Commercial Crew Spacecraft Competition

[Jim]

Why would the added ability be more complex than MPLM? OK, the present function of the trunk, solar array and cooling panels need to be kept. But what would be added is just a pressure container and a berthing mechanism.

You should agree because he is right.  It is more complex than MPLM because unlike a MPLM, it has to hold solar arrays, radiators and separation system.  And unlike a trunk, it has to hold pressure, have internal lighting and air recirculation ducts, and a berthing system.

[guckyfan]

Why would the added ability be more complex than MPLM? OK, the present function of the trunk, solar array and cooling panels need to be kept. But what would be added is just a pressure container and a berthing mechanism.

You should agree because he is right.  It is more complex than MPLM because unlike a MPLM, it has to hold solar arrays, radiators and separation system.  And unlike a trunk, it has to hold pressure, have internal lighting and air recirculation ducts, and a berthing system.

All of which I have mentioned and said the added complexity is not more than a MPLM.

Which is in a way a confirmation of what he said, yes. But it is still a very simple and therefore relatively cheap device compared to a Cygnus for example.

[Silmfeanor]

Why would the added ability be more complex than MPLM? OK, the present function of the trunk, solar array and cooling panels need to be kept. But what would be added is just a pressure container and a berthing mechanism.

You should agree because he is right.  It is more complex than MPLM because unlike a MPLM, it has to hold solar arrays, radiators and separation system.  And unlike a trunk, it has to hold pressure, have internal lighting and air recirculation ducts, and a berthing system.

All of which I have mentioned and said the added complexity is not more than a MPLM.

Which is in a way a confirmation of what he said, yes. But it is still a very simple and therefore relatively cheap device compared to a Cygnus for example.

But IT is more than a MPLM. That's the whole point; you saying that it isnt doesnt make it so.
How is it simple / cheap compared to Cygnus?

[guckyfan]

But IT is more than a MPLM. That's the whole point; you saying that it isnt doesnt make it so.

Which I confirmed by saying the added function is no more complex than the simplest possible system, that MPLM was as it does nothing at all by itself. It was placed at the ISS by the shuttle like this is by Dragon.

How is it simple/cheap compared to Cygnus?

Because it has no active components for maneuvering. Cygnus must perform orbit maneuvers and approach ISS, as Dragon does. The trunk by itself does not do these functions.

[Jim]

Which is in a way a confirmation of what he said, yes. But it is still a very simple and therefore relatively cheap device compared to a Cygnus for example.

NO, it is not cheap because a Dragon is connected to it.

[guckyfan]

Which is in a way a confirmation of what he said, yes. But it is still a very simple and therefore relatively cheap device compared to a Cygnus for example.

NO, it is not cheap because a Dragon is connected to it.

I am quite clearly talking about increments. Of course Dragon is there and it performs a task that is worthwile because it can do and does so many different things. The pressurized trunk is a cheap addon that stretches those abilities a lot for little extra money. Little money in spaceflight terms of course.

[Jim]

The pressurized trunk is a cheap addon that stretches those abilities a lot for little extra money. Little money in spaceflight terms of course.

It isn't cheap or a little extra money

[spectre9]

Jim is correct.

All pressure vessels cost big money. It's extremely customised hardware.

Not a big enough market for the stuff for the USA to even bother with such things.

Thales Alenia is the biggest supplier in the world as far as I know. That's if you don't count Progress I guess 

[guckyfan]

Jim is correct.

If you say so.

[spectre9]

Jim is correct.

If you say so.

My opinion might not mean much compared to the wealth of experience Jim has in the aerospace industry but that doesn't mean it's not worth anything and you can just hand wave it with a snide comment.

[guckyfan]

Jim is correct.

If you say so.

My opinion might not mean much compared to the wealth of experience Jim has in the aerospace industry but that doesn't mean it's not worth anything and you can just hand wave it with a snide comment.

Oh please! This is bordering on the absurd.

How much did SpaceX spend to develop Dragon? How much does a Dragon cost to build? Are you or Jim really trying to tell me developing and building an additional pressure vessel is anywhere near those costs? The additional berthing mechanism will be the biggest item in building.

[spectre9]

DDT&E

You can't skip any of it and expect working space hardware.

[guckyfan]

DDT&E

You can't skip any of it and expect working space hardware.

This has now definitely passed the border to the absurd. I never even remotely suggested anything like that.

The arguments are exchanged and every reader can form his opinion.

[spectre9]

It is my opinion you have unrealistic expectations of how cheaply SpaceX can produce space hardware.

Thanks for the discussion 

[guckyfan]

It is my opinion you have unrealistic expectations of how cheaply SpaceX can produce space hardware.

Thanks for the discussion 

I don't base my opinion on some assumption how cheap SpaceX can do something. I have no basis how to calculate that.

I base it on the opinion, that what I propose is by at least an order of magnitude simpler to develop than the development of Dragon was. So I assume the cost will be also be roughly an order of magnitude lower, independent on how cheap or expensive that develoment was.

That assumption may be wrong, but I don't think so.

Thanks for the discussion from me too.

[Jim]

Are you or Jim really trying to tell me developing and building an additional pressure vessel is anywhere near those costs?

It will be manrated and therefore much different requirements than the existing trunk.  It will be close to the costs of the Cygnus payload module.

[mmeijeri]

In an optimistic scenario where we have lots of commercial LEO traffic ten years from now, would a reusable capsule still be the preferred way to resupply pressurised cargo? Or would a disposable module similar to ATV's Pressurised Equipped Module be cheaper, perhaps using a capsule as its carrier for the "last mile"? Or perhaps even an unpressurised carrier that carried its own liquid air to resupply any air that was lost by having to use an airlock?

[guckyfan]

In an optimistic scenario where we have lots of commercial LEO traffic ten years from now, would a reusable capsule still be the preferred way to resupply pressurised cargo? Or would a disposable module similar to ATV's Pressurised Equipped Module be cheaper, perhaps using a capsule as its carrier for the "last mile"? Or perhaps even an unpressurised carrier that carried its own liquid air to resupply any air that was lost by having to use an airlock?

The majority of supplies may be on disposable modules. But the need for downmass dictates there are capsules capable of landing needed as well. From return capability to reusability is not that huge a step.

[baldusi]

Again, if you are having a reusable system and project a huge demand, you'd go with a big blunt object or lifting body. Think of either an enlarged Dream Chaser (at least 2X in each dimension, probably 3X) or look at the t/space proposal.