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Orion's Weight
by
spacenut
on 01 Mar, 2018 12:35
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Why is Orion so heavy in comparison to Dragon II and the CTS-100? Dragon was to be capable of circumnavigating the moon and return. Orion is supposed to do the same. Is there that much radiation protection to cause the weight to be double that of the other two?
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#1
by
Proponent
on 01 Mar, 2018 13:21
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Why is Orion so heavy in comparison to Dragon II and the CTS-100? Dragon was to be capable of circumnavigating the moon and return. Orion is supposed to do the same. Is there that much radiation protection to cause the weight to be double that of the other two?
I don't know that this is the only reason, but Orion has much more propulsive capability. It has the delta-V to enter a high lunar orbit and then return to earth. Dragon 2 can fly around the moon, but by itself it cannot go into lunar orbit.
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#2
by
UltraViolet9
on 01 Mar, 2018 14:34
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Why is Orion so heavy in comparison to Dragon II and the CTS-100? Dragon was to be capable of circumnavigating the moon and return. Orion is supposed to do the same.
Orion sustains a larger crew for that mission. Two additional crew, the vehicle wrap for their living volume, their life support, and their supplies weigh a lot.
There's logic behind two teams of two crew that can back each other up during surface lunar ops. But ESAS performed no sensitivity analysis on what price the vehicle would pay for that extra team (versus one team of two crew as in Apollo). In the absence of such analysis, Orion has suffered for that and other Griffin mandates.
Is there that much radiation protection to cause the weight to be double that of the other two?
There's radiation shielding for astronauts and radiation shielding and hardening for electronics.
For the former, AFAIK, the Orion vehicle has no polyethylene layers or other radiation shielding to protect astronauts incorporated in its construction. Rather, the team has explored how to rearrange cargo to absorb radiation from a solar event before it reaches the astronauts and StemRad vests on the astronauts to protect vital organs.
https://www.nasa.gov/feature/scientists-and-engineers-evaluate-orion-radiation-protection-planhttp://www.iflscience.com/space/nasa-to-test-mars-radiation-shield-on-its-mission-around-the-moon/Obviously, you could apply those radiation measures on Dragon or any another crewed spacecraft, too.
Someone else may be able to speak better on the electronics.
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#3
by
spacenut
on 01 Mar, 2018 15:03
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So Dragon II with a service module would weigh more, and the FH probably could not launch it to lunar orbit and return. Is that right? It may end up weighing as much as Orion, correct?
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#4
by
UltraViolet9
on 01 Mar, 2018 15:35
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So Dragon II with a service module would weigh more, and the FH probably could not launch it to lunar orbit and return. Is that right? It may end up weighing as much as Orion, correct?
No, for the circumlunar mission, D2 would have required a longer-range comm system and not much else in the way of changes. FH can launch that mission.
For now, SpaceX has decided they'd rather concentrate on BFR/BFS and use that system for the circumlunar mission instead of FH/D2.
Orion masses more because it is required to be able to carry twice as many crewmembers (4 vs. 2), and it enters a (very high) lunar orbit vice a free-return trajectory like D2 (and Apollo 13).
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#5
by
spacenut
on 01 Mar, 2018 15:45
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Are there any sketches showing Orion, Dragon II, and Starliner side by side, with dimensions and weight?
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#6
by
speedevil
on 01 Mar, 2018 15:58
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No, for the circumlunar mission, D2 would have required a longer-range comm system and not much else in the way of changes. FH can launch that mission.
If, of course, circumlunar is still desirable. BFS is on the borderline of being able to do it, but it's borderline, with no payload, and inherently limited creature comforts.
If a lunar mission is contemplated at all, it will have been after enough testing that the cost of several tanker flights are in the noise, and at that point, you can be, not just the first paying customers round, but the first paying customers on the moon.
It makes life support a lot easier, as you can trivially go fully open loop, and not have to worry about it much.
It also lets you check out the craft for a few days in LEO first.
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#7
by
UltraViolet9
on 01 Mar, 2018 16:09
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#8
by
spacenut
on 01 Mar, 2018 16:30
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Thanks, that is what I was looking for. So if SpaceX replaced their trunk with a service module with fuel and an engine, it would probably weigh as much as Orion. Same with Boeing. I was wondering why Orion was "so much better" than the other two for cis-lunar exploration. It is not just the weight of the capsule, but the service module, food, water, and fuel for the entire trip and be able to return.
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#9
by
brickmack
on 01 Mar, 2018 16:34
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I don't know that this is the only reason, but Orion has much more propulsive capability. It has the delta-V to enter a high lunar orbit and then return to earth. Dragon 2 can fly around the moon, but by itself it cannot go into lunar orbit.
Dragon can most likely enter and leave from LDRO as well, just not while carrying a comanifested payload. Its not a much more challenging mission profile than ISS rendezvous and deorbit. Though IMO the utility of Orion tugging along a <10 ton module is kinda dubious. It would have required a parachute landing though (not a concern any longer with propulsive landing dead until BFS)
Orion sustains a larger crew for that mission. Two additional crew, the vehicle wrap for their living volume, their life support, and their supplies weigh a lot.
There's logic behind two teams of two crew that can back each other up during surface lunar ops. But ESAS performed no sensitivity analysis on what price the vehicle would pay for that extra team (versus one team of two crew as in Apollo). In the absence of such analysis, Orion has suffered for that and other Griffin mandates.
Note that Apollo already demonstrated a 3 man crew for lunar-duration missions (alone, not with a LEM, on Apollo 17) using a smaller capsule than Orion has. And studies existed showing up to 5 crewmembers could be supported "reasonably" comfortably. If the Apollo CSM could do 3 crewmembers for that duration, I don't see any good reason Orion couldn't have supported 4+ for a comparable duration if it only had to do so on lunar surface missions (with a lander attached, ~doubling that volume). This has always been the big problem of Orion, the CM is grossly oversized for the mission, and the SM would have to be huge to match Apollo's delta v capacity.
