Author Topic: Griffin speech - Why one STS derived launch system would not work for Constellation  (Read 122691 times)

Offline kkattula

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Kaputnik - 20/2/2008  11:27 PM

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kkattula - 20/2/2008  1:05 PM
The Russians will soon be launching from Guyana anyway.

That's only true in the same way that they are currently launching from the Pacific.

I thought they were launching Salyut's not Zenit's?

Anyway, they can definitely launch propellant re-fills from either.

Offline Kaputnik

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kkattula - 20/2/2008  2:48 PM

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Kaputnik - 20/2/2008  11:27 PM

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kkattula - 20/2/2008  1:05 PM
The Russians will soon be launching from Guyana anyway.

That's only true in the same way that they are currently launching from the Pacific.

I thought they were launching Salyut's not Zenit's?

Anyway, they can definitely launch propellant re-fills from either.

What I meant was that it is ESA who are launching the Soyuz from Guyana, just like it is Sealaunch who launch the Zenits. AFAIK the 'Europeanised' Soyuz will be somewhat modified and will cost more too; it's main customer will be ESA, and Russian Soyuz launches will continue as normal.
"I don't care what anything was DESIGNED to do, I care about what it CAN do"- Gene Kranz

Online Lampyridae

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kkattula - 20/2/2008  10:05 PM

1. Study the rocket equation: that 6.3% is huge. For example for a LOX/LH2 SSTO mass ratio goes from 8.8 to 10.1 for an extra 6.3% delta v. That will eat your payload.

2. Leave the ISS as the laboratory it is. It doesn't have any of the facilities needed by a propellant depot except life support.
No tanks, spare power, spare docking adaptors, vehicle servicing equipment. You have to launch all those things anyway, so launch them to the best orbit. A propellant depot at 28.5 degrees, with minimal "lay-over" crew facilities.

3. The Russians will soon be launching from Guyana anyway.

1. SSTOs are not being flown. The orbiter manages to make it to ISS with a 20 tonne payload on top of the 70- odd tonnes of the orbiter itself. Assuming that 20 tonnes is the max to ISS (of 25 tonnes) that means there's about 5-6% MASS penalty.

2. Easier to add on to something than start from scratch. Plus you now have a dedicated crew to support. Pricey. Wingod's proposal is to use the ISS facilities for Shuttle-C recovery, as well as fuel depot etc.

3. True enough. But that by itself is not enough to negate the advantages offered by ISS (especially political curry like "paying back investment"), Also, I point out Kaputnik's comment.

Offline kkattula2

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SSTO was just an illustration of the effects of delta v increase.  

As I understand it, 6.3% is the effect on the total delta v of a lunar mission. Not shuttle ops to the ISS vs 28.5 LEO. That's probably in the range of 1-2% for that 5-6% mass penalty.  

Shuttle hides some of that mass penalty by doing a long OMS burn during main engine burn, to get some extra thrust. Reducing the normal in orbit OMS reserves.

Offline Patchouli

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Obama will likely dump Ares I too which is likely a good move it's only real value is as a test mule for Ares V and he may even seek to replace Orion with a series of much cheaper private vehicles.

The Orion makes no sense at all if you are not going to the moon if LEO is your destination then a vehicle like Dream Chaser or Dragon makes a lot more economic sense.

Offline Jim

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kkattula2 - 20/2/2008  8:49 PM  

As I understand it, 6.3% is the effect on the total delta v of a lunar mission. Not shuttle ops to the ISS vs 28.5 LEO. .

No, it is for ISS vs 28.5 LEO and most vehicles (not just shuttle)

The issue is (not using real numbers) this:

Payload capability

Delta IV 28 deg.   50klb   51.6 deg   47klb

STS  28 deg.   50klb   51.6 deg   35klb

the difference is the 6% is on the whole mass of the orbiter 250Klbs



Offline Patchouli

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Since there will be a space station in the 28.5 degree orbit the EDS/LSAM is going to be launched in anyway why not just have the Orion make a stop over at bigelow's skywalker station and wait for them?
The the bigelow station will be in a much higher orbit then the EDS parking orbit but then scrap ares  I for direct that gives Orion 700M/sec more delta V for doing maneuvers if nothing else is changed
so moving from a 275mile orbit to a 150 mile one becomes a minor issue.

Offline Scotty

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The mass fraction of a LOX/LH2 single stage to orbit vehicle is right around 89%.
That means 89% of the lift off mass is the fuel required just to reach LEO.
That leaves 11% for airframe, tankage, propulsion system, guidance system, and if anything is left over, payload (that would likely never exceed a couple percent).
Now if that is a reusable and manned SSTO vehicle, you have to also add to the vehicle (still remaining with in that 11% for everything else) crew cabin, life support, deorbit fuel, thermal protection system, and a landing-recovery package (be that wings, parachutes or something else).
The net deployable payload delivered to LEO would be little or nothing.
SSTO is more or less impossible for a manned and reusable vehicle using any chemical combustion propulsion system.

