Gilmour Space Technologies

[CameronD]

One of the many advantages of not using a cryogenic propellant is that you can pressurise with nitrogen.

I think a lot of people would be amused if they get to orbit with hybrid engines, HTP is just bonus points 

HTP can still be unpredictable and nasty to work with, as Armadillo discovered all those years ago.

[QuantumG]

HTP can still be unpredictable and nasty to work with, as Armadillo discovered all those years ago.

For sure, everything is a trade.

[CameronD]

HTP can still be unpredictable and nasty to work with, as Armadillo discovered all those years ago.

For sure, everything is a trade.

I wonder how much desert temperatures might make things worse?  There's a big difference in climate between Boulia and the Gold Coast.

[QuantumG]

I wonder how much desert temperatures might make things worse?  There's a big difference in climate between Boulia and the Gold Coast.

Storage becomes a lot more exciting.

[plugger.lockett]

Does anyone here know how they plan to reach orbit? Their One Vision rocket has HUGE fins. Their static motor tests don't appear to use a gimbaled nozzle. Cold gas maybe? Having a motor to get you there is a good start but unless they have a system to orient for orbital insertion I'm not sure how they plan to achieve it in practice.

[Steven Pietrobon]

HTP can still be unpredictable and nasty to work with, as Armadillo discovered all those years ago.

Are you referring to Armadillo using 50% HTP mixed with ethanol in a single solution? Of course that is going to be unpredictable and nasty to work with! British experience with 85% HTP was much better. They never had a single propulsion failure caused by HTP in their Black Knight and Black Arrow programs. One story from Woomera was a Blue Steel brought back to Edinburgh for servicing. The guy undid the plug, but the tank had not been properly drained. HTP poured all over the guy. He rushed to the nearby shower and threw his clothes to the ground. He was OK, but his clothes soon caught on fire! HTP treated with the same respect as other oxidisers is as safe, or safer since most of the time nothing bad happens if you mistreat it.

https://en.wikipedia.org/wiki/Armadillo_Aerospace

[QuantumG]

British experience with 85% HTP was much better. They never had a single propulsion failure caused by HTP in their Black Knight and Black Arrow programs. One story from Woomera was a Blue Steel brought back to Edinburgh for servicing. The guy undid the plug, but the tank had not been properly drained. HTP poured all over the guy. He rushed to the nearby shower and threw his clothes to the ground. He was OK, but his clothes soon caught on fire! HTP treated with the same respect as other oxidisers is as safe, or safer since most of the time nothing bad happens if you mistreat it.

Is this story from a book? Which one? I bet they say a thing or two about their storage techniques. But yes, most of the horror stories I've heard about HTP over the years have been about 90%+

[Steven Pietrobon]

Is this story from a book? Which one? I bet they say a thing or two about their storage techniques. But yes, most of the horror stories I've heard about HTP over the years have been about 90%+

The story is from Terry Clark, who used to work at Woomera.

https://digital.collections.slsa.sa.gov.au/nodes/view/2813
https://trove.nla.gov.au/work/229579621?q&versionId=252409794

[plugger.lockett]

Video is up.

https://video.wixstatic.com/video/9296f8_300e0ab9732e43f2bd97e38280f19b39/720p/mp4/file.mp4

[CameronD]

Video is up.

https://video.wixstatic.com/video/9296f8_300e0ab9732e43f2bd97e38280f19b39/720p/mp4/file.mp4

Ahh.. that didn't work so well.  Back to the drawing board?

EDIT:  I'm just sad they had to drive all that way for a few seconds of pain.

[plugger.lockett]

Ahh.. that didn't work so well.  Back to the drawing board?

EDIT:  I'm just sad they had to drive all that way for a few seconds of pain.

Ideally shouldn't this failure mode have been eliminated with a wet dress rehearsal test?

[Steven Pietrobon]

Just want to say thankyou to Gilmour for posting the video. Not everyone likes to show their failures, so its a refreshing change for a company to be open about this.

I had imagined the failure being a rupture down the wall of the HTP tank, with HTP pouring out from the side. We can now see that the tank ruptured at the base in a clean circle, with the top part of the vehicle heading skywards and then having a hard landing.

When the announcer says T-10 (seconds) the tank ruptured. Four seconds before this we see vapour at the base of the vehicle. At the time of rupture we see a large amount of vapour at the base of the HTP tank. We also see a small amount of vapour at the top of the HTP tank. This could be a pressure relief valiantly trying to relieve the huge pressurisation increase from the failed pressure regulator valve. Soon after the rupture we see two small black objects also heading upwards. It looks like the HTP quickly decomposed when it landed on the ground, generating a huge steam cloud.

The count goes all the way down to T-1 before they announce an anomaly. The press release says the pressure regulator failed at T-7 seconds, so perhaps there is a synchronisation problem between the video and audio.

Video of a previous test of the 80 kN motor shows that venting of HTP into the motor begins 11 seconds before ignition, with full thrust occurring less than a second later. If we assume the rupture was at T-7 seconds, then that would give a nominal time of 7+4 = 11 seconds before ignition, matching what we see in the video.

