[AR] Re: Falcon 9 flight today
- From: JMKrell@xxxxxxx
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 9 Oct 2013 15:22:47 -0400 (EDT)
1. Open a large orifice container of RP-1 in space, liquid or frozen, it
will completely evaporate.
2. Enclose the same RP-1 in a tank with a vent line that is significantly
smaller in diameter than the tank coupled with valves, bends, and a
temperature gradient across the line and open it to space. What happens?
Other than the obvious pressure drop. The temperature drop in the tank
quickly lowers the vapor pressure of the RP-1 below the pressure stagnation
point for the vent line. Isolating the tank via a molecular flow region from
the lower pressure of space. The low vapor pressure of RP-1 is significant
in this case. Its not a complete isolation of flow. Molecules will manage
to escape. The loss rate being small compared to the residual. I have made
numerous assumptions about the Falcon 9 vent line which could effect the
loss rate. I do not believe SpaceX has published the vent line dimensions,
pressure drop, or flow data.
What I have difficulty modeling is the amount of RP-1 that is carried with
the release of the pressurizing gas in zero-G. Have there been any
studies?
The lab experiments were conducted at temperatures between 0°C to -50°C
using different fluids and pressures down to millitorr. Very mild space
conditions. The water data was revalidated 2 years ago for a semiconductor
company. In the lab I did create complex flow and temperature gradient
conditions where my Knudsen flow sensor did not detect any flow.
Unless you're in sun synchronous orbit some part of each orbit will be in
the earth's shadow.
John Krell
In a message dated 10/9/2013 8:45:31 A.M. Pacific Daylight Time,
hkeithhenson@xxxxxxxxx writes:
50 F is 10 C, 0.031 psia is ~1.6 Torr so we are close enough on prope
rties.
However, I don't think you can orbit in the earth's shadow. You can
in the sun, i.e., sun synch, but I can't think of a way to stay in
shadow.
Keith
On Wed, Oct 9, 2013 at 12:16 AM, <JMKrell@xxxxxxx> wrote:
> My data lists RP-1 vapor pressure at <2 Torr @20C. In the earth's shadow,
> space is very cold.
>
> In a message dated 10/8/2013 5:34:51 P.M. Pacific Daylight Time,
> hkeithhenson@xxxxxxxxx writes:
>
> The vapor pressure of RP-1 at 50 deg F is given as 0.031 psia.
>
> That's not high, but open to space, the stuff is going to evaporate
> unless, as Henry says, it's awful cold.
>
>
>
> On Tue, Oct 8, 2013 at 4:00 PM, Henry Spencer <henry@xxxxxxxxxxxxxxx>
wrote:
>> On Tue, 8 Oct 2013 JMKrell@xxxxxxx wrote:
>>> > The vapor pressure of RP-1 isn't large by Earth standards, but it's
>>> > still substantial by vacuum standards. The RP-1 won't stay in the
>>> > tank, although it may leave a bit of residue behind.
>>>
>>> Henry, I agree with 99.9% of what you post, but on this I must go with
>>> my empirical data. Some RP-1 is expelled during the venting of the RP-1
>>> tank. The rest quickly gels and solidifies within the tank. Frozen
>>> fluids under high vacuum transfer mainly between hot and cold
>>> junctions... Most of the RP-1 remains a solid until the vehicle
reenters
>>> the atmosphere.
>>
>> Is that empirical data published? If so, references please! I have
>> trouble believing that the solid would be stable in vacuum for any
length
>> of time, unless the thermal situation was very unusual.
>>
>> Henry Spencer
>>
>> henry@xxxxxxxxxxxxxxx
>>
>> (hspencer@xxxxxxxxxxxxx)
>>
>> (regexpguy@xxxxxxxxx)
>>
>>
>
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