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91
So they anticipate being able to safe and remove the OneWeb booster in <10 hours after landing? 
Why would they need to do so?  Boosters have landed nearly simultaneously on LZ1 and 2 during four Falcon Heavy missions.  (As long as they remember to program the second not to land on the same Zone as the first!)

 - Ed Kyle

Because if Alex is correct and LZ-2 will not be utilized for either upcoming launch on the 6th/7th, both B1073-5 and B1069-4 will be conducting landings at LZ-1 within hours of one another.
92
Advanced Concepts / Re: Medusa concept using chemical explosives
« Last post by Beratnyi on Today at 01:38 am »
If you think outside the box, then comes the realization that the energy density of the fuel is almost irrelevant to the effectiveness of rockets. The main thing that matters is to what speed it was possiblet to disperse the exhaust gases

...which is related to the energy (from within the fuel or otherwise) by KE = 1/2 m v2.

No way around that pesky conservation of energy!
The temperature of the exhaust gases is affected not by the amount of energy, but by the rate at which this energy is transferred to the reaction mass.

...which is limited by the amount of energy. So it is affected.  ::)

That is why in the center of a nuclear explosion of a kiloton charge, the temperature reaches one hundred million degrees, which is enough to initiate a thermonuclear explosion, while if you blow up a kiloton of TNT, the temperature will be measured in thousands of degrees.

Equivalently you could say that a nuclear bomb has a higher energy density than TNT, and you'd be right.
Once again, rocket engine can feed an energy source with infinite energy density, but if it can only heat the reaction mass up to 1000 degrees Celsius, then any most primitive engine will do it. I did not just cite the NERVA engine as an example.

Hence

limited by

No matter how efficient your heat transfer, your exhaust velocity can never exceed the limiting value determined by the total amount of energy available.
I will cite as an example the Spitfire fighter, in which the amount of heat entering the radiator was equal to the amount of energy driving the propeller. However, the thrust from the radiator was negligible and barely covered its air resistance, and all because of the temperature of the antifreeze in the region of 100 degrees Celsius.
There is not only energy density, but also energy quality.
93
So they anticipate being able to safe and remove the OneWeb booster in <10 hours after landing? 
Why would they need to do so?  Boosters have landed nearly simultaneously on LZ1 and 2 during four Falcon Heavy missions.  (As long as they remember to program the second not to land on the same Zone as the first!)

 - Ed Kyle
94
I think that is a safe bet that Artemis III will be delayed by a year, from 2025 to 2026, given that Artemis I was delayed by a year, from 2021 to 2022. The delay of launching Starship to orbit by more than 6 months also contributes to that delay.

I noticed that Axiom's contract ends on July 8, 2026 which leads me to believe that the suits won't be ready before that time either.

https://forum.nasaspaceflight.com/index.php?topic=53612.msg2437302#msg2437302

NASA said that it would update the dates after Artemis I is completed.
We do not know if the Starship slip will affect the Artemis III slip. It depends on what is on the critical path (PERT/CPM strikes again...) My guess: SLS/Orion is still critical path and Starship is not, at least not yet. However, If SLS/Orion were not slipping and the spacesuits were not slipping, then Starship HLS would be on the critical path.
95
Advanced Concepts / Re: Medusa concept using chemical explosives
« Last post by Twark_Main on Today at 01:31 am »
If you think outside the box, then comes the realization that the energy density of the fuel is almost irrelevant to the effectiveness of rockets. The main thing that matters is to what speed it was possiblet to disperse the exhaust gases

...which is related to the energy (from within the fuel or otherwise) by KE = 1/2 m v2.

No way around that pesky conservation of energy!
The temperature of the exhaust gases is affected not by the amount of energy, but by the rate at which this energy is transferred to the reaction mass.

...which is limited by the amount of energy. So it is affected.  ::)

That is why in the center of a nuclear explosion of a kiloton charge, the temperature reaches one hundred million degrees, which is enough to initiate a thermonuclear explosion, while if you blow up a kiloton of TNT, the temperature will be measured in thousands of degrees.

