Author Topic: DIRECT Lunar Mission Performance Calculator  (Read 14233 times)

Offline MP99

Re: DIRECT Lunar Mission Performance Calculator
« Reply #20 on: 04/15/2009 05:15 PM »
Can I clarify how the 10% margin on the crewed flight works.

For the LV-40 CLV BB card, ascent propellant of 65,973Kg can lift 96,453Kg of payload.

For the "payload w/ additional 10% reserve", do you still load the JUS with the same 65,973Kg of ascent fuel, and simply load a max of 86,808Kg of payload? The additional JUS fuel is what actually provides the margin in the event of a performance shortfall?

Many thanks, Martin

Offline MP99

Re: DIRECT Lunar Mission Performance Calculator
« Reply #21 on: 04/15/2009 05:43 PM »
J-246-cargo has 12.2mT as the DM Base figure - should that be 11.2mT?

cheers, Martin


You scale the lander mass with the fuel load carried - 50% more fuel = 50% heavier lander.

This makes sense for the cargo lander, but if I understand correctly, the crewed lander is derived the cargo lander with some addtional subsystems (and some stuff taken off, I guess).

Simplistically, would it be sensible for you to scale the "cargo" portion of the lander, then add the 1.006mT difference for the crewed elements.

Admittedly, the payloads are fairly small on the crewed flight, so this would give a fairly small payload boost.

...or maybe I've misunderstood the relationship between the two beasts anyway!

cheers, Martin

Offline kraisee

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #22 on: 04/15/2009 06:28 PM »
Don't forget that the crew flight also requires that the LSAM performs the LOI while the CEV is attached to it.   That radically changes the dynamics between the two mission modes.

This is the optimal approach if you want a common lander for both.   You size for the larger mission, and then just use the same DM to land the smaller mission, accepting that there will be a small penalty.

In both the Ares and DIRECT scenario's the cargo mission requires the larger lander and determines its size.   So whatever Lander you need for that mission is the one you also have to use for the Crew flight.

When you then optimize the two solutions to get the most performance out of the crew flights, this is just what you end up with.

Ross.
« Last Edit: 04/15/2009 06:28 PM by kraisee »
"The meek shall inherit the Earth -- the rest of us will go to the stars"
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Offline MP99

Re: DIRECT Lunar Mission Performance Calculator
« Reply #23 on: 04/18/2009 02:45 PM »
Don't forget that the crew flight also requires that the LSAM performs the LOI while the CEV is attached to it.   That radically changes the dynamics between the two mission modes.

Ross,

I understand that there is a single lander design, and that it is sized for it's most demanding mission.

However, I don't understand why you are using / scaling the crewed lander (12.2mT, including crew life support and AM docking structure) to perform the cargo mission?

I would assume that most of the "things added to a cargo lander to make it a crewed lander" would be independent of the size of the basic lander's infrastructure.

CxP's crewed lander is 1.006mT more than the cargo lander, and it seems reasonable that this relationship should hold for your scaled lander, too.


Taking your cargo spreadsheet and setting cell AE2 to CxP's baseline cargo  lander mass (11,194Kg) results in a cargo lander of 16,697Kg, with payload 22,830Kg.

Setting the crewed lander to 16,697 + 1,006 = 17,703Kg, results in a net payload of 800Kg (gross = 7,368Kg).

cheers, Martin

PS I understand that the true scaling relationship is ITAR sensitive.


Edit: re-reading, the phrasing sounds rather confrontational. Not intended to be - just trying to help. Just wondering whether the spreadsheet is being a little too pessimistic.
« Last Edit: 04/18/2009 09:01 PM by MP99 »

Offline MP99

Re: DIRECT Lunar Mission Performance Calculator
« Reply #24 on: 04/20/2009 08:51 AM »
Okay, I have some updated and revised spreadsheets for y'all, including all of the latest information I've been able to pull together, plus the latest performance data of the Series 41 Jupiter-246 design too.

Ross.


