbit or interplanetary space, but Mars at night does not get that cold. In fact, the lowest temperature I saw recorded by Mars Global Surveyor for the southern pole was -140°C. And I doubt you would send humans to a Martian pole.

Yeah, interplanetary space is effing cold, so heating elements are required. From my very limited understanding, you don't want the running gear or track anywhere near Tg, especially if the parts are under load. So, heating elements are a requirement.

I was thinking that the tracks should be made from some kind of silicone compound with low Tg, maybe PVMQ.

I nearly forgot about radiation. I have no idea what the effects of radiation on UHMWPE or PVMQ are. I'm guessing it's not good.

So we need running gear and tracks with the following properties:

* Very low glass transition temperature
* Molding in heating elements into the parts
* Resistance to high UV exposure
* Resistance to moderate radiation exposure

All in all, a lot to consider.

RobertDyck wrote:

It's not advisable to expose UHMWPE to temperatures above 80 to 100°C for long periods of time. But the highest temperature I saw from MGS was +24°C. Some people claim they saw a few degrees above that, but don't expect Mars surface to get above +30°C. Ever. So high temperatures are not a concern. UHMWPE can withstand temperatures on Mars. However, UV is another concern.

High UV exposure and moderate radiation exposure are the biggest questions I would like answered. The physical and chemical properties of the materials are fairly well understood and are suitable for the application I want to use them for here on Earth.

RobertDyck wrote:

UHMWPE is a marvellous material. Sold under brand names Spectra or Dyneema, these are the core for mountain climbing ropes. I have hoped that it could be used as a tether for spin to produce artificial gravity. Temperatures swings in LEO exceed this materials limits, both high and low. Is it possible to design a sleeve to protect a rope core of UHMWPE? The goal of the sleeve would be to moderate temperature between the extreme heat of direct sunlight, and extreme cold of shade in space. That's two sides of the same rope, and the rope would be rotating so alternately exposed to sunlight or shade. It should be possible. But that's for LEO or interplanetary space. UHMWPE would not have a temperature problem on Mars; UV perhaps, but not temperature.

Maybe something like this would work for your tether and not require thermal conditioning or require less thermal conditioning:

https://ehb8.gsfc.nasa.gov/sbir/docs/pu … fchart.pdf

RobertDyck · 2015-04-14 22:36:47

This NASA website: What Is a Spacesuit?

In Earth orbit, conditions can be as cold as minus 250 degrees Fahrenheit. In the sunlight, they can be as hot as 250 degrees.

+250°F = +121.11°C, -250°F = -156.67°C

These extremes are just outside working temperatures for UHMWPE. Alternating between sunlight and shade should keep temperature moderate. Mountain climbing ropes have a sheath (mantle) of woven fibre designed to protect against abrasion from rubbing on sharp rocks. Space has micrometeoroids, temperature swings, UV, and radiation. Not much we can do about radiation, but we can make the mantle opaque. And thermal insulation between core and mantle. The mantle would probably be woven fibres of PTFE, the same yarn as Tenara architectural fabric that I mentioned for an inflatable structure on Mars, and the same yarn as Orthofabric. Would you weave a backing of Nomex like Orthofabric, or just use PTFE? The rope would need some stretch to deal with bounce impact, like a mountain climbing rope, so you wouldn't want Kevlar acting to stiffen it. So probably just PTFE; keep it simple. Multilayer insulation between mantle and core? Same insulation as a spacesuit? Or something else?

RobertDyck · 2015-04-14 23:14:47

That's an interesting rubber. A number of years ago I had looked at rubber for spacesuit boot soles. Viking 2 recorded temperature for more than a Martian year. One of the other members on this board was able to give me a link to a NASA archive that had hourly temperatures from Viking 2 for it's entire surface operation. The coldest it recorded was -111°C. I then went through the list of silicone rubber available from Dow Corning, there was one that didn't become brittle until -112°C. That's just barely good enough. But the document you linked claims this rubber is "Thermal stability over -140°C to 200°C".

GW Johnson · 2015-04-15 16:12:08

Thermal stability is not the same property as mechanical resilience. Marketing claims are not to be believed.

