Author Topic: Ares I 1st stage replacement  (Read 124138 times)

Online MATTBLAK

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Re: Ares I 1st stage replacment.
« Reply #40 on: 07/24/2008 11:37 AM »
Very interesting...
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Offline renclod

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Re: Ares I 1st stage replacment.
« Reply #41 on: 07/24/2008 12:45 PM »
Total sales, most recent fiscal year reported:
Lockheed Martin: $41.9 billion
ATK: $4.17 billion

Total sales to civil govt. , homeland sec., intel, NASA and commercial : 27% from LM sales.

Don't see why ATK such a bogeyman.


As for ATK's power - you have to realise that Boeing and Lockheed have similar sized lobby groups too. 

Define "similar sized" please. Reference, please.



« Last Edit: 07/24/2008 01:02 PM by renclod »

Offline MrTim

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Re: Ares I 1st stage replacment.
« Reply #42 on: 07/24/2008 06:54 PM »
Someone, earlier, introduced the fact that the SRB (compared to the liquid engines) will always light and won't shut down until it is supposed to. Is this still a factor?

Talk about turning a serious bug into a feature! That just had to have originated in a marketing department...

Engineer: "unlike our competitors, our product can't be stopped or controlled once you start it"
Marketing: "So... it's absolutely guaranteed to keep going until it runs out of fuel, right? hmmmm.... I see a glossy two-pager..."

brilliant  ::)

Offline guru

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Re: Ares I 1st stage replacment.
« Reply #43 on: 07/24/2008 07:28 PM »
Someone, earlier, introduced the fact that the SRB (compared to the liquid engines) will always light and won't shut down until it is supposed to.

Is this still a factor?


Well, I think its bigger advantages are that it is storable and has high energy density.  That is why it is useful for rapidly deployed ICBMs.  It doesn't always light on the first try (atleast that's what my model rocket building experience tells me), but without a good ground, it can light more easily than the separate fuel and oxidizer of a liquid when you don't want it to.
« Last Edit: 07/24/2008 07:29 PM by guru »

Offline Max_Peck

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Re: Ares I 1st stage replacment.
« Reply #44 on: 07/24/2008 07:55 PM »
All of these discussions have me wondering where I can purchase a copy of the Program to Optimize Simulated Trajectories (POST)? The license is supposed to cost betwen $1000 to $2000 and that some versions are ITAR (POST-II) and others are not (POST-3D). Can anyone tell me where I can buy it?

Offline gospacex

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Re: Ares I 1st stage replacment.
« Reply #45 on: 07/24/2008 08:15 PM »
Well, I think its bigger advantages are that it is storable and has high energy density.  That is why it is useful for rapidly deployed ICBMs.

Storability is a plus, but it's important only for military, not for space LVs.

Energy density is not important - total dV is, which is related but different metric - if you have lighter gases in exhaust, your Isp is higher at the same energy. A kerolox booster of same dimensions and thrust outperforms a SRM.

Offline guru

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Re: Ares I 1st stage replacment.
« Reply #46 on: 07/24/2008 08:51 PM »
Well, I think its bigger advantages are that it is storable and has high energy density.  That is why it is useful for rapidly deployed ICBMs.

Storability is a plus, but it's important only for military, not for space LVs.

That's why I didn't say "it is useful for shuttle boosters" - I believe liquids would be better.  I was pointing out real advantages that solids have, as opposed to marketing spins, and an application for which those advantages are useful (cheaper, expendable artillery, which you don't want to accidentally turn off anyway).



« Last Edit: 07/24/2008 08:52 PM by guru »

Offline guru

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Re: Ares I 1st stage replacment.
« Reply #47 on: 07/24/2008 09:28 PM »
Quote
Energy density is not important

Not true.  If the entire Saturn V only stored 1 Joule worth of chemical energy, then it's maximum velocity would be sqrt(2J / 3,000,000 kg) = .0008 m/s.  This explains why, in most cases, hydrogen is not used on the lower stage.  It has a lower energy density than kerosene and makes the first stage larger, and thus more expensive.  It is, as I'm sure you know, more useful on upper stages, where the higher energy per unit of mass makes it easier for the first stage to acclerate it, but the lower volumetric energy density doesn't necessarily make the upper stage so big that is prohibitively expensive to produce.

Quote
total dV is, which is related but different metric - if you have lighter gases in exhaust, your Isp is higher at the same energy. A kerolox booster of same dimensions and thrust outperforms a SRM.

You left out the mass ratio in your explanation, which is also in fact related to energy density of a rocket propellant (based on minimum delta V requirements), but I think we're both pretty well versed in the basics of rocketry and are arguing in agreement here.
« Last Edit: 07/24/2008 09:41 PM by guru »

Offline spacenut

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Re: Ares I 1st stage replacment.
« Reply #48 on: 07/24/2008 09:34 PM »
I think flyback kerolox reusable boosters would be better than the solids.  The flyback booster reusable as a single rocket could also launch the Orion capsule.  Less vibration on the suttle stack would also be safer for the shuttle from foam debris.  If you went with a kerolox shuttle engine with ground start, but throttled way down, you wouldn't have to insulate the tank, no foam problems.   

Offline spacenut

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Re: Ares I 1st stage replacment.
« Reply #49 on: 07/24/2008 09:36 PM »
The kerolox shuttle engine throttled way down would be throttled up to orbit when the boosters dropped off. 