Equivalently you could say that a nuclear bomb has a higher energy density than TNT, and you'd be right.
Once again, rocket engine can feed an energy source with infinite energy density, but if it can only heat the reaction mass up to 1000 degrees Celsius, then any most primitive engine will do it. I did not just cite the NERVA engine as an example.

Hence

limited by

No matter how efficient your heat transfer, your exhaust velocity can never exceed the limiting value determined by the total amount of energy available.
96
Q&A Section / ISS Yellow Handrails
« Last post by Timber Micka on Today at 01:28 am »
I noticed that on the official illustrations of the ISS from 1993 to 1997, the Shuttle-launched modules are shown with a very visible network of thick yellow handrails.
By 1997, construction of Node 1, the first American element, was well underway. But when it was launched the following year, it didn't have these handrails, but smaller, more discreet handrails, like the modules that followed.
What happened to the yellow handrails? Have they been built? If so, was there a plan to install them later on the station modules? Why was the design of the handrails changed?
97
I think that is a safe bet that Artemis III will be delayed by a year, from 2025 to 2026, given that Artemis I was delayed by a year, from 2021 to 2022. The delay of the launch of Starship to orbit by more than 6 months also likely contributes to that delay.

I noticed that Axiom's contract ends on July 8, 2026 which leads me to believe that the suits won't be ready before that time either.

https://forum.nasaspaceflight.com/index.php?topic=53612.msg2437302#msg2437302

NASA said that it would update the Artemis launch dates after Artemis I is completed.
98
NASA released the source selection statement for the xEVAS awards yesterday.

Can be found in either of the award announcements:

Axiom Space https://sam.gov/opp/2acfdeae77644a3285f1701a2392d5f3/view

Hamilton Sundstrand https://sam.gov/opp/33c62796d01c4448af94d2a9a9a5404e/view

(slightly confused, I thought Team Collins won the second award)

Copy is also attached.

Here are updates about the awards:

Axiom 80JSC022DA022:
https://www.usaspending.gov/award/CONT_IDV_80JSC022DA022_8000
https://www.usaspending.gov/award/CONT_AWD_80JSC022FA103_8000_80JSC022DA022_8000

Collins 80JSC022DA023:
https://www.usaspending.gov/award/CONT_IDV_80JSC022DA023_8000

I noticed that Axiom's contract for the Artemis III suits ends on July 8, 2026 which leads me to believe that the suits won't be ready before that time.

https://www.usaspending.gov/award/CONT_AWD_80JSC022FA103_8000_80JSC022DA022_8000
99
Advanced Concepts / Re: Medusa concept using chemical explosives
« Last post by Beratnyi on Today at 01:20 am »
If you think outside the box, then comes the realization that the energy density of the fuel is almost irrelevant to the effectiveness of rockets. The main thing that matters is to what speed it was possiblet to disperse the exhaust gases

...which is related to the energy (from within the fuel or otherwise) by KE = 1/2 m v2.

No way around that pesky conservation of energy!
The temperature of the exhaust gases is affected not by the amount of energy, but by the rate at which this energy is transferred to the reaction mass.

...which is limited by the amount of energy. So it is affected.  ::)

That is why in the center of a nuclear explosion of a kiloton charge, the temperature reaches one hundred million degrees, which is enough to initiate a thermonuclear explosion, while if you blow up a kiloton of TNT, the temperature will be measured in thousands of degrees.

Equivalently you could say that a nuclear bomb has a higher energy density than TNT, and you'd be right.
Once again, rocket engine can feed an energy source with infinite energy density, but if it can only heat the reaction mass up to 1000 degrees Celsius, then any most primitive engine will do it. I did not just cite the NERVA engine as an example.
The temperature inside a nuclear explosion is so high because of the thousands of times faster detonation velocity than any chemical explosive, and not at all because of the energy density.
100
Advanced Concepts / Re: Using shaped charges as a rocket engine
« Last post by Twark_Main on Today at 01:20 am »
the record is an incredible 90 km / s (9000s Isp)!

This calculation assumes that 100% of the mass of the explosive device is accelerated to 90 km/s. I find this highly unlikely, given how shaped charges work.

This paper mentions "beryllium jets" accelerated to 90 km/s. I note that beryllium is not a high explosive, so my skepticism seems to be warranted.




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