Using the kick stage lowers the cost of developing and testing upper stage in-space restart. Lets them address a larger portion of the market's needs while doing testing on-orbit. Saves on expensive ground vacuum testing and simultaneously provides better test environment. And since they had already developed their monopropellant under DARPA contract, it shouldn't have cost them all that much. Especially if they didn't have to develop much in the way of new avionics.
While I imagine a rocket engine using electric turbopumps such as the Rutherford would be easier to restart than one utilizing a gas generator, it's still probably simpler and more accurate to circularize an orbit with a low thrust unit instead of a relatively large 2nd stage engine with limited throttleability.
I'd love to know what they're using as a monoprop.
While I imagine a rocket engine using electric turbopumps such as the Rutherford would be easier to restart than one utilizing a gas generator, it's still probably simpler and more accurate to circularize an orbit with a low thrust unit instead of a relatively large 2nd stage engine with limited throttleability.
I'd love to know what they're using as a monoprop.
99.9% confident they would use the VLM they developed with DARPA funding.
Entirely possible they prioritized time to market and development cost over performance ...
Who else do we know like that?
(I love these guys. They launched a disco ball to orbit because they want people to look up.)
Entirely possible they prioritized time to market and development cost over performance ...
Who else do we know like that?
(I love these guys. They launched a disco ball to orbit because they want people to look up.)
Seems like Humanity Star was also flown on It's A Test. I was wondering what that shiny object was during launch. See at 1:52 of video.
Good catch! That makes a lot more sense in retrospect.
but they are exSpaceX staff.
You are not wrong but people put too much emphasis on that stuff. They were mostly short summer internships during their degree programs, then 1-2 years in very junior positions before they started Relativity:-
CTO
USC Bachelors degree 2010-2014
Blue Origin
Propulsion Intern (summer intern)
Dates Employed Jun 2013 – Aug 2013
Employment Duration 3 mos
SpaceX
In-Space Propulsion Intern (summer intern)
Dates Employed Jun 2014 – Sep 2014
Employment Duration 4 mos
Propulsion Development Engineer (full time)
SpaceX
Dates Employed Sep 2014 – Dec 2015
Employment Duration 1 yr 4 mos
CEO
USC Bachelors and Masters degrees 2008-2013
Turbomachinery Development (summer intern)
BLUE ORIGIN
Dates Employed May 2011 – Aug 2011
Employment Duration 4 mos
Propulsion Testing (summer intern)
BLUE ORIGIN
May 2012 – Aug 2012
Employment Duration 4 mos
Turbomachinery Development (summer intern)
BLUE ORIGIN
Dates Employed May 2013 – Aug 2013
Employment Duration 4 mos
Propulsion Development (full time)
BLUE ORIGIN
Dates Employed Jan 2014 – Dec 2015
Employment Duration 2 yrs
-
It's not nothing, but it's also a bit of a stretch to put a huge emphasis on that aspect.
Jimmy Cantrell is another one who makes his links to SpaceX seem more than it really is. He left SpaceX because after a few months "he didn't believe in it", or some such. If you think about it Jimmy is actually more like Ron Wayne, the guy who sold his Apple stock for $800...
Tim left out his internship at Masten Space Systems. He was one of the two interns the summer I left to start Altius.
~Jon
Entirely possible they prioritized time to market and development cost over performance ...
Who else do we know like that?
(I love these guys. They launched a disco ball to orbit because they want people to look up.)
Seems like Humanity Star was also flown on It's A Test. I was wondering what that shiny object was during launch. See at 1:52 of video.
Good find - i thought at the time this was part of the "It's A Test" dummy payload on the upper stage, but now that we know about the appearance of Humanity Star, it is quite clear, that an Humanity Star was also on the first launch.
I am curious, if there was also a Kick Stage on the first launch.
Using the kick stage lowers the cost of developing and testing upper stage in-space restart. Lets them address a larger portion of the market's needs while doing testing on-orbit. Saves on expensive ground vacuum testing and simultaneously provides better test environment. And since they had already developed their monopropellant under DARPA contract, it shouldn't have cost them all that much. Especially if they didn't have to develop much in the way of new avionics.
They tested restart AFTER separation of main commercial payload?
Using the kick stage lowers the cost of developing and testing upper stage in-space restart. Lets them address a larger portion of the market's needs while doing testing on-orbit. Saves on expensive ground vacuum testing and simultaneously provides better test environment. And since they had already developed their monopropellant under DARPA contract, it shouldn't have cost them all that much. Especially if they didn't have to develop much in the way of new avionics.
They tested restart AFTER separation of main commercial payload?
