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#201 2018-08-06 19:17:23

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 12,211

Re: Smallest Human Ascent or Descent Lander for Mars Or Earth

Fully recoverable Dragon cargo capsule
Overall Length: 6.1 m (20 ft)
Max Diameter: 3.7 m (12.1 ft)
Dry Mass: 4,200 kg (9,260 lbs)

Propulsion: 18 x Draco thrusters
Propellant: NTO / MMH

Payload Volume:
7 to 10 m3 (245 ft3) pressurized

• Trunk jettisoned prior to reentry
Power: twin solar panels providing 1,500 W average, 4,000 W peak, at 28 and 120 VDC
Payload Volume:
14 m3 (490 ft3) unpressurized
34 m3 (1,200 cu ft) unpressurized with extended trunk

Maximum LEO Falcon 9 Capacity with a payload shroud 10,459 kg (22,990 lbs)
• 6,000 kg (13,228 lbs) total combined up-mass capability
• Up to 3,000 kg (6,614 lbs) down mass

When I find the mass statements for the truck and fuel will add them in for the post plus the legs to have the values for scaling them.

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#202 2018-08-06 21:52:39

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,078
Website

Re: Smallest Human Ascent or Descent Lander for Mars Or Earth

Spacenut:

I worked out an analysis spreadsheet that sizes configurations for two types of Mars landers.  These are one-stage,  two-way,  reusable vehicles,  and two-stage,  two-way,  non-reusable vehicles.  The spreadsheet includes a worksheet for guessing inert mass fractions in an organized way.  If you email me that you want it,  I'd be happy to send it to you.  Or anyone else on these forums.

I used it to run a design study on these two types of landers.  What I found was the storable propellants work best,  due to the months of transit to Mars.  The increase in inert hardware to offset the boiloff negates the higher specific impulse effect,  for LCH4-LOX vs MMH-NTO. I wrote it all up in considerable detail,  and posted it over at my blog site,  exrocketman.blogspot.com. 

There is a navigation tool on the left:  click on 2018,  then August,  then the title "Exploring Mars Lander Configurations".  Right now,  it is the latest thing I have posted. 

The article also gives the date and title for another article I posted last year,  where I reported my reverse engineering of what the various versions of the Spacex Dragon can do. That one predates cancellation of Red Dragon,  so my estimates for what Red Dragon could do are there,  as well as crew Dragon,  and cargo Dragon.  I had to make some assumptions,  but they are realistic and well-identified in the article.  Most of the source data is what Spacex has published.   

GW

Last edited by GW Johnson (2018-08-06 22:11:08)


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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#203 2018-08-07 16:29:58

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 12,211

Re: Smallest Human Ascent or Descent Lander for Mars Or Earth

Thank you for the offer. Will dig through your site to search out more information as well.

Continuing to post the details that I have found thus far to aid in the scope of what do we need in a first mission to mars.

Dragon v2 manned capsule
same baseline size with a new mold line shape to accomodate the Eight side-mounted SuperDraco engines, clustered in redundant pairs in four engine pods, with each engine able to produce 71 kilonewtons (16,000 lbf) of thrust. They consumed their nearly two-ton load of hydrazine and nitrogen tetroxide propellant in less than six seconds, pushing the Dragon capsule a third of a mile above Cape Canaveral with a top speed of 345 mph. The capsule hovered in equilibrium for about 5 seconds, kept in balance by its 8 engines firing at reduced thrust to compensate exactly for gravity.

The legs on the Falcon 9 first stage:
https://www.reddit.com/r/spacex/comment … eg_design/
Current stage is about 25t at landing and has diameter of 3.7 m.

By the square-cube law, you'll need legs with cross-sectional area 8 times larger. If you only have 4 legs, you'll need legs with horizontal side of sqrt(8) = 2.83 times more than what we currently have.

Four legs, which are made of carbon fiber with aluminum honeycomb, will be placed symmetrically around the base of the rocket.

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#204 2018-08-07 18:58:11

kbd512
Member
Registered: 2015-01-02
Posts: 1,813

Re: Smallest Human Ascent or Descent Lander for Mars Or Earth

GW,

I'd like a copy of that spreadsheet.  I want to see if I can make a HTML page out of it using JavaScript.  Maybe we can create a tools section to this website that has online tools for estimating mass and performance for Mars missions.

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#205 2018-08-07 20:01:12

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 12,211

Re: Smallest Human Ascent or Descent Lander for Mars Or Earth

I do agree with that and Hope that we can push the technology we have to get the job done.

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#206 2018-08-09 07:58:43

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 3,078
Website

Re: Smallest Human Ascent or Descent Lander for Mars Or Earth

Just found the Mars lander spreadsheet request from Kbd512.  It's on its way to your email.  That's you and Spacenut so far. 

Have fun with the silly thing.  It's just playing games with the rocket equation,  mass fractions,  and some jigger factors for things like gravity and drag losses. 

The article on "exrocketman" where I looked at landers with this spreadsheet is drawing a lot of readership. 

Sorry there's no user's manual for the spreadsheet.  The article is the closest thing to a user's manual that I have.  The usual user inputs are highlighted yellow. 

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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