Community > Forum > Official Armadillo Aerospace Forum > Official Armadillo Q&A thread

Official Armadillo Q&A thread

Posted by: John Carmack - Tue Jun 15, 2004 8:01 am
Post new topic Reply to topic
 [ 2523 posts ] 
Go to page Previous  1 ... 5, 6, 7, 8, 9, 10, 11 ... 169  Next
Official Armadillo Q&A thread 
Author Message
Launch Director
Launch Director
avatar
Joined: Tue Jun 29, 2004 11:06 pm
Posts: 10
Post    Posted on: Tue Jul 06, 2004 4:50 pm
Will you be issuing an announcement/invitation to your climb-record flight from SRS?

And -- you don't have to answer this one... I just want a peek into the minds of Carmack & Co. -- politically/philosophically speaking, what are your feelings regarding launch licenses, vehicle certifications, etc.? Are you complying with the governments demands, er, *reluctantly*, or do you accept them as a matter of safety (or whatever they're for)?

Thanks,
--Jac


Back to top
Profile
Spaceflight Trainee
Spaceflight Trainee
User avatar
Joined: Tue Jul 06, 2004 9:37 pm
Posts: 44
Post    Posted on: Tue Jul 06, 2004 9:58 pm
Hi John, I am new here, and this is probably a dumb question, and sort of off topic,(more aimed to the area of an orbitol vehicle) but I was wondering, if/when your teams moves to staging your vehicles, would each of your stages be a fully Vtol "Armadillo" type vehicle? OR or they be parachute recovery? or something else.

Off the top of your head of course, if they were to be fully Vtol Armadillo type stages, how long, would you think a turnaround flight would be. Would it be any shorter than any other type of stage recovery system?


Back to top
Profile
Space Station Commander
Space Station Commander
User avatar
Joined: Mon Oct 06, 2003 9:22 pm
Posts: 843
Location: New York, NY
Post    Posted on: Thu Jul 08, 2004 12:38 am
if one of you guys gets on before the update, i don't suppose you'd mind giving us a brief idea of how the tests went tuesday? :D

_________________
Cornell 2010- Applied and Engineering Physics

Software Developer

Also, check out my fractals


Back to top
Profile
Spaceflight Participant
Spaceflight Participant
User avatar
Joined: Tue Jun 15, 2004 7:54 am
Posts: 94
Location: Dallas, TX
Post    Posted on: Thu Jul 08, 2004 8:07 am
>Have you considered using genetic algorithms? There is a flood of new nanotechnologies like
>rapid prototyping; have you considered using those to manufacture, or to use some
>supramolecular materials?

What do genetic algorithms have to do with rocket ships?
How is rapid prototyping a nanotechnology?
I had never heard of supramolecular materials, but a brief web search didn’t turn up anything particularly relevant.
In general, we want to use commonly available technologies for basically everything. In almost all cases, I will use a part that I can get next-day delivered from McMaster-Carr over a part that is twice as good, but has a multi-week lead time.

>catalyst and flameholder details

We are currently using dense (600 or 900 cells per square inch) rolled foil monoliths for the cold pack, and random packing pall rings for the hot section. We never fixed the operating engine stability problems with the 90 degree angle flameholders, so we are using the 50% open area perforated plates, which have a higher pressure drop for a given amount of flameholding, but don’t contribute to engine roughness.

http://media.armadilloaerospace.com/200 ... nolith.jpg
http://media.armadilloaerospace.com/200 ... talyst.jpg

>simulator software

It is just a straightforward C program that I wrote. This makes it much easier to debate results with range or federal authorities.

>announcement/invitation to climb-record flights.

No, definitely not. Sorry.

>feelings about the regulations.

The FAA airspace waiver to 3500’ at our test site is completely reasonable. The AST third party safety standards are completely reasonable. Some of the AST process standards are debatable. The environmental assessments are ridiculous. The 15 second burn time limit is actually counter-productive to any rational goal of the government.

