Across
The hours oddly spent churning over and over secret (4-4)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (churning over) of the even (oddly spent) letters of t H e H o U r S , repeated (over)
Stokes derides shifts (6)
Vertex of Summer Triangle – dependably evident nightly – essentially blue at the outset (5)
I haven't cracked this one yet — but Fifteensquared have:
Initial letters (at the outset) of Dependably Evident Nightly Essentially Blue – I had to rely on Google for this
Scintillating 7, in my flying visits, representative of the bigger picture (9)
New lander first to penetrate alien world (3,6)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (new) of LANDER + P[enetrate] + ET (the familiar alien)
Ara represents this single missing blue-green star (5)
Evidence of fall, meteoric for one boxer (6)
I haven't cracked this one yet — but Fifteensquared have:
A crater is evidence of (eg – ‘for one’) a meteoric fall and a crater could be a boxer (one who puts things in crates / boxes?)
Returning carrier ship receiving earth pictures, not immediately decipherable? (7)
I haven't cracked this one yet — but Fifteensquared have:
A reversal (returning) of UBER (carrier) + SS (steam ship) round E (earth)
Pounds, shillings and pence, steel warped (7)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (warped) of S (shillings) and P (pence) + STEEL
One helps out leading characters (6)
Sample from traveller in G-suit, features of Saturn (5)
Buzz’s first problem after shortage – result of huge collapse (5,4)
One new member of quartet, Tim Peake, gutted Virgin (9)
I haven't cracked this one yet — but Fifteensquared have:
I (one) N (new) VIOLA (member of quartet) + T[im peak]E
As an alternative, cut celestial path (5)
Cherished by SpaceX – Eternal City (6)
Linesman’s not one for stress plugging in Empire State (8)
I haven't cracked this one yet — but Fifteensquared have:
NY (New York – Empire State) in TENS[i]ON (stress) minus i (one)
Down
What about launching a Soviet climber? (6)
I haven't cracked this one yet — but Fifteensquared have:
A reversal (about) of EH (what) + a reversal (launching, in a down clue) of A RED (a Soviet)
Standards slipping, we fly at night (4-5)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (slipping) of STANDARDS – a type of moth
See Phoebe, Bull and edges of 7 flying in astronomical equipment (6,9)
I haven't cracked this one yet — but Fifteensquared have:
An anagram (flying) of SEE PHOEBE BULL and C[ome]T (answer to 7dn)
Discussion group remains animated (7)
People on radio to instruct landing outside Belgium are sadly cracking up (6,9)
I haven't cracked this one yet — but Fifteensquared have:
MEN (people) + TALK DOWN (on radio to instruct landing) round B (Belgium) + an anagram (sadly) of ARE
I circle the sun bed occupied by mining engineer (5)
Most assuredly ground-to-air ceasefires will include confines of space (8)
I haven't cracked this one yet — but Fifteensquared have:
A reversal (ground-to-air, in a down clue) of TRUCES (ceasefires) round first and last letters (confines) of S[pac]E
Having visited e.g. 10, astronaut’s back home at last, he says (6)
I haven't cracked this one yet — but Fifteensquared have:
[astronau]T + [hom]E in STAR
It takes a lot to learn (6,3)
Characteristic of fans not winning game (8)
Group aboard last couple of rockets set up midnight rendezvous (6)
I haven't cracked this one yet — but Fifteensquared have:
ABBA (group) in a reversal (set up) of [rocke]TS – a witches’ midnight meeting
University types created cycles in unit (7)
I haven't cracked this one yet — but Fifteensquared have:
A ‘cycling’ of MADE (created) in ACE (unit)
Hardly the sphere of the old-fashioned scientist! (6)
Type letters or click words in the clue