The Shuttle burns the orbital manuvering engines during powered flight (normally just after getting through Max Q) to burn off fuel, thus making the total weight carred to orbit lighter, not to gain extra performance by the 20,000 pounds of thrust the OMS provide.
Yes, there is a small gain in performance to the Shuttle with burning the OMS engines during the SSME burn, but the real reason behind the OMS burns, is just to burn off the fuel.
We are talking about thousands of pounds of hypergols here.

Online Lampyridae

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Patchouli - 21/2/2008  11:00 AM

1. Obama will likely dump Ares I too which is likely a good move it's only real value is as a test mule for Ares V and he may even seek to replace Orion with a series of much cheaper private vehicles.

2. The Orion makes no sense at all if you are not going to the moon if LEO is your destination then a vehicle like Dream Chaser or Dragon makes a lot more economic sense.

1. Pork, pork, pork. Ares V cancelled, yes. Ares I... unlikely. ATK needs to hang onto jobs, even if it means using a 5-seg and J-2X instead of man-rating an EELV.

2. If ESAS is cancelled, than maybe that's what will carry NASA astronauts to LEO. But ESAS is also about jobs, I don't expect it to be cancelled so quickly.

Offline luke strawwalker

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renclod - 19/2/2008  1:55 PM

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luke strawwalker - 19/2/2008  8:41 PM

If Ares I is going to be SO cheap and safe why not just launch the Orion first and have the LSAM/EDS meet up with it.
http://www.flightglobal.com/articles/2007/12/21/220464/nasas-moon-mission-could-see-major-change-in-concept-of.html

>> NASA is studying a major change to its Moon mission plan to cut the time its spacecraft have to wait in low Earth orbit before setting off. Loitering in LEO presents challenges for cryogenic propellant storage and spacecraft energy budget.

A revised mission plan could see the Ares I launcher, carrying the Orion crew exploration vehicle, lift off before an Ares V cargo launcher takes the Earth departure stage and Altair lunar lander into space.<<



Ahhh... Haven't seen this... news to me... :)  OL JR :)
NO plan IS the plan...

"His plan had no goals, no timeline, and no budgetary guidelines. Just maybe's, pretty speeches, and smokescreens."

Offline kkattula2

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Thanks Jim, so the ISS penalty is about 6% total orbiter mass, 25% payload and probably around 1-2% delta v?

Also, I thought the reason Columbia didn't visit the ISS was that it didn't have the correct docking adaptor.
Possibly because, being heavier, it couldn't carry both the adaptor and a worthwhile cargo.

Offline Jim

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kkattula2 - 20/2/2008  10:17 PM

Thanks Jim, so the ISS penalty is about 6% total orbiter mass, 25% payload and probably around 1-2% delta v?

Also, I thought the reason Columbia didn't visit the ISS was that it didn't have the correct docking adaptor.
Possibly because, being heavier, it couldn't carry both the adaptor and a worthwhile cargo.

Exactly.  Ask wingod for the exact numbers, I was showing the effect

Offline wingod

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Jim - 20/2/2008  9:21 PM

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kkattula2 - 20/2/2008  10:17 PM

Thanks Jim, so the ISS penalty is about 6% total orbiter mass, 25% payload and probably around 1-2% delta v?

Also, I thought the reason Columbia didn't visit the ISS was that it didn't have the correct docking adaptor.
Possibly because, being heavier, it couldn't carry both the adaptor and a worthwhile cargo.

Exactly.  Ask wingod for the exact numbers, I was showing the effect

The 6.3% is from both the Atlas and the Delta payload planners guides.



Offline kraisee

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Just tried this using our calculator.

Assuming the same Jupiter-232 Launch Vehicle for all launches, with an EDS massing 15,995kg inclusive of residuals, I was able to place the following payloads into circular orbit:-

To 130x130nm, 29.0deg
CLV: 102,766kg
CaLV: 104,396kg


To 220x220nm, 51.6deg
CLV: 99,232kg (3.56% difference)
CaLV: 98,206kg (6.31% difference)

Essentially, the final difference through TLI for these two configurations was all in the LSAM NET mass after TLI - where there was a 3,508kg difference in mass, with the 130nm, 29deg option delivering a 41,646kg LSAM through TLI vs. 38,138kg for the LSAM going via 220nm, 51.6deg - a 6.01% difference when the 20,185kg CEV is accounted for also.

This ultimately results in 1,743kg less mass landed on the Lunar surface with the ISS rendezvous option with 26,711kg vs. 24,968kg landed - a 6.98% difference.

Of course, the CxP target landed mass is 25,300kg and this difference means one option does close correctly, and the other does not.   Make of that what you will.

Ross.
"The meek shall inherit the Earth -- the rest of us will go to the stars"
-Robert A. Heinlein

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