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#101 2018-08-07 05:13:52

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,598

Re: Getting to Mars with REAL technology, & what's currently missing.

SpaceNut-

Please note that my reconfigured vehicle does NOT use the 8 Draco thrusters to land. I'm proposing a new, hypergolic fueled motor in gimbals for landing thrust.. The fuel capacity would be roughly 5x-7x  the Crew Dragon version. I'm nowhere near my notes from this proposal I ran about a year and half ago. Will be back in the States in about 3 weeks. Will complete my thoughts then.

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#102 2018-08-07 17:04:02

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,054

Re: Getting to Mars with REAL technology, & what's currently missing.

No worries for replying anytime soon.
I was looking at the superDraco's for launch escape use for not only earth return landing but also for a mars escape if it should not make orbit as they might be possible to fire them to try to get to orbit or to allow for a return to the base. This gives a chance under either risk of failure modes.
Still looking for the straight down facing engine versus the canted protect by the shield air stream answer for the mars lander design. The first stage of the falcon seems to answer but the speed is much slower than what we would see on mars unless we have fuel to burn earlier than normal when we come out of the heat shield mode to where parachutes speed would open.

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#103 2018-08-07 18:56:06

kbd512
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Registered: 2015-01-02
Posts: 2,717

Re: Getting to Mars with REAL technology, & what's currently missing.

SpaceNut,

I still think the SkyCrane / tractor design that places the payload on the bottom is the best way to do this.  It minimizes the mass of the landing gear, mitigates issues with egress in the case of a habitat module, and minimizes the need for cranes for surface cargo offloading.  The LEM system worked well because the lunar environment is very low gravity and there was sufficient storage space in the lander stage for the limited scientific experiment equipment.  Now people want to do something entirely different and are still trying to come up with ways to make the LEM propulsion system work at far greater scale.  It's not that it can't work, it's just not a very mass efficient way to do things and mass is at an extreme premium for a Mars mission.

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#104 2018-08-07 20:16:28

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,054

Re: Getting to Mars with REAL technology, & what's currently missing.

So could we up scale the skycrane to being the return to orbit with the super draco's doing the landing keeping the craft to a very small package. The system would land with the skycrane empty and then refuel on landing from the cargo landers. Another option is to use a drop tank design to rid the mass on the way up to orbit. Tanks could come from cargo landers to make the launch vehicle.

So sky scrane at the top, followed by the habitat section (small cygnus) then dragon capsule for 2. and landing legs...

So cygnus is cargo hold on return to orbit and is used for living space for the return. Once on orbit the sky crane is sent off so that we can mate up with the orbiting earth return booster with supplies for return home.

So we would boost from earth an eds plus the mars crew unit on a falcon heavy with a second heavy launching 2 cygnus less booster stage (only solar panels) full of supplies with return from mars stage once we mate up in orbit.

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#105 2019-01-05 21:28:33

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,054

Re: Getting to Mars with REAL technology, & what's currently missing.

Russia continues work on plasma engine for superfast space travel aimed at successfully harnessing the power of thermonuclear plasma for use in a rocket engine. With a temperature of 100,000 degrees to form the plasma, and reaching a sufficient density to provide them with data suitable for further work on the creation of a plasma-based rocket engine

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#106 2019-02-12 20:57:14

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 15,054

Re: Getting to Mars with REAL technology, & what's currently missing.

Not sure if Nasa is getting serious or just pretending to kick the can down the road.
Developing a flight strategy to land heavier vehicles on Mars

The heaviest vehicle to successfully land on Mars is the Curiosity Rover at 1 metric ton, about 2,200 pounds. Sending more ambitious robotic missions to the surface of Mars, and eventually humans, will require landed payload masses in the 5- to 20-ton range. To do that, we need to figure out how to land more mass. That was the goal of a recent study.

Normally, when a vehicle enters the Mars atmosphere at hypersonic speeds of about Mach 30,

After mach 3 firing engines to create a more horizontal flight to aid in slowing the vehicle down...

research paper

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#107 2019-03-09 06:32:24

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,054

Re: Getting to Mars with REAL technology, & what's currently missing.

