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#126 2008-04-06 06:16:34

RobertDyck
Member
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,270
Website

Re: Design Reference Mission 5.0

As Robert Zubrin pointed out in "The Case for Mars", course corrections in the plane of rotation can be made by waiting until the hab is aligned with the direction of the correction then firing thrusters away from the center of rotation. That always pulls the spent stage, no tangential forces. The trick then is to align the plane of rotation with the spacecraft's plane of orbit about the sun. The Earth and Mars are both orbit in the plane of the ecliptic, so a transfer orbit will be in that same plane.  Course corrections will also be in the same plane. Course corrections will also be in the same plane. Course corrections tend to be due to solar wind pushing the spacecraft, so that drift does not leave the plane.

Such alignment will be momentary so propulsive manoeuvres will have to be made with very short pulses - a very inefficient way to use fuel unless low thrust, low Isp thrusters are used.

Space shuttle RSC thrusters use N2O4/MMH for fuel, with Isp of 289 seconds. Arcjet thrusters use hydrazine monopropellant, with an electric arc to ignite it: 570 to 600 second Isp. That's considered a form of electric propulsion. Good enough?

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#127 2008-04-06 06:34:48

cIclops
Member
Registered: 2005-06-16
Posts: 3,230

Re: Design Reference Mission 5.0

Space shuttle RSC thrusters use N2O4/MMH for fuel, with Isp of 289 seconds. Arcjet thrusters use hydrazine monopropellant, with an electric arc to ignite it: 570 to 600 second Isp. That's considered a form of electric propulsion. Good enough?

Nope. Thrusters are used for attitude control and steering not course corrections, they can't provide enough dV for a 50MT space ship.


Let's go to Mars and far beyond -  triple NASA's budget !   #space channel !!    - videos !!!

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#128 2008-04-06 07:42:19

RobertDyck
Member
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 5,270
Website

Re: Design Reference Mission 5.0

Space shuttle RSC thrusters use N2O4/MMH for fuel, with Isp of 289 seconds. Arcjet thrusters use hydrazine monopropellant, with an electric arc to ignite it: 570 to 600 second Isp. That's considered a form of electric propulsion. Good enough?

Nope. Thrusters are used for attitude control and steering not course corrections, they can't provide enough dV for a 50MT space ship.

OME is the Orbital Maneuvering Engine, that is the engine in each pod of the Orbital Maneuvering System on the space shuttle. It is specifically for course corrections of a 100 metric tonne spacecraft. It can insert the orbiter into orbit once it achieves the correct altitude, and de-orbit the spacecraft so it can fall back into the atmosphere. Two engines are used at once, one in each pod, each with 26.700 kN force. Wouldn't a single engine do for a 50 metric tonne Mars craft? Rather proven technology.

By the way, same technology as RCS thrusters, only bigger.

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#129 2008-04-06 07:59:16

cIclops
Member
Registered: 2005-06-16
Posts: 3,230

Re: Design Reference Mission 5.0

That type of engine would have the thrust, but does it work in pulse mode? According to astronautix the typical burn time is a few minutes. Given that such a mission is many years in the future, there should be time to develop a suitable engine. This is just one problem that arises from a rotating spacecraft design, the key issue still remains - will it counter the effects of long duration spaceflight? The only way to answer this is by flight tests. A NEO mission of several months could be a good way to prove it out.  If that works, a fast return mission to Phobos would remove the risk of the transit without the landing issues, as well as demonstrate spacecraft reliability.


Let's go to Mars and far beyond -  triple NASA's budget !   #space channel !!    - videos !!!

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#130 2015-09-07 16:27:43

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 11,375

Re: Design Reference Mission 5.0

NASA’s Road Map Toward Possible Nuclear Rocket Flight Demo
With the capability of generating high thrust and 100% more specific impulse than the best chemical rockets, the time and cost-saving potential of nuclear thermal rockets (NTR) for deep-space missions is once again gaining interest at NASA. Although never flown, the NTR concept is relatively simple. The rocket engine is based around a nuclear fission reactor, which heats the liquid hydrogen (LH2) propellant instead of igniting combustible fuel

http://ntrs.nasa.gov/archive/nasa/casi. … 015032.pdf

http://ansnuclearcafe.org/2012/07/09/na … al-rocket/

NTREES.png

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#131 2015-09-07 17:10:29

Void
Member
Registered: 2011-12-29
Posts: 2,108

Re: Design Reference Mission 5.0

That suggests to me that they have not been entertaining the notion of a chemical drive trip to asteroids or Mars, and might suggest why their hardware does not seem to be able to do anything useful.  With a better propulsion unit, maybe it will make better sense.

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#132 2016-02-10 22:04:11

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 11,375

Re: Design Reference Mission 5.0

Mars Design Reference Architecture 5.0 (DRA5) which was released in 2009.Lunar COTS: An Economical and Sustainable Approach to Reaching Mars

Was reminded of this topic when I saw the sand chart on pg 3.

Much of this document talks about leveraging the insitu resourcess of going to the moon as the means to getting to mars.

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#133 2016-02-11 11:04:44

kbd512
Member
Registered: 2015-01-02
Posts: 1,418

Re: Design Reference Mission 5.0

There's simply no funding available for DRA 5 to function as intended and the rocket that was going to lift these massive NTR stages to LEO does not exist.  DRA 5 required Ares V.  SLS is not Ares V.  If NASA designed SLS the way they should have to begin with, namely using a 10M core for SLS and more powerful LOX/LH2 engines, then DRA 5 would have been workable, albeit extremely expensive.