>staging

Any future boosters are probably going to be just upsized VTVL’s very much like we are currently building. We expect upper stages to be disposable and launched out over the ocean until the systems mature, but eventually we expect them to be powered vertical landers just like the booster.

We think we could refly the booster in an hour. A powered lander upper stage won’t have the crossrange to do single orbit returns, so it will have to hang around in orbit until the recovery site phases correctly.

>Tuesday tests

We lifted off the big vehicle, and actually got it hung up on the strap by its lifting eye bolt, which was rather unexpected. The engine is running rough at 300 psi tank pressure, so we are going to have to cut it open and cut down the flow area on Saturday before flying again. Another shop test day required before boosted hops.

John Carmack


Back to top
Profile WWW
Spaceflight Enthusiast
Spaceflight Enthusiast
avatar
Joined: Sun Jun 20, 2004 1:53 am
Posts: 3
Post very interesting,   Posted on: Fri Jul 09, 2004 3:47 pm
after I had written a lengthy explanation for much of what I said, I decided better to let things run their course; i see now how the future will be won.


Back to top
Profile
Spaceflight Trainee
Spaceflight Trainee
avatar
Joined: Sat Jul 10, 2004 9:45 am
Posts: 22
Location: Smolensk, Russia
Post going orbital on 2 stages   Posted on: Sat Jul 10, 2004 9:53 am
One more question re the orbital vehicle: Are you going to go orbital with a 2 stage vehicle? As far as i undertstand rocket vehicle dynamics, you'll have to have a stage mass ratio of at least 1:10 to go orbital with the kind of Isp's you have: from 190 to 240 s in vacuum (mixed monoprop 1st stage gives around 145-150s on a ground level which should be around 190 s in vacuum, biprop with 90% peroxide and kerosene gives 200s on ground and probably 240s in vacuum or, at the most, 250s with 98% percent peroxide).

This seems impossible. Even without the excess fuel for powered landing. Even the fiberglass fuel tank weights 1 poind per gallon of capacity, which is 10.7% if we take 1.12 fuel density. Well a carbon fiber tank could give twice less, but it's still not enough - you'll have to fit engines, thrust structure, fairings, probably interstage and mid-stage skirt.

So a three-stage solution seems to be the minimal practical one, or am i missing something?


Back to top
Profile ICQ
Spaceflight Trainee
Spaceflight Trainee
avatar
Joined: Sat Jul 10, 2004 9:45 am
Posts: 22
Location: Smolensk, Russia
Post    Posted on: Sat Jul 10, 2004 10:24 am
Even for a 3 stage solution with the VTVL, i don't see any options giving more than 0.1% of launch mass orbital payload capacity even with carbon fiber tanks, taken that dead weight ratio will increase for smaller stages due to electronics etc. Using fiberglass tanks will eliminate any possibility for upper stage recovery and probably will limit the vehicle to just orbiting its last stage with no payload. With this scenario, it will be better to use a solid-fuel 3rd stage due to its lighter dead weight, comparable Isp and reliability.


Back to top
Profile ICQ
Space Walker
Space Walker
avatar
Joined: Tue Jun 22, 2004 12:26 am
Posts: 180
Post    Posted on: Sun Jul 11, 2004 2:08 am
What happens if the make the whole vehicle out of carbon fibers? Is that possible?


Back to top
Profile
Spaceflight Trainee
Spaceflight Trainee
avatar
Joined: Sat Jul 10, 2004 9:45 am
Posts: 22
Location: Smolensk, Russia
Post    Posted on: Sun Jul 11, 2004 6:55 am
Of course no. Carbon fiber is good for static, from inside-out, load (internal pressure). Engines, for example, are also subject to high thermal loads that carbon fiber can't tolerate. Thrust structure must be made of steel or titanium alloy, etc... Not to mention electronics, power, and passengers :-)


Back to top
Profile ICQ
Space Walker
Space Walker
avatar
Joined: Tue Jun 22, 2004 12:26 am
Posts: 180
Post    Posted on: Sun Jul 11, 2004 7:17 pm
Yes, of course not the electronics, but what about the "body" of the spaceship?