Ross,

Excel is reporting "Solver could not find a feasible solution" on the "crew" spreadsheet.

Seems to work OK if I change AE9=AE3 to AE9>=AE3, ie only fail the solution if crewed DM needs to be heavier than cargo DM.

cheers, Martin

Offline MP99

Re: DIRECT Lunar Mission Performance Calculator
« Reply #25 on: 04/21/2009 02:37 PM »
Sorry I've been in "away" mode for the last handful of days, but I'm back now.

I'm not going to go back through all the posts I missed, but if there were any specific questions which didn't get answered, I'd be happy to take a crack at them if they are asked again.


Ross,

if you have time to briefly look over the previous two posts in this thread - both related to the calculator spreadsheet.

Please also note the "edit" on the first post.

cheers, Martin

Offline MP99

Re: DIRECT Lunar Mission Performance Calculator
« Reply #26 on: 04/23/2009 04:13 PM »
Okay, I have some updated and revised spreadsheets for y'all, including all of the latest information I've been able to pull together, plus the latest performance data of the Series 41 Jupiter-246 design too.

Ross.


Ross,

LV-40 had a ~6.4mT CLV-to-EDS lift difference, with LV-41 the difference seems to have come down to ~4.1mT (103138 Kg vs 99026 Kg).

Is that a consequence of the lighter LV-41 core, or is the latter figure for an Altair-only (cargo) flight, and the crewed figure is lower? The difference is about right to accommodate a LAS on the crewed flight.

cheers, Martin

Offline MP99

Re: DIRECT Lunar Mission Performance Calculator
« Reply #27 on: 05/09/2009 03:21 PM »
Another minor correction to the spreadsheet - "EDS + ASE Jettison" should come before "CEV + LSAM Extraction".

This is presuming the sequence of events is simply to release the ASE, then accelerate the CEV + LSAM away from the EDS.

cheers, Martin

Offline kraisee

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #28 on: 05/10/2009 05:09 PM »
MP,
No, you definately need to be extracting the CEV/LSAM before you go jettisoning the EDS :)


FYI:   There are *many* corrections and alterations coming for this spreadsheet.   The MSFC guys have corrected a number of things for me over the last couple of weeks.   I was mistaken in soime of my earlier assumptions and they have helped put me on the right path now.   I will get you the latest versions as soon as I can -- I'm still working on a few bits.

Ross.
« Last Edit: 05/10/2009 05:10 PM by kraisee »
"The meek shall inherit the Earth -- the rest of us will go to the stars"
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Offline MP99

Re: DIRECT Lunar Mission Performance Calculator
« Reply #29 on: 05/10/2009 09:24 PM »
MP,
No, you definately need to be extracting the CEV/LSAM before you go jettisoning the EDS :)

Yes, but why does the extraction burn accelerate the combined mass of CEV, LSAM, ASE & EDS?

I had visualised that the LSAM-to-EDS connection would be broken (ie the "jettison"), and then the DM RCS would burn 3m/s to cause the CEV/LSAM to accelerate away from the EDS (ie the "extraction").



Quote
FYI:   There are *many* corrections and alterations coming for this spreadsheet.   The MSFC guys have corrected a number of things for me over the last couple of weeks.   I was mistaken in soime of my earlier assumptions and they have helped put me on the right path now.   I will get you the latest versions as soon as I can -- I'm still working on a few bits.

To be honest, I think it's only thee & me who actually care, but I do think this is a valuable part of DIRECT's openness.

cheers, Martin

Offline kraisee

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #30 on: 05/11/2009 05:06 AM »
Martin,
Here's an update which I've been trying to pull together recently.   It needs another set of eyes on it though.

And yes, I have noticed exactly how far off the mark the Ares solution is.

Ross.
« Last Edit: 05/11/2009 05:07 AM by kraisee »
"The meek shall inherit the Earth -- the rest of us will go to the stars"
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Offline HOTTOL

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #31 on: 05/12/2009 05:27 PM »
Ross,

I did some checking on "Profile_J-246_+_J-246-41-4004_EOR-LOR_Crew_5276kg__SIZED__(1).xls".