If NASA is pinning their manned Mars exploration aspirations to solid core NTR's, we're done.

There is no part of the manned Mars exploration mission that can't be easily accomplished using SEP-CTV's and storable chemical propellant kick stages.  I find the notion that we must start every mission in LEO because that's how it was done during the Apollo Program to be an absurd idea that completely ignores all technological advancement that occurred after that chapter of our manned space exploration program.

Quite frankly, the only real purpose I see for having SLS is lifting payloads to LEO that are dimensionally incompatible with commodity rockets like Falcon Heavy and Vulcan.  The habitat modules are the only payloads that fit that description.  Everything else can be launched aboard commodity rockets at greatly reduced cost.  Mating chemical kick stages to payloads is hardly an impossible task.  ISS was built using orbital assembly and any realistic manned Mars mission is going to use orbital assembly.

NASA has two propulsion development imperatives for manned exploration beyond LEO:

1. Develop a SEP-CTV to deliver heavy cargo to other planetary bodies

Solid fuel NTR's are not going to meaningfully improve cargo delivery capabilities per dollar expended towards that effort.  We either go for the jugular of the Isp problem with nuclear thermal propulsion through development of gas core NTR's (GCNR's) or move on.  Once your Isp is in the 3000s range, then delivery of heavy cargo using Hohmann transfer from LEO becomes possible.

2. Determine the feasibility of microwave cavity engines

President Obama gave NASA a mandate to develop better in-space propulsion technology.  Apart from SEP, there is no other in-space propulsion technology in development capable of delivering the tonnage required for manned exploration.  EM Drive is merely a SEP replacement that produces the same or slightly better thrust levels and removes the dependency on expensive inert gas propellants.  Whether physicists understand microwave engines or not, this is the closest advanced propulsion technology to reality that we have right now.

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#134 2016-02-11 19:56:33

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 11,375

Re: Design Reference Mission 5.0

We are in agreement on the points you made on NTR and fancy engines not required. As well as SLS not being the rocket that is needed as designed as its not the capability that was needed for this mission design.

As it was we wasted money from 2004 through 2011 on constellation to these same rocket monopolies that are bloating the costs of even the current version of sls.

The Orion capsule could have been launch on something other than the Ares I (aka Da Stick) but that design which would have used the 2 unmanned rated RS68 was not to be with the regular 4 segment srb's. Which even after Nasa did do engine work to uprev the ability was also wasted. Much as the redesign of the J2 engine as well that is in mothballs.

When I look at the SLS its a 70 and 130 mT unmanned chunk lifter with no need any men on board...This is just for the large stuff which if we do not need all that much does not make sense to put all the cash into it, so since we have done so then we need to show how to use it to send up what needs to be done in large chunks. One could send all the machinery needed to lunar surface to build a base to be able to launch from the moon instead of from the earth's deep gravity well with the SLS fully packed.

At this point orion is only good for Lunar return and little of anything else. So launch a ton of then into lunar orbit to await for when we need one to return from there.

There are lots of things we can do but we should not keep a standing army employed to keep skills or the lines ready for production...that is the point of automated machinery and good programing....

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#135 2016-02-12 13:02:37

kbd512
Member
Registered: 2015-01-02
Posts: 1,418

Re: Design Reference Mission 5.0

I can see the appeal of having a brute force solution to lift requirements when less capable solutions would significantly complicate the issue of getting all payload sub-assemblies to the required orbit.  Even so, brute force should be used sparingly.

I also think any super heavy lift rocket that can't deliver at least 125t to LEO is simply a solution in search of a problem.  Every trade study NASA conducted indicated that a 150t lift capability was required for manned Mars missions.  Somehow we wound up with a rocket that's only capable of 95t to LEO and 115t to LEO with advanced solid boosters.  With composite core stage tanks and composite solid rocket casings, we could potentially hit that 125t figure, but we're never going to hit 150t.

The liquid boosters require a redesign of the ground facilities and the composite casing solid boosters require a significant development and testing program.  Either way, both solutions are incredibly expensive and only net a 30t to 40t improvement in lift capability at a cost that would far exceed any practical benefits.  In other words, SLS was improperly designed because it can't provide the required lift capability without a re-development program.

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#136 2017-01-14 20:36:43

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 11,375

Re: Design Reference Mission 5.0

ITEM
DRA 5.0 Reference (kg)
Structure 2,020
Crew Accommodations 4,210
Environmental Control & Life Support 3,950
Thermal Management System 1,260
Power System 5,840
Avionics 290
EVA Systems 870
Mass Growth Allowance (30%) 4,920
Additional Spares 4,180
Crew 560
Total Transit Habitat Mass 28,100
Food (Return + Outbound Trip) 5,480
Food (Contingency) 7,600
Total Consumables Mass 13,080
TOTAL MASS IN LEO 41,340

Artificial Gravity at 8.2 m
Moon     0.16    7 rpm
Mars      0.38  12 rpm
Earth     1.00  18 rpm

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#137 2018-01-08 18:06:31

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 11,375

Re: Design Reference Mission 5.0

2010 NASA Human Space Exploration Development

bump just to add link

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