Back to top
Profile
Spaceflight Trainee
Spaceflight Trainee
User avatar
Joined: Tue Jul 06, 2004 9:37 pm
Posts: 44
Post    Posted on: Sun Jul 11, 2004 7:44 pm
Hi john, what would you think of a 4 engine 4 actuator design?

(Engine) Actuator (Engine)
Actuator ----+---- Actuator
(Engine) Actuator (Engine)

So that each actuator has a vane on either end. I don't know, are a few smaller engines better(redundancy?) or does a one big engine work much better. I guess it would lack roll control. Could it be fin stablized? What if there were another actuator with some kind of transmission adding a third vane from the outside edge for roll control would it be prohibitively heavy? How about some jointing on the 4 main actuactors to solve the Roll problem, also too heavy?

I guess that is sort of off topic. :oops:

How has the software design gone form your prespective? Has it been easier or harder than you first thought when under taking this project.

I look forward to your updates on the big vehicle :wink:


Back to top
Profile
Spaceflight Trainee
Spaceflight Trainee
avatar
Joined: Mon Jun 28, 2004 6:05 pm
Posts: 22
Post    Posted on: Mon Jul 12, 2004 2:22 am
More engines = more complexity. This has to be weighted against the redundancy benefit, I suppose.

But I think Armadillo was using four engines in their previous design for differential throttling, not redundancy.

_________________
- Lars


Back to top
Profile
Spaceflight Trainee
Spaceflight Trainee
User avatar
Joined: Tue Jul 06, 2004 9:37 pm
Posts: 44
Post    Posted on: Mon Jul 12, 2004 6:13 am
Well, it's true, but I was just trying to think of a way to increase the redundancy of the engines without increasing the number of actuators. Each nozzle would have only 2 vanes acting on the thrust.

I guess a twin engine would be just as good using only 4 actuators.

If you had 4 engines and 4 actuators you could have thrust differential as a back up system incase of actuator failure and vise versa. but you are right it would be much more complicated.


Back to top
Profile
Spaceflight Enthusiast
Spaceflight Enthusiast
avatar
Joined: Thu Jun 24, 2004 8:35 am
Posts: 2
Post    Posted on: Mon Jul 12, 2004 7:03 am
If you want to get any benefit from having redundant engines, you have to be able to fly with one engine out. That means not only that you need enough extra thrust to keep from crashing, but you also need enough control authority to point the thrust vector so that it passes through the center of gravity of the vehicle.

Jet vanes only redirect a small part of the thrust, and they're probably not going to be able to make up for an engine failure. You'll at least have to throttle down the matching engine, and probably shut it down completely. That drops you to 50% thrust which may not be enough to fly.

You also have to look at where failures happen. There are a lot of failures that can happen that are not helped by redundancy. Fuel contamination, electrical problems, software failures. The only thing that redundancy helps is when the engine itself is the source of the problem. This might be something to worry about if you're talking about an SSME, but it's not a big deal for a pressure-fed monoprop engine.


Back to top
Profile
Spaceflight Trainee
Spaceflight Trainee
User avatar
Joined: Tue Jul 06, 2004 9:37 pm
Posts: 44
Post    Posted on: Mon Jul 12, 2004 4:17 pm
I can see I'm on the losing end here. :)

But if you throttled down the matching engine you would still have 4 actuators working the thrust, so you would stil have control.

At 50% thrust your vehicle should fly as long as you dumped 1/2 your weight right? If all the stages were VTVL then the entire thing could break up and all the stages could survive as long as you were high enough to do a proper abort.

Anyways as pointed out engine problems are unlikely and complexity is high. Oh well back to the drawing board. :D


Back to top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2523 posts ] 
Go to page Previous  1 ... 5, 6, 7, 8, 9, 10, 11 ... 169  Next

Who is online 

Users browsing this forum: No registered users and 16 guests


© 2014 The International Space Fellowship, developed by Gabitasoft Interactive. All Rights Reserved.  Privacy Policy | Terms of Use