Keep the same 3.9 meter capsule diameter from Apollo, but use modern materials and computers and propulsion to shave the mass down and add performance margin, should have ended up with a spacecraft significantly lighter than Apollo. Not heavier yet less capable.
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#10
by
mike robel
on 01 Mar, 2018 16:35
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Boeing's offering always reminds of me Gemini but blown up to an Apollo in size without the Apollo SM and only the Gemin Retro/Equipment Modules.
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#11
by
Jim
on 01 Mar, 2018 17:27
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I don't know that this is the only reason, but Orion has much more propulsive capability. It has the delta-V to enter a high lunar orbit and then return to earth. Dragon 2 can fly around the moon, but by itself it cannot go into lunar orbit.
Dragon can most likely enter and leave from LDRO as well, just not while carrying a comanifested payload. Its not a much more challenging mission profile than ISS rendezvous and deorbit. Though IMO the utility of Orion tugging along a <10 ton module is kinda dubious. It would have required a parachute landing though (not a concern any longer with propulsive landing dead until BFS)
Orion sustains a larger crew for that mission. Two additional crew, the vehicle wrap for their living volume, their life support, and their supplies weigh a lot.
There's logic behind two teams of two crew that can back each other up during surface lunar ops. But ESAS performed no sensitivity analysis on what price the vehicle would pay for that extra team (versus one team of two crew as in Apollo). In the absence of such analysis, Orion has suffered for that and other Griffin mandates.
Note that Apollo already demonstrated a 3 man crew for lunar-duration missions (alone, not with a LEM, on Apollo 17) using a smaller capsule than Orion has. And studies existed showing up to 5 crewmembers could be supported "reasonably" comfortably. If the Apollo CSM could do 3 crewmembers for that duration, I don't see any good reason Orion couldn't have supported 4+ for a comparable duration if it only had to do so on lunar surface missions (with a lander attached, ~doubling that volume). This has always been the big problem of Orion, the CM is grossly oversized for the mission, and the SM would have to be huge to match Apollo's delta v capacity.
Keep the same 3.9 meter capsule diameter from Apollo, but use modern materials and computers and propulsion to shave the mass down and add performance margin, should have ended up with a spacecraft significantly lighter than Apollo. Not heavier yet less capable.
Orion was sized for 20 day lunar stays
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#12
by
whitelancer64
on 01 Mar, 2018 17:37
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#13
by
spacenut
on 01 Mar, 2018 17:47
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So if SpaceX's and Boeing's capsules were set up to do a 20 day stay in lunar orbit, and have the ability to return to earth, they would both increase in weight like Orion? Would either be as heavy as Orion with these upgrades? Could Falcon Heavy or Vulcan ACES get either to lunar Orbit if they were lighter than Orion and be able to do the same thing? I'm just wondering if Orion could have some future competition?
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#14
by
Lars-J
on 01 Mar, 2018 18:02
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So if SpaceX's and Boeing's capsules were set up to do a 20 day stay in lunar orbit, and have the ability to return to earth, they would both increase in weight like Orion? Would either be as heavy as Orion with these upgrades? Could Falcon Heavy or Vulcan ACES get either to lunar Orbit if they were lighter than Orion and be able to do the same thing? I'm just wondering if Orion could have some future competition?
No, they should still be smaller. The living area and number of astronauts for such a mission would be more constrained, leading to less mass and a less heavy service module.
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#15
by
whitelancer64
on 01 Mar, 2018 18:04
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One of the big things that Orion has that Starliner and Dragon v2 do not is a toilet. So keep that in mind for long-duration mission planning.
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#16
by
envy887
on 01 Mar, 2018 18:10
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One thing driving the weight difference is size: Orion has about 20 cubic meters of pressurized volume and Dragon has about 10.
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#17
by
Lars-J
on 01 Mar, 2018 18:17
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One of the big things that Orion has that Starliner and Dragon v2 do not is a toilet. So keep that in mind for long-duration mission planning.
I don't think Orion has a toilet. Can you provide a reference?
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#18
by
spacenut
on 01 Mar, 2018 18:36
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I see the internal volume on the charts. So even to compete with Orion, the other companies would have to have multiple launches for living modules, service modules, food and fuel, either assembled in orbit or at say L1. Orion could still be cramped for 4 without a living module at a cis-lunar region and a toilet, especially for a long duration mission.
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#19
by
IRobot
on 01 Mar, 2018 18:46
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One of the big things that Orion has that Starliner and Dragon v2 do not is a toilet. So keep that in mind for long-duration mission planning.
AFAIK, it was later rejected, so back to plastic bags.
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#20
by
UltraViolet9
on 01 Mar, 2018 21:41
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I see the internal volume on the charts. So even to compete with Orion, the other companies would have to have multiple launches for living modules, service modules, food and fuel, either assembled in orbit or at say L1. Orion could still be cramped for 4 without a living module at a cis-lunar region and a toilet, especially for a long duration mission.
Orion's mass is driven by both questionable design choices and questionable requirements choices.
You could probably revisit some of Orion's design choices (like its diameter, toilet, etc.) and reduce mass. Maybe that alone would get it down to D2 mass, but my gut doubts it. (Maybe close.)
I think you'd have to fundamentally revisit the requirements from the ESAS study (mission duration, crew size, etc.) and rethink the mission architecture to get down to D2 mass.
D2 can do lunar missions. It just can't do the large, long lunar missions as dictated by Griffin's requirements to ESAS.
[soapbox on]
Requirements are everything. Stick to the minimum necessary for the mission as defined by your stakeholders. Or, if you're going to add requirements, understand very well their incremental costs to your program's budget, schedule, and risk.
Unfortunately for Orion, Griffin and ESAS did neither.
[/soapbox off]
AFAIK, it was later rejected, so back to plastic bags.