GW

SpaceNut · 2015-04-19 18:45:38

While the topic seems to not be a go for man it does have merit for anything else coming down....

TVA SELECTED BY NASA FLIGHT OPPORTUNITIES PROGRAM FOR DEMONSTRATION OF SMALL PAYLOAD RETURN CAPSULE AND TECHNOLOGIES via a high-altitude drop test. This activity is directly aligned with TVA's efforts to develop a small reentry device, RED-4U, capable of returning the payload mass and volume equivalent of four or more CubeSats.

Ya seems small but maybe they will try for larger masses later....

SpaceNut · 2016-01-05 18:26:04

Bump now maybe it can be found.....

SpaceNut · 2016-01-05 18:29:11

kbd512 wrote:

Why are people so obsessed with large and complicated Mars landing systems, let alone reusable Mars landing systems? Money isn't going to magically appear in NASA's coffers for their development. If you give up trying to land multiple people in a properly tested multi-person capsule system with a bunch of consumables, your reentry solution becomes much lighter and far less costly to properly test.
Land cargo separately. If more complicated methods for landing heavier payloads are required, so be it. Don't apply the same technology to landing humans if it isn't necessary.
Land each astronaut individually in unpressurized micro capsules with minimal consumables. HIAD works on Earth. It'll work on Mars, too. There's only one problem to solve with the micro capsule design- inflation of a deployment bladder on a large ringsail using a CO2 cartridge to force the parachute open. If you can make the parachute large enough and still deploy it successfully, propulsive landings are unnecessary. With something as complicated as reentry and soft landing on another planet, simpler is always better.
It does not matter whether or not you land your astronauts in one large, heavy, and complicated multi-person capsule or in individual capsules. If something goes wrong during reentry, they die. If the astronauts land too far from their habitat or rover, they die. The only difference between those two solutions is that with the multi-person capsule, if something goes wrong during reentry, you lose everyone at the same time. Assuming the astronauts landed successfully, but landed significantly off target, the only difference between the multi-person capsule and micro capsule solutions is the elapsed time between landing and loss of crew/mission. Either way, the results are the same.

SpaceNut · 2016-01-05 18:30:17

RobertDyck wrote:

Separating cargo from crew is a good idea. Keeping the crew lander small and simple is also good. However, I don't think you know what that means. Landing crew alive is not that simple. One reason for separating cargo is that you can take risks with cargo that you can't take with crew. If a cargo lander fails, destroying the vehicle and payload, then it's expensive but it's just money. If a crew lander fails, people die.
This is what an individual capsule actually looks like:
https://upload.wikimedia.org/wikipedia/ … nderLK.jpg
YouTube video. I downloaded this as an .mp4 file, and tried to convert to an animated .gif, but the result had 1 frame per 2 seconds.
Landing
Ascent

SpaceNut · 2016-01-05 18:30:59

kbd512 wrote:

Rob,
That's what an individual capsule looks like when you include more consumables than are required for immediate survival and active propulsion. It was also intended for lunar landings. Our target has an atmosphere.
The Mars reentry capsule has two primary functions:
1. Survive entry into Mars atmosphere from LMO.
2. Soft land the person inside.
Anything more sophisticated than a capsule that performs those two tasks is expensive and complicated extravagance.
The micro capsule I have in mind is a two piece unpressurized aeroshell so small and light that the astronaut inside can open it by hand after he or she has landed. The top shell contains a parachute and perhaps a backup parachute. The bottom shell contains HIAD. While still in orbit, a small service module provides propellant and thrusters for attitude control and deceleration used for reentry.
The astronaut inside wears a MCP suit, he or she sits on a fabric seat suspended by bungees inside the shell. The avionics are incorporated into the astronaut's suit and instrumentation readouts are projected onto the astronaut's visor. The only flight controls are a pull handle to release the parachute and a hand controller to orient the capsule for reentry.
It's a real capsule versus a suit designed for a Red Bull style stunt, but it's a minimalist design that performs two functions and only two functions. It doesn't do anything else because it doesn't need to do anything else.
Everyone here and at NASA keeps trying to "what-if" all the possible contingency scenarios ad nauseam rather than accept that certain landing scenarios are not survivable, short of simply landing the crew in a fully functional surface habitat module.
As you stated, if the cargo that makes this mission possible doesn't land successfully, then all we've lost is some expensive hardware. The reentry system should be stupidly simple, lightweight, and inexpensive. Complication cravings should be satisfied elsewhere.
What's more complicated and expensive to design and test?
A: Multi-person pressurized capsule propulsively landed and refueled for return to the MTV (or Earth, as some here would like to do) on another planet
B: Single-person unpressurized capsule parachute landed and thrown away
Edit:
The entire point of landing the habitat modules and other equipment first is to have everything required for surface survival in place before the astronauts arrive. I think it's a really good idea, but that solution also requires a separate crew landing. There's no reason to replicate a miniature version of the surface habitat vis-a-vis a multi-person capsule system. It only ensures that funding for such an endeavor is years or even decades away.
A micro capsule is something that NASA can develop in the interim that doesn't cost so much that absolutely no development of human landing technology occurs in the interim, which is exactly what we have now.
Land the humans in the surface habitat or land the humans in a capsule that only lands them, rather than attempts to replicate what the habitat provides. Pick one, not both.