Offline imcub

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Re: Ares I 1st stage replacment.
« Reply #50 on: 07/24/2008 10:54 PM »
I think flyback kerolox reusable boosters would be better than the solids.  The flyback booster reusable as a single rocket could also launch the Orion capsule.  Less vibration on the suttle stack would also be safer for the shuttle from foam debris.  If you went with a kerolox shuttle engine with ground start, but throttled way down, you wouldn't have to insulate the tank, no foam problems.   

The lox part of kerolox will still need some insulation ...

Offline edkyle99

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Re: Ares I 1st stage replacment.
« Reply #51 on: 07/25/2008 01:04 AM »
RD-180 would be more likely than RD-171 because it is already being imported by ULA, etc..

Even though you say that Pratt and Whitney is abandoning their RD-AMROSS effort?

PWR isn't abandoning RD-AMROSS.  RD-AMROSS is the PWR/Energomash joint venture that imports and delivers the RD-180 engines from Russia to ULA.  It was also the likely entity that would have produced domestic RD-180s, but ULA funding for domestic production research appears to have recently ended. 

 - Ed Kyle

Offline edkyle99

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Re: Ares I 1st stage replacment.
« Reply #52 on: 07/25/2008 01:09 AM »
Running some numbers quickly, this *might* be able to fly the current ~22,500kg Lunar-capable Orion.

T:W at liftoff carrying a full Ares-I Upper Stage is only 1.03 and first stage performance carrying that is truly awful. So, to get any sort of reasonable performance you're looking at the US needing to being shrunk quite a bit.

Dropping it to around the optimum, which appears to be around 50,000kg capacity, the first stage still seems underpowered with a T:W 1.19. I can insert an Orion to 130x130nm, 29.0deg, but dynamic pressure (max-Q) is obscenely high, well above 1000psf.   All my runs assumed the full 108% RS-68 and the full 294,000lb thrust J-2X....

Ross.

Ross,

Which concept are you discussing?  Both of the EELV-derived first stage with J-2X second stage alternatives I considered had liftoff T/W ratios of about 1.4 and used upper stages that were lighter than Ares I, but still carried roughly 100 tonnes of propellant.

 - Ed Kyle
« Last Edit: 07/26/2008 10:37 PM by edkyle99 »

Offline Antares

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Re: Ares I 1st stage replacment.
« Reply #53 on: 07/25/2008 04:01 AM »
Regarding big domestic RP engine available in early 00s: it's debatable whether Atlas V would have gone that route since RD-180 was so cheap.

Regarding ATK vs Boeing/LM NASA revenue: the Boeing Board has recently gone hardline on insufficient profit margin in space.  This was one of the main drivers behind the formation of ULA.  Maybe the ATK Board is not so strict, trying to make it up in volume.
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Offline Lampyridae

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Re: Ares I 1st stage replacment.
« Reply #54 on: 07/25/2008 06:31 AM »
The kerolox shuttle engine throttled way down would be throttled up to orbit when the boosters dropped off. 

Shuttle engine would probably have to be throttled to max at launch anyway to get off the ground. Load paths would be worse with a LOX / kero ET because it would be so much heavier.

If a full LOX / kero design is what you're after then may as well design a 3CCB configuration, leading to something like the Falcon 9H or Zenit with strapons.
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Offline clongton

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Re: Ares I 1st stage replacment.
« Reply #55 on: 07/25/2008 11:09 AM »
Running some numbers quickly, this *might* be able to fly the current ~22,500kg Lunar-capable Orion.

T:W at liftoff carrying a full Ares-I Upper Stage is only 1.03 and first stage performance carrying that is truly awful. So, to get any sort of reasonable performance you're looking at the US needing to being shrunk quite a bit.

Dropping it to around the optimum, which appears to be around 50,000kg capacity, the first stage still seems underpowered with a T:W 1.19. I can insert an Orion to 130x130nm, 29.0deg, but dynamic pressure (max-Q) is obscenely high, well above 1000psf.   All my runs assumed the full 108% RS-68 and the full 294,000lb thrust J-2X.
Ross.

These numbers could be increased significantly if a TAN were used on the RS-68. T/W would be absolutley no problem then. However, that would require the introduction of new technology onto the critical path to get off the ground for IOC. The TAN itself shouldn't be any problem because it's already been researched extensively and demonstrated effective, but getting it into play in time to reduce the gap could be the long pole, on a par with introducing the J-2X.
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Offline gospacex

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Re: Ares I 1st stage replacment.
« Reply #56 on: 07/25/2008 11:13 AM »
Regarding big domestic RP engine available in early 00s: it's debatable whether Atlas V would have gone that route since RD-180 was so cheap.

BTW: RD-180s are sold to US for $10 million apiece. RD-170s, which are essentially 2xRD-180, are sold $7 million apiece for Zenit rocket. Draw your own conclusions regarding real costs to manufacture one RD-180.

Offline Magnus_Redin

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Re: Ares I 1st stage replacment.
« Reply #57 on: 07/26/2008 08:39 AM »
These numbers could be increased significantly if a TAN were used on the RS-68.

TAN?

Offline gospacex

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Re: Ares I 1st stage replacment.
« Reply #58 on: 07/26/2008 09:35 AM »
Quote
Energy density is not important
Not true.  If the entire Saturn V only stored 1 Joule worth of chemical energy, then it's maximum velocity would be sqrt(2J / 3,000,000 kg) = .0008 m/s.

Apparently you are having fun. Why did you remove the second half of my sentence, "total dV is"? What is "not true" about it? If you have two rockets of same mass and shape, which one is better - one with higher energy density or one with higher total dV?

Offline rsp1202

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Re: Ares I 1st stage replacment.
« Reply #59 on: 07/26/2008 01:16 PM »

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