[Steven Pietrobon]

Gilmour Space Technologies have a new logo. Also heard a rumour that they are switching from HTP to LOX.

https://video.wixstatic.com/video/9296f8_5ecf446b1a274c91af39d81b6ad964d4/720p/mp4/file.mp4

[CameronD]

Gilmour Space Technologies have a new logo. Also heard a rumour that they are switching from HTP to LOX.

Well, that might slow them down a bit..

[Tywin]

Well I prefer the old logo, than this...

Gilmour Space Technologies have a new logo. Also heard a rumour that they are switching from HTP to LOX.

Well, that might slow them down a bit..

Yeahh, almost with his first suborbital rocket ready they make this change now?

A little weird...and maybe they will need reschedule, her orbital rocket...

[plugger.lockett]

Well I prefer the old logo, than this...

Gilmour Space Technologies have a new logo. Also heard a rumour that they are switching from HTP to LOX.

Well, that might slow them down a bit..

Yeahh, almost with his first suborbital rocket ready they make this change now?

A little weird...and maybe they will need reschedule, her orbital rocket...

Yea, this makes little sense to me. The one reasonably mature aspect of Gilmour's program was their engine. To my knowledge they've never successfully flown and recovered any rocket. But their hybrid motor had been ground tested numerous times. Now they're changing that up as well?

It brings to mind the interview with Peter Beck on Ars earlier this year when he stated  "If they're making a big song-and-dance about engine tests, you know they’re miles away,". I can't help but think that comment is applicable here.

[Steven Pietrobon]

First orbital launch delayed to 2022.

"A typical upstream company is Gilmour Space. In June 2016, the company successfully flew the country’s first privately developed hybrid rocket to an altitude of 5km using proprietary 3D printed fuel. Since then, Gilmour Space’s Peter Kinne says the company has raised a total of $24 million in funding from venture capital firms, and received R&D grants in Singapore and Australia.

Mr Kinne says the company has plans to launch its first rockets to Low Earth Orbit by 2022. An attempted launch earlier this year failed to clear the launch pad, although the company says it learned a great deal from the failure."

https://www.spatialsource.com.au/government-policy/moonshot-will-australias-space-sector-benefit

[Steven Pietrobon]

Interview with Adam Gilmour.

* Launch failure was due to a design change in the wiring of sensors which controlled the helium pressure regulator. "We set up a system when we tested it on the ground and we wired in sensors a certain way. For some reason that we don't really know why the decision was made, there's a logical step, we wired it differently. So when we wired it differently, the signal was getting received, but it was taking longer to receive. So when the pressure started to increase from the helium tank into the oxidiser tank the regulator thought it was filling slower. So the oxidiser tank filled up quicker. So you got like a brain here saying "I let more in, I let more in", it doesn't realise because the sensor is too slow "I've let enough in. I've let enough in."
* The next flight will test the third stage of their Eris launch vehicle to over 100 km. Launch in 18 months or mid 2021.
* Orbital flight one year later in mid 2022.
* Launch site for both vehicles is Whaler's Bay, here in South Australia.
* They are designing a vehicle for Lunar and Mars missions.
* Hired 20 people this year and will hire 10 more people next year.

Unfortunately, the interviewer did not follow up on what the oxidiser is when they were discussing the propellants. Solid fuel is proprietary "Its kind of related to plastic." My understanding is that it is ABS plastic. The white board shows a formula with Gox in it, but that could be either HTP or LOX, as they both produce GOX.

[Steven Pietrobon]

I've had confirmation from Gilmour that they are changing to LOX. Here's a reply I sent to them explaining why I think this is a really bad idea.

Number 1 reason why changing from HTP to LOX is a bad idea.
*Schedule* Gilmour has a working motor that can do the job. Changing to a different propellant combination means a complete redesign of the motor along with all the required testing to make sure its working. That adds at least one year (and probably longer) to Gilmour's schedule. Listen to Elon Musk "If the schedule is long it's wrong, if it's tight it's right."

Number 2 reason why changing from HTP to LOX is a bad idea.
*Reliability* LOX needs to be cryogenically cooled down to -183 C. This means that anything that is not designed to work at cryogenic temperatures will freeze up. This means valves, regulators, connectors and other moving parts on both the launch vehicle and pad need to be specially designed. This takes additional time and money to get right. Even then, Gilmour will very likely still have problems, either causing a launch failure or delaying the launch. Some examples:
Ausroc I (22 Oct 1992): LOX valve froze. Vehicle exploded on pad.
Ausroc II (26 May 1995): LOX helium pressure regulator froze. Vehicle greatly under performed.
Falcon 9/AMOS 6 (1 Sep 2016): LOX froze in helium tank wall. Vehicle exploded on pad.
Space Shuttle/STS-122 (7 Feb 2008): Ice froze in ET/Space Shuttle connector. Launch delayed by two months to fix.
Delta IV Heavy/Orion EFT-1 (5 Dec 2014): Valves getting too cold due to long hold time, resulting in slow response time. One day delay.

