Reaction Engines Ltd

[Flibble]

Beati Dogu said:

Yes, it seems they plan to start re-entry early and at a shallower angle. So it'll take much longer

The physically smaller Shuttle and various capsules take a more brute force approach.

Depending on your heatshield design it can be better to come in steeper. Higher heat flux but for a shorter period can give lower overall heat absorption in the heatshield. Some unmanned probes have come in at very steep angles as they don't have the g force constraints of manned flights.

[Eric Mc]

Apollo had a very high heat load during re-entry because of its lunar re-entry speed and a steep re-entry angle. But the high load only had to be endured for 4 to 5 minutes.

Because the Shuttle was a winged space plane, it had a much shallower entry angle in comparison and was re-entering at slower, earth orbit, velocities. However, it had to endure those loads for up to 15 minutes.

[lost in espace]

Excellent long interview with Alan Bond on the Interplantary Podcast. https://www.interplanetary.org.uk/single-post/2019...

[hidetheelephants]

I remember reading an article about hypersonic vehicles which considered that aerospikes might have application in controlling skin heating, at least for LEO or sub-orbital flight.

[DeejRC]

The Reaction boys are decent chaps, we have shared quite a bit of staff with them. They are in the offices along the corridor.
Much interesting talks last week!

[Liokault]

DeejRC said:

The Reaction boys are decent chaps, we have shared quite a bit of staff with them. They are in the offices along the corridor.
Much interesting talks last week!

Right next to the space they use for the speed awareness courses?

I went into Reaction for an interview and told them I already knew how to find them as I was there the week before for my telling off...went ok.

Edited by Liokault on Saturday 4th May 12:21

[Toaster]

DeejRC said:

The Reaction boys are decent chaps, we have shared quite a bit of staff with them. They are in the offices along the corridor.
Much interesting talks last week!

Its great to hear this, its also nice to hear something being developed in the UK.

[Beati Dogu]

I love that they're right next to where they hold speed awareness courses. That's so damn British somehow.

[NormalWisdom]

Now successfully tested at speeds representing Mach 5!!!

https://www.reactionengines.co.uk/news/reaction-en...

[prand]

NormalWisdom said:

Now successfully tested at speeds representing Mach 5!!!

https://www.reactionengines.co.uk/news/reaction-en...

I saw this earlier in the week. A long way to go to be able to commute from a private island in Micronesia to London, but with the current maximum jet aircraft speed is what, Mach 3, so this at paves the way for a Mach 5 air breathing jet engine.

One thing I'm wondering about is how much is progress is being made developing a supporting airframe. I remember Concorde (and the Blackbird) had some significant technical design challenges to overcome to go as fast as they did/do, (such as the expansion of metal and stresses of travelling at this speed), so is there anything being developed that can actually fly at Mach 5, let alone the Mach 25 to go into space?

Edited by prand on Thursday 14th November 16:34

[hidetheelephants]

prand said:

NormalWisdom said:

Now successfully tested at speeds representing Mach 5!!!

https://www.reactionengines.co.uk/news/reaction-en...

I saw this earlier in the week. A long way to go to be able to commute from a private island in Micronesia to London, but with the current maximum jet aircraft speed is what, Mach 3, so this at paves the way for a Mach 5 air breathing jet engine.

One thing I'm wondering about is how much is progress is being made developing a supporting airframe. I remember Concorde (and the Blackbird) had some significant technical design challenges to overcome to go as fast as they did/do, (such as the expansion of metal and stresses of travelling at this speed), so is there anything being developed that can actually fly at Mach 5, let alone the Mach 25 to go into space?

The answer is just climb until the airframe heating becomes manageable, so it might be 200,000'.

[Eric Mc]

Yep - the Space Shuttle and all other rockets have to cope with that as well but heating during ascent is negligible due to the fact that within about 4 minutes the craft was above 90% of the atmosphere.

[Flibble]

I think the 1000C at Mach 5 is the maximum temperature as after that the air thins and heat flux drops.
The X-15 is the fastest plane ever made, it managed over Mach 6 without burning up due to the high altitudes it was flown at.

[hidetheelephants]

Flibble said:

I think the 1000C at Mach 5 is the maximum temperature as after that the air thins and heat flux drops.
The X-15 is the fastest plane ever made, it managed over Mach 6 without burning up due to the high altitudes it was flown at.

It did get lightly toasted though...

[Flooble]

hidetheelephants said:

Flibble said:

I think the 1000C at Mach 5 is the maximum temperature as after that the air thins and heat flux drops.
The X-15 is the fastest plane ever made, it managed over Mach 6 without burning up due to the high altitudes it was flown at.

It did get lightly toasted though...

350,000 feet for the highest flight apparently, so a long way up to avoid the heating. Could be interesting actually finding a sweet spot where you have enough atmosphere to provide oxygen to the engine without burning up.

[Talksteer]

The issue with Skylon isn't heating on the ascent, heating of an airframe is only really in issue for super sonic aircraft which sustain flight at elevated mach for a significant time.

When NASA was looking at two stage fully reusable shuttles they had reusable boosters made of aluminium which could surrive mach 6-8 re-entries as the heat pulse is relatively brief. The reusable boosters today surrvive on the same basis.

The issue for Skylon is the placement of the engines, NASA did a study a few years ago that indicated as the craft climbs out of the atmosphere and the engine plume starts to expand is impinges on the rear fuselage and over the course of the several minute burn of the engines in rocket mode heats the rear fuselge much more than reentry would.

This is why more recent Skylon concepts have it being a reusable first stage with a very high staging velocity.

https://www.nas.nasa.gov/assets/pdf/papers/Mehta_U...

[Eric Mc]

Flooble said:

350,000 feet for the highest flight apparently, so a long way up to avoid the heating. Could be interesting actually finding a sweet spot where you have enough atmosphere to provide oxygen to the engine without burning up.

X-15 flights usually were split between two types - low and fast (200,000 feet - Mach 5 plus) or higher and slower (350,000 feet - mach 3ish).

It was the low and fast flights that caused the most heating problems.

[AshVX220]

Eric Mc said:

Flooble said:

350,000 feet for the highest flight apparently, so a long way up to avoid the heating. Could be interesting actually finding a sweet spot where you have enough atmosphere to provide oxygen to the engine without burning up.

X-15 flights usually were split between two types - low and fast (200,000 feet - Mach 5 plus) or higher and slower (350,000 feet - mach 3ish).

It was the low and fast flights that caused the most heating problems.

The altitude being the defining factor surely? Low and fast would still generate more heat as high and fast (if the velocity were the same), just through air density?

[Eric Mc]

Yes - it was the low and fast runs that generated the most airframe heating - through friction and shock wave compression.

The X-15 was deliberately designed to probe these high temperature zones.

[Flooble]

Interesting conundrum then. If you stay slow while low, you burn more fuel than if you get out of the bulk of the atmosphere as quickly as possible. But if you go too fast too early you will overheat your airframe.

So they will still have to balance fuel burn with airframe heating. And I guess that if the X15 was burning up at Mach 5 within the bulk of the atmosphere that puts a cap on the speed you can do while there is still lots of atmospheric oxygen to use. Meaning you need your onboard oxygen for the Mach 5 to Mach 25 acceleration.