Articles just last week on the waste disposal system in the emergency suits state that Orion still has a toilet:
Like the space shuttle before it, Orion will be equipped with a toilet, but NASA is making contingency plans in case of emergencies, including the possibility that the Orion capsule depressurizes and the astronauts have to remain in their suits to survive. In fact, the agency wants astronauts to be able to survive in their suits for up to six days — meaning the men and women would have to be able to do things like eat, urinate and defecate without taking them off.
https://www.space.com/39710-orion-spacesuit-waste-disposal-system.html But someone working the program may know better.
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#21
by
joek
on 01 Mar, 2018 22:12
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All things considered, the Orion crew + service module mass is not too bad given its intended purpose.
The real porker is the LAS, which accounts for ~22% of Orion's launch mass (7463kg of 35384kg). A few other odds-and-ends consume an additional ~4% of non-injected mass.
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#22
by
Steven Pietrobon
on 02 Mar, 2018 05:22
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The reason Orion is so much heaver is simple its huge size. For a pressure vessel, the mass is proportional to its volume. The Apollo CM mass was 5.84 t with a 3.91 m diameter. Orion is 5.0 m diameter, so directly scaling gives 5.84*(5/3.91)³ = 5.84*2.09 = 12.21 t. Orion CM mass is 19% less less at 9.89 t, probably due to using lighter materials, such as aluminium instead of steel for the pressure vessel, lithium-ion batteries and modern electronics. Orion was originally going to carry six crew so that it could be used for ISS and Mars missions. Had Orion been sized for four crew, its diameter would have been 3.91*(4/3)^{1/3} = 4.3 m. That would have reduced its mass to between 9.89*(4.3/5)³ = 6.29 t (Orion model) and 5.84*(4.3/3.91)³ = 7.77 t (Apollo model). Lets use the average of 7.03 t, which is a 29% reduction in mass. So instead of a 25.85 t Orion, it would now be a 18.37 t Orion, which would allow it to be launched by Atlas V and Falcon 9, instead of the only option being the very expensive Delta-IV Heavy.
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#23
by
envy887
on 02 Mar, 2018 14:04
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The reason Orion is so much heaver is simple its huge size. For a pressure vessel, the mass is proportional to its volume. The Apollo CM mass was 5.84 t with a 3.91 m diameter. Orion is 5.0 m diameter, so directly scaling gives 5.84*(5/3.91)³ = 5.84*2.09 = 12.21 t. Orion CM mass is 19% less less at 9.89 t, probably due to using lighter materials, such as aluminium instead of steel for the pressure vessel, lithium-ion batteries and modern electronics. Orion was originally going to carry six crew so that it could be used for ISS and Mars missions. Had Orion been sized for four crew, its diameter would have been 3.91*(4/3)^{1/3} = 4.3 m. That would have reduced its mass to between 9.89*(4.3/5)³ = 6.29 t (Orion model) and 5.84*(4.3/3.91)³ = 7.77 t (Apollo model). Lets use the average of 7.03 t, which is a 29% reduction in mass. So instead of a 25.85 t Orion, it would now be a 18.37 t Orion, which would allow it to be launched by Atlas V and Falcon 9, instead of the only option being the very expensive Delta-IV Heavy.
Interestingly, a 5-meter diameter aluminum sphere capable of holding 1.25 atmospheres would weigh about 105 kg and have 3.5x the pressurized volume of Orion.
A truncated cone is not an efficient pressure vessel design, and most of the structural mass is not related to containing internal pressure but more likely external loads, puncture resistance, MMOD, etc.
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#24
by
the_other_Doug
on 02 Mar, 2018 15:49
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All things considered, the Orion crew + service module mass is not too bad given its intended purpose.
The real porker is the LAS, which accounts for ~22% of Orion's launch mass (7463kg of 35384kg). A few other odds-and-ends consume an additional ~4% of non-injected mass.
NASA's Orion system is mass-starved, as have been almost all spacecraft systems to date -- certainly all American spacecraft, anyway. The mantra has always been to make flight hardware as light as possible, allowing more performance from your propulsion stages. (Shuttle's airframe was an exception, but other Shuttle systems were built as light as possible, to gain performance edges.)
In such a mass-starved system design, who in the world came up with Enormo the Fairing? Granted, it is dropped early enough in the launch that it has less impact than it would if, say, it was retained to orbit. But, in a mass-starved system, why increase the mass of the fairing so ridiculously high? Why not just fly a reasonably light boost protective cover, a la Apollo? As originally designed?
Are they trying to make an SRB field joint failure survivable from a flying debris perspective, or something?
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#25
by
whitelancer64
on 02 Mar, 2018 16:19
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One of the big things that Orion has that Starliner and Dragon v2 do not is a toilet. So keep that in mind for long-duration mission planning.
AFAIK, it was later rejected, so back to plastic bags.
I haven't heard about it being deleted from the Orion design.
Last I heard there will be a demonstration toilet flown to the ISS for testing.
"Universal Waste Management System: Demonstration of common compact toilet for ISS and Orion (Oct. 2018)"
www.nasa.gov/sites/default/files/atoms/files/moore_aes_tagged.pdfCan anyone dig up a notification or report where that was cancelled?
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#26
by
whitelancer64
on 02 Mar, 2018 16:19
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One of the big things that Orion has that Starliner and Dragon v2 do not is a toilet. So keep that in mind for long-duration mission planning.
I don't think Orion has a toilet. Can you provide a reference?
"The crew module contains four seats that the astronauts will fold and stow after launch. “Orion won’t be a roomy ship, but it does have 150 percent more elbow room than Apollo,” says Rick Mastracchio, the astronaut office’s representative to the Orion program. The galley is spartan, with just a water dispenser and food warming case. Nearby is a small, resistive exercise machine.
Tucked into the lower deck will be a very compact toilet compartment, rigged with pop-up curtains to preserve a modicum of privacy."
https://aerospaceamerica.aiaa.org/departments/building-orion/
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#27
by
whitelancer64
on 02 Mar, 2018 17:02
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All things considered, the Orion crew + service module mass is not too bad given its intended purpose.
