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Orbiter English => Dan's add-ons => Topic started by: mgefvert on 24 February 2016, 17:09:13

Title: Safe limits for hover engine
Post by: mgefvert on 24 February 2016, 17:09:13

Hi,

I have finally come up with a nice and accurate way to do reentries. It involves using the Map MFD to aim for the base you want to land at, dropping into the atmosphere at 7 km/s, bleeding off speed at about 40 G, and then flying around for a little while before the temperature cools down from 70 000 C to a tolerable 200 C. Obviously I have activated chicken mode. :)

However, the most difficult part (surprisingly) is transitioning safely from a flying motion to using the hover engine. What I do is that I try to fly level, dropping the speed down to about ~120 m/s, and then turning on the autopilot to catch me and heading for the landing pad.

But frequently I seem to break the hover engine ... the speed is too high, and the hover doors are ripped off or something.

So my question is ... what are the safe speed limits for the hover engine?

Thanks
Matt

Title: Re: Safe limits for hover engine
Post by: Mars Bleu on 25 February 2016, 14:26:28

Welcome to you, mgefvert!

I think it may depend of the used spacecraft.
For the Xr2, the global dynamic pressure is a limit for the whole hull.(150 kPa)
The hover doors must be closed during reentry in order to prevent
the inner hull from overheating.(XR- flight operation manual)

Did this help you?

Title: Re: Safe limits for hover engine
Post by: mgefvert on 27 February 2016, 01:04:55

Hi :)

How silly of me to leave out the most important detail :) It's the DeltaGliderIV-3 I'm talking about.

The hover doors are closed all the way down until I'm at an altitude of usually 2000 m, and the aircraft has cooled down below 200 C. It's just the switch between using the normal flying mode and relying on the hover engine that's a little tricky to always get right.

I suppose it's the same way if you're just flying along normally and suddenly switch to hover mode -- the hover engine seems to be very sensitive to speed.

Matt

Title: Re: Safe limits for hover engine
Post by: Mars Bleu on 27 February 2016, 13:47:12

I don't know DG IV's limits. Maybe  a task of investigations to test the limits
in all possible cases would be usefull...

Title: Re: Safe limits for hover engine
Post by: Cras on 29 February 2016, 03:12:50

Why exactly are you looking to transition from flight to hover mode?  Why not just fly her all the way down?

but if you really want to transition into a hover landing on Earth, basically stall the DG out, pull way up on the stick, send your AoA way up to create a huge amount of drag.  Yes you will cause some climb buy you will kill your speed very quickly, then fire those hovers up to prevent yourself from just free falling to your death.