1- I don't understand the "-921 kg" of Cargo payload.
2- Why 4 days of loitering in LLO (line 34) ?
3- I understand AM and SM engines don't boiloff. So what's the use of lines 56, 60, 62, 65 in your spreadsheet ?
4- The mass of the crew doesn't show off. Moving this mass from SM to AM and back would influence the Station Keeping phase and the Return phase (AM Disposal. SM MPS and RCS).

François

Offline mmeijeri

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #32 on: 05/12/2009 05:34 PM »
2- Why 4 days of loitering in LLO (line 34) ?

It saves a plane change, they're waiting for the moon to rotate under them.
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Offline HOTTOL

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #33 on: 05/12/2009 05:58 PM »
Martijn,

Yes, but ... there is a "Plane Change Burn" (line 33) !

François

Offline mmeijeri

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #34 on: 05/12/2009 06:19 PM »
Yes, but ... there is a "Plane Change Burn" (line 33) !

A fairly minor one I think, only 28 m/s IIRC, enabled by the 4 day loiter. It is interesting NASA have relaxed their requirements, an extra 4 days in orbit was previously a no-no.
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Offline kraisee

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #35 on: 05/12/2009 06:31 PM »
That's right.

The only alternative was to add an extra ~350-400m/s to the Plane Change dV requirement.   Spending 4 days in LLO on the outbound voyage was just 'more' acceptable.   The return voyage doesn't loiter.

Ross.
« Last Edit: 05/12/2009 06:31 PM by kraisee »
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Offline HOTTOL

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #36 on: 05/12/2009 06:51 PM »
Ros, Martijn,

So, OK about my point number 2.

Point 3 is more a clean-up issue than a real question.

What about point 1 and 4 ?

François

Offline mmeijeri

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #37 on: 05/12/2009 07:04 PM »
The only alternative was to add an extra ~350-400m/s to the Plane Change dV requirement.

Now, now, 'only'? ;)

Quote
   Spending 4 days in LLO on the outbound voyage was just 'more' acceptable.   The return voyage doesn't loiter.

And don't forget the three days rendez-vousing with EDS + Altair in LEO on the outward journey.
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Offline MP99

Re: DIRECT Lunar Mission Performance Calculator
« Reply #38 on: 05/13/2009 07:20 AM »
Quote
   Spending 4 days in LLO on the outbound voyage was just 'more' acceptable.   The return voyage doesn't loiter.

And don't forget the three days rendez-vousing with EDS + Altair in LEO on the outward journey.


EDS + Altair (CxP) or EDS (DIRECT) loiters up to 4 days waiting for a safe launch & approach of the crewed vehicle.

The spreadsheet shows a 3.25 day EDS loiter waiting for the crewed launch, another 0.75 day loiter by both EDS & CEV as they approach, rendezvous & dock, then a 0.25 day loiter for checkout before TLI.

This is about ensuring a safe, no-pressure, crewed launch, not an efficient orbital manoeuvre to save fuel.

cheers, Martin

Offline mmeijeri

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Re: DIRECT Lunar Mission Performance Calculator
« Reply #39 on: 05/13/2009 12:07 PM »
EDS + Altair (CxP) or EDS (DIRECT) loiters up to 4 days waiting for a safe launch & approach of the crewed vehicle.

The spreadsheet shows a 3.25 day EDS loiter waiting for the crewed launch, another 0.75 day loiter by both EDS & CEV as they approach, rendezvous & dock, then a 0.25 day loiter for checkout before TLI.

Thanks, I didn't know it would be so short, I was thinking it would be a three day procedure, as with the ISS.

Quote
This is about ensuring a safe, no-pressure, crewed launch, not an efficient orbital manoeuvre to save fuel.

Yeah, I know, but if another five days in orbit are allowed, slightly longer routes through L1 could not be disqualified on those grounds. ;)
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