The real porker is the LAS, which accounts for ~22% of Orion's launch mass (7463kg of 35384kg). A few other odds-and-ends consume an additional ~4% of non-injected mass.
NASA's Orion system is mass-starved, as have been almost all spacecraft systems to date -- certainly all American spacecraft, anyway. The mantra has always been to make flight hardware as light as possible, allowing more performance from your propulsion stages. (Shuttle's airframe was an exception, but other Shuttle systems were built as light as possible, to gain performance edges.)
In such a mass-starved system design, who in the world came up with Enormo the Fairing? Granted, it is dropped early enough in the launch that it has less impact than it would if, say, it was retained to orbit. But, in a mass-starved system, why increase the mass of the fairing so ridiculously high? Why not just fly a reasonably light boost protective cover, a la Apollo? As originally designed?
Are they trying to make an SRB field joint failure survivable from a flying debris perspective, or something?
It's Enormo, the LAS. Yep, the LAS has to be very beefy to pull the Orion away from chunks of an exploding SRB.
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#28
by
Zed_Noir
on 02 Mar, 2018 23:04
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The reason Orion is so much heaver is simple its huge size. For a pressure vessel, the mass is proportional to its volume. The Apollo CM mass was 5.84 t with a 3.91 m diameter. Orion is 5.0 m diameter, so directly scaling gives 5.84*(5/3.91)³ = 5.84*2.09 = 12.21 t. Orion CM mass is 19% less less at 9.89 t, probably due to using lighter materials, such as aluminium instead of steel for the pressure vessel, lithium-ion batteries and modern electronics. Orion was originally going to carry six crew so that it could be used for ISS and Mars missions. Had Orion been sized for four crew, its diameter would have been 3.91*(4/3)^{1/3} = 4.3 m. That would have reduced its mass to between 9.89*(4.3/5)³ = 6.29 t (Orion model) and 5.84*(4.3/3.91)³ = 7.77 t (Apollo model). Lets use the average of 7.03 t, which is a 29% reduction in mass. So instead of a 25.85 t Orion, it would now be a 18.37 t Orion, which would allow it to be launched by Atlas V and Falcon 9, instead of the only option being the very expensive Delta-IV Heavy.
That is contrary to the wishes of Mike Griffin to make the Orion large enough to be unable to be lofted up with any EELV, including the Delta IV Heavy. So he can foisted
the stick into the mix.
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#29
by
MATTBLAK
on 02 Mar, 2018 23:12
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Yes - I'm with Steven Pietrobon on this. Orion is too large! 4.3 or 4.4 meters should have been it's diameter. And at about 12 tons, it's a real boomsticks.
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#30
by
joek
on 03 Mar, 2018 03:53
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Jeepers... "Orion should have been..." It should have been a lot of things. So now you want to re-engineer it given 20-20 hindsight. Reduce it's size to reduce it's mass. Sure, why not. You want to pony up the $$$ to do that today? Where were all you experts way-back-when? No where. So please spare us the retrospective what-should-have-been. Your 20-20 hindsight is not constructive and your harping on it is annoying.
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#31
by
MATTBLAK
on 03 Mar, 2018 05:46
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Jeepers... "Orion should have been..." It should have been a lot of things. So now you want to re-engineer it given 20-20 hindsight. Reduce it's size to reduce it's mass. Sure, why not. You want to pony up the $$$ to do that today? Where were all you experts way-back-when? No where. So please spare us the retrospective what-should-have-been. Your 20-20 hindsight is not constructive and your harping on it is annoying.
You're obviously new around here, or are you just feigning ignorance?! We
HAVE been saying and doing what you suggest - since 2005...
And so have some of the senior members of NSF who have worked for or are still working for NASA and it's contractors. Also; Nasaspaceflight.com is and was regularly viewed by those who conceived and designed Orion, the Ares rockets and most other elements of 'Project Constellation'. Research the 'Direct' project. The reservations and arguments against poor design choices and architecture problems were
presented directly to the concerned NASA, Senatorial and Congressional personnel,
years ago.
Did it have any effect? Somewhere between nil and negligible...
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#32
by
MATTBLAK
on 03 Mar, 2018 06:01
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... And many of the experts here are
not 'so-called'
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#33
by
UltraViolet9
on 03 Mar, 2018 12:27
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#34
by
spacenut
on 03 Mar, 2018 13:22
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I think Orions size and mass was originally for 6 or 7 astronauts and was 5.5 meters in diameter. Also to carry enough supplies and water for a long duration deep space mission. Then they realized it was too big. They cut it back to 5 meters, but I guess that still isn't enough.
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#35
by
Proponent
on 03 Mar, 2018 14:30
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Where were all you experts way-back-when?
There were voices in the wilderness:
http://rocketsandsuch.blogspot.com/2007/09/launch-abort.html....
Very interesting. I wish I had been reading that blog at the time.
I believe, though, that the first-linked of Rocket Man's blog posts contains one small historical error:
Soyuz T-10-1 and Soyuz 18a both employed a launch abort system similar to (based directly on Max Faget's design for which Max received an award acknowledging that fact from the Russians many years later) the American design.Although Soyuz 18A did abort short of orbit, I believe the maneuver was performed after the escape tower had been jettisoned.
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#36
by
kevinof
on 03 Mar, 2018 15:02
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Interesting to read through those blogs (and then bang head repeatedly off desk in frustration!). I always felt that SLS (and what came before it) was trying to do too much. I know it's been hashed out before but I would have liked Orion to launch without crew and therefore no fairing and no LAS. Would have saved a ton of money, time and importantly weight. Send the crew up in CST or Dragon, dock and go.
Yes it's extra expense, but I think it would have solved a lot of problems and also given more flights to commercial crew which always helps.