SpaceNut · 2016-01-05 18:32:23

RobertDyck wrote:

And some people think my idea is too spartan. And some think Mars Direct is too spartan. Your idea is way beyond that.
I said to land in a capsule. Just a capsule. Just a seat for each astronaut, heat shield, parachute, landing rockets, and landing legs with shock absorbers. Nothing fancy. You could think of an air bag to cushion the astronauts for final touch-down, but you can't delete the landing rockets, just-bounce-and-roll like Pathfinder/Spirit/Opportunity. That produced up to 35g acceleration, which isn't survivable for humans. And my idea includes an inflatable habitat and open rover. The reason is to ensure all that stuff is immediately available. Some people don't like the idea of an all-inflatable habitat, no hard walls at all. But this idea was to fit a Mars mission on the Russian Energia, devised when Boris Yeltsin was still president of Russia. Today, well, SLS block 2B has more lift capacity.
And some think my idea of a Mars Assent vehicle is too spartan. I said just a seat for each astronaut, place to strap down sample containers, and a fairing for high-speed assent through Mars atmosphere. No pressurized hull at all, astronauts would ride in their spacesuits. The MAV would have extra large propellant tanks, because the entire MAV would dock to the Interplanetary Transit Vehicle, acting as the TEI stage.
Your micro capsule sounds like MOOSE: Man Out Of Space Easiest
https://upload.wikimedia.org/wikipedia/en/4/49/Operation_MOOSE_%28figure_110%29.PNG
http://www.astronautix.com/graphics/m/moose3v.jpg

SpaceNut · 2016-01-05 18:33:54

louis wrote:

I like the "Keep it simple" approach. I too advocate pre-landing of habs and supplies.
However, I am not entirely convinced of landing individuals in solo pods. Personally I feel we need to be assured the crew can rest upon arrival rather than immediately find themselves in an EVA situation. It would be better in my view if they have a couple of days' supplies with them on landing. Then one or two people, after say six hours of health and equipment checks following landing, can leave the lander and test the hab. If there is a problem with the hab (unlikely but cannot be ruled out), then the whole crew move to a pre-landed ascent vehicle and exit the scene.
Basically I think the lander needs to be "as small as possible".
There might be an argument for single person lander/ascent craft. So, if - say - this was a 6 person mission, you would ferry people down one at a time. The advantage then would be that the craft could be kept as small as possible. Each time the craft returned to the orbiting transit craft, it would be refuelled. It might tkae several sols to land everybody. But it might make the whole mission a lot easier to mount.
Question: How small could a single person lander and ascent craft be and how much fuel would be required for landing and ascent?