That's pure speculation. I have no definitive information about this in relation to actual disclosed activities on this mission. More just a logical surmise. In order to support the flight rate RocketLab hopes to achieve, it will help to be able deliver payloads to the widest possible range of potential orbits. With the expanding nature of the current small sat market, who knows what payloads are going to be looking for a ride. Having upper stage restart capability is useful in that respect. It also could be useful for other ride-sharing launches where different payloads are going to different orbits. So, from the starting point of believing that they will want to eventually add this capability to their operations toolbox, my surmise is that testing post payload separation would be a good time to start moving themselves toward it. Could have been as small scale as attempting to settle props and see what happens to their fluid flows after coast, etc. Even without any intention of actually relighting the engine, there's lots they can learn about their vehicle so long as it's still alive. /speculation
Sounds like it's chemically similar to solids but with granules suspended in a liquid.
This is really impressive, these folks are the real deal. Three stages, likely all with novel propulsion technology. Not something you expect to see in 2018.
No it's liquid (probably water, could be something else) with a lot of the propellant dissolved into it. The propellant (or maybe some additives on top) make it "thixotropic." IOW it's like non drip paint or "super multigrade" motor oils. Like treacle at rest, or moving slowly, but thinning out as its put through a pump. However it's a single phase liquid, not a two phase mixture.
However it's a single phase liquid, not a two phase mixture.
While the bulk of the propellant can be liquid phase (up to 80% carrier fluid) the patent states that solid particles (indissoluble powdered oxidizers or "thermic" ingredients, maybe powdered aluminum) are suspended in the liquid phase, which would make a two-phase mixture. And the patent covers mixtures ranging up to 95% solids.
CLAIMS(26)
1. A viscous liquid monopropellant (VLM) mixture comprising:
a. a carrier-fluid present in an amount ranging from about 5% to 80% by mass, and
b.a solid fraction comprising from about 20% to 95% by mass dispersed, suspended or emulsified in the carrier-fluid
These monopropellants are comprised of a variety of liquid and solid components, mixed together to form a homogenous fluid, although heterogeneous in composition. The solid constituents are retained within the liquid phase by dispersion, suspension, bonding or chemical emulsification techniques, so as when a motive force is applied to the propellant, all the constituents are also transported, and held in correct proportion whilst doing so.
https://www.google.com/patents/US20120234196So technically, it's a two-phase mixture, like an emulsion.
So technically, it's a two-phase mixture, like an emulsion.
Yeah, I'm basically picturing the propulsion properties of a throttleable, restartable solid propellant and the bulk physical properties of mayonnaise. My intuition is the viscosity makes it probably not that useful for station keeping, which is in the millinewtons or even lower, but for >newton thrust it's one of the best monopropellants I've ever heard of. One of the Youtube videos Rocket Lab has of a VLM test claims 300 ISP.
Also for an LOL from the patent:
The propellant feed rate is preferably high enough that it exceeds the burn rate of the propellant.
Yes... that would be preferable.
So I have finally registered an account here
I have watched last week's launch video
(https://www.youtube.com/watch?v=Lwi44sPAQDE) again in a bit more detail and have come up with some conclusions/questions, maybe some of you have had the same thoughts?
* At 20:55, the ejection of the prominent battery pack can clearly be seen, but a fraction of a second later, a second pack can be seen at the top of the frame, making me think they ejected two packs at once.
* To go back a bit: At 16:53, the first stage is separated. There seems to be an immediate incidence correction around 17:00 when the second stage engine starts up. Does anyone know why the attitude correction looks so large?
* I have also been wondering about why they paint their launcher black (or leave the carbon fibre surface as is). From my experience, usually white paint is used to minimise solar irradiance. Surely they must have problems with aeroheating? At 17:28, the outside of one fairing half can be seen, and it looks positively glossy, so no apparent heat "damage". If that is just a "clear-coated" carbon fibre surface, how do they get away without using any kind of thermal protection?
Does anyone know why the attitude correction looks so large?
Prior callout was for an AOA (Angle of Attack) minimisation, i.e. turning the rocket to point directly along the line of flight, just before staging. Presumably to minimise the aerodynamic forces applying sideways onto the stages during staging, to prevent the nozzle clipping the inner edge of the interstage due to windshear. The correction after staging would be to point the second stage back towards the desired angle it was travelling at before the minimisation manoeuvre.
Does anyone know why the attitude correction looks so large?
Prior callout was for an AOA (Angle of Attack) minimisation, i.e. turning the rocket to point directly along the line of flight, just before staging. Presumably to minimise the aerodynamic forces applying sideways onto the stages during staging, to prevent the nozzle clipping the inner edge of the interstage due to windshear. The correction after staging would be to point the second stage back towards the desired angle it was travelling at before the minimisation manoeuvre.
Ah, thanks -- that's what I get for watching on mute!