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#37
by
Proponent
on 03 Mar, 2018 15:19
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I like your thinking, but I'd take it a step further: skip Orion altogether. Having clearly defined the objectives (wishful thinking here, of course) let NASA contract for in-space modules as needed. Use commercial crew, as you suggest to get the crew to LEO. If the optimal mission architecture calls for the crew making a direct return to earth at the end of the mission, ask the commercial-crew contractors to bid on re-entry modules, which would no doubt be variations on their commercial-crew vehicles.
Obviously, this is impossible, because it neglects poor old Lockheed Martin... unless maybe it could get contracts for in-space modules?
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#38
by
joek
on 03 Mar, 2018 19:47
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You're obviously new around here, or are you just feigning ignorance?! We HAVE been saying and doing what you suggest - since 2005... And so have some of the senior members of NSF who have worked for or are still working for NASA and it's contractors. Also; Nasaspaceflight.com is and was regularly viewed by those who conceived and designed Orion, the Ares rockets and most other elements of 'Project Constellation'. Research the 'Direct' project. The reservations and arguments against poor design choices and architecture problems were presented directly to the concerned NASA, Senatorial and Congressional personnel, years ago.
Did it have any effect? Somewhere between nil and negligible...
I certainly appear to have put my foot in it, and apologies to anyone who feels diss'd by my comment.
The point is that attempting to re-design or -engineer Orion at this point is a lost cause. There are no good outcomes other than likely...
I like your thinking, but I'd take it a step further: skip Orion altogether.
...
Debates which focus on its weight appear to assume that solving that problem will address more fundamental problems. It will not. Orion and the architecture it is based on are fundamentally flawed; its weight is a quibble in the greater debate.
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#39
by
Proponent
on 04 Mar, 2018 15:47
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There were voices in the wilderness and warnings galore: ....
On the official side, there was also the Booz Allen Hamilton study in 2011 (attached
here), according to the publicly released summary of which (we peasants weren't allowed to see the whole thing), costs estimates for Orion/SLS beyond a 3-5-year horizon (i.e., after 2014-16) were based on unjustified optimism.
The report produced howls of criticism and allegations of bias and "slow-rolling" in this forum, but it has proved
eerily prophetic.
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#40
by
Patchouli
on 04 Mar, 2018 23:46
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The reason Orion is so much heaver is simple its huge size. For a pressure vessel, the mass is proportional to its volume. The Apollo CM mass was 5.84 t with a 3.91 m diameter. Orion is 5.0 m diameter, so directly scaling gives 5.84*(5/3.91)³ = 5.84*2.09 = 12.21 t. Orion CM mass is 19% less less at 9.89 t, probably due to using lighter materials, such as aluminium instead of steel for the pressure vessel, lithium-ion batteries and modern electronics. Orion was originally going to carry six crew so that it could be used for ISS and Mars missions. Had Orion been sized for four crew, its diameter would have been 3.91*(4/3)^{1/3} = 4.3 m. That would have reduced its mass to between 9.89*(4.3/5)³ = 6.29 t (Orion model) and 5.84*(4.3/3.91)³ = 7.77 t (Apollo model). Lets use the average of 7.03 t, which is a 29% reduction in mass. So instead of a 25.85 t Orion, it would now be a 18.37 t Orion, which would allow it to be launched by Atlas V and Falcon 9, instead of the only option being the very expensive Delta-IV Heavy.
Interestingly, a 5-meter diameter aluminum sphere capable of holding 1.25 atmospheres would weigh about 105 kg and have 3.5x the pressurized volume of Orion.
A truncated cone is not an efficient pressure vessel design, and most of the structural mass is not related to containing internal pressure but more likely external loads, puncture resistance, MMOD, etc.
One reason early in the program LM considered a lifting body design as then the pressure vessel would have been a more efficient cylinder shape.
Though the edges of the cone are not used as part of of the pressurized volume they placed the fuel tanks for the RCS and some of the avionics there.
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#41
by
MATTBLAK
on 05 Mar, 2018 00:54
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Unless I'm mistaken, it was John Young and a couple other Apollo veterans (Stafford & Garriott?) who strongly advocated for the Apollo shape and against the lifting body shape. But Young said almost from day one that anything much bigger than Apollo was a waste of space and too darned heavy. And he reiterated that again in other publications right up to and past his retirement from NASA. A full composite pressure vessel, between 4 and 4.5 meters in diameter would be what I would have given the thumbs up to (
for what my opinion's worth -
not much). Combined with a Service Module that came with 2x versions of propellant quantity; 2x propellant tanks for Earth orbital missions, 4x prop tanks for deep space missions - then one version could be lifted by an Atlas V, the other by a Delta IV-Heavy, Vulcan/ACES or the SLS.
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#42
by
Patchouli
on 05 Mar, 2018 01:42
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I just thought it was kinda silly to reuse the Apollo shape when we knew so much more about reentry than we did back in the 1960s.
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#43
by
Lars-J
on 05 Mar, 2018 03:21
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I just thought it was kinda silly to reuse the Apollo shape when we knew so much more about reentry than we did back in the 1960s.
It shouldn't surprise anyone. Redoing Apollo (with Shuttle contractors) was always the goal of Constellation, and then SLS/Orion. Whenever there was a choice between doing it the Apollo way or some new direction, the finger on the scale always slammed down hard for the Apollo way.
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#44
by
MATTBLAK
on 05 Mar, 2018 03:26
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A case of whatever works; just use it. Big data base and experience etc. Nothing wrong with the Apollo shape - it's just in the Orion context too big for the job, as this thread has been talking about. And nobody has ever done a ballistic, 40,000 kph atmospheric entry in a lifting body/biconic shape to my knowledge. Funnily enough, in 1996 I wrote letters to the late Test Pilot William H Dana and his Dryden colleague about lifting body shapes doing Apollo speed entries. They said there wasn't much data around on that and that the concept probably could be done, but it would be challenging in a number of ways.
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#45
by
Oberon_Command
on 05 Mar, 2018 03:38
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Where were all you experts way-back-when?
