Augustine commission/Ares alternatives

[Zatnikitelman]

Well would you have to sidemount the whole thing? I think I saw one variant with the engines mounted in a pod and the capsule at the top of the ET.

 

[Orbinaut Pete]

Well would you have to sidemount the whole thing? I think I saw one variant with the engines mounted in a pod and the capsule at the top of the ET.

Yes, "Shuttle-B"

I don't think it is currently under consideration as an alternative to Ares.

 

[Insane]

I guess another "less desirable" feature of the side mount is the MPS is not recovered. One consept with Shuttle-C was having the SSMEs and aft compartment able to re-enter and be recovered for reuse.

Oh well, just have to wait to see what happends. I hope that a side mount add-on gets made.

Zerofay32

John Shannon said, in his presentation of Sidemount, that it's actually more economical to produce expendable SSMEs. In case anyone didn't see the presentation but wants to and doesn't know where to find it - [ame="http://vimeo.com/5340181"]U.S. Human Space Flight Committee-Washington, DC Part 7 on Vimeo[/ame] - all other meetings are there too I think. I'd encourage people to watch it if they haven't, Shannon's a very good speaker. Possibly inadvertantly advertises a lot of the benefits of Direct as well

 

[Donamy]

It should shorten the gap.

 

[Orbinaut Pete]

It should shorten the gap.

YouTube - SD HLLV

WOW!!! :speakcool:

Don, you should become the official mesh guy for all Ares alternatives groups (DIRECT, EELV, HLV sidemount, COTS etc.).

Maybe then you could finally get paid for your work!

 

[Donamy]

Ya, in my dreams !! Thanks Pete.

I would like to see a 8 or 10 person Orion.

 

[Orbinaut Pete]

I would like to see a 8 or 10 person Orion.

8-10 person Orion??

I would question the need for such capacity.

ISS flights would need 3-4 seats max (because Russia isn’t going to stop flying the Soyuz, just because America gets a long-duration spacecraft).

And would lunar flights really need 8-10 people??

I should think 5-6 max.


Imagine 10 people trying to live inside Orion...

 

[Insane]

Could probably fit 8 in this little contraption - http://www.lockheedmartin.com/data/assets/ssc/Orion/Toolkit/asteroidScene2_toolkit.gif

 

[ijuin]

You know, I don't particularly care WHAT Orion and Altair launch on as long as we can actually get them to the moon reasonably soon.

On launching more than six people on Orion, we could fit eight people into one if we accept the same amount of cabin space per crew member as was available in the Apollo command module, and twelve if we accepted the just-enough-space-to-take-a-crap setup of Gemini (which the Gemini VI crew endured for two weeks).

 

[movieman]

John Shannon said, in his presentation of Sidemount, that it's actually more economical to produce expendable SSMEs.

And probably much more economical to buy RS68s...

 

[Urwumpe]

And probably much more economical to buy RS68s...

With certainty, but the RS-68 has as gas generator cycle a lower specific impulse - what you save at the engine end, could be added as material and production costs.

 

[Insane]

And probably much more economical to buy RS68s...

Aren't they the engines that they recently discovered would get destroyed due to the heat from the SRBs if used in a Shuttle type stack? Hence why Nasa is looking into making them regeneratively cooled for Ares V (yet more cost and time to develop). I can't remember the reasoning behind Ares V not just going back to SSMEs off hand. Doubt price is much of a factor.

I don't like getting into the technical aspects of things because as I said, I'm not educated in that field, but I thought I'd respond since that's what I've picked up from reading and you quoted me. If someone else is more knowledgeable in this area, please correct me if I'm going wrong somewhere.

EDIT - just thought I'd add, for completeness' sake, that DIRECT v2 involved using RS68s rather than SSMEs, but the above problem with them necessitated a change to SSMEs again, since when they've spoken with PWR about making expendable versions, and it seems viable, and cheaper.

 

[Urwumpe]

Aren't they the engines that they recently discovered would get destroyed due to the heat from the SRBs if used in a Shuttle type stack? Hence why Nasa is looking into making them regeneratively cooled for Ares V (yet more cost and time to develop). I can't remember the reasoning behind Ares V not just going back to SSMEs off hand. Doubt price is much of a factor.

AFAIR, the regenerative cooling was rather needed as earlier planned performance upgrade for the EELVs, by heating the fuel, you get more specific impulse. The heat emitted by the SRBs is extreme by temperature and mass flow, but should still not be impossible for ablative cooling.

 

[tblaxland]

The heat emitted by the SRBs is extreme by temperature and mass flow, but should still not be impossible for ablative cooling.

It was at least on the table for Ares V:
http://www.nasaspaceflight.com/2008/12/ssme-ares-v-undergoes-evaluation-potential-switch/

The exhaust plumes of six RS-68 engines, combined with the two SRBs, interact to reduce the efficiency of the engines, and cause extreme heating on the base of the core stage.[...]The regenerative nozzle protects both the inside and the outside of the nozzle, versus the ablative nozzle which is designed to deal with heat from only the inside.

 

[Insane]

Could well be true, but certainly the effect of the SRBs altered DIRECT's plan, and NASA apparently studied reverting to SSMEs as well.

Couple links -

http://www.nasaspaceflight.com/2008/12/ssme-ares-v-undergoes-evaluation-potential-switch/

http://www.launchcomplexmodels.com/Direct/documents/DIRECT_Analysis_Rebuttal_Final_090518.pdf (P.112)

Edit - Darn, beat me to it tblaxland

 

[Andy44]

SSMEs are one of the best pieces of technology to come out of the STS program. Building an expendable version and production-lining it seems to be a wise idea over the long run, though it would be a bit pricey at first. I just hate to see NASA throw away yet another good engine.

 

[movieman]

With certainty, but the RS-68 has as gas generator cycle a lower specific impulse - what you save at the engine end, could be added as material and production costs.

But the money you'll save over using SSMEs would almost certainly cover any increase in flight rate. Pushing for 'efficiency' over cost has been one of NASA's biggest problems over the last couple of decades.

 

[ijuin]

I agree on the efficiency/cost item. The measure of efficiency should be grams of payload delivered to orbit per dollar spent, NOT grams to orbit per grams of liftoff mass. The only other consideration should be for safety. Why do you think marine vessels--even the US Navy--use a lower grade of fuel than jet aircraft, even though it means cutting into cargo capacity by enlarging the fuel tanks? They do it because it's cheaper!

 

[Urwumpe]

They do it because it's cheaper!

Actually, they do so because the fuel is available in almost any port they enter. It makes no sense to use special fuel, if this means you need a fleet of tankers for getting it from selected naval bases to the units.

 

[ijuin]

Well yes, but also why they don't use the higher grade fuel when it IS on hand (e.g. in home ports).

Anyway, for rocketry, mass fractions are secondary to cost as long as total payload is high enough. This will remain true as long as labor costs grossly outstrip materials and fuel costs in the construction and launching of rockets.