Author Topic: Orion Discussion Thread 2  (Read 75467 times)

Offline Coastal Ron

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Re: Orion Discussion Thread 2
« Reply #300 on: 07/28/2017 04:55 PM »
Wikipedia lists Dragon 2 pressurized volume at 10 cubic meters while the Apollo CSM is listed at 10.4 cubic meters pressurized.

The Wikipedia page I'm looking at for the Apollo Command/Service Module lists the internal volume as 6.2 cubic meters. For Orion Wikipedia lists the habitable pressurized volumes as 8.95 cubic meters. If we were only looking at habitable volume it would appear that Dragon Crew has the larger internal area of the three vehicles.

However all of these capsules are really just meant for basic transportation. In fact I would argue that for any capsule the farther is gets from Earth orbit the less efficient the design becomes, because their core competency is returning safely to Earth through Earth's atmosphere - every other function they may be pressed into doing in space can be done far better by space-only elements.

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The propulsion system of Dragon v2 wouldn't be very good at efficient insertion into NRHO because the efficient trajectories include powered lunar flybys. The draco thruster has 2 orders of magnitude less thrust than then the OMS engine on Orion and the super-draco thrusters have poor vacuum isp and off axial thrust.

All of this can be fixed by beefing up the trunk into a service module for dragon v2. But it is no where near ready to go as it was designed for LEO crew transportation.

Except for the lunar fly-by, I think SpaceX is assuming it will be leaving LEO in some version of an ITS, not a Dragon, so I think we can ignore Dragon what-if's.

Big picture though, if we are only thinking about having four people in space at a time, then sure, Orion can be a capable vehicle for cislunar operations. Not the most comfortable ride, but those going would put up with such discomforts for the chance to do what few have done in space.

But I would hope we are setting our sights at having more than four people in space at any one time, which is one of my touchstones for critiques of any HSF hardware. Does it allow & promote the expansion of humanity out into space? With expansion in this case not meaning distance, but the number of people.

And because adding people to space means money, we either have to get a bigger pot of money (not likely to happen for NASA), or we have to somehow reduce the cost for doing anything in space. And it is from the perspective of cost that I have the most objection to the SLS & Orion, because I see them as slowing down our expansion out into space, not accelerating it.

My $0.02
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Robotbeat

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Re: Orion Discussion Thread 2
« Reply #301 on: 07/28/2017 05:04 PM »
How anyone GETS to the lander though is anyone's guess.

Some Dragon or CST-100 type vehicle?

Yeah one would probably be better off discussing that in more detail here: https://forum.nasaspaceflight.com/index.php?topic=35787.100

Probably wouldn't be quick and easy. Starliner is limited to 60 hour free flight, Dragon at least lacks the dV, and is a tight ride.  ....
False, on both accounts. And yeah, you should have discussed it in that thread.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline TrevorMonty

Re: Orion Discussion Thread 2
« Reply #302 on: 07/28/2017 05:16 PM »
Coastal is right about capsules(/reentry vehicles) not being ideal for BLEO travel. A OTV with attached habitat module would be better and far more flexible. But require fuel depots and in orbit refuelling, as BLEO -LEO DV is same as LEO-BLEO.


Offline woods170

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Re: Orion Discussion Thread 2
« Reply #303 on: 07/28/2017 06:43 PM »
Sorry for the tangent I've sent this thread on Chris!

Back to a more Orion specific focus:
 https://twitter.com/SciGuySpace/status/890972613706690560
Quote from: Eric Berger
Summary: Crew on EM-1 would have accelerated NASA exploration. Unfortunately, they weren't sure the heat shield would work. Also, money.

This is the first I've heard on the heat shield, I know they wanted to redesign for lowered cost.  Anyone that can summarize why the heat shield wouldn't be up to the task?
New design. Heatshield is now made out of multiple blocks in stead of being monolithic. A modular Avcoat heatshield has never been tested before.