There were voices in the wilderness and warnings galore:
http://rocketsandsuch.blogspot.com/2007/09/launch-abort.html
Given the arguments in the blog, I find it fascinating that neither commercial crew entrant is using a tractor escape system, while Orion continues to do so. Come to think of, DreamChaser and New Shepard use "pushers", too. DreamChaser and Dragon 2's reasons for avoiding tractors is pretty clear, but I wonder what drove NS and CST-100 to avoid them, too?
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#46
by
brickmack
on 05 Mar, 2018 04:03
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What that source seems to ignore is that no extra propellant is actually needed for a SM-mounted liquid-fueled pusher escape system. If the LAS had dedicated propellant tanks, then the extra mass of the SM would surely be more than an abort tower. But since Starliner shares the propellant tanks between RCS, orbital maneuvering engines, and abort engines (and on a nominal mission, the fuel mass needed for orbital maneuvering/attitude control is surely at least as great as would be needed by an abort), the only added mass is some plumbing and the engines themselves. Maybe a few dozen kg. But a tower is going to be a decent chunk the mass of the capsule.
As for NS, reusability is probably the only concern. No significant mass difference is likely to exist with either option, being that its a single stage vehicle (if it had an abort tower, it wouldn't be jettisoned until after MECO anyway, so you don't get the slight gain of not bringing it all the way up). And the pusher system should be able to refly many times before expiring, assuming its not ever used.
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#47
by
su27k
on 05 Mar, 2018 04:10
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#48
by
Oberon_Command
on 05 Mar, 2018 04:27
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Where were all you experts way-back-when?
There were voices in the wilderness and warnings galore:
http://rocketsandsuch.blogspot.com/2007/09/launch-abort.html
Given the arguments in the blog, I find it fascinating that neither commercial crew entrant is using a tractor escape system, while Orion continues to do so. Come to think of, DreamChaser and New Shepard use "pushers", too. DreamChaser and Dragon 2's reasons for avoiding tractors is pretty clear, but I wonder what drove NS and CST-100 to avoid them, too?
He took some of the arguments back in a later blog: https://rocketsandsuch.blogspot.com/2007/09/launch-abort-reclaima-little.html
Some of them - but his reasons for retraction seem to be that it came out that MLAS still jettisoned the abort system partway into the launch and the ability to fire the abort system motors during a nominal ascent to save mass. Neither CC entrant is planning either of those two things (though CST-100 would be capable of it), are they?
It makes me wonder if the same voices that were opposed to MLAS are also opposed (and as vocally) to CC's pusher escape systems, or if they've come around to the "dual-use liquid pusher" way of thinking.
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#49
by
Patchouli
on 05 Mar, 2018 05:12
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A case of whatever works; just use it. Big data base and experience etc. Nothing wrong with the Apollo shape - it's just in the Orion context too big for the job, as this thread has been talking about. And nobody has ever done a ballistic, 40,000 kph atmospheric entry in a lifting body/biconic shape to my knowledge. Funnily enough, in 1996 I wrote letters to the late Test Pilot William H Dana and his Dryden colleague about lifting body shapes doing Apollo speed entries. They said there wasn't much data around on that and that the concept probably could be done, but it would be challenging in a number of ways.
True the existing data points removed need to fly something sub-scale like the X-23 prime and then tweaking the shape based on it's data.
Though seeing how long the LV is taking I think if the block I Orion was base lined for an existing LV it probably would much farther along maybe even already be flying no matter what basic design they choose.
Given the arguments in the blog, I find it fascinating that neither commercial crew entrant is using a tractor escape system, while Orion continues to do so. Come to think of, DreamChaser and New Shepard use "pushers", too. DreamChaser and Dragon 2's reasons for avoiding tractors is pretty clear, but I wonder what drove NS and CST-100 to avoid them, too?
Dream Chaser and Blue Origin's biconic definitely would have issues with a tractor style LAS since part of the primary TPS is on the nose of the vehicle where it would attach.
But Dragon and the CST-100 probably would work with one and I think some early versions of crewed Dragon even featured it.
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#50
by
woods170
on 05 Mar, 2018 06:55
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#51
by
john smith 19
on 05 Mar, 2018 06:59
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Where were all you experts way-back-when?
There were voices in the wilderness and warnings galore:
http://rocketsandsuch.blogspot.com/2007/09/launch-abort.html
But there's not much that can be done when contractors and congressional stakeholders have bought into agency leadership's bad direction. (They don't call it the "iron triangle" for nothing.) Only time and inevitable programmatic implosion eventually forces the White House (or the next White House) to take action.
Ahh, 2007, when it looked like the programme would
only cost $6-9 Bn.
I'm feeling quite nostalgic.
On the upside NASA has now actually launched an Orion.
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#52
by
woods170
on 05 Mar, 2018 07:05
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Where were all you experts way-back-when?
There were voices in the wilderness and warnings galore:
http://rocketsandsuch.blogspot.com/2007/09/launch-abort.html
But there's not much that can be done when contractors and congressional stakeholders have bought into agency leadership's bad direction. (They don't call it the "iron triangle" for nothing.) Only time and inevitable programmatic implosion eventually forces the White House (or the next White House) to take action.
Ahh, 2007, when it looked like the programme would only cost $6-9 Bn.
I'm feeling quite nostalgic.
On the upside NASA has now actually launched an Orion.
Hmmm. NASA has launched a bare-bones version of part of Orion (crew module only).
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#53
by
MATTBLAK
on 05 Mar, 2018 08:38
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Yeah - more than three years ago!!
I read around here once, someone had the fairly good idea of launching EM-1 instead to the ISS, unmanned on a Delta IV-Heavy - because the Delta is not man-rated. It docks with the Station and then a two-person test crew goes aboard and then takes it for a three or four day 'shakedown' in the relative vicinity of the ISS. That way; if some urgent-ish system failure happened the crew could translate back to ISS. Then, the Orion could splashdown in the Pacific or be disposed in the atmosphere if something fundamental were wrong with it. If it were all good, then do an Apollo 7 like test flight in orbit and then successfully bring back the crew.