Number 3 reason why changing from HTP to LOX is a bad idea.
*Complexity* As Elon Musk says, "The best part is the part that is not required". With LOX, Gilmour will need an ignition source to ignite the fuel. With HTP, the high decomposition temperature allows automatic ignition. This makes in-flight ignitions as simple as opening up the main propellant valve. Using LOX, if the ignition source fails, that's a launch failure. Overcoming all the cryogenic problems will also increase complexity.

Of course, HTP has its disadvantages. It is more costly than LOX, but as propellant costs are a small fraction of total launch cost, the effect is minor. Its also very sensitive to contaminants, but the required level is the same as for LOX. Contamination of LOX with hydrocarbons or debris can be catastrophic (as past experience has shown).

The performance advantage of LOX over HTP for orbital launches is also very small. What is not appreciated by many rocket scientists is how propellant density affects performance, especially for the first stage. It is true that LOX has better Isp, but HTP has higher propellant density. I think we can all understand that if two propellants have the same Isp, the one with the higher propellant density will result in a smaller vehicle and thus more payload into orbit. When there is a tradeoff between Isp and density, more analysis is required. In this case, we need real numbers to decide which is better. As Gilmour hasn't published what they are using, I'm going to make some educated guesses. My assumptions are: chamber pressure Pc = 3.45 MPa, area expansion ratio = 19, engine efficiency 97.4%, 98%HTP density = 1.4297 kg/L, LOX density = 1.149 kg/L and high density polyethylene (HDPE) density = 0.941 kg/L. Although Gilmour may initially start off with a lower concentration, say 90%HTP, it is possible to purchase 98%HTP right now.

http://jakusz-spacetech.com/en/?noredirect=en_US

Thus long term, this is the combination to aim for. Higher concentrations of HTP have a dual benefit, as both density and Isp increase. Using the USAF Isp program I get the following results.

             MR   ve (m/s)  dp (kg/L)  Id (Ns/L)
98%HTP/HDPE: 7.25  2955.9    1.3451    3976.0
LOX/HDPE     2.6   3182.0    1.0825    3444.5

MR is the oxidiser to fuel mixture ratio, ve is the effective vacuum exhaust speed (divide by g = 9.80665 m/s˛ to get Isp), dp is the average propellant density and Id = ve*dp is the impulse density. It can be shown that for low delta-V dv, that dv ~= Id*Vp/mf where Vp is the propellant volume and mf is the final mass [R1]. Thus, for the first stage, both ve and dp are equally important. We can see that HTP has ve 7% less than LOX, but dp is 24% greater! Overall, HTP has a 15.4% greater Id than LOX. For the second stage though, ve is king, as performance of the second stage is dependent on total mass and not propellant volume.

For an ideal vehicle we can plot dv = ve*ln(1+dp*Vp/mf) against Vp/mf, i.e., the volume of propellant required to the mass delivered. Attached are the two curves for HTP and LOX. In order to get into orbit, we typically require between 9 and 10 km/s to account for drag, gravity and engine back pressure losses. At 9 km/s, we see that at low dv, HTP performs slightly better, but that at high dv, LOX performs slightly better. At 9 km/s, the difference is very small. LOX has Vp/mf = 14.705 kg/L, while HTP requires 14.872 kg/L. That is, LOX has a 1.1% advantage.

Another consideration is that for similar size vehicles, the greater launch mass of HTP results in a small reduction in the dv required to get into orbit. Like the heavy ocean liners of the past, the drag on the vehicle is constant. However, the force required to move the vehicle is greater. Thus the relative drag acceleration is less for a heavy vehicle. Another small advantage is that the lower Isp results in a faster acceleration profile, helping to reduce gravity losses. My simulations show that the combined effect results in a reduction of the required dv to get into orbit of about 50 m/s when using HTP compared to LOX (this was with RP-1 as the fuel) [R2].

[R1] S. S. Pietrobon, "High density liquid rocket boosters for the Space Shuttle," J. of the British Interplanetary Society, vol. 52, pp. 163-168, May/June 1999.
http://www.sworld.com.au/steven/pub/lrb.pdf

[R2] S. S. Pietrobon, "A flexible reusable space transportation system," J. of the British Interplanetary Society, vol. 53, pp. 276-288, May/June 2000.
http://www.sworld.com.au/steven/pub/nsto.pdf

4-12-2019 Corrected performance results.

[TrevorMonty]

RL are succesful because they stayed focus on getting to orbit and stayed course on their LV design. With reliable LV and solid customer base they can now afford to play around with more radical ideas eg reuse, even new engines and fuels.

Gilmour don't have this luxury they need fly ASAP with whatever well tested engine they have. Redesigns can come later when they have solid customer base. The small LV market well only support a few players and late comers well find it very difficult market to enter against proven LV providers.