kbd512 wrote:
Rob,
That's what an individual capsule looks like when you include more consumables than are required for immediate survival and active propulsion. It was also intended for lunar landings. Our target has an atmosphere.
The Mars reentry capsule has two primary functions:
1. Survive entry into Mars atmosphere from LMO.
2. Soft land the person inside.
Anything more sophisticated than a capsule that performs those two tasks is expensive and complicated extravagance.
The micro capsule I have in mind is a two piece unpressurized aeroshell so small and light that the astronaut inside can open it by hand after he or she has landed. The top shell contains a parachute and perhaps a backup parachute. The bottom shell contains HIAD. While still in orbit, a small service module provides propellant and thrusters for attitude control and deceleration used for reentry.
The astronaut inside wears a MCP suit, he or she sits on a fabric seat suspended by bungees inside the shell. The avionics are incorporated into the astronaut's suit and instrumentation readouts are projected onto the astronaut's visor. The only flight controls are a pull handle to release the parachute and a hand controller to orient the capsule for reentry.
It's a real capsule versus a suit designed for a Red Bull style stunt, but it's a minimalist design that performs two functions and only two functions. It doesn't do anything else because it doesn't need to do anything else.
Everyone here and at NASA keeps trying to "what-if" all the possible contingency scenarios ad nauseam rather than accept that certain landing scenarios are not survivable, short of simply landing the crew in a fully functional surface habitat module.
As you stated, if the cargo that makes this mission possible doesn't land successfully, then all we've lost is some expensive hardware. The reentry system should be stupidly simple, lightweight, and inexpensive. Complication cravings should be satisfied elsewhere.
What's more complicated and expensive to design and test?
A: Multi-person pressurized capsule propulsively landed and refueled for return to the MTV (or Earth, as some here would like to do) on another planet
B: Single-person unpressurized capsule parachute landed and thrown away
Edit:
The entire point of landing the habitat modules and other equipment first is to have everything required for surface survival in place before the astronauts arrive. I think it's a really good idea, but that solution also requires a separate crew landing. There's no reason to replicate a miniature version of the surface habitat vis-a-vis a multi-person capsule system. It only ensures that funding for such an endeavor is years or even decades away.
A micro capsule is something that NASA can develop in the interim that doesn't cost so much that absolutely no development of human landing technology occurs in the interim, which is exactly what we have now.
Land the humans in the surface habitat or land the humans in a capsule that only lands them, rather than attempts to replicate what the habitat provides. Pick one, not both.

SpaceNut · 2016-01-05 20:48:14

SpaceNut wrote:

kbd512 if you look at the link I actually opened the other topic as a result of our discusions and I do believe that we can go much smaller than the big Nasa designs but it does come with a price as we must beat the odds of landing with the possibility of being no where near the consumables that we did not bring if we go to small.
I am reposting this into the smallest human for further discusion there please and thank you to all to do so as well.

louis · 2016-01-06 10:42:12

Thanks for the reminder of this thread, Spacenut.

I think the issue probably comes down to this:

1. Is there any clear benefit in landing individuals separately in spacesuits or pods (assuming it's possible)? Bear in mind we are (I think) focussed on the first mission, and it is vital we get it right.

2. If the answer to 1 is no, then I think the next issue is whether a multi person lander/ascender or single person lander/ascender provides the better option.

4. The argument for a single person lander is that it might be so light that it can be landed substantially by parachute, so saving on fuel and machinery mass - a bit like the Mercury capsule (which weighed in at 1.4 kgs). It could perhaps be refuelled on the surface of Mars using either pre-landed fuel or fuel robotically manufactured on the surface in preceding months and years and then sent back to the orbiting transit vehicle for the next person to use.

5. The argument for a multi-person lander is "safety in numbers" (if one person falls sick or is injured, the others can step into the breach) and proportionate per capita savings on structural mass, potentially (as either RD or GWJ pointed out I think). However, as it would presumably require a lot of retro-engine action, any proportionate structural mass saving might be lost in terms of fuel and engine mass.

6. My hunch is that a refuellable 3 person lander/ascent vehicle that could be used twice over on a six person mission might be the best solution. But it would be supplies-light,as the Mission plan would be for crew to disembark within six hours and enter the larger surface hab that will have been pre-landed.

