Forum | Armadillo Aerospace's take on OTRAG style modular boosters

buy cipro cipro purchase buy famvir low famvir 500mg price buy flagyl flagyl forte buy plavix plavix 75mg clopidogrel prices buy amoxil amoxicillin to buy online uk
You must be logged in to post login Login register Register

Search Forums:


searchicon 






topic

Armadillo Aerospace's take on OTRAG style modular boosters

small tagNo Tags
UserPost

3:31 am
November 22, 2009


Luke Maurits

Adelaide, Australia

Admin

posts 396

offline
link
print
1

Today I learned that John Carmack's volunteer aerospace startup Armadillo Aerospace have been thinking for some time about using an OTRAG style modular booster to get things into orbit, just like us (in fact, they've even been corresponding with Lutz Kayser about it).  Their website's FAQ section contains a few sections on this idea that are probably worth us paying attention to.

The first thing has an idea that we may want to consider, with regard to minimising drag during launches:

With your current modular design, won't drag on a high number of modules be a deal-breaker? What about adding a fairing?

Our current plan of record is to fly the modular clusters at subsonic speeds through the thickest parts of the atmosphere. This means that typical concerns about transonic conditions and high drag are not as relevant. We will pay a price in efficiency, since delaying higher speeds until much higher altitudes expends more energy, but we feel we will more than make up for that in the simplicity and flexibility of the modular design. As such, we feel a fairing may not be necessary, only adding unnecessary weight. But higher altitude testing will prove this out.

The second thing addresses reliability concerns with the OTRAG design, which I seem to recall being a worry for some people back at /r/tothemoon on Reddit:

Won't the modular approach be more prone to mishaps since there will be more individual systems within which things can go wrong?

Very simple modules should have much higher reliability than conventional, complex rockets. Even without that:

If each module only had 99% reliability, an eight module system would have an 7.7% chance of having a failure of some kind (1.0 – 0.99^ 8 ). However, the configurations we will likely use would require two modules in opposite "banks" to both fail to bring the vehicle down, which would only have a (1.0 – 0.99^4) * (1.0 – 0.99^4) = 0.00155 chance of happening. We expect the real number to be much smaller than that, because we expect we will have better than 99% reliability per module. Each bank should have its own guidance electronics as well, so that will also be redundant.

Main workgroup: Navigation and Guidance. Side interests: Propulsion, Computer Systems, Communications. Skill set: Mathematics major, good knowledge of Newtonian physics, decent programming (Python, C, Java, PHP)

9:26 pm
December 13, 2009


Snyder

Lakewood CO, USA

Member

posts 4

offline
link
print
2

Of course the problem with going slow in the atmosphere is the propellant waste. Every extra minute it takes to fly to orbit is basically an extra minute of propellant at hover. (more or less)

The Term is 'Gravity Losses". The most efficient launcher is a gun on an airless world.


The parallel failure mode reliability calculations are also heavily influenced by development and test money spent on each stage.

If you have 3 stages, and each is developed and tested independently, It costs atleast 3 times as much. If you put that same,  or even less, into development of a single module, it is safe to assume that you modules will be more reliable than the stages.


-Gar


9:36 pm
December 13, 2009


Luke Maurits

Adelaide, Australia

Admin

posts 396

offline
link
print
3

Snyder said:

If you have 3 stages, and each is developed and tested independently, It costs atleast 3 times as much. If you put that same,  or even less, into development of a single module, it is safe to assume that you modules will be more reliable than the stages.


While I can't speak much about Armadillo's plans, in the original OTRAG designs, and in our current Selene designs (which are really more concepts than designs at this stage), each stage is simply a different sized cluster of the one very small, cheap and simple.  These simple modules are (so goes the theory) cheap and simple enough that they can be extensively tested and made very reliable.

This approach is appealing to us due to the ease with which we can slowly scale things up by clustering more and more modules, and due to the fact that a single module might be cheap enough for us to actually have a hope of building one!

I don't know to what extent you can talk about this, for ITAR and other reasons, but are OLF's launch vehicle plans loosely based on the OTRAG approach or a more traditional "separate big stages" approach?

Main workgroup: Navigation and Guidance. Side interests: Propulsion, Computer Systems, Communications. Skill set: Mathematics major, good knowledge of Newtonian physics, decent programming (Python, C, Java, PHP)

small tagNo Tags

About the CSTART forum

Most Users Ever Online:

28


Currently Online:

4 Guests

Forum Stats:

Groups: 4

Forums: 31

Topics: 184

Posts: 1009

Membership:

There are 42 Members

There has been 1 Guest

There are 2 Admins

There are 0 Moderators

Top Posters:

Rocket-To-The-Moon – 255

brmj – 136

rpulkrabek – 38

noumena – 29

johnnyping – 15

gerbal – 12

Administrators: Luke Maurits (396 Posts), Rizwan (61 Posts)




  • Share/Bookmark