Helo Speed Records

This is becoming an aerospace video blog. 🙂

The eighties

Versus the teens

Westland Lynx only reached 90 m/s while X2 is doing 130 m/s. The ability to let the rotor spin slowly since only the advancing blade needs to lift in a counter rotating rotor allows the X2 reach a high speed.

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Airline vs Spaceline Safety

62 mile club has a writeup of a beta “customer qualification program” for XCOR’s Lynx suborbital craft. This highlights the differences and current state of play. Rocketships will not be as safe as airliners in the near future, and they don’t need to be. There are millions of things that are less safe than airliners – scuba diving, ballooning, general aviation, motorcycling, probably even driving a car. And yet people do those things because they have the judgement and can decide for themselves.

The key difference is an informed consent. The suborbital rocket traveler should be told of the risks truthfully so that they can decide for themselves if they want to do it or not. This, I gather, has always been XCOR’s principle.

Airlines are not directed at such customers because they are a mass means of travel – the customer is not briefed specially but is expecting reasonably good safety – and there are thus governmental and intergovernmental bodies regulating the airlines and trying to constantly improve safety.

It would not make the slightest sense to regulate suborbital passenger rockets at this time at airline level – there are only a few passengers and the companies should have the time and resources to screen and brief them very well on what it will be like and what the risks are. (This is a must though – you shouldn’t advertise the service as something as safe as airlines.)

There should be some very simple regulation of rocketships regarding the risk to the uninvolved public of course – most companies deal with this adequately by just flying from remote enough locations. And of course there’s environmental regulation – it’s not cool to put tonnes of methanol into the ground water for example. Yet these are small no brainer issues (I’ve heard stories of over-eager environmental protection agencies though).

Nontoxic (or those that quickly decompose to such in nature) fuels and oxidizers should help a lot in this regard. Suborbital rocketry is not that performance critical anyway – it is a great way to find the lowest investment and operating cost approaches to rocketry – and these drive towards “nice” systems. Safe, easy, nontoxic, nonhazardous, redundant.

Regeneratively cooled LOX-ethanol or LOX-methane engines could be good in this regard – propellant spills and dumps are not that horrible to the environment or to the public, and the engine could in theory run indefinitely without any parts replaced if it is just refuelled.

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XCOR Lynx

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Oh well, there actually is more info about the vehicle outside XCOR’s press release (why didn’t they put that there?). Here, at Clark Lindsey’s Hobbyspace. Seems my speculations were a bit off-base, the dry mass was fine but the mass ratio is a lot bigger, about 3. I noticed after posting from the flight profile that the burn is quite long, 3 minutes, giving more gravity losses… So, with all this taken into account, a big part of the speculation below is wrong.
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Well, I didn’t expect this, I thought XCOR had gotten an outside contract when they announced early this week they’d announce something on wednesday.

2 people to 62 km. All-rocket propulsion, horizontal takeoff, glide landing.

Interesting though, I had talked about this to a friend in February, how such vehicle would make perfect sense as a start: liquid engine with pumps to ensure very low operations cost: essentially just refuel and go again – and small size (one passenger) to enable low capital cost and easy improvability.

I was already going through Lynx in my head in the day, itching to reverse engineer the engine specs, so here goes. 🙂

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