Jump to content

Dragon v2 or Orion

Voyager275

By Voyager275
in Science & Spaceflight

 Share

Recommended Posts

Nibb31

Nibb31

Posted
Posted (edited)

Better for what ?

Which is better, a Land Rover or a Mini? Same thing, it depends on the mission.

Dragon and CST are like the Mini, designed for short and frequent commutes in relative comfort. Orion is a Land Rover, designed for extreme environments and longer journeys with higher versatility and robustness.

You can go shopping in a Land Rover and you can cross the Kalahari in a Mini, but neither are the best vehicles for the job.

Edited by Nibb31
Link to comment
Share on other sites
YNM

YNM

Posted
Posted

Better in what direction ? I'll take the structure: both are safe, dragon might be lighter thanks to no tiles on it's top. Orion might be roomier.

Proof that it's safe: both survived reentry. Or, for a worser one, think of this: does DragonV2's any safer than Soyuz ? Both returns succesfully.

We only see the hardware to this date for Orion; only a small part of the software also for Dragon (I believe there's no internal display yet on Dragon). You can't tell something well until you see it.

Link to comment
Share on other sites
K^2

K^2

Posted
Posted (edited)
Unlike Orion it is going to be successful and can/will be used for interplanetary voyages.

Yeah... Dragon isn't built for interplan. It might manage a Lunar mission, but you aren't going much further than that for just so many reasons.

Edited by K^2
Link to comment
Share on other sites
Nibb31

Nibb31

Posted
Posted (edited)
My personal favorite, by far, is Dragon v2. Unlike Orion it is going to be successful and can/will be used for interplanetary voyages.

Not in any recognizable form it won't.

The requirements are different. Exploration missions require extra shielding, a beefier heat shield, longer duration life support, longer loiter capability, long distance communication, EVA capability for contingencies, redundancy and repirability, etc... They specifically don't require soft rocket powered landing or reusability, which will just add extra weight and complexity to the vehicle.

Taking a Dragon on an interplanetary mission would be like taking a Mini across the Sahara. You might be able to modify it to survive the journey, but you would be better off using a Land Rover.

Edited by Nibb31
Link to comment
Share on other sites
Kibble

Kibble

Posted
Posted

I think Orion is prettier, and I am very fond of the ATV-derived service module, and its classic R4 and AJ10 rocket engines. Piloted spacecraft just don't look right without the launch escape tower on top!

Link to comment
Share on other sites
tater

tater

Posted
Posted

Neither are "interplanetary" alone, all that matters for that distinction is what they can cope with in terms of direct reentry trajectories. The D2 heat shield is capable of high speed reentry, supposedly, but we'd have to see a test to known for sure (and Orion was only tested below a lunar reentry as well, so while they can make a far better inference, it's untested as well).

Link to comment
Share on other sites
hugix

hugix

Posted
Posted

Taking a Dragon on an interplanetary mission would be like taking a Mini across the Sahara. You might be able to modify it to survive the journey, but you would be better off using a Land Rover.

Mini is actually one of the higest classifying type of car in the Dakar races.

Link to comment
Share on other sites
tater

tater

Posted
Posted

Taking an Orion on an interplanetary mission would be like taking that mini across the sahara, too. The 2 vehicles are transfer/reentry vehicles, nothing more. I don't think any of us want to spend a few years in the <10m^3 D2 (unsure if that's total pressurized, or habitable), or 8.95m^3 Orion (habitable volume)... Apollo was 6.2m^3 for reference.

Link to comment
Share on other sites
SargeRho

SargeRho

Posted
Posted (edited)

They'd likely stick an inflatable hab under the Orion and once the burns are complete, rotate the Orion to be able to access it. They'd do a similar thing with Dragon - in fact, an inflatable module with 16m³ of living space is going to fly in the trunk of a Dragon to the ISS later this year.

http://en.wikipedia.org/wiki/Bigelow_Expandable_Activity_Module

Edited by SargeRho
Link to comment
Share on other sites
tater

tater

Posted
Posted

What about it is BEO aside from reentry speed vs D2?

I think until we see PICA vs AVCOAT the reentry velocity issue is up in the air. Does Orion have a toilet or something, making it more suitable for long duration flights? Additionally, what was Orion's test reentry? It was a sub-lunar return velocity, right? Also sub astroid return, so effectively untested.

Orion as built now (block 1) is a 3 week endurance. Dragon 2 specs (again, just as "on paper" as Orion's) say 1 week to 2 years. The latter seems odd, but if one week, there is no reason why 3 weeks would not be simple (we're in Gemini territory there, frankly, pretty trivial).

So how is Orion "built" for BEO in a way that is meaningfully different than D2? (aside from the interior being wallpapered with billions of pork dollars).

Link to comment
Share on other sites
Hcube

Hcube

Posted
Posted

So how is Orion "built" for BEO in a way that is meaningfully different than D2? (aside from the interior being wallpapered with billions of pork dollars).

Even though, as you pointed out, re-entry test wasn't effective, i'm pretty sure Orion is more suited to high re-entry speeds than dragon v2 is. Also, we must realize that even a sub-orbital re-entry test can provide very good data about how a vehicle would handle re-entry at much higher speeds...

Dragon V2 is more of a LEO shuttle, and i don't think that it is planned for it to have good radiation coating like Orion has, making it less suited for BEO.

Link to comment
Share on other sites
tater

tater

Posted
Posted (edited)

It is using modified PICA (PICA-X 3.0 (2.0 is used on dragons now)). PICA has the record reentry speed (or did, anyway) at 12.9 km/s. I don't see how improved PICA is somehow worse than Orion. I'm not saying either is better, I don't have a dog in the fight (other than my tax dollars as pork to Orion). What I am saying is that saying "Orion is better" without a good reason is equally silly. Quoting ad copy from lockmart (or spacex) doesn't count, I'd like to see some real data/specs.

It apparently took them 6 months to hand "gun" the avcoat into the honeycomb (basically a guy squirts the material like caulking into 330,000 holes, one at a time). Turns out people don't apply the goop in a very regular way, so the properties are not what they should be. Maybe avcoat was selected because it generates the most man-hours of work?

Maybe Orion has better radiation shielding?

I should add that more importantly, what is the mission for Orion. Not what mission can be invented for it, what mission, with a launch date (EDIT: they claim 2021)? CST-100, and D2 have an actual mission that is wanted/needed, and will fly in 2017. Orion is a spacecraft no one actually wants. I think it makes sense to design a spacecraft for a specific mission, and I think it makes sense to alter an existing design if possible for a specific mission. It's odd to design a spacecraft with no mission, then start shopping around for a mission for it.

Edited by tater
Link to comment
Share on other sites
Nibb31

Nibb31

Posted
Posted (edited)

Nobody said Orion is better. They are two different vehicles built for different purposes. Dragon is "better" to shuttle crew to the ISS, because that's what it was designed for. Orion is "better" for BEO exploration because that's what it was designed for. It would suck for ISS crew rotations.

The requirements that Dragon is lacking for BEO missions are:

- Radiation shielding

- Hardened electronics

- Redundant systems

- Life support duration

- Mission duration

- Reentry speed

- Navigation systems

- Communication systems

- EVA capability

Dragon systems are not certified with the same requirements. It is optimized to be economical for short trips to the ISS and back. You might be able to modify each system to meet the requirements for BEO exploration missions, but you would need to go through the entire design and certification process again and you would end up with a very different vehicle.

Edited by Nibb31
Link to comment
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
 Share
Go to topic listing
×
×
  • Create New...