I imagine this would be designated 'EFT-2'. This could allow time for the SLS Exploration Upper Stage to be developed, funding permitting. Then, EM-2 could be redesignated as EM-1, but with a crew this time. Then; a whole SLS test flight could actually carry a useful payload in addition to the Orion. Heh; providing there was money for any other payloads
Digression, Etc and so on......So if the composite structure ends up being a bit of a bust; then that brings us back to the 4.5 meter or less aluminum-lithium one that should weigh thousands of pounds less than the 5 meter behemoth.
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#54
by
Proponent
on 05 Mar, 2018 13:07
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What that source seems to ignore is that no extra propellant is actually needed for a SM-mounted liquid-fueled pusher escape system....
There's also the fact that if an escape tower fails to jettison, the crew dies. If the escape system is needed, say, on one in 1000 flights, then it harms crew safety as much as it helps if there is a 0.1% chance of failing to jettison.
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#55
by
Patchouli
on 06 Mar, 2018 06:18
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What that source seems to ignore is that no extra propellant is actually needed for a SM-mounted liquid-fueled pusher escape system....
There's also the fact that if an escape tower fails to jettison, the crew dies. If the escape system is needed, say, on one in 1000 flights, then it harms crew safety as much as it helps if there is a 0.1% chance of failing to jettison.
True esp if the launch vehicle has tight margins as it might not make it to a stable orbit though you still need parachute cover and any extra modules to jettison as well for safe reentry and landing.
Which is why I think the crewed Dream Chaser might have been the safest of the new vehicles and the Shuttle probably was safer than Soyuz during EDL so long as the vehicle did not suffer significant damage during launch.
Though I do expect Orion to still be much safer then previous spacecraft.
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#56
by
john smith 19
on 06 Mar, 2018 06:45
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What that source seems to ignore is that no extra propellant is actually needed for a SM-mounted liquid-fueled pusher escape system....
There's also the fact that if an escape tower fails to jettison, the crew dies. If the escape system is needed, say, on one in 1000 flights, then it harms crew safety as much as it helps if there is a 0.1% chance of failing to jettison.
Except the Russians have needed to use the LES twice and it worked fine both times.
Of course they copied the idea, not the implementation.
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#57
by
john smith 19
on 06 Mar, 2018 06:46
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Yeah - more than three years ago!! I read around here once, someone had the fairly good idea of launching EM-1 instead to the ISS, unmanned on a Delta IV-Heavy - because the Delta is not man-rated. It docks with the Station and then a two-person test crew goes aboard and then takes it for a three or four day 'shakedown' in the relative vicinity of the ISS. That way; if some urgent-ish system failure happened the crew could translate back to ISS. Then, the Orion could splashdown in the Pacific or be disposed in the atmosphere if something fundamental were wrong with it. If it were all good, then do an Apollo 7 like test flight in orbit and then successfully bring back the crew.
I like this, but I guess after the Delta IV launch it's now viewed as "safe," within the NASA context that any necessary waivers have been signed etc.
So onward to a fully crewed mission then just as soon as SLS is ready to fly.
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#58
by
UltraViolet9
on 06 Mar, 2018 13:45
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Though I do expect Orion to still be much safer then previous spacecraft.
It's not. Orion's projected LOC for a simple circumlunar mission is lower than the projected LOC for STS at program termination. ASAP commented on this back in 2014.
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#59
by
Rocket Science
on 06 Mar, 2018 13:55
-
A case of whatever works; just use it. Big data base and experience etc. Nothing wrong with the Apollo shape - it's just in the Orion context too big for the job, as this thread has been talking about. And nobody has ever done a ballistic, 40,000 kph atmospheric entry in a lifting body/biconic shape to my knowledge. Funnily enough, in 1996 I wrote letters to the late Test Pilot William H Dana and his Dryden colleague about lifting body shapes doing Apollo speed entries. They said there wasn't much data around on that and that the concept probably could be done, but it would be challenging in a number of ways.
True the existing data points removed need to fly something sub-scale like the X-23 prime and then tweaking the shape based on it's data.
Though seeing how long the LV is taking I think if the block I Orion was base lined for an existing LV it probably would much farther along maybe even already be flying no matter what basic design they choose.
Given the arguments in the blog, I find it fascinating that neither commercial crew entrant is using a tractor escape system, while Orion continues to do so. Come to think of, DreamChaser and New Shepard use "pushers", too. DreamChaser and Dragon 2's reasons for avoiding tractors is pretty clear, but I wonder what drove NS and CST-100 to avoid them, too?
Dream Chaser and Blue Origin's biconic definitely would have issues with a tractor style LAS since part of the primary TPS is on the nose of the vehicle where it would attach.
But Dragon and the CST-100 probably would work with one and I think some early versions of crewed Dragon even featured it.
They could use a boost cover that transferred the abort loads to the bottom (aft end) of a lifting body spacecraft. Ingress would be thought a boost hatch cover similar to Apollo... Not really a problem as I see it...
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#60
by
Oli
on 06 Mar, 2018 17:53
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The ESAS report is always an interesting read:
5.3.2.5 CEV Split Versus Single Volume
A considerable amount of time was spent analyzing the advantages and disadvantages of a
CEV split versus single volume. Separating the CEV volume into a CM used primarily for
ascent and entry and a mission module that could be sized and outfitted for each particular
mission has operational advantages depending on the mission to be supported. Also, separation
of the mission module with the SM after the Earth deorbit burn provides the lightest and
smallest reentry shape.
The difficulty in minimizing the ascent/entry volume of the vehicle became a driving factor
because this volume must accommodate a maximum crew of six for the Mars return mission.
Once the ascent/entry volume for six was determined, all other DRM crew sizes by definition
will fit in this volume. A CEV sized for the six-crew DRM is the minimum size for the ascent/
entry module.