Offline Robotbeat

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Re: Orion Discussion Thread 2
« Reply #304 on: 07/28/2017 10:24 PM »
Coastal is right about capsules(/reentry vehicles) not being ideal for BLEO travel. A OTV with attached habitat module would be better and far more flexible. But require fuel depots and in orbit refuelling, as BLEO -LEO DV is same as LEO-BLEO.
Disagree. It only takes 3 days to reach lunar orbit or back. That compares to a couple days to launch or return from ISS, and up to 2 weeks for Shuttle missions. Cislunar transport doesn't need extra space than is needed for typical LEO capsule missions.

A separate cislunar transport craft (in addition to a capsule and a lander) doesn't make sense to me. Just another development project to amortize and another docking event.

Orion (or any other capsule) is fine.
« Last Edit: 07/29/2017 02:51 AM by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Khadgars

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Re: Orion Discussion Thread 2
« Reply #305 on: 07/28/2017 10:59 PM »
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Big picture though, if we are only thinking about having four people in space at a time, then sure, Orion can be a capable vehicle for cislunar operations. Not the most comfortable ride, but those going would put up with such discomforts for the chance to do what few have done in space.

But I would hope we are setting our sights at having more than four people in space at any one time, which is one of my touchstones for critiques of any HSF hardware. Does it allow & promote the expansion of humanity out into space? With expansion in this case not meaning distance, but the number of people.


I don't understand this pure fantasy.  We have not in anyway proven how to live and survive in deep space without the aid of earth.  Until that is well known and proven, you can't start building spacecraft for 100s of people, its just too risky.

You are acting like we're on the verge of Star Trek technology or something.
« Last Edit: 07/28/2017 11:00 PM by Khadgars »

Offline Coastal Ron

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Re: Orion Discussion Thread 2
« Reply #306 on: 07/30/2017 07:44 PM »
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Big picture though, if we are only thinking about having four people in space at a time, then sure, Orion can be a capable vehicle for cislunar operations. Not the most comfortable ride, but those going would put up with such discomforts for the chance to do what few have done in space.

But I would hope we are setting our sights at having more than four people in space at any one time, which is one of my touchstones for critiques of any HSF hardware. Does it allow & promote the expansion of humanity out into space? With expansion in this case not meaning distance, but the number of people.


I don't understand this pure fantasy.

???  You think having more than four people in space is pure fantasy?

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We have not in anyway proven how to live and survive in deep space without the aid of earth.

I don't understand what you are responding to. Where did I make such a claim?

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Until that is well known and proven, you can't start building spacecraft for 100s of people, its just too risky.

Again, where did I make such a claim?

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You are acting like we're on the verge of Star Trek technology or something.

I guess you don't keep up with what NASA thinks is a near-term possibility?



If the ISS has shown us anything is that we can occupy space with more than four humans at a time, and I advocate that our goal should be to start focusing on expanding that number - I don't care what the rate is, as long as the numbers go up and not down.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline Coastal Ron

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Re: Orion Discussion Thread 2
« Reply #307 on: 07/30/2017 07:52 PM »
Coastal is right about capsules(/reentry vehicles) not being ideal for BLEO travel. A OTV with attached habitat module would be better and far more flexible. But require fuel depots and in orbit refuelling, as BLEO -LEO DV is same as LEO-BLEO.

I'm reordering some of what you wrote:

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Orion (or any other capsule) is fine.

I never said it wouldn't work. But it depends on what the goals are whether it fits the needs.

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Disagree. It only takes 3 days to reach lunar orbit or back. That compares to a couple days to launch or return from ISS, and up to 2 weeks for Shuttle missions. Cislunar transport doesn't need extra space than is needed for typical LEO capsule missions.

If you're going to limit the passengers to people that have been highly trained, then sure, they can put up with each other for those few days. But that assumes we're not expanding the number of humans in space.

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A separate cislunar transport craft (in addition to a capsule and a lander) doesn't make sense to me. Just another development project to amortize and another docking event.

Depends on how many people are going to be in transit. If there will only be four people per year, then no, you don't need anything else. But if you are going to be having a constant stream of people going out to a DSG, and then down to the Moon and/or on to other destinations, then pretty soon a four person disposable capsule starts becoming a limitation, not an asset.

So it depends on what the goals are.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

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