Community > Forum > Google Lunar X PRIZE > SFS News: ARCA - Haas Orbital Rocket Launcher for Google Lun

SFS News: ARCA - Haas Orbital Rocket Launcher for Google Lun

Posted by: Rob Goldsmith - Tue Dec 23, 2008 10:48 am
Post new topic Reply to topic
 [ 80 posts ] 
Go to page Previous  1, 2, 3, 4, 5, 6
SFS News: ARCA - Haas Orbital Rocket Launcher for Google Lun 
Author Message
Space Station Member
Space Station Member
User avatar
Joined: Mon Feb 25, 2008 9:51 am
Posts: 448
Location: Vienna, Austria, Europe, Earth
Post Re: SFS News: ARCA - Haas Orbital Rocket Launcher for Google Lun   Posted on: Fri Oct 08, 2010 2:57 pm
REDrake wrote:
It's a rocket not a spaceship. How can one place a camera on a rocket and not expect it to burn?

NASA does it
ULA does it
SpaceX does it
and I bet somebody else is doing it as well, I just can't remember.

If your rocket works, only the fuel burns, not the casing, so why should the camera be affected?

REDrake wrote:
What do you want to see? Some dot on a screen while checking the radar?

What I want to see:
a) a public statement where they acknowledge that their "stabilization method" relies in fact on aerodynamic forces and has nothing to do with gravity like they claim.
b) a video of a ground (test) launch or at least form a VERY low altitude balloon where we can see the rocket on ground based cameras! (OR provide onboard video)

So far they have shown nothing that proves any of their concepts is feasible (apart form the balloon of course).

_________________
pride comes before a fall


Back to top
Profile
Space Walker
Space Walker
User avatar
Joined: Thu May 07, 2009 2:40 am
Posts: 160
Location: Austin, Texas
Post Re: SFS News: ARCA - Haas Orbital Rocket Launcher for Google Lun   Posted on: Fri Oct 08, 2010 4:28 pm
Without providing more data the only thing that ARCA can really claim is that they hoisted a payload above the clouds using a zero-pressure helium balloon. They haven't provided many details on the rocket, but it appears to be the second stage that was to be used on Mission 4.

There are some pictures of the rocket from Mission 4. One picture shows some men standing next to stage 1, which provides us some scale information. Based on that picture I would estimate that stage 1 is about 73 cm in diameter, and 2.9 meters long. I estimate that the fuel tank has a volume of less than 0.2 cubic meters, and the total volume of the rocket is about 0.6 cubic meters.

It appears that stage 2 is about 15% smaller than stage 1. It's fuel tank would hold less than 0.12 cubic meters of fuel, and it's total volume would be around 0.36 cubic meters. The pictures from mission 4a show that the rocket floats in the water with slightly more than half of it under water -- I'll estimate it at 60% under water. That means that the rocket is displacing about 0.22 cubic meters of water, which means it has a mass of about 220 Kg.

If we add in the weight of the cables and payload it's probably around 300 Kg. So it seems that ARCA could claim that they hoisted a 300 Kg payload above the clouds.

With the information that ARCA provided there is no way to know whether the rocket motor worked and it reach 40,000 meters, or whether the motor failed and it just fell 14,000 meters to the sea.

Dave


Back to top
Profile WWW
Space Walker
Space Walker
User avatar
Joined: Thu May 07, 2009 2:40 am
Posts: 160
Location: Austin, Texas
Post Re: SFS News: ARCA - Haas Orbital Rocket Launcher for Google Lun   Posted on: Sat Oct 09, 2010 3:38 am
I ran a few simulations of the ARCA rocket, and I am not able to get the results that ARCA is claiming. I used a launch altitude of 14,000 meters, a rocket diameter of 62 cm, a propellant mass of 150 Kg, and an empty mass of 70 Kg. I also assumed a constant thrust during the 30 second burn duration.

With an Isp of 100 I got a altitude of 21.0 km. Even if I use a very generous Isp value of 140 I still only get 24.2 km.

ARCA claims that the shape of the Helen 2 rocket is not a problem because there is not much air resistance at 14,000 meters. This is clearly not the case. There is a significant air density at 14,000 meters, and the shape of the Helen 2 rocket causes a lot of aerodynamic drag.

In my opinion, there is no way the Helen 2 rocket could have reached an altitude of 40 km.

Dave

Edit: I ran a few more simulations with lower drag coefficients, and I was able to get an altitude of 40 km with a Cd of 0.19. However, a drag coefficient that low would require a more conventional looking rocket with a nosecone and a straight body. I don't believe the Helen 2 rocket could have a drag coefficient that low. I also did not include the effect of the cables and payload hanging behind the rocket, which would produce additional drag.


Back to top
Profile WWW
Rocket Constructor
Rocket Constructor
User avatar
Joined: Mon Sep 27, 2010 2:47 pm
Posts: 5
Location: Munich, Germany
Post Re: SFS News: ARCA - Haas Orbital Rocket Launcher for Google Lun   Posted on: Mon Oct 11, 2010 6:33 pm
Congratulations to the ARCA team for getting the balloon launched!

I looked at the photos and everyone is clearly very happy with how the mission went.

As others have mentioned here, it would be great to see some hard data about the rocket firing.

Maybe there is data to be gleaned from the photo posted here:
- http://picasaweb.google.com/arcaorbital ... 0572244626 ?

Can anyone interpret what we're seeing on the computer screen?

I am not sure we're seeing any altitude information, only translational distance and directions.


Back to top
Profile WWW
Space Walker
Space Walker
User avatar
Joined: Thu May 07, 2009 2:40 am
Posts: 160
Location: Austin, Texas
Post Re: SFS News: ARCA - Haas Orbital Rocket Launcher for Google Lun   Posted on: Mon Oct 11, 2010 8:12 pm
I believe that monitor is showing the latitude and longitude of the balloon. If you type "44.15n, 29.37e" into Google maps you will be located about 50 km east of Constanta in the Black Sea. The video at http://www.youtube.com/user/dragosmur#p/u/3/buuFieP6lVo describes the Mission 4b command station. There are monitors dedicated to displaying video from the rocket and the payload. The video mentions that they can observe the rocket ignition on one of the monitors. For some reason, ARCA has not shown the video received from these cameras.


Back to top
Profile WWW
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 80 posts ] 
Go to page Previous  1, 2, 3, 4, 5, 6
 

Who is online 

Users browsing this forum: No registered users and 7 guests


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