The study found a single volume, which is less complex from a build-and-integrate standpoint,
to be more mass-efficient and volume-efficient for a given mass. A larger single-volume vehicle
also has lower entry heating and g’s as a result of a larger surface area, and thereby lower ballistic
coefficient, than a smaller ascent/entry split volume. A mission module was determined to
not be required for the ISS and the Mars return DRMs and was of limited value to the lunar
DRM, if the single volume is large enough, and the CEV is not taken all the way to the lunar
surface.
5.3.1.2 Blunt Bodies Versus Slender Bodies Trade
The shape study trade was initiated between major vehicle classes. The primary classes
considered were capsules (blunt bodies), slender bodies, lifting bodies, and winged vehicles.
Winged bodies and lifting bodies (such as X–38, X–24, HL–10, etc.) were eliminated at the
outset due to several factors, including: (1) the extreme heating (especially on empennages)
these would encounter on lunar return entries, (2) the additional development time required
due to multiple control surfaces, and (3) the increased mass associated with wings, fins, and
control surfaces which are huge liabilities in that they must be carried to the Moon and back
simply for use on entry. Thus, the trade space involved capsules versus slender bodies. It was
planned that, after a desirable class of vehicle was selected, the shape would be optimized
within that class.
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#61
by
Rocket Science
on 06 Mar, 2018 19:39
-
The ESAS report is always an interesting read:
5.3.2.5 CEV Split Versus Single Volume
A considerable amount of time was spent analyzing the advantages and disadvantages of a
CEV split versus single volume. Separating the CEV volume into a CM used primarily for
ascent and entry and a mission module that could be sized and outfitted for each particular
mission has operational advantages depending on the mission to be supported. Also, separation
of the mission module with the SM after the Earth deorbit burn provides the lightest and
smallest reentry shape.
The difficulty in minimizing the ascent/entry volume of the vehicle became a driving factor
because this volume must accommodate a maximum crew of six for the Mars return mission.
Once the ascent/entry volume for six was determined, all other DRM crew sizes by definition
will fit in this volume. A CEV sized for the six-crew DRM is the minimum size for the ascent/
entry module.
The study found a single volume, which is less complex from a build-and-integrate standpoint,
to be more mass-efficient and volume-efficient for a given mass. A larger single-volume vehicle
also has lower entry heating and g’s as a result of a larger surface area, and thereby lower ballistic
coefficient, than a smaller ascent/entry split volume. A mission module was determined to
not be required for the ISS and the Mars return DRMs and was of limited value to the lunar
DRM, if the single volume is large enough, and the CEV is not taken all the way to the lunar
surface.
5.3.1.2 Blunt Bodies Versus Slender Bodies Trade
The shape study trade was initiated between major vehicle classes. The primary classes
considered were capsules (blunt bodies), slender bodies, lifting bodies, and winged vehicles.
Winged bodies and lifting bodies (such as X–38, X–24, HL–10, etc.) were eliminated at the
outset due to several factors, including: (1) the extreme heating (especially on empennages)
these would encounter on lunar return entries, (2) the additional development time required
due to multiple control surfaces, and (3) the increased mass associated with wings, fins, and
control surfaces which are huge liabilities in that they must be carried to the Moon and back
simply for use on entry. Thus, the trade space involved capsules versus slender bodies. It was
planned that, after a desirable class of vehicle was selected, the shape would be optimized
within that class.
So I guess with all their "gifted" foresight in selection everything is working out just fine then...
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#62
by
Proponent
on 07 Mar, 2018 01:23
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There's also the fact that if an escape tower fails to jettison, the crew dies. If the escape system is needed, say, on one in 1000 flights, then it harms crew safety as much as it helps if there is a 0.1% chance of failing to jettison.
Except the Russians have needed to use the LES twice and it worked fine both times.
Only once (Soyuz T-10), I believe. The Soyuz 18A abort occurred late in the ascent, by which time the escape tower would have been jettisoned.
But the fact that an escape tower has saved a crew does not mean it does not carry its own risks. If, for example, there is a 1% of needing a tower to escape a failing launch vehicle (roughly the demonstrated rate over the life of Soyuz) and a 0.1% that the tower itself will kill the crew, then the tower clearly increases safety. If the likelihood of needing the tower is 0.1%, as one might reasonably hope for newer launch vehicles, then it provides no net gain in safety.
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#63
by
Phillip Clark
on 07 Mar, 2018 09:06
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Correct about the use of the Soyuz launch escape system. At the time of the manned Soyuz 18-1 abort in 1975 it had already been discarded. It was used for the Soyuz-T 10-1 off-the-pad abort in September 1983 with two cosmonauts on board.
For the latter mission the two men experienced up to 18-20g. Cosmonaut Anatoli Artsebarski said at a meeting of the British Interplanetary Society in 2015 that during training the cosmonauts are only trained up to about 8-9g, so cosmonauts don't get a single "abort profile" experience unless it actually happens.
Remember also that during the L-1 and L-3 programmes unmanned Soyuz-class descent modules were rescued successfully from exploding Proton-K and N-1 launch vehicles using their launch escape systems.
As for "Orion's Weight", the title of this thread, in orbit of course it's zero.
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#64
by
MaxTeranous
on 07 Mar, 2018 09:59
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As for "Orion's Weight", the title of this thread, in orbit of course it's zero.
Ahh, technically correct, the best kind of correct !
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#65
by
MATTBLAK
on 07 Mar, 2018 10:04
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Mass vs weight; yes, all true. But the weight is certainly relevant when discussing what launcher classes can get Orion off the ground and also; the amount of stress the weight will cause for it's recovery systems. Particularly the parachutes.
And so have some of the senior members of NSF who have worked for or are still working for NASA and it's contractors. Also; Nasaspaceflight.com is and was regularly viewed by those who conceived and designed Orion, the Ares rockets and most other elements of 'Project Constellation'. Research the 'Direct' project. The reservations and arguments against poor design choices and architecture problems were 