7. Of course the lander/ascent vehicle relates to the type of mission you are mounting.

kbd512 · 2016-01-06 12:45:52

louis wrote:

Thanks for the reminder of this thread, Spacenut.
I think the issue probably comes down to this:
1. Is there any clear benefit in landing individuals separately in spacesuits or pods (assuming it's possible)? Bear in mind we are (I think) focussed on the first mission, and it is vital we get it right.

The major benefit is that you can thoroughly test the reentry capsule at Mars multiple times because it's so light, simple, and therefore inexpensive that you can send multiple unmanned capsules to Mars aboard a Falcon Heavy rocket to test under a variety of atmospheric conditions and simulate various failures to determine potential recovery methods.

louis wrote:

2. If the answer to 1 is no, then I think the next issue is whether a multi person lander/ascender or single person lander/ascender provides the better option.

I would love to have a combination MDV/MAV/habitat solution. Do you want to wait 10 or 20 years for funding for that type of solution?

louis wrote:

4. The argument for a single person lander is that it might be so light that it can be landed substantially by parachute, so saving on fuel and machinery mass - a bit like the Mercury capsule (which weighed in at 1.4 kgs). It could perhaps be refuelled on the surface of Mars using either pre-landed fuel or fuel robotically manufactured on the surface in preceding months and years and then sent back to the orbiting transit vehicle for the next person to use.

My argument is that if your parachute is big enough, you don't need retropropulsion. A passive EDL solution (HIAD + parachute) is simpler than an active EDL solution (ADEPT + parachute + retropropulsion) and far less expensive. This means development and testing could be completed in this decade as opposed to the next decade.

Cargo requires an active EDL solution. The cost and complexity will ensure that this solution is not as thoroughly tested by the time the first human landings occur. Humans only require an active EDL solution if we insist on making the capsule so massive that active EDL is required.

louis wrote:

5. The argument for a multi-person lander is "safety in numbers" (if one person falls sick or is injured, the others can step into the breach) and proportionate per capita savings on structural mass, potentially (as either RD or GWJ pointed out I think). However, as it would presumably require a lot of retro-engine action, any proportionate structural mass saving might be lost in terms of fuel and engine mass.

Individual landings happen within an hour or so of each other. If a crew member is so severely injured during landing that he or she requires immediate medical attention, what's the probability of that person's survival? What's the probability that the other crew members won't also be severely injured if they were all in the same capsule?

Four pressurized rovers ring the landing area. Unless you land so wildly off target that you'd die no matter what you landed in (short of a habitat module), there's no argument here.

Safety in numbers only applies when you're not all affected by the same event. Passengers in a jumbo jet that crashes aren't "more safe" than passengers in a commuter aircraft that crashes. They're all subject to the results of the same event. The only argument to be made is that the jumbo jet passengers are in a more robust aircraft and the aircraft is so large that some passengers may not be equivalently affected by the crash. Using that analogy, no matter how much better built the multi-person lander is, every passenger is literally inches from the next and the number of passengers in the lander is equivalent to what a very small commuter aircraft would carry. Mass being the primary problem for this mission, it's unlikely that the multi-person capsule will be so much more robust than the single person capsule that crash results would be different. In other words, the 747 vs Cessna argument doesn't square very well with reality. Any crash with either solution is very likely to be a show stopper.

louis wrote:

6. My hunch is that a refuellable 3 person lander/ascent vehicle that could be used twice over on a six person mission might be the best solution. But it would be supplies-light,as the Mission plan would be for crew to disembark within six hours and enter the larger surface hab that will have been pre-landed.

There's no spacecraft I am aware of that has been reused after reentry without refurbishment. Anything is possible, but I'm going to go way out on a limb and say that's going to cost more than NASA can afford.

louis wrote:

7. Of course the lander/ascent vehicle relates to the type of mission you are mounting.

My requirement for the MDV/MAV solution is minimum cost and complexity with maximum testing on Mars prior to human use. Although the MDV/MAV solution is critical to the success of the mission, that hardware is used for a tiny fraction of mission duration. Spend the big bucks on the MTV, Mars surface habitats and/or rovers, and CL-ECLSS. Habitat problems will kill the crew just as surely as a botched landing and they're in continuous use for a far greater portion of the mission duration.

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