Not fo void but for the topic

kbd512 wrote:

Void,

NASA has determined that pound-for-pound, the best defense against SPE's and GCR's would be a woven BNNT fabric or composite.  They're trying to determine how to use it as a structural material to save weight, because it's also very strong and light, but a woven blanket or mat of the material is also suitable for shielding purposes.  I've already posted docs for this in another thread dedicated to radiation shielding.

The AFRL has determined that aerographite would also be good shielding material against electromagnetic radiation, though probably not against SPE's and GCR's.  It's one of the lightest structural foam materials known to man, lighter than structural aerogel foam, much stronger than aerogel, and far more compressible without cracking or permanent deformation.

Physical Properties of 3D Interconnected Graphite Networks - Aerographite

Water would be great, but it's too heavy for space applications.  We'd still need lots of it for other purposes, but probably can't deliver enough to use it as passive radiation shielding.  I think NASA determined that they'd need 2m or more to keep radiation dose rates within currently allowable limits.

Nice to see food for thought on how to solve mass versus exposure.

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#108 2019-03-09 14:30:45

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,492
Website

Re: Getting to Mars with REAL technology, & what's currently missing.

Most of the propellants we use should have radiation-shielding properties at least crudely similar to water. 

Why not just hide behind the propellant you are going to use for the arrival burn?

This would be particularly convenient for an orbit-to-orbit spaceship design that has a significant arrival burn in order to enter Mars orbit,  instead of a direct landing with nearly all aerodynamic braking.

GW


GW Johnson
McGregor,  Texas

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

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#109 2019-03-09 14:43:13

Void
Member
Registered: 2011-12-29
Posts: 2,954

Re: Getting to Mars with REAL technology, & what's currently missing.

I like it sir.


I like people who criticize angels dancing on a pinhead.  I also like it when angels dance on my pinhead.

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#110 2019-03-09 22:37:39

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,054

Re: Getting to Mars with REAL technology, & what's currently missing.

Here is the measurements for a water barrel approach to having the habitat inside them.
https://space.stackexchange.com/questio … hielding-i

Let's say that the Mars vehicle that will get them there and back is a cylinder roughly 3.5m by 20m (same as was used for the MARS-500 experiments; that is a very small tin can in which to spend 3 1/2 years with 4 or 5 other people). With 1m of shielding water around all surfaces of that cylinder, the outer hull would be about 5.5m by 22m.

The volume of shielding water needed is the difference between those two cylinders, or $22\cdot\pi\cdot2.75^2 - 20\cdot\pi\cdot1.75^2 \approx 522.68 - 192.42 = 330.26 m^3$. As one cubic meter of water weighs 1 metric ton (1,000kg), that's 330,260kg to get into space.

Each 7cm (http://www.nist.gov/pml/data/xraycoef/index.cfm) of water divides the radiation by a factor of 2. Thus the total required is 38 * 7cm or 266 cm. Use 300 cm / 3 meters to make calculation easier and it provides an extra safety margin which makes the calculation easier.

https://www.nasa.gov/feature/goddard/re … n-on-mars/

https://www.quora.com/How-much-thicknes … -colonists

It has been determined that 16 feet (5 meters) of Martian soil would be needed to provide the same level of protection against solar radiation as the Earth's atmosphere does.

This number, however, is at least in part determined based on the water and/or hydrogen content in the Martian soil (hydrogen acts as good shielding against radiation). Just a few inches of water can have the same effect as 16 feet of Martian soil.

Looks to me like we are going to need a different means to build up the ship for long term use for the journey as well as for Mars surface life....

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#111 2019-04-05 16:38:51

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 15,054

Re: Getting to Mars with REAL technology, & what's currently missing.

Someday we will need to do better than this
10620573_1554149384808418_8554491756511265866_n.jpg

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#112 2019-04-05 17:21:56

kbd512
Moderator
Registered: 2015-01-02
Posts: 2,717

Re: Getting to Mars with REAL technology, & what's currently missing.

SpaceNut,

If we use hybrid electric propulsion, then we don't need absurd quantities of fuel to establish a stable orbit.  We can still use chemical rockets to break orbit at Earth or place the transfer vehicle into a highly elliptical orbit.  After we're on our merry way, then we may as well use a cruise propulsion system.  GW can relate to this as a cruise missile with a solid rocket booster.  The booster blasts the missile out of its launch tube and into the air, whereupon the much lower thrust turbojet engine takes over.

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